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Al-Sharify NT, Nser HY, Ghaeb NH, Al-Sharify ZT, See OH, Weng LY, Ahmed SM. Influence of different parameters on the corneal asphericity (Q value) assessed with progress in biomedical optics and imaging - A review. Heliyon 2024; 10:e35924. [PMID: 39224364 PMCID: PMC11367468 DOI: 10.1016/j.heliyon.2024.e35924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 07/20/2024] [Accepted: 08/06/2024] [Indexed: 09/04/2024] Open
Abstract
The corneal eye diseases such as Keratoconus cause weakening of the cornea, with this disease the cornea can change in shape. This condition affects between 1 in 3,000 to 1 in 10,000 people. The main reason for the development of such conditions is unknown and can have significant impacts. Over the last decade, with advancements in computerized corneal topography assessments, researchers have increasingly expressed interest in corneal topography for research as well as clinical activities. Up till now, several aspheric numerical models have been developed as well as proposed to define the complex shape of the cornea. A commonly used term for characterizing the asphericity in an eye is the Q value, a common indicator of the aspherical degree of the cornea. It is one of the critical parameters in the mathematical description model of the cornea as it represents the cornea's shape and the eye's characteristics. Due to the utmost importance of this Q value of the cornea, a couple of studies have attempted to explore this parameter and its distribution, merely in terms of its influence on the human eye's optical properties. The corneal Q value is an important factor that needs to be determined to treat for any refractive errors as corneal degeneration are disease that can lead to potential problems with the structure of the cornea. This study aims to highlight the need to understand Q value of the cornea as this can essentially assist with personalising corneal refractive surgeries and implantation of intraocular lenses. Therefore, the relevance of corneal Q value must be studied in association with different patients, especially ones who have been diagnosed with cataracts, brain tumours, or even COVID-19. To address this issue, this paper first carries out a literature review on the optics of the cornea, the relevance of corneal Q value in ophthalmic practice and studies corneal degenerations and its causes. Thereafter, a detailed review of several noteworthy relevant research studies examining the Q value of the cornea is performed. To do so, an elaborate database is created, which presents a list of different research works examined in this study and provides key evidence derived from these studies. This includes listing details on the age, gender, ethnicity of the eyes assessed, the control variables, the technology used in the study, and even more. The database also delivers important findings and conclusions noted in each study assessed. Next, this paper analyses and discusses the magnitude of corneal Q value in various scenarios and the influence of different parameters on corneal Q value. To design visual optical products as well as to enhance the understanding of the optical properties of an eye, future studies could consider the database and work presented in this study as useful references. In addition, the work can be used to make informed decisions in clinical practice for designing visual optical products as well as to enhance the understanding of the optical properties of an Eye.
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Affiliation(s)
- Noor T. Al-Sharify
- Department of Electrical & Electronic Engineering, College of Engineering, Universiti Tenaga Nasional, Malaysia
- Medical Instrumentation Engineering Department, Al-Esraa University College, Baghdad, Iraq
| | - Husam Yahya Nser
- Department of Electrical & Electronic Engineering, College of Engineering, Universiti Tenaga Nasional, Malaysia
| | - Nebras H. Ghaeb
- Biomedical Engineering Department, Al Khawarezmi, Engineering College, University of Baghdad, Iraq
| | - Zainab T. Al-Sharify
- Department of Pharmacy, Al Hikma University College, Baghdad, Iraq
- School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT, Birmingham, United Kingdom
| | - Ong Hang See
- Department of Electrical & Electronic Engineering, College of Engineering, Universiti Tenaga Nasional, Malaysia
| | - Leong Yeng Weng
- Department of Electrical & Electronic Engineering, College of Engineering, Universiti Tenaga Nasional, Malaysia
| | - Sura M. Ahmed
- Department of Electrical & Electronic Engineering, College of Engineering, Universiti Tenaga Nasional, Malaysia
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Davies LN, Biswas S, Bullimore M, Cruickshank F, Estevez JJ, Khanal S, Kollbaum P, Marcotte-Collard R, Montani G, Plainis S, Richdale K, Simard P, Wolffsohn JS. BCLA CLEAR presbyopia: Mechanism and optics. Cont Lens Anterior Eye 2024; 47:102185. [PMID: 38796331 DOI: 10.1016/j.clae.2024.102185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2024]
Abstract
With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.
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Affiliation(s)
- Leon N Davies
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK.
| | - Sayantan Biswas
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK
| | | | - Fiona Cruickshank
- Division of Pharmacy and Optometry, School of Health Sciences, Faculty of Biology, Medicine and Health, University of Manchester, UK
| | - Jose J Estevez
- Caring Futures Institute, College of Nursing and Health Sciences, Optometry and Vision Science, Flinders University, Adelaide, Australia; Flinders Centre for Ophthalmology, Eye and Vision Research, Department of Ophthalmology, Flinders University, Adelaide, Australia
| | - Safal Khanal
- Department of Optometry and Vision Science, The University of Alabama at Birmingham, USA
| | | | | | | | - Sotiris Plainis
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK; Laboratory of Optics and Vision, School of Medicine, University of Crete, Greece
| | | | - Patrick Simard
- School of Optometry, Universite de Montreal, Montreal, Quebec, Canada
| | - James S Wolffsohn
- School of Optometry, College of Health and Life Sciences, Aston University, Birmingham, UK
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Bhutani U, Dey N, Chowdhury SK, Waghmare N, Mahapatra RD, Selvakumar K, Chandru A, Bhowmick T, Agrawal P. Biopolymeric corneal lenticules by digital light processing based bioprinting: a dynamic substitute for corneal transplant. Biomed Mater 2024; 19:035017. [PMID: 38471165 DOI: 10.1088/1748-605x/ad3312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Accepted: 03/12/2024] [Indexed: 03/14/2024]
Abstract
Digital light processing (DLP) technology has gained significant attention for its ability to construct intricate structures for various applications in tissue modeling and regeneration. In this study, we aimed to design corneal lenticules using DLP bioprinting technology, utilizing dual network bioinks to mimic the characteristics of the human cornea. The bioink was prepared using methacrylated hyaluronic acid and methacrylated gelatin, where ruthenium salt and sodium persulfate were included for mediating photo-crosslinking while tartrazine was used as a photoabsorber. The bioprinted lenticules were optically transparent (85.45% ± 0.14%), exhibited adhesive strength (58.67 ± 17.5 kPa), and compressive modulus (535.42 ± 29.05 kPa) sufficient for supporting corneal tissue integration and regeneration. Puncture resistance tests and drag force analysis further confirmed the excellent mechanical performance of the lenticules enabling their application as potential corneal implants. Additionally, the lenticules demonstrated outstanding support for re-epithelialization and stromal regeneration when assessed with human corneal stromal cells. We generated implant ready corneal lenticules while optimizing bioink and bioprinting parameters, providing valuable solution for individuals suffering from various corneal defects and waiting for corneal transplants.
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Affiliation(s)
- Utkarsh Bhutani
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Namit Dey
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Suvro Kanti Chowdhury
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Neha Waghmare
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Rita Das Mahapatra
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Kamalnath Selvakumar
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Arun Chandru
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
| | - Tuhin Bhowmick
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
- Pandorum International Inc., San Francisco, CA, United States of America
| | - Parinita Agrawal
- Pandorum Technologies Private Limited, Bangalore Bioinnovation Centre, Helix Biotech Park, Electronic City, Phase 1, Bengaluru 560100, India
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Meek KM, Knupp C, Lewis PN, Morgan SR, Hayes S. Structural control of corneal transparency, refractive power and dynamics. Eye (Lond) 2024:10.1038/s41433-024-02969-7. [PMID: 38396030 DOI: 10.1038/s41433-024-02969-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 12/11/2023] [Accepted: 01/26/2024] [Indexed: 02/25/2024] Open
Abstract
The cornea needs to be transparent to visible light and precisely curved to provide the correct refractive power. Both properties are governed by its structure. Corneal transparency arises from constructive interference of visible light due to the relatively ordered arrangement of collagen fibrils in the corneal stroma. The arrangement is controlled by the negatively charged proteoglycans surrounding the fibrils. Small changes in fibril organisation can be tolerated but larger changes cause light scattering. Corneal keratocytes do not scatter light because their refractive index matches that of the surrounding matrix. When activated, however, they become fibroblasts that have a lower refractive index. Modelling shows that this change in refractive index significantly increases light scatter. At the microscopic level, the corneal stroma has a lamellar structure, the parallel collagen fibrils within each lamella making a large angle with those of adjacent lamellae. X-ray scattering has shown that the lamellae have preferred orientations in the human cornea: inferior-superior and nasal-temporal in the central cornea and circumferential at the limbus. The directions at the centre of the cornea may help withstand the pull of the extraocular muscles whereas the pseudo-circular arrangement at the limbus supports the change in curvature between the cornea and sclera. Elastic fibres are also present; in the limbus they contain fibrillin microfibrils surrounding an elastin core, whereas at the centre of the cornea, they exist as thin bundles of fibrillin-rich microfibrils. We present a model based on the structure described above that may explain how the cornea withstands repeated pressure changes due to the ocular pulse.
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Affiliation(s)
- Keith M Meek
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK.
| | - Carlo Knupp
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Philip N Lewis
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Siân R Morgan
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK
| | - Sally Hayes
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, CF24 4HQ, UK
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Mao X, Chen H, Zhao Y, Ji S, Dai J. Impact of the preoperative cylinder on astigmatism correction in femtosecond lenticule extraction (FLEX): a prospective observational study. Graefes Arch Clin Exp Ophthalmol 2024; 262:631-639. [PMID: 37725147 DOI: 10.1007/s00417-023-06211-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 08/08/2023] [Accepted: 08/15/2023] [Indexed: 09/21/2023] Open
Abstract
PURPOSE To explore the impact of the preoperative manifest cylinder on astigmatism correction via femtosecond lenticule extraction (FLEX), or small incision lenticule extraction (SMILE). METHODS This was a prospective observational study. Eyes were categorized into mild (n = 88), moderate (n = 46), and severe (n = 53) astigmatism groups, based on the preoperative manifest cylinder. Vector analysis was conducted with the back vertex distance set at 12 mm. The primary outcome was the correction index (CI), with secondary outcomes including the safety, efficacy, predictability, and vectoral alterations related to FLEX. RESULTS The average target-induced astigmatism was 0.45 ± 0.20 D, 0.95 ± 0.17 D, and 1.99 ± 0.65 D in the three groups (P < 0.001), and the average CI was 1.12± 0.05, 1.01 ± 0.03, and 0.95 ± 0.02 (P = 0.020), with the severe astigmatism group displaying a notably lower CI. The efficacy, safety, predictability, or stability of FLEX did not demonstrate any significant differences among the three groups. The CIs exhibited a significant difference in eyes with with-the-rule (WTR) astigmatism and against-the-rule (ATR) astigmatism from the mild to severe astigmatism group. In eyes with oblique astigmatism, the average CI exceeded one. CONCLUSION Patients with manifest cylinder exceeding 1.25 D have a heightened risk of under-correction in WTR and ATR astigmatism compared to those with mild astigmatism, and mild over-correction may occur in cases of oblique astigmatism.
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Affiliation(s)
- Xiuyu Mao
- Department of Ophthalmology, Zhongshan Hospital Affiliated to Fudan University, Shanghai, 200032, China
- Department of Ophthalmology, Eye & ENT Hospital Affiliated to Fudan University, Shanghai, 200031, China
| | - Han Chen
- Department of Ophthalmology, Eye & ENT Hospital Affiliated to Fudan University, Shanghai, 200031, China
- Fujian Provincial Hospital, Fuzhou, 350001, China
| | - Yinzhen Zhao
- Department of Ophthalmology, Zhongshan Hospital Affiliated to Fudan University, Shanghai, 200032, China
| | - Shunmei Ji
- Department of Ophthalmology, Zhongshan Hospital Affiliated to Fudan University, Shanghai, 200032, China
- Department of Ophthalmology, Eye & ENT Hospital Affiliated to Fudan University, Shanghai, 200031, China
| | - Jinhui Dai
- Department of Ophthalmology, Zhongshan Hospital Affiliated to Fudan University, Shanghai, 200032, China.
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Salvador-Roger R, Albarrán-Diego C, Garzón N, García-Montero M, Muñoz G, Micó V, Esteve-Taboada JJ. Revisiting Javal's rule: a fresh and improved power vector approach according to age. Graefes Arch Clin Exp Ophthalmol 2024; 262:249-260. [PMID: 37552315 PMCID: PMC10805827 DOI: 10.1007/s00417-023-06195-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/19/2023] [Accepted: 07/30/2023] [Indexed: 08/09/2023] Open
Abstract
PURPOSE The scientific community has established Javal's rule as a model linking refractive (RA) and keratometric (KA) astigmatism since its appearance more than 100 years ago. The aim was to improve the accuracy of this relationship according to subject's age by applying the power vector analysis. Posterior corneal curvature has also been studied. METHODS The IOLMaster 700 optical biometer was used to measure the corneal thickness and the radius of curvature of the anterior and posterior corneal surfaces. Refractive error was determined by a non-cycloplegic subjective refraction process with trial lenses. Linear regression analyses were applied using J0 and J45 power vector components. An evaluation was carried out according to the subject's age resulting into eight regression relationships for each astigmatic vector component for each relationship. RESULTS A total of 2254 right eyes from 2254 healthy subjects were evaluated. A trend towards against-the-rule astigmatism (ATR) was found with aging, both for refractive astigmatism (RA) and keratometric astigmatism (KA), with 95.2% of subjects under 20 years old having with-the-rule (WTR) KA, and only 22.8% above 79 years old. The following regression equations were found between RA and KA: [Formula: see text] = 0.73 × [Formula: see text] - 0.18 (R = 0.78) and [Formula: see text] = 0.70 × [Formula: see text] + 0.04 (R = 0.69) and between RA and total corneal astigmatism (TCA): [Formula: see text] = 0.73 × [Formula: see text] + 0.13 (R=0.78) and [Formula: see text] = 0.70 × [Formula: see text] - 0.06 (R = 0.68) for the whole sample, but with sensible differences among age groups, both in the slope and in the intercept. CONCLUSION Ignoring the age of the subject when using Javal's rule could lead to an error in the final cylinder calculation that would increase in high astigmatisms. Applying this new power vector approach based on subject's age could improve the accuracy of the astigmatism prediction.
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Affiliation(s)
- Raquel Salvador-Roger
- Department of Optics and Optometry and Vision Sciences, University of Valencia, 46100, Burjassot, Valencia, Spain.
| | - César Albarrán-Diego
- Department of Optics and Optometry and Vision Sciences, University of Valencia, 46100, Burjassot, Valencia, Spain
| | - Nuria Garzón
- Department of Optometry and Vision, Universidad Complutense de Madrid, 28037, Madrid, Spain
| | - María García-Montero
- Department of Optometry and Vision, Universidad Complutense de Madrid, 28037, Madrid, Spain
| | - Gonzalo Muñoz
- Marqués de Sotelo Ophthalmological Clinic, 46002, Valencia,, Spain
- Baviera Castellón Ophthalmological Clinic, 12003, Castelló de la Plana, Spain
| | - Vicente Micó
- Department of Optics and Optometry and Vision Sciences, University of Valencia, 46100, Burjassot, Valencia, Spain
| | - José J Esteve-Taboada
- Department of Optics and Optometry and Vision Sciences, University of Valencia, 46100, Burjassot, Valencia, Spain
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Tachikawa T, Ueno R, Mita T, Yuzurihara D, Noda T. Corneal refractive error and astigmatism in patients aged 6 to 18 years with a history of retinopathy of prematurity and birth weight of <1500 g. Jpn J Ophthalmol 2024; 68:42-49. [PMID: 38001368 DOI: 10.1007/s10384-023-01026-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Accepted: 09/05/2023] [Indexed: 11/26/2023]
Abstract
PURPOSE To investigate corneal refractive power (CR) and astigmatism (AS) in 6- to 18-year-old children with a history of retinopathy of prematurity (ROP) and birth weight of <1500 g who either did or did not undergo retinal photocoagulation (PC). STUDY DESIGN Retrospective study. METHODS We examined 143 eyes of 77 children in 2021. The children were divided into three groups for evaluation of CR and AS: those with a birth weight of ≥2500 g (normal birth weight [NBW] group, 13 eyes) as controls, those with spontaneously resolved ROP (sr-ROP group, 27 eyes), and those who underwent PC for treatment of ROP (PC-ROP group, 103 eyes). Swept-source anterior segment optical coherence tomography was used to analyze the cornea. RESULTS The median CR in the NBW, sr-ROP, and PC-ROP groups was 42.2 (41.3, 42.8) diopters (D), 44.5 (43.2, 45.5) D, and 45.2 (43.8, 46.6) D, respectively. The median AS in the NBW, sr-ROP, and PC-ROP groups was 1.2 (1.0, 1.5) D, 1.1 (0.8, 1.6) D, and 2.1 (1.4, 2.7) D. In the PC-ROP group, the with-the-rule astigmatic axis was 97%. In all three groups, a strong positive correlation was found between the mean anterior and posterior CR (NBW: r=0.795, sr-ROP: r=0.842, PC-ROP: r=0.890) and AS (NBW: r=0.883, sr-ROP: r=0.841, PC-ROP: r=0.860). CONCLUSION CR was significantly higher in the sr-ROP (p=0.013) and PC-ROP (p<0.001) groups than in the NBW group. The PC-ROP group had significantly more AS than the sr-ROP group. There was a strong correlation between the anterior and posterior CR and AS.
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Affiliation(s)
- Takako Tachikawa
- Department of Ophthalmology, Tokyo Metropolitan Ohtsuka Hospital, Minami-Ohtsuka 2-8-1, Toshima-ku, Tokyo, 170-8476, Japan.
| | - Ritsuko Ueno
- Department of Ophthalmology, Tokyo Metropolitan Ohtsuka Hospital, Minami-Ohtsuka 2-8-1, Toshima-ku, Tokyo, 170-8476, Japan
| | - Tetsuko Mita
- Department of Ophthalmology, Tokyo Metropolitan Ohtsuka Hospital, Minami-Ohtsuka 2-8-1, Toshima-ku, Tokyo, 170-8476, Japan
| | - Daisuke Yuzurihara
- Department of Ophthalmology, Tokyo Metropolitan Ohtsuka Hospital, Minami-Ohtsuka 2-8-1, Toshima-ku, Tokyo, 170-8476, Japan
| | - Toru Noda
- Department of Ophthalmology, NHO Tokyo Medical Center, Tokyo, Japan
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Antonov AA, Volzhanin AV, Klinicheva EA, Karpilova MA. [Influence of corneal curvature and peripheral thickness on tonometry readings]. Vestn Oftalmol 2024; 140:43-50. [PMID: 38739130 DOI: 10.17116/oftalma202414002243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
PURPOSE This study investigates the influence of peripheral corneal thickness (PCT) and its curvature on tonometry readings. MATERIAL AND METHODS The study included 49 patients (49 eyes) who were indicated for glaucoma surgery. Using bidirectional applanation tonometry, the following parameters were obtained: IOPcc, IOPg - intraocular pressure (IOP) corrected for corneal compensation, taken as the most reliable indicator; IOP converted to Goldmann measurement, taken as the result of applanation tonometry, ΔIOP (IOPcc-IOPg), CH and CRF (corneal hysteresis and corneal resistance factor). During corneal topography, the corneal thickness was studied in the center, PCT at 1.5; 2, 3, 4 and 5 mm from the center in four meridians, as well as ΔPCT (PCT 3 mm - PCT 1.5 mm), the curvature of the anterior and posterior surfaces of the cornea and the depth of the anterior chamber. Aberrometry was used to obtain refractometry data and the curvature of the anterior surface of the cornea. The influence of the studied parameters on ΔIOP was evaluated. RESULTS ΔIOP correlated with CRF (r= -0.652), CH (r= -0.873), central corneal thickness (r= -0.293), PCT at all distances except 5 mm (r= -0.297; -0.287; -0.302; -0.303), with the strong and weak meridians of the anterior surface of the cornea (r=0.328; r=0.315), with the strong and weak meridians of the posterior surface, as well as the average curvature of the posterior surface (r=0.307; r=0.332; r=0.328). After step-by-step selection of the above parameters for creating a linear regression model for ΔIOP calculation, CH, CRF and PCT1.5mm remained in the model. The model describes ΔIOP with high accuracy (R2=0.974). CONCLUSION Biomechanical parameters of the cornea are the leading factor of applanation tonometry error. Individual linear dimensions of the cornea (thickness, curvature) have a lesser effect.
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Affiliation(s)
- A A Antonov
- Krasnov Research Institute of Eye Diseases, Moscow, Russia
| | - A V Volzhanin
- Krasnov Research Institute of Eye Diseases, Moscow, Russia
| | - E A Klinicheva
- Krasnov Research Institute of Eye Diseases, Moscow, Russia
| | - M A Karpilova
- Krasnov Research Institute of Eye Diseases, Moscow, Russia
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Yoon SH, Song JR, Lee SH, Eom Y, Hyon JY, Jeon HS. Actual anterior-posterior corneal radius ratio in eyes with prior myopic laser vision correction according to axial length. Sci Rep 2023; 13:14267. [PMID: 37652933 PMCID: PMC10471610 DOI: 10.1038/s41598-023-41062-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2022] [Accepted: 08/21/2023] [Indexed: 09/02/2023] Open
Abstract
We retrospectively evaluate the actual anterior-posterior (AP) corneal radius ratio in eyes with previous laser correction for myopia (M-LVC) according to axial length (AL) using biometry data exported from swept-source optical coherence tomography between January 2018 and October 2021 in a tertiary hospital (1018 eyes with a history of M-LVC and 19,841 control eyes). The AP ratio was significantly higher in the LVC group than in the control group. Further, it was significantly positively correlated with AL in the LVC group. We also investigated the impact of the AP ratio, AL and keratometry (K) on the absolute prediction error (APE) in 39 eyes that underwent cataract surgery after M-LVC. In linear regression analyses, there were significant correlations between APE and AL/TK, while APE and AP ratio had no correlation. The APE was significantly lower in the Barrett True-K with total keratometry (Barrett True-TK) than in the Haigis-L formula on eyes with AL above 26 mm and K between 38 and 40 D. In conclusion, in eyes with previous M-LVC, AP ratio increases with AL. The Barrett True-K or Barrett True-TK formulas are recommended rather than Haigis-L formula in M-LVC eyes with AL above 26 mm and K between 38 and 40D.
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Affiliation(s)
- Seung Hee Yoon
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea
| | - Jae Ryong Song
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 82, Gumi-Ro 173Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea
| | - Seung Hyen Lee
- Department of Ophthalmology, Nowon Eulji Medical Center, Eulji University College of Medicine, Seoul, Republic of Korea
| | - Youngsub Eom
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Republic of Korea
- Department of Ophthalmology, Korea University Ansan Hospital, 123, Jeokgeum-ro, Danwon-gu, Ansan-si, Gyeonggi-do, 15355, Republic of Korea
- Department of Ophthalmology, Emory University School of Medicine, Atlanta, GA, USA
| | - Joon Young Hyon
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 82, Gumi-Ro 173Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea
| | - Hyun Sun Jeon
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Republic of Korea.
- Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, 82, Gumi-Ro 173Beon-Gil, Bundang-Gu, Seongnam-Si, Gyeonggi-Do, Republic of Korea.
- Department of Ophthalmology, Korea University College of Medicine, Seoul, Republic of Korea.
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Almorín-Fernández-Vigo I, Sánchez-Guillén I, Fernández-Vigo JI, Burgos-Blasco B, De-Pablo-Gómez-de-Liaño L, Fernández-Vigo JÁ, Macarro-Merino A. Normative Topographic Anterior and Posterior Corneal Astigmatism: Axis Distribution and Its Relations with Ocular and Biometric Parameters. J Clin Med 2023; 12:jcm12113664. [PMID: 37297859 DOI: 10.3390/jcm12113664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Revised: 05/16/2023] [Accepted: 05/23/2023] [Indexed: 06/12/2023] Open
Abstract
Corneal astigmatism correction is a key factor when planning refractive treatment for ametropies with intraocular lenses. We aim to obtain normative anterior and posterior corneal astigmatism (ACA and PCA, respectively) data in a local population and to describe their axis distribution and their association with other parameters. A total of 795 patients with no ocular diseases were evaluated with corneal tomography and optical biometry. Only data of the right eye were included. Mean ACA and PCA were 1.01 ± 0.79 and 0.34 ± 0.17 D, respectively. Vertical steep axis distribution was 73.5% for ACA and 93.3% for PCA. Axis orientation between ACA and PCA matched best for vertical orientation (especially 90° to 120°). Vertical ACA orientation frequency decreased with age, with a more positive sphere and less ACA. Vertical PCA orientation frequency increased with higher PCA. Eyes with vertical ACA orientation were younger and showed a greater white-to-white (WTW) measurement, anterior corneal elevations, ACA and PCA. Eyes with vertical PCA orientation were younger and showed greater anterior corneal elevations and PCA. Normative ACA and PCA data in a Spanish population were presented. Steep axis orientations presented differences with age, WTW, anterior corneal elevations and astigmatism.
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Affiliation(s)
| | - Inés Sánchez-Guillén
- Centro Internacional de Oftalmología Avanzada, 06010 Badajoz, Spain
- Department of Ophthalmology, Hospital Perpetuo Socorro, 06010 Badajoz, Spain
| | - José Ignacio Fernández-Vigo
- Centro Internacional de Oftalmología Avanzada, 28010 Madrid, Spain
- Department of Ophthalmology, Hospital Clínico San Carlos, 28040 Madrid, Spain
| | | | | | - José Ángel Fernández-Vigo
- Centro Internacional de Oftalmología Avanzada, 06010 Badajoz, Spain
- Centro Internacional de Oftalmología Avanzada, 28010 Madrid, Spain
- School of Medicine, Universidad de Extremadura, 06006 Badajoz, Spain
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Martínez-Albert N, Nieto-Fernández JC, García-Marqués JV. Keratometry Agreement Between Two Swept-Source OCT Devices in Healthy and Post-refractive Surgery Eyes. J Refract Surg 2023; 39:347-353. [PMID: 37162395 DOI: 10.3928/1081597x-20230202-02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
PURPOSE To evaluate the keratometry agreement between two swept-source devices for healthy and post-refractive surgery eyes and compare them. METHODS One hundred volunteers between 20 and 55 years of age were recruited for this study including both healthy and post-refractive surgery eyes. Three consecutive measurements of simulated keratometry (Sim K), posterior keratometry (PK), and total keratometry (TK) were obtained with the IOLMaster 700 and Anterion. The agreement was assessed through the Bland-Altman method. Limits of agreement (LoA) were calculated as mean difference ±1.96·SD and it represents the 95% of the differences between devices. RESULTS For both groups, Sim K measurements exhibited a mean difference close to 0 and within a range of ±0.30 and ±0.36 diopters (D) for the control and post-refractive surgery groups, respectively. Meanwhile, the IOLMaster 700 provided flatter PK values (0.30 D on average) for both groups. In general, the post-refractive surgery group exhibited slightly greater mean differences and wider 95% LoA than the control group for Sim K and PK. Steeper TK values were obtained by the IOLMaster in both groups (control = 0.50 D and post-refractive surgery = 0.75 D). TK differences between devices were significantly greater in the post-refractive surgery group (ranging from 0.38 to 1.14 D) compared to the control group (ranging from 0.15 to 0.85 D). CONCLUSIONS The IOLMaster 700 and Anterion are not interchangeable for TK measurements and eyes that had corneal refractive surgery even decreased the agreement between devices. Differences between devices for Sim K and PK measurements should be clinically judged, particularly in eyes with previous corneal surgery. [J Refract Surg. 2023;39(5):347-353.].
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12
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Rabinovich M, Baumgartner JM, Bovet J. Posterior Corneal Asphericity and the Refractive Outcome after Combined Phacovitrectomy. Klin Monbl Augenheilkd 2023; 240:435-439. [PMID: 37164402 DOI: 10.1055/a-2013-2329] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
BACKGROUND We assessed the correlation of posterior corneal asphericity and the refractive prediction error of the SRK-T and Barrett II Universal formulas for eyes following phacovitrectomy with peeling of the internal limiting membrane (ILM). PATIENTS AND METHODS We retrospectively analyzed 41 eyes of 41 patients following a combined phacovitrectomy with ILM peeling. Surgeries were performed by one fellowship-trained vitreoretinal surgeon between 2016 and 2021. RESULTS Of the 41 patients, 41 eyes were included, with all having at least 1 month of postoperative data. Of the 41 eyes, 19 eyes were female (46%) and 22 were male (54%). The average age of the study population was 77.5 ± 10.7 years. The mean axial length (AL) was 22.7 ± 4.6 mm and the mean anterior chamber depth (ACD) was 3 ± 0.8 mm. The mean posterior Q value was - 0.29 ± 0.27. The mean absolute error (MAE) values 1-month postoperatively for the SRK-T and Barrett II Universal formulas were 0.73 and 0.65, respectively. Regression analysis yielded a significant correlation between posterior corneal asphericity and SRK-T MAE (r = 0.35, R2 = 0.12, p < 0.05) only. CONCLUSIONS Posterior corneal surface asphericity is correlated to the refractive error of the SRK-T formula for eyes following phacovitrectomy.
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Towler J, Consejo A, Zhou D, Romano V, Levis H, Boote C, Elsheikh A, Geraghty B, Abass A. Typical localised element-specific finite element anterior eye model. Heliyon 2023; 9:e13944. [PMID: 37101628 PMCID: PMC10123217 DOI: 10.1016/j.heliyon.2023.e13944] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Revised: 11/19/2022] [Accepted: 02/15/2023] [Indexed: 03/07/2023] Open
Abstract
Purpose The study presents an averaged anterior eye geometry model combined with a localised material model that is straightforward, appropriate and amenable for implementation in finite element (FE) modelling. Methods Both right and left eye profile data of 118 subjects (63 females and 55 males) aged 22-67 years (38.5 ± 7.6) were used to build an averaged geometry model. Parametric representation of the averaged geometry model was achieved through two polynomials dividing the eye into three smoothly connected volumes. This study utilised the collagen microstructure x-ray data of 6 ex-vivo healthy human eyes, 3 right eyes and 3 left eyes in pairs from 3 donors, 1 male and 2 females aged between 60 and 80 years, to build a localised element-specific material model for the eye. Results Fitting the cornea and the posterior sclera sections to a 5th-order Zernike polynomial resulted in 21 coefficients. The averaged anterior eye geometry model recorded a limbus tangent angle of 37° at a radius of 6.6 mm from the corneal apex. In terms of material models, the difference between the stresses generated in the inflation simulation up to 15 mmHg in the ring-segmented material model and localised element-specific material model were significantly different (p < 0.001) with the ring-segmented material model recording average Von-Mises stress 0.0168 ± 0.0046 MPa and the localised element-specific material model recording average Von-Mises stress 0.0144 ± 0.0025 MPa. Conclusions The study illustrates an averaged geometry model of the anterior human eye that is easy to generate through two parametric equations. This model is combined with a localised material model that can be used either parametrically through a Zernike fitted polynomial or non-parametrically as a function of the azimuth angle and the elevation angle of the eye globe. Both averaged geometry and localised material models were built in a way that makes them easy to implement in FE analysis without additional computation cost compared to the limbal discontinuity so-called idealised eye geometry model or ring-segmented material model.
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Affiliation(s)
- Joseph Towler
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | | | - Dong Zhou
- Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool, UK
| | - Vito Romano
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
- Department of Medical and Surgical Specialities, Radiological Sciences, And Public Health, Ophthalmology Clinic, University of Brescia, Italy
| | - Hannah Levis
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Craig Boote
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
| | - Ahmed Elsheikh
- Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool, UK
- Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China
- NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
| | - Brendan Geraghty
- Institute of Life Course and Medical Sciences, University of Liverpool, Liverpool, UK
| | - Ahmed Abass
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool, UK
- Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Egypt
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The CRW1 Index: Identification of Eyes with Previous Myopic Laser Vision Correction Using Only a Swept-Source OCT Biometer. Am J Ophthalmol 2023; 247:79-87. [PMID: 36370839 DOI: 10.1016/j.ajo.2022.10.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2022] [Revised: 10/30/2022] [Accepted: 10/31/2022] [Indexed: 11/11/2022]
Abstract
PURPOSE To develop and test a novel index (Cooke-Riaz-Wendelstein [CRW1]) that uses swept-source optical coherence tomography (SS-OCT) biometry measurements (IOLMaster700, Zeiss Meditec), including total keratometry, to alert clinicians that previous myopic laser vision correction (M-LVC) was present in a measured eye. DESIGN Retrospective, multicenter, comparative diagnostic analysis. METHODS The study took place at 6 centers in the United States and Austria. Anonymized SS-OCT biometry datasets acquired between 2018 and 2020 and containing 49,199 eyes were analyzed. The LVC status, as identified by the biometrist, was used to segregate eyes into LVC and non-LVC eyes. Data were split into training (10,780 eyes) and validation (38,419 eyes) sets. Subset analysis was performed for CRW1 Index accuracy compared to posterior/anterior corneal curvature ratio (Rpost/Rant), topography with corneal analysis software (Atlas 9000 with Pathfinder II, Zeiss Meditec), tomography (Pentacam, Oculus), dual Scheimpflug-Placido system (Galilei G6, Ziemer), and a cloud-based platform for cataract surgery planning (Veracity, Zeiss Meditec). A positive predictive value (PPV) of ≥90% was targeted for the CRW1 index. True positives, true negatives, sensitivity, and specificity were recorded. RESULTS The CRW1 Index compared favorably against Rpost/Rant showing a higher PPV (93% vs 65%), with fewer false-positive results (29 vs 180). CRW1 performed similarly to topography software and better than the corneal imaging devices. The CRW1 cutoff value can be adjusted to increase sensitivity (CRW1-IS) to detect additional M-LVC eyes. CONCLUSIONS The CRW1 and CRW1-IS indices offer surgeons and researchers a readily accessible method to use only SS-OCT biometry measurements to detect eyes with a high probability of previous M-LVC.
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Zhang J, Zheng L, Zhang Y, Wang K. Analysis of Asphericity and Corneal Longitudinal Spherical Aberration of 915 Chinese Myopic Adult Eyes. Clin Ophthalmol 2023; 17:591-600. [PMID: 36814783 PMCID: PMC9939669 DOI: 10.2147/opth.s404437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 02/09/2023] [Indexed: 02/16/2023] Open
Abstract
Purpose To analyze the corneal asphericity, longitudinal spherical aberration (LSA), and related factors in Chinese myopic adult eyes. Methods This was a retrospective study of myopic adult patients. The corneal asphericity and LSA were measured at 3.0, 4.0, 5.0, 6.0, and 7.0 mm diameter apertures using corneal tomography. Age and refractive power were recorded for correlation analysis. Results In total, 531 females and 384 males were included. At the above five diameter settings the corneal asphericity values (Q) of the anterior surface were -0.09±0.21, -0.14±0.16, -0.15±0.13, -0.17±0.11, and -0.20±0.11, and those of the posterior surface were 0.23±0.49, 0.06±0.29, -0.01±0.22, -0.07±0.16, and -0.08±0.15, respectively. The anterior corneal LSA values at these diameters were 0.39±0.19, 0.63±0.27, 0.97±0.36, 0.90±0.30, and 0.83±0.29 D, respectively and the whole corneal values were 0.26±0.20, 0.44±0.27, 0.70±0.36, 0.66±0.30, and 0.59±0.28 D, respectively. Corneal asphericity and peripheral LSA showed no or weak correlation with age or spherical equivalent (all r < 0.2). Conclusion Corneal anterior and posterior Q values in myopia patients are negatively correlated with corneal diameter. Corneal anterior and whole corneal LSA increased significantly with diameter up to 5 mm, then decreased slightly with diameter. Corneal asphericity and peripheral LSA showed very weak or no correlation with age or spherical equivalent. Clinical Trial Registration Number ChiCTR1800015985.
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Affiliation(s)
- Jun Zhang
- Department of Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, People’s Republic of China,Correspondence: Jun Zhang, Department of Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, People’s Republic of China, Tel +86-18667046602; +86-0571 85064148, Email
| | - Li Zheng
- Department of Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, People’s Republic of China
| | - Yixuan Zhang
- Department of Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, People’s Republic of China
| | - Ke Wang
- Department of Ophthalmology, Hangzhou MSK Eye Hospital, Hangzhou, People’s Republic of China
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Hashemi H, Khabazkhoob M, Jamali A, Emamian MH, Fotouhi A. Three-year change in corneal asphericity in children at the age of emmetropisation. Ophthalmic Physiol Opt 2023; 43:160-169. [PMID: 36183360 DOI: 10.1111/opo.13056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 08/25/2022] [Accepted: 08/26/2022] [Indexed: 12/27/2022]
Abstract
PURPOSE To determine the 3-year changes in anterior and posterior values of corneal asphericity (Q) in 6- to 12-year-old children. METHODS The first and second phases of the study were conducted in 2015 and 2018, respectively. The target population in the first phase was 6- to 12-year-old students in Shahroud, Iran. Multistage cluster sampling was performed on urban students. Additionally, all rural students in Shahroud county were invited to participate. Corneal imaging and ocular biometry were performed using the Pentacam-HR and Allegro Biograph, respectively. RESULTS A total of 4961 right eyes were analysed in this report. The mean (95% confidence interval) anterior and posterior Q values for an 8-mm chord diameter were -0.38 ± 0.11 (-0.39 to -0.38) and -0.32 ± 0.12 (-0.33 to -0.32) in the first phase of the study, respectively. The mean 3-year changes in anterior and posterior Q values were 0.00 ± 0.08 (95% CI: 0.00-0.00) and -0.01 ± 0.06 (95% CI: -0.01 to -0.01), respectively. Based on a multiple regression model, advancing age (β = -0.002; [-0.003 to -0.001]), 3-year increase in mean keratometry (β = -0.04; [-0.06 to -0.02]), central corneal thickness (β = -0.001; [-0.001 to -0.000]), lens thickness (-0.05; [-0.11 to -0.003]) and anterior chamber depth (-0.09; [-0.15 to -0.03]) showed a statistically significant association with increased anterior Q prolation. Increased axial length was associated with a decrease in Q (β = 0.02; [0.004 to 0.03]). In addition, female gender (β = -0.004; [-0.007 to -0.001]) was significantly associated with a more prolate posterior Q value, while rural residence (β = 0.005; [0.002 to 0.009]) was significantly associated with a more oblate posterior Q value. CONCLUSION Three-year changes in anterior and posterior Q values were very small. The cornea tends to become more prolate with increasing age.
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Affiliation(s)
- Hassan Hashemi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Mehdi Khabazkhoob
- Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Alireza Jamali
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Mohammad Hassan Emamian
- Ophthalmic Epidemiology Research Center, Shahroud University of Medical Sciences, Shahroud, Iran
| | - Akbar Fotouhi
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
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Miażdżyk M, Consejo A, Iskander DR. Assessing and compensating for the confounding factors in Scheimpflug-based corneal densitometry. BIOMEDICAL OPTICS EXPRESS 2022; 13:6258-6272. [PMID: 36589572 PMCID: PMC9774844 DOI: 10.1364/boe.473534] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Revised: 10/17/2022] [Accepted: 10/17/2022] [Indexed: 06/17/2023]
Abstract
Scheimpflug-based corneal densitometry is a clinically verified method for assessing corneal transparency. Nevertheless, the estimates of corneal densitometry appear to be correlated with age and eye biometry parameters, such as the anterior chamber depth or the pupil size, and that ensues a convoluted conditional estimation problem, where it is difficult to interpret the results. This study aims at devising a methodology for compensating for such confounding factors by using, as a research platform, a commercially available Scheimpflug camera that allows exporting images in a dynamic fashion, allowing averaging the results from multiple acquisitions. Two approaches are considered, one based on appropriately normalizing the line densitometry signal and one based on image histogram equalization. Then, three parameters for describing corneal densitometry are derived including the mean value of backscatter and the scale and shape parameters of the Weibull distribution estimated in regions of interest encompassing parts of corneal stroma. The results show that, unlike the non-normalized measures, the proposed approaches lead to parameters that are not correlated with age nor the eye biometry.
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Affiliation(s)
- Maria Miażdżyk
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland
| | - Alejandra Consejo
- Department of Applied Physics, University of Zaragoza, Zaragoza, Spain
| | - D. Robert Iskander
- Department of Biomedical Engineering, Wroclaw University of Science and Technology, Wybrzeze Wyspianskiego 27, 50-370 Wroclaw, Poland
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Wallerstein A, Gauvin M, Bernstein A, Qi SR, Cohen M. Posterior Corneal Astigmatism Does Not Influence Manifest-Treated Topography-guided LASIK Outcomes. J Refract Surg 2022; 38:780-790. [PMID: 36476302 DOI: 10.3928/1081597x-20221108-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE To investigate whether the magnitude of posterior corneal astigmatism (PCA) impacts refractive and visual outcomes of primary topography-guided laser in situ keratomileusis (LASIK) and to provide guidance on treating eyes with high PCA. METHODS Comparative retrospective analysis of 4,541 consecutive eyes treated with Contoura (Alcon Laboratories, Inc) on the manifest refractive astigmatism. Standard outcomes of the 1,514 eyes with the lowest PCA (first tercile; low PCA group) were compared to the 1,514 eyes with the highest PCA (last tercile; high PCA group). Pearson correlation coefficient was used to assess relationships between variables. RESULTS Preoperatively, 20.9% of eyes presented with PCA of 0.50 diopters (D) or greater. The mean PCA was 0.18 ± 0.07 D in eyes with low PCA, and 0.50 ± 0.11 D in eyes with high PCA. An equivalent number of eyes achieved a cumulative postoperative unilateral uncorrected distance visual acuity of 20/20 in both the low PCA and high PCA groups (95.3% vs 94.7%; P = .4489). The efficacy index of both low and high PCA eyes was identical (0.99 ± 0.06 vs 0.99 ± 0.08; P = .3192), as was the safety index (1.00 ± 0.02 vs 1.00 ± 0.03; P = .0110). The magnitude of preoperative PCA was weakly correlated with postoperative refractive astigmatism (R = 0.1323), but not with postoperative defocus equivalent (R = -0.0414) or spherical equivalent (R = -0.0128). CONCLUSIONS PCA does not negatively impact the outcomes of topography-guided LASIK targeting the manifest refraction, having identical accuracy, efficacy, and safety in eyes with both low and high PCA. There is no scientific basis to measure and consider PCA in topography-guided LASIK planning software or nomograms if the excimer laser treatment input targets the manifest refraction. [J Refract Surg. 2022;38(12):780-790.].
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Amorim AR, Bret B, González-Méijome JM. Opto-Mechanical Eye Models, a Review on Human Vision Applications and Perspectives for Use in Industry. SENSORS (BASEL, SWITZERLAND) 2022; 22:7686. [PMID: 36236784 PMCID: PMC9573708 DOI: 10.3390/s22197686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Revised: 06/22/2022] [Accepted: 06/25/2022] [Indexed: 06/16/2023]
Abstract
The purpose of this review is to aggregate technical information on existent optomechanical eye models (OME) described in the literature, for image quality assessment in different applications. Several physical eye models have been reviewed from peer-reviewed papers and patent applications. A typical eye model includes an artificial cornea, an intraocular lens or other lens to simulate the crystalline lens, an aperture as the pupil, and a posterior retinal surface, which may be connected to a light sensor. The interior of the eye model may be filled with a fluid to better emulate physiological conditions. The main focus of this review is the materials and physical characteristics used and the dimensional aspects of the main components including lenses, apertures, chambers, imaging sensors and filling medium. Various devices are described with their applications and technical details, which are systematically tabulated highlighting their main characteristics and applications. The models presented are detailed and discussed individually, and the features of different models are compared when applicable, highlighting strengths and limitations. In the end there is a brief discussion about the potential use of artificial eye models for industrial applications.
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Affiliation(s)
- André Rino Amorim
- Clinical and Experimental Optometry Research Lab, Center of Physics, University of Minho, 4710-057 Braga, Portugal
| | - Boris Bret
- Bosch Car Multimedia Portugal, S.A., 4705-285 Braga, Portugal
| | - José M. González-Méijome
- Clinical and Experimental Optometry Research Lab, Center of Physics, University of Minho, 4710-057 Braga, Portugal
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Chang YC, Cabot F, Heilman BM, Meza L, Ruggeri M, Ho A, Yoo SH, Parel JM, Manns F. Predictability of pseudophakic refraction using patient-customized paraxial eye models. J Cataract Refract Surg 2022; 48:1016-1022. [PMID: 35297814 PMCID: PMC9420759 DOI: 10.1097/j.jcrs.0000000000000934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 03/10/2022] [Indexed: 11/26/2022]
Abstract
PURPOSE To determine whether patient-customized paraxial eye models that do not rely on exact ray tracing and do not consider aberrations can accurately predict pseudophakic refraction. SETTING Bascom Palmer Eye Institute, Miami, Florida. DESIGN Prospective study. METHODS Cataract surgery patients with and without a history of refractive surgery were included. Manifest refraction, corneal biometry, and extended-depth optical coherence tomography (OCT) imaging were performed at least 1 month postoperatively. Corneal and OCT biometry were used to create paraxial eye models. The pseudophakic refraction simulated using the eye model was compared with measured refraction to calculate prediction error. RESULTS 49 eyes of 33 patients were analyzed, of which 12 eyes from 9 patients had previous refractive surgery. In eyes without a history of refractive surgery, the mean prediction error was 0.08 ± 0.33 diopters (D), ranging from -0.56 to 0.79 D, and the mean absolute error was 0.27 ± 0.21 D. 31 eyes were within ±0.5 D, and 36 eyes were within ±0.75 D. In eyes with previous refractive surgery, the mean prediction error was -0.44 ± 0.58 D, ranging from -1.42 to 0.32 D, and the mean absolute error was 0.56 ± 0.46 D. 7 of 12 eyes were within ±0.5 D, 8 within ±0.75 D, and 10 within ±1 D. All eyes were within ±1.5 D. CONCLUSIONS Accurate calculation of refraction in postcataract surgery patients can be performed using paraxial optics. Measurement uncertainties in ocular biometry are a primary source of residual prediction error.
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Affiliation(s)
- Yu-Cherng Chang
- From the Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida (Chang, Cabot, Heilman, Meza, Ruggeri, Ho, Yoo, Parel, Manns); Department of Biomedical Engineering, University of Miami College of Engineering, Coral Gables, Florida (Chang, Heilman, Meza, Ruggeri, Ho, Yoo, Parel, Manns); Anne Bates Leach Eye Hospital, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida (Cabot, Yoo, Parel); Brien Holden Vision Institute Limited, Sydney, New South Wales, Australia (Ho, Parel)
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Evaluation of ocular biometry in the Japanese population using a multicenter approach: Prospective observational study. PLoS One 2022; 17:e0271814. [PMID: 35895708 PMCID: PMC9328560 DOI: 10.1371/journal.pone.0271814] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 07/07/2022] [Indexed: 11/21/2022] Open
Abstract
This prospective observational study aimed to evaluate the ocular biometry of Japanese people through a multicenter approach. The uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively) in the log minimum angle of resolution (logMAR), subjective and objective spherical equivalent values (SE) of ocular refraction, anterior and posterior corneal curvature (ACC and PCC, respectively), anterior and posterior corneal asphericity (ACA and PCA, respectively), central corneal thickness (CCT), anterior chamber depth (ACD), and ocular axial length (AL) were measured in the eyes of 250 participants (mean age = 46.5 ± 18.0 years, range: 20–90 years) across five institutions in Japan. The mean UDVA, CDVA, subjective SE, objective SE, ACC, PCC, ACA, PCA, CCT, ACD, and AL were 0.68, −0.08, −2.42 D, −2.66 D, 7.77 mm, 6.33 mm, −0.31, −0.39, 0.55 mm, 2.92 mm, and 24.78 mm, respectively. Age-related changes and sex-based differences were noted in the visual acuity, refraction, corneal shape, ACD, and AL. Our results serve as basis for future studies aiming to develop refractive correction methods and various vision-related fields.
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22
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Zeng Z, Ye X, Chen Q, Jia C, Zhang G. Intraocular lens power calculation after two different successive corneal refractive surgeries. Am J Ophthalmol Case Rep 2022; 26:101547. [PMID: 35514797 PMCID: PMC9062137 DOI: 10.1016/j.ajoc.2022.101547] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 02/06/2022] [Accepted: 04/18/2022] [Indexed: 11/25/2022] Open
Abstract
Purpose To report two challenging intraocular lens power calculation cases with patients each underwent different successive corneal refractive surgeries, respectively. Observations Biometry data, including the Back to Front corneal radii ratio (B/F ratio), were collected by Lenstar, IOL Master, and Pentacam AXL for Case 1 (received radial keratotomy (RK) and photorefractive keratectomy (PRK)) and Case 2 (received RK and laser-assisted in situ keratomileusis (LASIK)). The IOL power calculation was determined by several methods, including Shammas, Haigis-L, and Barrett True-K, which are available in the American Society of Cataract and Refractive Surgery online calculator and Pentacam AXL. The Barrett True-K (no history, post-RK) was more accurate in Case 1 (increased B/F ratio), whereas the Shammas, Haigis-L, and Barrett True-K (no history, post-LASIK/PRK) were more accurate in Case 2 (decreased B/F ratio). Conclusion and importance The B/F ratio may be a factor to be considered when selecting the IOL power calculation formula for patients who undergo two different corneal refractive surgeries. The further study focusing on this issue should be performed to clarify the results in the future.
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Rabinovich M, Aramburu Del Boz A, Birk U, Al Khatib D, Shoham-Hazon N, Bovet J. Influence of Posterior Corneal Asphericity On Power Calculation Error After Laser In Situ Keratomileusis or Photorefractive Keratectomy for Myopia. Eye Contact Lens 2022; 48:239-241. [PMID: 35333788 DOI: 10.1097/icl.0000000000000877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2021] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To assess the impact of posterior corneal asphericity on postoperative calculation error using the Haigis-L and the Barrett formulas for eyes after laser in situ keratomileusis or photorefractive keratectomy (PRK). METHODS We assessed the mean absolute error (MAE) of two power calculation formulas, Barrett true-K and Haigis-L formulas, in a retrospective analysis of 34 eyes of 34 patients who underwent cataract surgery. We performed a regression analysis between corneal parameters (anterior and posterior Q values, Kmax, K1, and K2) and the MAE of each formula. RESULTS In the cohort, 11 eyes were of women and 23 of men. The average age of the study population was 66.5±8.6 years. The mean axial length was 24±4.7 mm, the mean anterior chamber depth was 3.27±0.7 mm, and the mean posterior Q-value was -0.15±0.28. The MAE of Haigis-L and Barrett true-K formulas were 0.72 and 0.68, respectively (P=0.54). The regression analysis showed a statistically significant relationship only between the error in refraction prediction and the posterior Q-value regardless of the formula used. The coefficient of determination was higher for the Barrett true-K formula (r=0.52; R2=0.28; P<0.05), compared with the Haigis-L (r=0.49; R2=0.25; P<0.05). CONCLUSIONS Posterior corneal surface asphericity influences the refractive error of calculation using both Haigis-L and Barrett true-K formulas for eyes after a myopic PRK or laser-assisted in situ keratomileusis surgery.
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Affiliation(s)
- Mark Rabinovich
- OnO (M.R., A.A.d.B., U.B., D.A.K., N.S.-H.J.B.), Ophthalmology Network Organisation, Clinique de l'Oeil SA, Onex, Geneva, Switzerland; and Miramichi EyeNB Centre of Excellence (N.S.-H.), Miramichi, NB, Canada
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24
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Tang C, Du Z, Wu G, Tan X, Zang S, Yu H, Hu Y. The Distribution Pattern of Ocular Residual Astigmatism in Chinese Myopic Patients. Front Med (Lausanne) 2022; 9:763833. [PMID: 35685410 PMCID: PMC9171385 DOI: 10.3389/fmed.2022.763833] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
Purpose We aimed to investigate the distribution of ocular residual astigmatism (ORA) and its associations with age, gender, manifest refraction, and other ocular indicators in Chinese patients with myopia. Design This is a multi-center retrospective cross-sectional study. Method The study included 7,893 patients with myopia (7,893 eyes) aged 18–40 years from five ophthalmic centers. Anterior segment biometrics of the eyes were collected from the Pentacam. ORA and its summated vector mean were calculated using Alpins vector analysis. Compensation factor (CF) was used to evaluate the relation between ORA and corneal astigmatism. ORA in different age, gender, and refraction groups was compared. The Spearman correlation was adopted to reveal multiple ocular indicators associated with ORA, which were integrated into a multiple linear regression model to predict ORA. Results Distribution of ORA was slightly positively skewed (Skewness= 2.111, Kurtosis = 19.660, KS P < 0.0001). Mean ORA was 0.74 ± 0.39 D (95% normal range: 0.14–1.54 D). Among all the subjects, 22.4% of the eyes had an ORA magnitude of 1.0 D or more. Undercompensation or full-compensation of anterior corneal astigmatism (ACA) by ORA prevailed in both J0 (76.99%) and J45 (58.48%). Women had higher ORA power than men (0.77 ± 0.36 D vs. 0.73 ± 0.41 D, P < 0.0001). Participants with less negative spherical equivalent (SE) or higher manifest astigmatism (MA) also had higher ORA (all P < 0.0001). ORA was significantly correlated with ACA (r = 0.405) and posterior corneal astigmatism (PCA, r = 0.356). The multivariate logistic regression analysis showed strong predictability of ORA magnitude >1.0 D using anterior segment parameters (area under the receiver operating characteristic curve: 0.739). Conclusion ORA is present in Chinese adults with myopia and is affected by multiple ocular factors. Our findings may provide valuable information about ORA distribution in candidates for refractive surgery, helping optimize the outcome of astigmatism correction.
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Affiliation(s)
- Changting Tang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Affiliated Hospital of Guilin Medical University, Guilin, China
| | - Zijing Du
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Guanrong Wu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
| | - Xuanyun Tan
- Affiliated Hospital of Guilin Medical University, Guilin, China
| | - Siwen Zang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Honghua Yu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Honghua Yu
| | - Yijun Hu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- Aier Institute of Refractive Surgery, Refractive Surgery Center, Guangzhou Aier Eye Hospital, Guangzhou, China
- Aier School of Ophthalmology, Central South University, Changsha, China
- *Correspondence: Yijun Hu
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Tafti MF, Aghamollaei H, Moghaddam MM, Jadidi K, Alio JL, Faghihi S. Emerging tissue engineering strategies for the corneal regeneration. J Tissue Eng Regen Med 2022; 16:683-706. [PMID: 35585479 DOI: 10.1002/term.3309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Revised: 04/16/2022] [Accepted: 04/19/2022] [Indexed: 11/10/2022]
Abstract
Cornea as the outermost layer of the eye is at risk of various genetic and environmental diseases that can damage the cornea and impair vision. Corneal transplantation is among the most applicable surgical procedures for repairing the defected tissue. However, the scarcity of healthy tissue donations as well as transplantation failure has remained as the biggest challenges in confront of corneal grafting. Therefore, alternative approaches based on stem-cell transplantation and classic regenerative medicine have been developed for corneal regeneration. In this review, the application and limitation of the recently-used advanced approaches for regeneration of cornea are discussed. Additionally, other emerging powerful techniques such as 5D printing as a new branch of scaffold-based technologies for construction of tissues other than the cornea are highlighted and suggested as alternatives for corneal reconstruction. The introduced novel techniques may have great potential for clinical applications in corneal repair including disease modeling, 3D pattern scheming, and personalized medicine.
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Affiliation(s)
- Mahsa Fallah Tafti
- Stem Cell and Regenerative Medicine Group, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran
| | - Hossein Aghamollaei
- Chemical Injuries Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | | | - Khosrow Jadidi
- Vision Health Research Center, Semnan University of Medical Sciences, Semnan, Iran
| | - Jorge L Alio
- Department of Research and Development, VISSUM, Alicante, Spain.,Cornea, Cataract and Refractive Surgery Department, VISSUM, Alicante, Spain.,Department of Pathology and Surgery, Division of Ophthalmology, Faculty of Medicine, Miguel Hernández University, Alicante, Spain
| | - Shahab Faghihi
- Stem Cell and Regenerative Medicine Group, National Institute of Genetic Engineering and Biotechnology, Tehran, Iran
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26
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de Andrade Ramos L, Seullner Brandão CV, Guillermo Arce C, Haddad Pinho R, Garbelotti Gonçalves L, Padovani CR. Dual-Scheimpflug-Placido-disc corneal analysis in cats. Vet Ophthalmol 2022; 25:360-366. [PMID: 35544443 DOI: 10.1111/vop.12993] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 05/02/2022] [Accepted: 05/02/2022] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To evaluate the corneal topography and tomography of cats using a dual Scheimpflug and Placido disc device. ANIMAL STUDIED Sixteen mixed-breed cats (32 eyes). PROCEDURE(S) Cats were sedated using meperidine (4.3 mg/kg/IM) and xylazine (0.5 mg/kg/IM), and evaluated using the software Galilei™. Values assessed included anterior and posterior corneal curvature, total corneal power, and corneal thickness. RESULTS Ten males and six females aged between 18 and 48 months were evaluated. The simulated keratometry (SimK) was 38.37 ± 0.83D, mean posterior keratometry -4.89 ± 0.34D, and mean total corneal power 38.04 ± 0.94D. The mean central corneal thickness (CCT) was 617.34 ± 53.38 μm with a mean thinnest point of 583.74 ± 60.60 μm. CONCLUSION The Galilei™ examination was feasible in cats, enabling a detailed study of the cornea. To the best of our knowledge, this is the first study evaluating the corneal topography and tomography of cats using a device that integrates data from a dual Scheimpflug and Placido disc system.
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Affiliation(s)
- Letícia de Andrade Ramos
- Department of Veterinary Surgery and Animal Reproduction. School of Veterinary Medicine and Animal Science, São Paulo State University - UNESP, São Paulo, Brazil
| | - Cláudia Valéria Seullner Brandão
- Department of Veterinary Surgery and Animal Reproduction. School of Veterinary Medicine and Animal Science, São Paulo State University - UNESP, São Paulo, Brazil
| | - Carlos Guillermo Arce
- Contact Lens, Cornea, Refractive Surgery, Research & Technology Sectors, Ophthalmologic Hospital and Eye Bank of Sorocaba, São Paulo, Brazil
| | - Renata Haddad Pinho
- Department of Veterinary Surgery and Animal Reproduction. School of Veterinary Medicine and Animal Science, São Paulo State University - UNESP, São Paulo, Brazil
| | - Lenise Garbelotti Gonçalves
- Department of Veterinary Surgery and Animal Reproduction. School of Veterinary Medicine and Animal Science, São Paulo State University - UNESP, São Paulo, Brazil
| | - Carlos Roberto Padovani
- Department of Biostatistics, Bioscience Institute, São Paulo State University - UNESP, São Paulo, Brazil
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Yaghoubi V, Setayeshnasab H, Mosaddegh P, Kadkhodaei M. A stochastic approach to estimate intraocular pressure and dynamic corneal responses of the cornea. J Mech Behav Biomed Mater 2022; 130:105210. [PMID: 35397406 DOI: 10.1016/j.jmbbm.2022.105210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2021] [Revised: 03/17/2022] [Accepted: 03/26/2022] [Indexed: 11/15/2022]
Abstract
IntraOcular Pressure (IOP) is one of the most informative factors for monitoring the eye-health. This is usually measured by tonometers. However, the outputs of the tonometers depend on the physical and geometrical properties of the cornea. Therefore, the common practice is to develop a numerical model to generate some correction factors. The main challenge here is the accuracy and efficiency of a numerical model in predicting the IOP and Dynamic Corneal Response (DCR) of each patient. This study addresses this issue by developing a two-step surrogate model based on adaptive sparse Polynomial Chaos Expansion (PCE) for fast and accurate prediction of the IOP. In this regard, first, an FE model of the cornea has been developed to predict the DCR parameters. This FE model has been replaced with a PCE-based surrogate model to speed up the simulation step. The uncertainties in the geometry and material model of the cornea have been propagated through the surrogate model to estimate the distributions of the DCR parameters. In the second step, the combination of DCR parameters and the input parameters provide a proper parameter space for developing an efficient data-driven PCE model to predict the IOP. Moreover, sensitivity analysis by using PCE-based Sobol indices has been performed. The results demonstrate the accuracy and efficiency of the proposed method in predicting the IOP. Sensitivity analysis revealed that IOP measurement was influenced mostly by deflection amplitude and applanation time. The analysis indicates the importance of the interactions between the parameters.
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Affiliation(s)
- Vahid Yaghoubi
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran; Structural Integrity & Composites, Faculty of Aerospace Engineering, Delft University of Technology, 2629 HS, Delft, Netherlands.
| | - Hamed Setayeshnasab
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Peiman Mosaddegh
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
| | - Mahmoud Kadkhodaei
- Department of Mechanical Engineering, Isfahan University of Technology, Isfahan, 84156-83111, Iran
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Volatier T, Schumacher B, Cursiefen C, Notara M. UV Protection in the Cornea: Failure and Rescue. BIOLOGY 2022; 11:biology11020278. [PMID: 35205145 PMCID: PMC8868636 DOI: 10.3390/biology11020278] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 01/28/2022] [Accepted: 01/28/2022] [Indexed: 01/07/2023]
Abstract
Simple Summary The sun is a deadly laser, and its damaging rays harm exposed tissues such as our skin and eyes. The skin’s protection and repair mechanisms are well understood and utilized in therapeutic approaches while the eye lacks such complete understanding of its defenses and therefore often lacks therapeutic support in most cases. The aim here was to document the similarities and differences between the two tissues as well as understand where current research stands on ocular, particularly corneal, ultraviolet protection. The objective is to identify what mechanisms may be best suited for future investigation and valuable therapeutic approaches. Abstract Ultraviolet (UV) irradiation induces DNA lesions in all directly exposed tissues. In the human body, two tissues are chronically exposed to UV: the skin and the cornea. The most frequent UV-induced DNA lesions are cyclobutane pyrimidine dimers (CPDs) that can lead to apoptosis or induce tumorigenesis. Lacking the protective pigmentation of the skin, the transparent cornea is particularly dependent on nucleotide excision repair (NER) to remove UV-induced DNA lesions. The DNA damage response also triggers intracellular autophagy mechanisms to remove damaged material in the cornea; these mechanisms are poorly understood despite their noted involvement in UV-related diseases. Therapeutic solutions involving xenogenic DNA-repair enzymes such as T4 endonuclease V or photolyases exist and are widely distributed for dermatological use. The corneal field lacks a similar set of tools to address DNA-lesions in photovulnerable patients, such as those with genetic disorders or recently transplanted tissue.
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Affiliation(s)
- Thomas Volatier
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 62, 50937 Cologne, Germany; (C.C.); (M.N.)
- Correspondence:
| | - Björn Schumacher
- Cologne Excellence Cluster for Cellular Stress Responses, Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany;
| | - Claus Cursiefen
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 62, 50937 Cologne, Germany; (C.C.); (M.N.)
- Center for Molecular Medicine Cologne (CMMC), Faculty of Medicine and University Hospital Cologne, University of Cologne, 21, 50931 Cologne, Germany
| | - Maria Notara
- Department of Ophthalmology, Faculty of Medicine and University Hospital Cologne, University of Cologne, 62, 50937 Cologne, Germany; (C.C.); (M.N.)
- Cologne Excellence Cluster for Cellular Stress Responses, Aging-Associated Diseases (CECAD) and Center for Molecular Medicine (CMMC), University of Cologne, Joseph-Stelzmann-Strasse 26, 50931 Cologne, Germany;
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Namba H, Sugano A, Murakami T, Utsunomiya H, Sato H, Nishitsuka K, Ishizawa K, Kayama T, Yamashita H. Ten-year longitudinal investigation of astigmatism: The Yamagata Study (Funagata). PLoS One 2022; 17:e0261324. [PMID: 35007309 PMCID: PMC8746748 DOI: 10.1371/journal.pone.0261324] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 11/30/2021] [Indexed: 11/18/2022] Open
Abstract
Despite numerous investigations into ocular or corneal astigmatism, the dynamic nature of astigmatism remains poorly understood. To reveal potential associations between age and astigmatism, 264 Japanese participants who underwent systemic and ophthalmological examinations in Funagata Town (Yamagata Prefecture, Japan) were evaluated over a 10-year period. Astigmatism was evaluated with regard to the cylinder power, cylinder axis, and vector analyses. Whereas the refractive cylinders showed age-related increases in patients in their 40s to 60s, the corneal cylinders did not change over 10 years. Nevertheless, cylindrical axis of the cornea demonstrated a continuous shift toward against-the-rule (ATR) astigmatism. Vector analyses revealed that the astigmatic shift toward ATR progressed continually after patients reached their 40s, although the shift did not accelerate with age. These novel insights may pave the way for the development of potential strategies for vision correction, including refractive surgeries, and vision-quality maintenance in the elderly.
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Affiliation(s)
- Hiroyuki Namba
- Faculty of Medicine, Department of Ophthalmology and Visual Sciences, Yamagata University, Yamagata City, Yamagata, Japan
- * E-mail:
| | - Akira Sugano
- Ideganka Hospital, Yamagata City, Yamagata, Japan
| | - Takanori Murakami
- Faculty of Medicine, Department of Ophthalmology and Visual Sciences, Yamagata University, Yamagata City, Yamagata, Japan
- Department of Ophthalmology, Yamagata Prefectural Central Hospital, Yamagata City, Yamagata, Japan
| | - Hiroshi Utsunomiya
- Faculty of Medicine, Department of Ophthalmology and Visual Sciences, Yamagata University, Yamagata City, Yamagata, Japan
| | - Hidenori Sato
- Faculty of Medicine, Genome Informatics Unit, Institute for Promotion of Medical Science Research, Yamagata University, Yamagata City, Yamagata, Japan
| | - Koichi Nishitsuka
- Faculty of Medicine, Department of Ophthalmology and Visual Sciences, Yamagata University, Yamagata City, Yamagata, Japan
| | - Kenichi Ishizawa
- Faculty of Medicine, Department of Neurology, Hematology, Metabolism, Endocrinology and Diabetology, Yamagata University, Yamagata City, Yamagata, Japan
| | - Takamasa Kayama
- Faculty of Medicine, Department of Advanced Medicine, Yamagata University, Yamagata City, Yamagata, Japan
| | - Hidetoshi Yamashita
- Faculty of Medicine, Department of Ophthalmology and Visual Sciences, Yamagata University, Yamagata City, Yamagata, Japan
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Fůs M, Pitrová Š. ANALYSIS OF CORNEAL ANTEROPOSTERIOR RATIO OF OPTICAL POWER USING OCT. CESKA A SLOVENSKA OFTALMOLOGIE : CASOPIS CESKE OFTALMOLOGICKE SPOLECNOSTI A SLOVENSKE OFTALMOLOGICKE SPOLECNOSTI 2022; 78:228-232. [PMID: 36220362 DOI: 10.31348/2022/23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
AIMS The aim of the study was to analyse the values of the anteroposterior corneal optical power ratio (AP ratio), to compare the resulting values with those of theoretical models of the eye, and to define the effect of using an individual ratio value on the approximation of the total corneal power. MATERIAL AND METHODS A total of 406 eyes were included. Each patient underwent an OCT (RTVue XR) examination, according to which the AP ratio of the cornea was determined, as well as the biometric parameters of the eye (Lenstar LS900). The correlation between the biometric parameters of the eye and the individual AP ratio values was evaluated using Pearsons correlation coefficient. In the analysis, the AP ratio results were compared with selected schematic models of the eye. Using Gaussian equations, a theoretical calculation of the total corneal optical power (KG) was performed, by fitting the AP ratio value and comparing it with the actually measured total corneal power (TCP). RESULTS The mean value of the individually determined AP ratio was 1.17 ±0.02. The most frequently represented interval (33.74 %) was 1.17 to 1.18 AP ratio values, with the vast majority of eyes (79.56 %) in the range of 1.15 to 1.20. Individual values of total corneal optical power were statistically significantly different (p < 0.05) from the theoretical values of TCP (except in the Liu-Brennan eye model, where p = 0.06). The lowest mean difference of values was found for the Navarro schematic model. The dependence of the measured AP ratio values and biometric parameters reached a moderate negative correlation (r = -0.50 for p < 0.05) with the parameter corneal posterior surface curvature (Rp), as well as a weak negative correlation with limbal diameter WtW (r = -0.26 for p < 0.05) and a weak positive correlation with central corneal thickness CCT (r = 0.17 for p < 0.05). CONCLUSION The assumption of a constant value of the AP ratio according to the selected schematic models of the eye is statistically significantly different from the actual measured values and was defined to have only a negative weak correlation with the size of the limbus diameter. Using the resulting average value of the determined AP ratio (1.17 ±0.02), a lower difference between real and calculated total corneal optical power was achieved.
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Singh VM, Ramappa M, Murthy SI, Rostov AT. Toric intraocular lenses: Expanding indications and preoperative and surgical considerations to improve outcomes. Indian J Ophthalmol 2021; 70:10-23. [PMID: 34937203 PMCID: PMC8917572 DOI: 10.4103/ijo.ijo_1785_21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Since the introduction of the first toric intraocular lens (IOLs) in the early 1990s, these lenses have become the preferred choice for surgeons across the globe to correct corneal astigmatism during cataract surgery. These lenses allow patients to enjoy distortion-free distance vision with excellent outcomes. They also have their own set of challenges. Inappropriate keratometry measurement, underestimating the posterior corneal astigmatism, intraoperative IOL misalignment, postoperative rotation of these lenses, and IOL decentration after YAG-laser capsulotomy may result in residual cylindrical errors and poor uncorrected visual acuity resulting in patient dissatisfaction. This review provides a broad overview of a few important considerations, which include appropriate patient selection, precise biometry, understanding the design and science behind these lenses, knowledge of intraoperative surgical technique with emphasis on how to achieve proper alignment manually and with image-recognition devices, and successful management of postoperative complications.
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Affiliation(s)
| | - Muralidhar Ramappa
- Cataract and Refractive Services; The Cornea Institute, L V Prasad Eye Institute, Hyderabad, Telangana, India
| | - Somasheila I Murthy
- Cataract and Refractive Services; The Cornea Institute, L V Prasad Eye Institute, Hyderabad, Telangana, India
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Tang C, Wu Q, Liu B, Wu G, Fan J, Hu Y, Yu H. A Multicenter Study of the Distribution Pattern of Posterior-To-Anterior Corneal Curvature Radii Ratio in Chinese Myopic Patients. Front Med (Lausanne) 2021; 8:724674. [PMID: 34988088 PMCID: PMC8720933 DOI: 10.3389/fmed.2021.724674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 11/29/2021] [Indexed: 11/13/2022] Open
Abstract
Estimation of corneal refractive power (CRP) is of crucial importance to refractive and cataract surgery. The ratio of posterior to anterior curvature radii of the cornea (P/A ratio) is one of the key factors to determine the actual CRP (True-K). While the traditional method to calculate the CRP (Sim-K) is based on a constant P/A ratio (0.82), it is suggested that the P/A ratio varies in different people and exhibits a distribution pattern, which may have an impact on the accuracy of CRP estimation and postoperative refractive outcome. In this multicenter study, we aimed to investigate the distribution pattern of the P/A ratio in a large number of myopic patients, and further explore the relationship between P/A ratio and ΔK (the difference between True-K and Sim-K). We found that distribution of the P/A ratio ranged from 0.72 to 0.86 with an average value of 0.82 ± 0.01. The compensation effect of the refractive power of the posterior on the anterior surface of the cornea decreased with the increase of P/A ratio. There was a significant correlation between P/A ratio and ΔK in all eyes (r = 0.9764, P < 0.0001). A change of 0.1 in P/A ratio could cause a change of 0.75 D in ΔK. Our study suggests that the actual P/A ratio should be taken into consideration in refractive and cataract surgery when calculating the CRP and power of the intraocular lens in eyes with significantly deviated P/A ratios.
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Affiliation(s)
- Changting Tang
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- Affiliated Hospital of Guilin Medical University, Guilin, China
| | - Qiaowei Wu
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Baoyi Liu
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Guanrong Wu
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Jing Fan
- Affiliated Hospital of Guilin Medical University, Guilin, China
| | - Yijun Hu
- Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- Refractive Surgery Center, Aier Institute of Refractive Surgery, Guangzhou Aier Eye Hospital, Guangzhou, China
- Aier School of Ophthalmology, Central South University, Changsha, China
| | - Honghua Yu
- The Second School of Clinical Medicine, Southern Medical University, Guangzhou, China
- Department of Ophthalmology, Guangdong Eye Institute, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
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Chen J, Tang Y, Jing Q, Lu Y, Jiang Y. Analysis of Corneal Spherical Aberrations in Chinese Bilateral Ectopia Lentis Patients. Front Med (Lausanne) 2021; 8:736686. [PMID: 34869429 PMCID: PMC8639512 DOI: 10.3389/fmed.2021.736686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 10/19/2021] [Indexed: 12/01/2022] Open
Abstract
Purpose: To analyze the anterior, posterior, and total corneal spherical aberrations (ASA, PSA, and TSA) in patients with Chinese bilateral ectopia lentis (EL). Methods: A cross-sectional study was conducted to evaluate corneal spherical aberration (CSA) using a Pentacam system at the 6-mm optical zone. Axial length, keratometry, astigmatism, and corneal asphericity were also determined. Results: This study included 247 patients (420 eyes) with a mean age of 18.1 years. The values of ASA, PSA, and TSA were 0.136 ± 0.100 μm, −0.118 ± 0.030 μm, and 0.095 ± 0.095 μm, respectively. In the EL patients with Marfan syndrome (MFS), ASA and TSA were significantly lower than in the non-MFS patients (0.126 ± 0.094 μm vs. 0.155 ± 0.107 μm, P = 0.004 for ASA; 0.085 ± 0.091 μm vs. 0.114 ± 0.099 μm, P = 0.003 for TSA), whereas PSA was not significantly different (P = 0.061). The values of ASA and TSA were significantly higher in the patients with EL aged ≥ 40 years old than in younger patients, whereas ASA and PSA were lower in patients aged <10 years old than in older patients (all P < 0.05). In the multiple linear regression analysis, age, keratometry, astigmatism, anterior asphericity, higher-order aberration (HOA), and lower-order aberration (LOA) were positively or negatively correlated with TSA in the patients with EL (r = 0.681, P < 0.001). Conclusions: Corneal spherical aberration was low in the patients with EL especially for MFS and tended to increase with aging. Preoperatively, individual measurement of CSA was necessary for bilateral EL patients with MFS.
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Affiliation(s)
- Jiahui Chen
- Department of Ophthalmology and Vision Science, Eye Ear Nose and Throat Hospital of Fudan University, Shanghai, China.,National Health Commission (NHC) Key Laboratory of Myopia (Fudan University), Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.,Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
| | - Yating Tang
- Department of Ophthalmology and Vision Science, Eye Ear Nose and Throat Hospital of Fudan University, Shanghai, China.,National Health Commission (NHC) Key Laboratory of Myopia (Fudan University), Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.,Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
| | - Qinghe Jing
- Department of Ophthalmology and Vision Science, Eye Ear Nose and Throat Hospital of Fudan University, Shanghai, China.,National Health Commission (NHC) Key Laboratory of Myopia (Fudan University), Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.,Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
| | - Yi Lu
- Department of Ophthalmology and Vision Science, Eye Ear Nose and Throat Hospital of Fudan University, Shanghai, China.,National Health Commission (NHC) Key Laboratory of Myopia (Fudan University), Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.,Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
| | - Yongxiang Jiang
- Department of Ophthalmology and Vision Science, Eye Ear Nose and Throat Hospital of Fudan University, Shanghai, China.,National Health Commission (NHC) Key Laboratory of Myopia (Fudan University), Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai, China.,Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
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Ran Z, Moore J, Jiang F, Guo H, Eliasy A, Lopes BT, Bao F, Jiang J, Abass A, Elsheikh A. A new approach for quantifying epithelial and stromal thickness changes after orthokeratology contact lens wear. ROYAL SOCIETY OPEN SCIENCE 2021; 8:211108. [PMID: 34950488 PMCID: PMC8692962 DOI: 10.1098/rsos.211108] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2021] [Accepted: 11/29/2021] [Indexed: 05/03/2023]
Abstract
The aim of the study was to develop an automatic segmentation approach to optical coherence tomography (OCT) images and to investigate the changes in epithelial and stromal thickness profile and radius of curvature after the use of orthokeratology (Ortho-K) contact lenses. A total of 45 right eyes from 52 participants were monitored before, and after one month of, uninterrupted overnight Ortho-K lens wear. The tomography of their right eyes was obtained using optical OCT and rotating Scheimpflug imaging (OCULUS Pentacam). A custom-built MATLAB code for automatic segmentation of corneal OCT images was created and used to assess changes in epithelial thickness, stromal thickness, corneal and stromal profiles and radii of curvature before, and after one month of, uninterrupted overnight wear of Ortho-K lenses. In the central area (0-2 mm diameter), the epithelium thinned by 12.8 ± 6.0 µm (23.8% on average, p < 0.01) after one month of Ortho-K lens wear. In the paracentral area (2-5 mm diameter), the epithelium thinned nasally and temporally (by 2.4 ± 5.9 µm, 4.5% on average, p = 0.031). The stroma thickness increased in the central area (by 4.8 ± 16.1 µm, p = 0.005). The radius of curvature of the central corneal anterior surface increased by 0.24 ± 0.26 mm (3.1%, p < 0.01) along the horizontal meridian and by 0.34 ± 0.18 mm (4.2%, p < 0.01) along the vertical meridian. There were no significant changes in the anterior and posterior stromal radius of curvature. This study introduced a new method to automatically detect the anterior corneal surface, the epithelial posterior surface and the posterior corneal surface in OCT scans. Overnight wear of Ortho-K lenses caused thinning of the central corneal epithelium. The anterior corneal surface became flattered while the anterior and posterior surfaces of the stroma did not undergo significant changes. The results are consistent with the changes reported in previous studies. The reduction in myopic refractive error caused by Ortho-K lens wear was mainly due to changes in corneal epithelium thickness profile.
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Affiliation(s)
- Ziying Ran
- School of Engineering, University of Liverpool, Liverpool, UK
| | - Joshua Moore
- School of Engineering, University of Liverpool, Liverpool, UK
- Department of Mathematical Sciences, School of Physical Sciences, University of Liverpool, Liverpool, UK
| | - Fan Jiang
- Eye Hospital, Wenzhou Medical University, Wenzhou, People's Republic of China
| | - Hongmei Guo
- College of Biomedical Engineering, Taiyuan University of Technology, Taiyuan City, Shanxi Province, People's Republic of China
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, UK
| | - Bernardo T. Lopes
- School of Engineering, University of Liverpool, Liverpool, UK
- Federal University of São Paulo, 1500 Vila Clementino, São Paulo 04021-001, Brazil
| | - FangJun Bao
- Eye Hospital, Wenzhou Medical University, Wenzhou, People's Republic of China
| | - Jun Jiang
- Eye Hospital, Wenzhou Medical University, Wenzhou, People's Republic of China
| | - Ahmed Abass
- School of Engineering, University of Liverpool, Liverpool, UK
- Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Port Fuad, Egypt
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK
- Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, People's Republic of China
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
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Sobczak M, Asejczyk M. Birefringent properties of the cornea measured by a Mueller type polarimeter in healthy adults and children. BIOMEDICAL OPTICS EXPRESS 2021; 12:7872-7885. [PMID: 35003872 PMCID: PMC8713654 DOI: 10.1364/boe.440274] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 10/30/2021] [Accepted: 10/31/2021] [Indexed: 06/14/2023]
Abstract
Mueller type polarimeter was used for in vivo measurements of the anisotropic parameters (retardation and azimuth angle) of corneas. To determine birefringence, corneal thickness was measured with a Scheimpflug camera (Corvist ST). The retardation distributions in the nasal-temporal cross-section in both children (N=7) and adults (N=38) groups occurred asymmetrical. The asymmetry in birefringence distributions was observed only in adults group. The geometrical analysis of the first order isochromes in both age groups showed the asymmetry of its shapes. The changes of symmetry in birefringent properties with age may have potential relationship with changing corneal biometry.
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Consejo A, Fathy A, Lopes BT, Ambrósio R, Abass A. Effect of Corneal Tilt on the Determination of Asphericity. SENSORS 2021; 21:s21227636. [PMID: 34833714 PMCID: PMC8618126 DOI: 10.3390/s21227636] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2021] [Revised: 11/08/2021] [Accepted: 11/16/2021] [Indexed: 11/16/2022]
Abstract
Purpose: To quantify the effect of levelling the corneal surface around the optical axis on the calculated values of corneal asphericity when conic and biconic models are used to fit the anterior corneal surface. Methods: This cross-sectional study starts with a mathematical simulation proving the concept of the effect that the eye's tilt has on the corneal asphericity calculation. Spherical, conic and biconic models are considered and compared. Further, corneal asphericity is analysed in the eyes of 177 healthy participants aged 35.4 ± 15.2. The optical axis was determined using an optimization procedure via the Levenberg-Marquardt nonlinear least-squares algorithm, before fitting the corneal surface to spherical, conic and biconic models. The influence of pupil size (aperture radii of 1.5, 3.0, 4.0 and 5.0 mm) on corneal radius and asphericity was also analysed. Results: In computer simulations, eye tilt caused an increase in the apical radii of the surface with the increase of the tilt angle in both positive and negative directions and aperture radii in all models. Fitting the cornea to spherical models did not show a significant difference between the raw-measured corneal surfaces and the levelled surfaces for right and left eyes. When the conic models were fitted to the cornea, changes in the radii of the cornea among the raw-measured corneal surfaces' data and levelled data were not significant; however, significant differences were recorded in the asphericity of the anterior surfaces at radii of aperture 1.5 mm (p < 0.01). With the biconic model, the posterior surfaces recorded significant asphericity differences at aperture radii of 1.5 mm, 3 mm, 4 mm and 5 mm (p = 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively) in the nasal temporal direction of right eyes and left eyes (p < 0.01, p < 0.01, p < 0.01 & p < 0.01, respectively). In the superior-inferior direction, significant changes were only noticed at aperture radii of 1.5 mm for both right and left eyes (p = 0.05, p < 0.01). Conclusions: Estimation of human corneal asphericity from topography or tomography data using conic and biconic models of corneas are affected by eyes' natural tilt. In contrast, the apical radii of the cornea are less affected. Using corneal asphericity in certain applications such as fitting contact lenses, corneal implant design, planning for refractive surgery and mathematical modelling when a geometrical centre of the eye is needed should be implemented with caution.
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Affiliation(s)
- Alejandra Consejo
- Department of Applied Physics, University of Zaragoza, 50009 Zaragoza, Spain;
- Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warsaw, Poland
| | - Arwa Fathy
- Sixth Form, Wirral Grammar School for Girls, Bebington CH63 3AF, UK;
| | - Bernardo T. Lopes
- Department of Ophthalmology, Universidade Federal de São Paulo, 1500 Vila Clementino, São Paulo 04021-001, Brazil; (B.T.L.); (R.A.J.)
- Department of Civil Engineering and Industrial Design, School of Engineering, University of Liverpool, Liverpool L69 3GH, UK
| | - Renato Ambrósio
- Department of Ophthalmology, Universidade Federal de São Paulo, 1500 Vila Clementino, São Paulo 04021-001, Brazil; (B.T.L.); (R.A.J.)
| | - Ahmed Abass
- Department of Mechanical, Materials and Aerospace Engineering, School of Engineering, University of Liverpool, Liverpool L69 3GH, UK
- Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Port Said 42526, Egypt
- Correspondence:
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Posterior Corneal Asphericity Effect on Postoperative Astigmatism after EDOF Intraocular Lens Implantation in Cataract Patients. J Ophthalmol 2021; 2021:1877516. [PMID: 34777856 PMCID: PMC8580693 DOI: 10.1155/2021/1877516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Revised: 09/30/2021] [Accepted: 10/27/2021] [Indexed: 11/30/2022] Open
Abstract
Aim To assess the impact of posterior corneal asphericity on postoperative astigmatism. Methods We included retrospectively 70 eyes of 70 patients that underwent cataract surgery. We included data of the Q value, Kmax, K1, K2, astigmatism AL, and ACD. We performed a vectorial analysis to calculate the astigmatic vectors. Results Seventy eyes were evaluated. 40 eyes were of females (58%) and 30 of males (42%). The average cohort age was 73 ± 8.9 years. Axial length (AL) was 23.5 ± 0.9, anterior chamber depth (ACD) was 3.13 ± 0.3, and the average posterior Q value was −0.35 ± 0.2. The only significant predictive variable for the correction index (CI) was the posterior Q value (r = 0.24, p < 0.05) and for the surgically induced astigmatism (SIA) (β = 0.34, r = 0.58, p < 0.05). Conclusion Posterior corneal surface asphericity significantly influences the surgically induced astigmatism and the overcorrection for cataract patients after Lucidis EDOF IOL implantation.
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Motamed-Gorji N, Jafari A, Mohammadi SF, Ashrafi E, Aliyari R, Emamian MH, Hashemi H, Fotouhi A. Associated factors and distribution of posterior corneal astigmatism in a middle-aged population. Clin Exp Optom 2021; 105:806-812. [PMID: 34751109 DOI: 10.1080/08164622.2021.1992249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
CLINICAL RELEVANCE Posterior corneal astigmatism has an important role in diagnosis and treatment of astigmatism, but it is usually overlooked. BACKGROUND This cross-sectional study aimed to investigate the distribution of posterior corneal astigmatism (PCA) and its associated factors in a middle-aged population that participated in the Shahroud Eye Cohort Study (ShECS) phase II. METHODS Anterior corneal astigmatism (ACA) and PCA values were measured using rotating Scheimpflug System (Pentacam HR, Oculus). With-the-rule (WTR) astigmatism was considered when the steepest corneal meridian was aligned within 90° ± 30°, and against-the-rule (ATR) astigmatism when the steepest meridian was 0 ± 30°. All the remaining values were considered as oblique astigmatism. Logistic regression models were used for evaluating the association of PCA magnitudes with other factors. RESULTS The current study consisted of 3871 eyes with available Pentacam data. Mean age of participants was 55.4 ± 6.1 years and 1557 (40.2%) subjects were male. Means of ACA and PCA were 0.77 ± 0.67 and -0.24 ± 0.15 D, respectively. The majority of PCA consisted of WTR astigmatism (82.43%), while ACA mostly showed ATR astigmatism (55.46%). PCA > 0.3 D was associated with male sex (OR = 1.16, P-value = 0.028) and spherical equivalent (OR = 0.93, P-value = 0.011) in the adjusted model, while PCA > 0.5 dioptre was strongly associated with myopia (OR = 4.6, P-value < 0.001). CONCLUSION The most common forms of ACA and PCA in middle-aged Iranian adults were ATR and WTR, respectively. While the shape of posterior corneal surface remained mostly unchanged across ages of 45 to 69 years, ACA was associated with a decrease in ATR proportion. Moreover, the most significant factors associated with higher magnitudes of PCA were male sex and myopia.
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Affiliation(s)
- Nazgol Motamed-Gorji
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Ali Jafari
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Seyed Farzad Mohammadi
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Elham Ashrafi
- Translational Ophthalmology Research Center, Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran
| | - Roqayeh Aliyari
- Ophthalmic Epidemiology Research Center, Shahroud University of Medical Sciences, Shahroud, Iran
| | - Mohammad Hassan Emamian
- Ophthalmic Epidemiology Research Center, Shahroud University of Medical Sciences, Shahroud, Iran
| | - Hassan Hashemi
- Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran
| | - Akbar Fotouhi
- Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
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Choi A, Kwon H, Jeon S. Accuracy of Total Corneal Power Calculation for Multifocal Toric Intraocular Lens Implantation: Swept-Source OCT-Based Biometer vs Scheimpflug Tomographer. J Refract Surg 2021; 37:686-692. [PMID: 34661471 DOI: 10.3928/1081597x-20210610-01] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
PURPOSE To evaluate the accuracy of total corneal power calculation from a swept-source optical coherence tomography-based biometer and a rotating Scheimpflug tomographer for the Acrysof IQ Panoptix toric TFNT intraocular lens (IOL) (Alcon Labroatories, Inc). METHODS A retrospective study was undertaken on 145 eyes implanted with the TFNT IOL. The accuracy of total corneal power calculation from a SS-OCT-based biometer (IOLMaster 700; Carl Zeiss Meditec AG; total keratometry [TK]) and a rotating Scheimpflug tomographer (Oculus Optikgeräte GmbH; total corneal refractive power at 3 mm [TCRP3] and at 4 mm [TCRP4]) were compared. The surgically induced astigmatism vector, difference vector, angle of vector, correction index, index of success, coefficient of adjustment, and flattening index were analyzed using the VectrAK analysis program (ASSORT). RESULTS The index of success showed a significant difference between the three methods (P = .035, analysis of variance test). The mean ± standard deviation of the index of success was the best in TK (0.43 ± 0.20), followed by TCRP4 (0.47 ± 0.24, P = .400, Bonferroni HSD test) and TCRP3 (0.50 ± 0.22, P = .030, Bonferroni HSD test). The preoperative refractive astigmatism prediction error was within ±0.50 diopters (D) in 62 eyes (42.8%) when using TCRP4 and in 66 eyes (45.5%) when using TK. CONCLUSIONS These study results suggest that the refractive accuracy of TFNT implantation using total corneal power from TCRP4 and TK was favorable. [J Refract Surg. 2021;37(10):686-692.].
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Rabinovich M, Aramburu Del Boz AM, Al-Khatib D, Genestier JP, Bovet J. Influence of Posterior Corneal Asphericity on Refractive Error of SRK-T and Barrett Formulas for Lucidis IOL. Klin Monbl Augenheilkd 2021; 240:683-688. [PMID: 34535025 DOI: 10.1055/a-1583-9723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
PURPOSE To evaluate the influence of posterior corneal asphericity on the refractive error using SRK-T and Barrett formulas for the intraocular lens (IOL) power calculation for Lucidis Extended Depth of Focus (EDOF) IOL. SETTING This study was carried out at a tertiary ophthalmology center in Geneva, Switzerland. DESIGN A retrospective study. Medical records from all enrolled patients were analyzed and the following information was extracted retrospectively, over 1 month following surgery. METHODS We retrospectively reviewed 75 eyes that underwent cataract surgery and were implanted with a Lucidis EDOF IOL. We measured the posterior corneal asphericity (Q value), axial length (AL), and anterior chamber depth (ACD) and then calculated the IOL power using SRK-T and Barrett formulas. RESULTS Seventy-five eyes were included, all of which had 1-month postoperative data. In the cohort, 32 eyes were from females (43%) and 43 from males (57%). The mean age of the study population was 73 ± 8.8 years. The mean AL was 23.5 ± 0.98 and the mean ACD was 3.13 ± 0.3. The mean posterior Q value was - 0.35 ± 0.2. In a regression analysis, we found a statistically significant relationship between the error in refraction prediction and the posterior Q value, irrespective of the formula used. The relationship between posterior corneal asphericity and the refraction prediction error was stronger for the Barrett II Universal formula than for the SRK-T formula. CONCLUSIONS Posterior corneal asphericity was correlated with the refractive error of calculation of both SRK-T and Barrett formulas, with a stronger correlation to the latter formula.
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Affiliation(s)
| | | | | | | | - Jerome Bovet
- Ophthalmology, Clinique de l'Oeil Onex, Onex, Switzerland
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Patel S, Tutchenko L. Spotlight on the Corneal Back Surface Astigmatism: A Review. Clin Ophthalmol 2021; 15:3157-3164. [PMID: 34345163 PMCID: PMC8323854 DOI: 10.2147/opth.s284616] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2021] [Accepted: 07/14/2021] [Indexed: 11/23/2022] Open
Abstract
Recent evidence indicates that the corneal back surface astigmatism (CBSA) contributes to the refractive state of the eye in cataract surgery, especially with the implantation of toric intraocular lenses. But this has been met with some scepticism. A review of key studies performed over the past three decades shows that the mean CBSA power ranges from 0.18(±0.16)D to 1.04(±0.20)D. The clinical assessment of CBSA is problematic. There is poor agreement between the current automated systems for assessment of CBSA and it is assumed that these systems directly measure the CBSA. But CBSA cannot be measured directly in vivo. A historical review of methods used to quantify the curvature of the posterior corneal surface reveals that CBSA estimated by current systems is based on values for corneal front surface astigmatism, corneal refractive index, central corneal thickness, corneal thickness at peripheral locations and the exact distance between the corneal apex and each one of these peripheral locations. Doubts and errors in these values, coupled with the precise details of the algorithm incorporated to estimate CBSA, are the likely sources of the lack of agreement between current systems. These systematic errors cloud the assessment of CBSA. Mean CBSA may be low, but it varies from case to case. There is a clear need for a realistic, practical procedure for clinicians to independently calibrate systems for estimating CBSA. This would help to reduce uncertainty and the discrepancies between instruments designed to measure the same parameter.
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Affiliation(s)
- Sudi Patel
- "Svjetlost" Speciality Eye Hospital, School of Medicine, University of Rijeka, Zagreb, Croatia
| | - Larysa Tutchenko
- Kyiv City Clinical Ophthalmological Hospital "Eye Microsurgical Center", Kyiv, Ukraine
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Tutchenko L, Patel S, Voytsekhivskyy O, Skovron M, Horak O. The influence of routine uncomplicated phacoemulsification on the orthogonality of the cornea. Indian J Ophthalmol 2021; 69:1073-1079. [PMID: 33913835 PMCID: PMC8186582 DOI: 10.4103/ijo.ijo_1168_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Purpose: The aim of this study was to determine the effect of routine uncomplicated phacoemulsification on the orthogonal distribution of mass within the central optical zone of the cornea. Methods: Astigmatism at both corneal surfaces was evaluated using Orbscan II (Bausch &and Lomb) before and up to 3 months after routine phacoemulsification (one eye/patient). The data were subjected to vector analysis to estimate the pre-and postoperative total astigmatism of the cornea (TCA). Results: Reporting the chief findings in minus cylinder (diopters, DC) over the central 3 mm (A) and 5 mm (B) optical zones. Mean TCA powers (±sd) at pre- and 3-months postop were A) –4.45DC (±2.00) and –5.69DC (±2.69), B) –2.91DC (±2.22) and –2.71DC (±1.60). Change in mean power was significant over 3 mm (P < 0.01, n = 49) but not over 5 mm. Inter-zonal differences were significant (P < 0.01). There was a significant linear relationship between the change in TCA power (y = preoperative-postoperative) and TCA at preoperative stage (x) where, A) y = 0.45x + 3.12 (r = 0.336, n = 49, P = 0.018), B) y = x + 2.65 (r = 0.753, n = 49, P = <0.01). Over the central 3 mm zone only, change (preoperative-postoperative) in axis (°) of TCA (y1) was significantly associated with TCA axis at preoperative stage (x1) where y1 = 1.391x1-0.008x12-0.701 (r = 0.635, n = 49, P < 0.01). Conclusion: Changes in TCA power and axis at 3 months postop, determined using Orbscan II, are indicative of orthogonal alterations in the distribution of corneal tissue. Over the central 3 mm zone, the association between y1 and x1 shows that a change in TCA axis is more profound when preoperative axis is near 90° i.e., against-the-rule.
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Affiliation(s)
- Larysa Tutchenko
- Department of Ophthalmology, Shupyk National Medical Academy of Postgraduate Education; Kyiv City Clinical Ophthalmological Hospital "Eye Microsurgical Center", Kyiv, Ukraine
| | - Sudi Patel
- NHS National Services Scotland, Edinburgh, United Kingdom
| | | | - Mykhailo Skovron
- Kyiv City Clinical Ophthalmological Hospital "Eye Microsurgical Center", Kyiv, Ukraine
| | - Olha Horak
- Kyiv City Clinical Ophthalmological Hospital "Eye Microsurgical Center", Kyiv, Ukraine
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Predicted and Measured Changes in Posterior Corneal Astigmatism after Uncomplicated Femtosecond Assisted LASIK (FsLASIK) and Microkeratome LASIK Correction for Myopia and Low Astigmatism. Semin Ophthalmol 2021; 36:832-838. [PMID: 34010104 DOI: 10.1080/08820538.2021.1928243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Purpose: To compare predicted and measured changes in astigmatism at the posterior corneal surface (PCS) after FsLASIK or LASIK.Methods: Astigmatism was measured at both corneal surfaces (PentacamTM) before and 3 months after unremarkable FFsLASIK (roup 1,n = 100) or LLASIK (roup 2,n = 100) for myopia (-7.25DS to -0.75DS) and low astigmatism (≤1.00DC). Photoablation was achieved using Schwind Amaris750STM laser (Aberration Free profile, centered on corneal vertex). Pre-and postop astigmatic data, according to subjective refraction and estimates for the corneal surfaces (over the central 3.2 mm zone), were subjected to vector analysis to calculate surgically induced astigmatism (SIA) by refraction (SIAR), at the anterior (SIAFact) and posterior corneal surfaces (SIABact). The difference vector between SIAR and SIAFact was regarded as the predicted SIA at the PCS (SIABest).Results: Reporting key findings. Mean(±sd,95%CI) SIABest and SIABact powers in group 1 were -0.52DC(±0.35,-0.56 to -0.45) and -0.11DC(±0.08,-0.13 to -0.10) in group 1, -0.35DC(0.20,-0.39 to -0.32) and -0.08DC(0.07,-0.09 to -0.06) in group 2. Differences between SIABest and SIABact were significant for powers but not axes. Significant correlations(p < .01) were revealed between (I) SIAR and SIAFact powers [Group 1, SIAR = 0.370.SIAFact-0.292,r = 0.299. Group 2, SIAR = 0.484.SIAFact-0.394,r = 0.519] but not the axes and (II) ΔC (difference between pre-[x1] and postop measured PCS astigmatic powers) and x1 [Group 1, ΔC = 0.384x1 + 0.119,r = 0.423. Group 2, ΔC = 0.135x1 + 0.047,r = 0.229,p = .022]. There was no correlation between SIABest and SIABact powers or axes.Conclusion: The changes in posterior corneal astigmatic powers according to Pentacam measurements are small and do not account for the deficit between SIAR and SIAFact after FsLASIK or LASIK.
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Hashemi H, Nabovati P, Aghamirsalim M, Mahboubipour H, Yekta A, Khabazkhoob M. Corneal asphericity and related factors in the geriatric population: A population-based study. Ophthalmic Physiol Opt 2021; 41:691-701. [PMID: 33998696 DOI: 10.1111/opo.12831] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Accepted: 03/08/2021] [Indexed: 11/28/2022]
Abstract
PURPOSE To determine the distribution of the corneal asphericity coefficient (Q value) and related factors in an Iranian geriatric population. METHODS This population-based study was conducted in 2019 in Tehran, using stratified multistage random cluster sampling. The study population was ≥60 years of age. Participants underwent corneal imaging using a Pentacam HR. Mean keratometry, corneal astigmatism, central corneal thickness, anterior chamber depth and the overall anterior and posterior Q values (for 8 mm chord diameter) were recorded. Axial length measurements were performed using the IOL Master 500. RESULTS 2457 eyes of 2457 individuals were analysed. The mean age was 67.3 ± 5.82 years and 1479 (60.2%) were female. The mean Q value for the anterior corneal surface was -0.35 ± 0.17 (95% CI: -0.35 to -0.34). The anterior Q value showed a statistically significant inverse relationship with axial length and mean keratometry, and a significant direct association with anterior chamber depth and corneal astigmatism. The mean posterior Q value was -0.41 ± 0.15 (95% CI: -0.42 to -0.40). The posterior Q value had a significant direct relationship with age, anterior chamber depth, mean keratometry and corneal astigmatism. CONCLUSION The corneal Q values in this geriatric Iranian population were more negative than the values reported in most previous studies. Corneal asphericity was greater affected by ocular biometry and corneal curvature than demographic factors and refractive status.
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Affiliation(s)
- Hassan Hashemi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Payam Nabovati
- Department of Optometry, School of Rehabilitation Sciences, Rehabilitation Research Center, Iran University of Medical Sciences, Tehran, Iran
| | - Mohamadreza Aghamirsalim
- Translational Ophthalmology Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | | | - Abbasali Yekta
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mehdi Khabazkhoob
- Department of Basic Sciences, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Rosales P, De castro A, Jiménez‐alfaro I, Marcos S. Intraocular lens alignment from Purkinje and Scheimpflug imaging. Clin Exp Optom 2021; 93:400-8. [DOI: 10.1111/j.1444-0938.2010.00514.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Patricia Rosales
- Instituto de Óptica ‘Daza de Valdés’, Consejo Superior de Investigaciones Científicas, Madrid, Spain
- Centro de Investigaciones de la Armada, Madrid, Spain
| | - Alberto De castro
- Instituto de Óptica ‘Daza de Valdés’, Consejo Superior de Investigaciones Científicas, Madrid, Spain
| | | | - Susana Marcos
- Instituto de Óptica ‘Daza de Valdés’, Consejo Superior de Investigaciones Científicas, Madrid, Spain
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Kim J, Whang WJ, Kim HS. Analysis of total corneal astigmatism with a rotating Scheimpflug camera in keratoconus. BMC Ophthalmol 2020; 20:475. [PMID: 33272234 PMCID: PMC7713345 DOI: 10.1186/s12886-020-01747-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Accepted: 11/25/2020] [Indexed: 12/01/2022] Open
Abstract
Background To analyze mean corneal powers and astigmatisms on anterior, posterior, and total cornea in patients with keratoconus as calculated according to various keratometric measurements using a Scheimpflug camera. Methods We examined the left eyes of 64 patients (41 males and 23 females; mean age 29.94 ± 6.63 years) with keratoconus. We measured simulated K (Sim-K), posterior K, true net power (TNP) and four types of total corneal refractive powers (TCRP). We then used the obtained values to analyze mean K, and corneal astigmatism. TCRP were measured at 2.0 ~ 5.0 mm. Results Mean corneal powers from Sim K, posterior K, and TNP were 49.12 ± 3.99, − 7.39 ± 0.79, and 47.78 ± 4.09 diopters, respectively. For TCRP centered on the pupil, mean K tended to decrease with measurement area (all p < 0.01). While, both mean K and astigmatism measured using TCRP centered on the apex decreased with measurement area (all p < 0.001). TCRP centered on the apex were greater than those centered on the pupil for mean K values calculated using TCRP (all p < 0.001). The proportion of WTR was greatest on the anterior and total cornea. As the measurement area moved to the periphery, the proportion of WTR increased. Conclusions Mean corneal powers and astigmatisms on total cornea with keratoconus change depending on calculation methods and measurement areas.
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Affiliation(s)
- Jinho Kim
- Department of Ophthalmology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea
| | - Woong-Joo Whang
- Department of Ophthalmology, Yeouido St. Mary's Hospital, College of Medicine, The Catholic University of Korea Korea, Seoul, South Korea.
| | - Hyun-Seung Kim
- Department of Ophthalmology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, South Korea
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Hosny M, Badawy A, Khazbak L, Anis M, Azzam S. Contribution of Posterior Corneal Astigmatism to Total Corneal Astigmatism in a Sample of Egyptian Population. Clin Ophthalmol 2020; 14:3325-3330. [PMID: 33116383 PMCID: PMC7569024 DOI: 10.2147/opth.s265647] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 08/19/2020] [Indexed: 11/23/2022] Open
Abstract
Purpose To determine the percentage of contribution of the magnitude of posterior corneal astigmatism to total corneal astigmatism using Scheimpflug imaging. Methods This prospective cross-sectional study was conducted on 356 eyes of 356 patients, where the total corneal astigmatism was calculated by addition of anterior and posterior corneal astigmatism using vector analysis and then the percentage of posterior to total corneal astigmatism was calculated. Results The percentage of contribution of posterior to total corneal astigmatism was about 30% in patients with With The Rule astigmatism and about 8% in patients with Against The Rule astigmatism. Conclusion Posterior corneal astigmatism should not be neglected during calculation of total corneal astigmatism as neglecting posterior corneal astigmatism can result in errors during calculation and correction of astigmatism.
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Affiliation(s)
| | - Alaa Badawy
- Ophthalmology, Cairo University, Giza, Egypt
| | | | | | - Sarah Azzam
- Ophthalmology, Cairo University, Giza, Egypt
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Abstract
Astigmatism causes deterioration of the retinal image and affects vision quality. Maintenance and improvement of visual function requires an understanding of the prevalence, age-related changes, and mechanisms of astigmatism. In this article, we discuss the findings of studies that investigated astigmatism. Some of these studies showed that the prevalence of high degrees of astigmatism in childhood typically decreases with emmetropization. With-the-rule astigmatism occurs most commonly in young adults. With age, the prevalence of astigmatism increases, and the axis shifts from a predominance of with-the-rule astigmatism to a predominance of against-the-rule astigmatism. This age-related change is caused by alterations in corneal curvature. Although the cause of this change is not fully understood, alterations in the position and tension of the eyelid, corneal stromal collagen fibrils, Descemet membrane, and extraocular muscles may influence the shape of the cornea. Furthermore, genetic factors may contribute to the development of astigmatism. Technological advances in ophthalmology are expected to improve our understanding of the etiology of astigmatism and enable the maintenance of quality of vision.
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Hu Y, Zhu S, Xiong L, Fang X, Liu J, Zhou J, Li F, Zhang Q, Huang N, Lei X, Jiang L, Wang Z. A multicenter study of the distribution pattern of posterior corneal astigmatism in Chinese myopic patients having corneal refractive surgery. Sci Rep 2020; 10:16151. [PMID: 32999411 PMCID: PMC7527519 DOI: 10.1038/s41598-020-73195-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Accepted: 09/11/2020] [Indexed: 11/24/2022] Open
Abstract
Including posterior corneal astigmatism (PCA) into consideration may increase the accuracy of astigmatism correction after corneal refractive surgery. In the present study we aim to investigate the distribution pattern of PCA in a large number of myopic patients from multiple ophthalmic centers. There were 7829 eyes retrospectively included in the study. Pentacam data of the eyes were retrieved from the machine and only results with image quality labelled with ‘OK’ were included. Distribution of PCA was slightly positively skewed (Skewness = 0.419, Kurtosis = 0.435, KS P < 0.0001). Mean PCA was 0.34 ± 0.14 D (range: 0.00 D-0.99 D). PCA was ≥ 0.25 D in 74.91% of the eyes and was ≥ 0.50 D in 11.61% of the eyes. In 97.55% of the eyes the steep meridian of PCA was vertical (SMV). PCA magnitude was significantly higher in eyes with SMV PCA (P < 0.0001) or high manifest astigmatism (MA, P < 0.0001). There was a significant correlation between anterior corneal astigmatism (ACA) magnitude and PCA magnitude in all of the eyes (r = 0.704, P < 0.0001). There was also a trend of decreasing frequency and magnitude of SMV PCA with aging (both P < 0.0001). In conclusion, PCA is present in myopic patients having corneal refractive surgery and PCA magnitude is increased with higher MA or ACA. Consideration of the impact of PCA on laser astigmatism correction may be necessary.
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Affiliation(s)
- Yijun Hu
- Aier Institute of Refractive Surgery, Refractive Surgery Center, Guangzhou Aier Eye Hospital, Guangzhou, China. .,Aier School of Ophthalmology, Central South University, Fourth Floor, New Century Mansion, 198 Middle Furong Road, Changsha, 410015, China.
| | - Shanqing Zhu
- Aier Institute of Refractive Surgery, Refractive Surgery Center, Guangzhou Aier Eye Hospital, Guangzhou, China
| | - Lu Xiong
- Aier Institute of Refractive Surgery, Refractive Surgery Center, Guangzhou Aier Eye Hospital, Guangzhou, China
| | - Xuejun Fang
- Aier School of Ophthalmology, Central South University, Fourth Floor, New Century Mansion, 198 Middle Furong Road, Changsha, 410015, China.,Refractive Surgery Center, Shenyang Aier Eye Hospital, Shenyang, China
| | - Jia Liu
- Refractive Surgery Center, Shenyang Aier Eye Hospital, Shenyang, China
| | - Jin Zhou
- Refractive Surgery Center, Chengdu Aier Eye Hospital, Chengdu, China
| | - Fangfang Li
- Refractive Surgery Center, Chengdu Aier Eye Hospital, Chengdu, China
| | - Qingsong Zhang
- Refractive Surgery Center, Wuhan Aier Eye Hospital, Wuhan, China
| | - Na Huang
- Refractive Surgery Center, Wuhan Aier Eye Hospital, Wuhan, China
| | - Xiaohua Lei
- Refractive Surgery Center, Hankou Aier Eye Hospital, Wuhan, China
| | - Li Jiang
- Refractive Surgery Center, Hankou Aier Eye Hospital, Wuhan, China
| | - Zheng Wang
- Aier Institute of Refractive Surgery, Refractive Surgery Center, Guangzhou Aier Eye Hospital, Guangzhou, China. .,Aier School of Ophthalmology, Central South University, Fourth Floor, New Century Mansion, 198 Middle Furong Road, Changsha, 410015, China.
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Moore J, Shu X, Lopes BT, Wu R, Abass A. Limbus misrepresentation in parametric eye models. PLoS One 2020; 15:e0236096. [PMID: 32970690 PMCID: PMC7514007 DOI: 10.1371/journal.pone.0236096] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 06/29/2020] [Indexed: 11/20/2022] Open
Abstract
Purpose To assess the axial, radial and tangential limbus position misrepresentation when parametric models are used to represent the cornea and the sclera. Methods This retrospective study included 135 subjects aged 22 to 65 years (36.5 mean ±9.8 STD), 71 females and 64 males. Topography measurements were taken using an Eye Surface Profiler topographer and processed by a custom-built MATLAB code. Eye surfaces were freed from edge-effect artefacts and fitted to spherical, conic and biconic models. Results When comparing the radial position of the limbus, average errors of -0.83±0.19mm, -0.76±0.20mm and -0.69±0.20mm were observed within the right eye population for the spherical, conic and biconic models fitted up to 5mm. For the same fitting radius, the average fitting errors were -0.86±0.23mm, -0.78±0.23mm and -0.73±0.23mm for the spherical, conic and biconic models respectively within the left eye population. For the whole cornea fit, the average errors were -0.27±0.12mm and -0.28±0.13mm for the spherical models, -0.02±0.29mm and -0.05±0.27mm for the conic models, and -0.22±0.16mm and 0.24±0.17mm for the biconic models in the right and left eye populations respectively. Conclusions Through the use of spherical, conic and biconic parametric modelling methods, the eye’s limbus is being mislocated. Additionally, it is evident that the magnitude of fitting error associated with the sclera may be propagating through the other components of the eye. This suggests that a corneal nonparametric model may be necessary to improve the representation of the limbus.
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Affiliation(s)
- Joshua Moore
- Department of Mathematical Sciences, University of Liverpool, Liverpool, United Kingdom
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Xuhan Shu
- College of Physical Sciences, University of Guelph, Guelph, Canada
| | - Bernardo T. Lopes
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
- Department of Ophthalmology, Federal University of Sao Paulo, Sao Paulo, Brazil
| | - Richard Wu
- Department of Optometry, Central Taiwan University of Science and Technology, Taichung, Taiwan
- College of Optometry, Pacific University, Forest Grove, Oregon, United States of America
| | - Ahmed Abass
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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