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Cohen KL, Patel NK. Using Total Corneal Astigmatism With Femtosecond Laser Cataract Surgery and Arcuate Keratotomy(ies) to Treat Low Amounts of Astigmatism. Cornea 2024; 43:999-1007. [PMID: 38289747 DOI: 10.1097/ico.0000000000003482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 12/17/2023] [Indexed: 02/01/2024]
Abstract
PURPOSE The aim of this study was to evaluate outcomes using total corneal astigmatism (TCA) to calculate arcuate keratotomy(ies) (AK) parameters performed with femtosecond laser-assisted cataract surgery to reduce low corneal astigmatism. METHODS Patients who had femtosecond laser-assisted cataract surgery and AK with 0.50 diopter (D) to 1.30 D of TCA were included. Exclusion criteria were intraoperative complications, preexisting corneal surgery, and comorbidities that might adversely affect outcomes. Corneal tomography (Galilei G4, Zeimer Ophthalmic Systems AG) was performed preoperatively and 1 month postoperatively. TCA was input into the Donnenfeld limbal relaxing incisions nomogram to calculate the AK parameters. Preoperative and postoperative tomographic and subjective refractive measurements were compared. The Alpins method for vector analysis evaluated results. RESULTS Eighty-two eyes of 82 patients were included. Mean preoperative TCA was significantly reduced from 0.80 ± 0.19 D to 0.51 D ± 0.26 D ( P < 0.001). Preoperative posterior corneal astigmatism, -0.28 ± 0.13 D, was unchanged, postoperative posterior corneal astigmatism, -0.28 ± 0.14 D ( P = 0.653). Target-induced astigmatism arithmetic mean (0.82 ± 0.21 D) was greater than that of the surgically induced astigmatism (0.70 ± 0.40 D), resulting in an arithmetic mean difference vector of 0.51 ± 0.27 D with a summated mean at 0.16 D at 20 degrees. The correction index was 0.87, indicating undercorrection. Angle of error arithmetic mean, -1.27 ± 23.27 degrees, indicated good alignment. CONCLUSIONS Inputting TCA for calculation of femtosecond laser AK parameters can reduce low amounts of preoperative corneal astigmatism, thereby improving uncorrected vision.
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Affiliation(s)
- Kenneth L Cohen
- School of Medicine, Department of Ophthalmology and the Kittner Eye Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
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Hashemi H, Mesbahi S, Jamali A, Ostadimoghaddam H, Yekta A, Khabazkhoob M. The association between ocular biometric components and corneal aberrations. Clin Exp Optom 2024; 107:609-615. [PMID: 37844336 DOI: 10.1080/08164622.2023.2258126] [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: 08/19/2023] [Accepted: 09/08/2023] [Indexed: 10/18/2023] Open
Abstract
CLINICAL RELEVANCE Evaluating factors affecting corneal higher-order aberration component has a very important role in interpreting the characteristics of the formed image on the retina. BACKGROUND To determine the relationship between ocular biometric components and corneal higher-order aberrations in an elderly population. METHODS This report is related to a subsample of the Tehran Geriatric Eye study (TGES), a population-based cross-sectional study that was conducted on individuals aged 60 years and above in Tehran city, Iran using multistage stratified random cluster sampling. All study participants underwent ocular examinations including visual acuity measurement, refraction and slit-lamp biomicroscopy. Anterior segment imaging and corneal aberrometry were performed using Pentacam AXL. RESULTS In the present study, 644 eyes of 415 individuals (56.9% female) with mean age of 66.36 ± 4.70 years were evaluated. According to a multiple generalised estimating equation model, the root mean square of total higher-order aberrations was related to age (β = 0.081, p = 0.002), crystalline lens thickness (β = 0.08, p < 0.001), and corneal diameter (β = -0.04, p = 0.014). The root mean square of total coma aberration was directly related to the female sex (β = 0.02, p = 0.05), and crystalline lens thickness (β = 0.06, p < 0.001). There was a direct relationship between the root mean square of third- and fourth-order higher-order aberrations and crystalline lens thickness (p < 0.001). Spherical aberration was directly related to the male sex (β = -0.02, p = 0.004), axial length (β = 0.05, p < 0.001) and central corneal thickness (β = 0.001, p = 0.025), and was inversely related to anterior chamber depth (β = -0.07, p = 0.031) and crystalline lens thickness (β = -0.25, p < 0.001). CONCLUSION Ocular biometric components are related to corneal aberrations in the elderly. These factors need to be considered in respect of medical and surgical procedures required for the elderly.
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Affiliation(s)
- Hassan Hashemi
- Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran
| | - Shima Mesbahi
- Department of Optometry, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Alireza Jamali
- Rehabilitation Research Center, Department of Optometry, Iran University of Medical Sciences, Tehran, Iran
| | - Hadi Ostadimoghaddam
- Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Abbasali Yekta
- Department of Optometry, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mehdi Khabazkhoob
- Department of Basic Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Kwon Y, Han SB, Che SA, Koh K, Han SY, Choi CY, Lee YW. Effect of Corneal and Lens Eccentricity Difference on Rigid Corneal Lens Treatment in Patients With Keratoconus. Eye Contact Lens 2024; 50:255-258. [PMID: 38652487 DOI: 10.1097/icl.0000000000001088] [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: 02/10/2024] [Indexed: 04/25/2024]
Abstract
OBJECTIVE To evaluate the effects of rigid corneal lenses (RCL) in patients with keratoconus, based on eccentricity. METHODS Eighty-four eyes from 84 patients were included in this retrospective comparative study. Based on the median value of eccentricity difference between the cornea and back surface of the RCL, the patients were divided into groups 1 (<0.08) and 2 (≥0.08). Visual acuity, refractive index, and corneal topography indices were compared before and three months after lens use. RESULTS Visual acuity, astigmatism, refractive error, corneal curvature, and corneal thickness improved significantly in both groups. Apical power and anterior elevation improved significantly in group 1, with small differences in eccentricity, but not in group 2. Changes in apical power before and after lens use were significantly different between the two groups. CONCLUSION The RCL was effective for the cornea of keratoconus, especially when the prescription was made with a small difference in eccentricity.
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Affiliation(s)
- Younga Kwon
- GS Eye Clinic (Y.K.), Seoul, Korea; Department of Ophthalmology (S.B.H., S.-A.C., Y.W.L.), Kangwon National University Hospital, Kangwon National University School of Medicine, Chuncheon, Korea; Department of Ophthalmology (K.K.), Kim's Eye Hospital, Konyang University College of Medicine, Seoul, Korea; and Department of Ophthalmology (S.Y.H., C.Y.C.), Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea
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Catania F, Vinciguerra P, Di Maria A. Low Rate of Postoperative Pterygium Recurrence in Patients under Treatment with Low-Dose Oral Doxycycline for Chronic Blepharitis: A First Report. Diagnostics (Basel) 2024; 14:715. [PMID: 38611627 PMCID: PMC11012025 DOI: 10.3390/diagnostics14070715] [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: 12/27/2023] [Revised: 03/02/2024] [Accepted: 03/21/2024] [Indexed: 04/14/2024] Open
Abstract
PURPOSE Low doses of systemic doxycycline (LD-SD) inhibit angiogenesis and the expression of matrix metalloproteases, which are determinants of pterygium progression. This study aimed to compare the recurrence rate and visual outcome of pterygium excision in patients undergoing chronic treatment with LD-SD for chronic refractory blepharitis and LD-SD-naive patients. METHODS A retrospective analysis of patients that underwent surgical excision and conjunctival graft apposition was conducted. Patients were divided in a TETRA group (under LD-SD treatment at the moment of surgery) and a control group. The main outcome was the rate of recurrence at 1 year postoperatively. Secondary outcomes were the comparisons of surface regularity, visual quality, and dry-eye symptoms at 6-week, 6-month, and 1-year follow-up in the two groups. RESULTS The TETRA group showed a significantly lower rate of 1-year recurrence both in primary (p = 0.034) and recurrent (p < 0.001) pterygia. The best corrected visual acuity (BCVA), astigmatic error, corneal total root mean square (RMS), and ocular surface disease index (OSDI) significantly reduced during the follow-up in both groups. The surface asymmetry index and high-order aberrations (HOAs) significantly reduced only in the TETRA group. The final BCVA was significantly higher, while the OSDI score and total RMS and HOAs were significantly lower in the TETRA group compared to the control. CONCLUSIONS Patients under treatment with LD-SD showed a lower rate of recurrence at 1-year follow-up compared to controls. These patients also experienced higher BCVA and surface regularity and less dry-eye symptoms.
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Affiliation(s)
- Fiammetta Catania
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072 Pieve Emanuele, Italy;
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Italy;
| | - Paolo Vinciguerra
- Department of Biomedical Sciences, Humanitas University, Via Rita Levi Montalcini 4, 20072 Pieve Emanuele, Italy;
- IRCCS Humanitas Research Hospital, via Manzoni 56, 20089 Rozzano, Italy;
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Badian RA. Schematic sectioning approaches for corneal and retinal surfaces used in ophthalmology and vision-related clinical practice and research. Exp Eye Res 2023; 230:109442. [PMID: 36940902 DOI: 10.1016/j.exer.2023.109442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 03/01/2023] [Accepted: 03/16/2023] [Indexed: 03/22/2023]
Abstract
Schematically, the corneal surface area and other similar surfaces such as the retinal surface and the visual field area have been represented by a circle. While there are different types of schematic sectioning patterns in use, not all patterns are recognized or referred to with their respective appropriate terminology. In scientific communications, as well as in clinical practice, when dealing with corneal or retinal surfaces, it is imperative to have the ability to refer to specific areas with an as high degree of accuracy as possible. The necessity arises in many situations, either when performing tests such as corneal surface staining, corneal sensitivity test, scanning the corneal surface, reporting of the findings related to any specific corneal surface area, or using a sectioning pattern for parts of the retinal surface when locating retinal lesions, or when referring to loci with changes in the visual field. Applying the appropriate geometric terms when any pattern is used for sectioning of surfaces such as cornea or retina, for precise localization and description of the findings or changes with a high degree of accuracy using the correct terminology is a sine qua non. Hence, the idea for this work is to gain an overview of the sectioning methods that are available and in use as methodological guidance in different sectioning patterns related to the corneal, retinal, and visual field.
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Affiliation(s)
- Reza A Badian
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway.
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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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Niu L, Ding L, Qian Y, Zhou X. Comparison of Two Scheimpflug Systems in the Measurements of Eyes with Corneal Diameter Smaller than 11.1 mm. Ophthalmol Ther 2023; 12:125-138. [PMID: 36244046 PMCID: PMC9834470 DOI: 10.1007/s40123-022-00591-y] [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: 08/31/2022] [Accepted: 10/04/2022] [Indexed: 01/16/2023] Open
Abstract
INTRODUCTION This article aimed to evaluate the measurements of ectasia parameters by two Scheimpflug-based tomography devices, Pentacam and Sirius, for eyes with different corneal diameters (CDs). METHODS This cross-sectional research included subjects from the Fudan University EENT Hospital Refractive Center Database that were followed once a year for at least 3 years with unremarkable slit-lamp examination and normal topography. Pentacam and Sirius examinations were performed on these subjects and the ectasia indices were compared between different CD groups. RESULTS The right eyes of 153 subjects were included (CD ≤ 11.1 mm, n = 50; 11.2-12 mm, n = 52; > 12.0 mm, n = 51). For the ectasia parameters from Pentacam, CD had the greatest influence on the deviation of normality of back elevation (Db, R2 = 0.371, β = - 1.119, P < 0.001), overall deviation of normality (BAD-D, R2 = 0.305, β = - 0.589, P < 0.001), and minimum pachymetric progression index (PPImin, R2 = 0.282, β = - 0.131, P < 0.001). For parameters derived from Sirius, CD had the greatest influence on Baiocchi-Calossi-Versaci index of the back surface (BCVb, R2 = 0.138, β = - 0.179, P < 0.001), keratoconus vertex of the back surface (KVb, R2 = 0.099, β = - 2.273, P < 0.001), and BCV (R2 = 0.071, β = - 0.078, P = 0.001). CD had little influence on surface asymmetry index of the front (SIf) and back surface (SIb), keratoconus vertex of the front surface (KVf), Baiocchi-Calossi-Versaci index of the front surface (BCVf), and Sirius classifier (P > 0.05). CONCLUSIONS For Pentacam, CD mainly influenced indices related to back elevation (BE) and pachymetry progression, whereas for Sirius, CD mainly influenced indices related to BE and corneal aberration.
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Affiliation(s)
- Lingling Niu
- Department of Ophthalmology, Eye and ENT Hospital, NHC Key Laboratory of Myopia, Fudan University, Shanghai, People’s Republic of China
| | - Lan Ding
- Department of Ophthalmology, Eye and ENT Hospital, NHC Key Laboratory of Myopia, Fudan University, Shanghai, People’s Republic of China
| | - Yishan Qian
- Department of Ophthalmology, Eye and ENT Hospital, NHC Key Laboratory of Myopia, Fudan University, Shanghai, People’s Republic of China
| | - Xingtao Zhou
- Department of Ophthalmology, Eye and ENT Hospital, NHC Key Laboratory of Myopia, Fudan University, Shanghai, People’s Republic of China
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Khanjian AT, Khodzhabekyan NV, Tarutta EP, Harutyunyan SG, Milash SV. [Changes in the wavefront and peripheral defocus profile after excimer laser and orthokeratology corneal reshaping in myopia]. Vestn Oftalmol 2023; 139:87-92. [PMID: 38235634 DOI: 10.17116/oftalma202313906187] [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: 01/19/2024]
Abstract
PURPOSE This study compares the trends of changes in corneal asphericity, corneal and total aberrations and peripheral refraction in myopic eyes after excimer laser and orthokeratology correction. MATERIAL AND METHODS Aberrometry (OPD-Scan III; Nidek, Japan) was performed in 63 patients (126 eyes) with moderate and high myopia before and after femtosecond laser-assisted in situ keratomileusis (Femto-LASIK; 88 eyes, group 1) and photorefractive keratectomy (PRK; 38 eyes, group 2). Peripheral refraction (Grand Seiko AutoRef/Keratometer) at 15° and 30° from the center of the fovea was observed in 12 patients of group 1 and in 18 patients with a background of orthokeratology correction (group 3). RESULTS Corneal asphericity factor Q transitioned to positive values after PRK and Femto-LASIK. Corneal aberrations: root mean square higher order aberration (RMS HOA) increased in both groups, Tilt 1 increased in group 1 and became negative in group 2, Tilt 2 increased in group 2 and went negative in group 1. Trefoil 6 did not change in group 1 and decreased in group 2. Coma 7 and 8 increased synchronously in both groups. Spherical aberrations (SA) increased in group 1, and went negative in group 2. Total aberrations changed to a lower degree, and these changes were not synchronous with the corneal ones; RMS HOA decreased in group 1 (while corneal RMS increased significantly), and in the PRK group it increased, but much less than the corneal. Total SA increased in group 1 and did not change in group 2. Peripheral myopic defocus formed in all cases, after Femto-LASIK the maximum was in the zone of 30º, after orthokeratology lenses - in the zone of 15º. CONCLUSION Using excimer laser and orthokeratology to reshape the cornea in full accordance with its different profiles have different effects on the wavefront and peripheral refraction of the eye. The internal optics of the eye partially compensates corneal aberrations induced by the excimer laser.
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Affiliation(s)
- A T Khanjian
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - N V Khodzhabekyan
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - E P Tarutta
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - S G Harutyunyan
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - S V Milash
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
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González-Cruces T, Villarrubia A, Sánchez Ventosa Á, Palacín Miranda E, Castillo Eslava R, Gomera Martinez A, García Párrizas JA, Torres Huelva P, Sánchez-González JM, Cano-Ortiz A. Comparison Between the Wavefront-Optimized and Custom-Q Aspheric Ablation Profiles in Myopic Eyes With Two Different Q-targets: A Contralateral Eye Study. J Refract Surg 2022; 38:698-707. [DOI: 10.3928/1081597x-20221005-01] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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Comparison of Anterior Corneal Aberrometry, Keratometry and Pupil Size with Scheimpflug Tomography and Ray Tracing Aberrometer. Vision (Basel) 2022; 6:vision6010018. [PMID: 35324603 PMCID: PMC8951144 DOI: 10.3390/vision6010018] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 03/15/2022] [Accepted: 03/16/2022] [Indexed: 11/17/2022] Open
Abstract
This study aimed to assess the anterior corneal wavefront aberrations, keratometry, astigmatism vectors and pupil size between Pentacam HR® (Oculus Optikgeraete GmbH, Wetzlar, Germany) and iTrace® (Tracey Technologies Corp., Houston, TX, USA). In this observational study, 100 eyes (50 healthy volunteers) were scanned in mesopic light condition with a Pentacam HR® and iTrace®. Anterior corneal aberrations (spherical aberration (Z40), vertical coma (Z3 − 1), horizontal coma (Z3 + 1)), keratometry in the flattest (K1) and steepest meridian (K2), mean astigmatism, astigmatic vectors (J0 and J45), and pupil size were measured. We found a significant difference in Z40 (Pentacam®: +0.30 ± 0.11 µm and iTrace®: −0.03 µm ± 0.05 µm; p < 0.01) with no correlation between the devices (r = −0.12, p = 0.22). The devices were in complete agreement for Z3 − 1 (p = 0.78) and Z3 + 1 (p = 0.39), with significant correlation between the machines (r = −0.38, p < 0.01 and r = −0.6, p < 0.01). There was no difference in K1, K2 and mean astigmatism. J0 was negative with both devices (against-the-rule astigmatism), but there was no correlation. J45 was negative with the Pentacam HR® (more myopic oblique astigmatism) but significantly correlated between the devices. Pupil size was smaller with Pentacam HR® (p < 0.01). In summary, these devices cannot be used interchangeably. Corneal Z40 was significantly different with more negative Z40 with iTrace® compared to Pentacam HR®. iTrace® operates with lower illumination, giving larger pupil size than Pentacam HR®, which uses intense blue light during measurement. No correlation was found for J0. Pentacam HR® had a trend to record more negative J45 (myopic oblique astigmatism).
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Langenbucher A, Szentmáry N, Cayless A, Münninghoff L, Wortmann R, Wendelstein J, Hoffmann P. Translation model for anterior segment tomographic data to corneal spherical aberration derived from a Monte-Carlo simulation based on raytracing. Acta Ophthalmol 2022; 100:e1665-e1674. [PMID: 35233935 DOI: 10.1111/aos.15125] [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: 12/14/2021] [Revised: 01/23/2022] [Accepted: 02/18/2022] [Indexed: 11/30/2022]
Abstract
BACKGROUND Intraocular lenses with a negative aspherical design for correction of corneal spherical aberration (SA) have gained popularity in recent decades. In most cases, a 'one size fits all' concept is followed, where all eyes receive lenses with the same SA correction. The purpose of this study is to develop a strategy based on raytracing using anterior segment tomography data to extract corneal SA and to provide simple multivariable linear models for prediction of corneal SA. METHODS The analysis was based on a large dataset of 8737 measurements of 8737 eyes from 1 clinical centre, using the Casia2 anterior segment tomographer. An optical model based on: corneal front and back surface radius Ra and Rp, asphericities Qa and Qp, corneal thickness CCT, anterior chamber depth ACD, and pupil centre position (X-Y position: PupX and PupY ), was defined for each measurement. Corneal SA was derived using a 6-mm aperture perpendicular to the incident ray and centred on the chief ray, and linear prediction models were derived for SA using biometric data. Cross-validation was used for model performance evaluation. RESULTS Using raytracing, the wavefront error within an aperture (6-mm diameter centred on the intersection of the chief ray with the cornea) was calculated and corneal SA was extracted. After identifying the relevant effect sizes (Ra, Qa, Rp Qp, ACD, PupX and PupY ) using stepwise linear regression, linear mixed-effects models (model 1: all effect sizes, model 2: Ra, Qa, Rp and Qp, model 3: Ra and Qa) were set up on the training data in terms of a Monte-Carlo simulation. On the test data (training data), model 1 with a mean absolute/root-mean-squared prediction error of 0.0095/0.0130 (0.0095/0.0127) performed similarly to model 2 with 0.0097/0.0131 (0.0096/0.0127), and both outperformed model3 with 0.0152/0.0197 (0.0148/0.0190). CONCLUSION Based on the Casia2 anterior segment tomographer, corneal SA could be derived using shape data (curvature and asphericities) of both corneal surfaces (model 2). This information could easily be used for selection of the appropriate negative aspherical lens design in cataract surgery.
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Affiliation(s)
- Achim Langenbucher
- Department of Experimental Ophthalmology Saarland University Homburg/Saar Germany
| | - Nóra Szentmáry
- Dr. Rolf M. Schwiete Center for Limbal Stem Cell and Aniridia Research Saarland University Homburg/Saar Germany
- Department of Ophthalmology Semmelweis‐University Budapest Hungary
| | - Alan Cayless
- School of Physical Sciences The Open University Milton Keynes UK
| | | | | | - Jascha Wendelstein
- Department of Experimental Ophthalmology Saarland University Homburg/Saar Germany
- Medical Faculty Johannes Kepler University Linz Linz Austria
| | - Peter Hoffmann
- Augen‐ und Laserklinik Castrop‐Rauxel Castrop‐Rauxel Germany
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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: 1] [Impact Index Per Article: 0.3] [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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Neroev VV, Tarutta EP, Khanjian AT, Harutyunyan SG, Markosian GA, Khodzhabekyan NV. [Optical aberrations of the eyes with various degrees of myopia]. Vestn Oftalmol 2021; 137:14-21. [PMID: 34726853 DOI: 10.17116/oftalma202113705114] [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: 11/17/2022]
Abstract
Purpose - to comparatively analyze the wavefront aberrations and biometric parameters of the eyes with various degrees of myopia. MATERIAL AND METHODS The study included 134 eyes of 67 patients with mild, moderate and high myopia aged 7-28 (mean age 19.3±1.5 years). The following biometric parameters were examined: anterior chamber depth (ACD), lens thickness (LT), axial length (AL), as well as corneal and total aberrations. The parameters were studied on the Galilei G6 system (Ziemer Ophthalmic Systems AG, Switzerland) and the OPD-Scan III aberrometer (Nidek, Japan). Spherical aberration (SA) was estimated as the sum of Z4+Z8+Z12. RESULTS As the refraction increased, the root mean square higher-order aberrations (RMS HOA) also increased significantly: from 0.24±0.02 μm in mild myopia to 0.45±0.03 μm in high myopia, and in eyes with AL of ≥27.0 mm - to 0.57±0.02 μm (p=0.01). An increase in vertical tilt, vertical coma and vertical trefoil were also observed. Total SA was positive and increased in eyes with moderate myopia compared to those with low myopia (from 0.02±0.01 μm to 0.06±0.02 μm, p=0.02), which coincided with changes in the internal optics of the eye: an increase in ACD and a decrease in LT. At the same time, no differences in corneal aberrations were observed among patients with low and moderate myopia. A significant decrease of SA occurred in high myopia (from 0.06 μm in low myopia to 0.015±0.02 μm in high myopia). The average value of SA was 0.005±0.01 μm in eyes with AL of ≥27.0 mm and appeared to be negative in 40% of cases. The average value of corneal SA was negative (-0.002±0.01μm) in eyes with AL of ≥27.0 mm. This group had predominantly patients with congenital myopia. CONCLUSION An increase of total positive SA in patients with moderate myopia compared to those with low myopia is associated with changes in the internal optics of the eye (ACD, LT). Significant increase of higher-order aberrations and decrease of SA with the transition to negative values was observed in patients with high axial myopia.
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Affiliation(s)
- V V Neroev
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - E P Tarutta
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - A T Khanjian
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - S G Harutyunyan
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - G A Markosian
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
| | - N V Khodzhabekyan
- Helmholtz National Medical Research Center of Eye Disease, Moscow, Russia
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Gatinel D, Malet J, Dumas L, Azar DT. Comparison of Low Degree/High Degree and Zernike Expansions for Evaluating Simulation Outcomes After Customized Aspheric Laser Corrections. Transl Vis Sci Technol 2021; 10:21. [PMID: 34003958 PMCID: PMC7991963 DOI: 10.1167/tvst.10.3.21] [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] [Indexed: 11/25/2022] Open
Abstract
Purpose The purpose of this study was to compare the low degree/high degree (LD/HD) and Zernike Expansion simulation outcomes evaluating the corneal wavefront changes after theoretical conventional and customized aspheric photorefractive ablations. Methods Initial anterior corneal surface profiles were modeled as conic sections with pre-operative apical curvature, R0, and asphericity, Q0. Postoperative apical curvature, R1, was computed from intended defocus correction, D, diameter zone, S, and target postoperative asphericity, Q1. Coefficients of both Zernike and LD/HD polynomial expansions of the rotationally symmetrical corneal profile were computed using scalar products. We modeled different values of D, R0, Q0, S, and ΔQ = Q1 to Q0. The corresponding postoperative changes in defocus (Δz20 vs. Δg20), fourth order (Δz40 vs. Δg40) and sixth order (Δz60 vs. Δg60) Zernike and LD/HD spherical aberrations (SAs) were compared. In addition, retrospective clinical data and wavefront measurements were obtained from two examples of two patient eyes before and after corneal laser photoablation. Results The z20, varied with both R0 and Q0, whereas the LD/HD defocus coefficient, g20, was relatively robust to changes in asphericity. Variations of apical curvature better correlated with defocus and ΔQ with SA coefficients in the LD/HD classification. The impact of ΔQ was null on g20 but induced significant linear variations in z20 and fourth order SA coefficients. LD/HD coefficients provided a good correlation with the visual performances of the operated eyes. Conclusions Simulated variations in postoperative corneal profile and wavefront expansion using the LD/HD approach showed good correlations between defocus and asphericity variations with variations in corneal curvature and SA coefficients, respectively. Translational Relevance The relevance of this study was to provide a clinically relevant alternative to Zernike polynomials for the interpretation of wavefront changes after customized aspheric corrections.
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Affiliation(s)
- Damien Gatinel
- Department of Anterior Segment and Refractive Surgery, Rothschild Ophthalmic Foundation Hospital, Paris, France
| | - Jacques Malet
- Department of Anterior Segment and Refractive Surgery, Rothschild Ophthalmic Foundation Hospital, Paris, France
| | - Laurent Dumas
- Laboratoire de Mathématiques de Versailles, UVSQ, CNRS, Université Paris-Saclay, Versailles, France
| | - Dimitri T Azar
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago College of Medicine, Chicago, IL, USA
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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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Influence of corneal shape parameters on corneal deformation responses measured with a Scheimpflug camera. Int Ophthalmol 2021; 41:2853-2859. [PMID: 33880682 DOI: 10.1007/s10792-021-01844-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 04/08/2021] [Indexed: 10/21/2022]
Abstract
PURPOSE To investigate the effect of corneal shape parameters on corneal deformation responses measured with a Scheimpflug camera. METHODS A total of 241 eyes of 241 participants were enrolled in this study. The anterior and posterior corneal curvature radii (CCR), anterior and posterior corneal Q-values, and corneal diameters of the participants were measured using the Pentacam HR. A total of 17 corneal deformation parameters including time, velocity, deflection amplitude, length, and area during ingoing applanation, highest concavity, and outgoing applanation were recorded by corneal visualization using Scheimpflug technology (Corvis ST). The effect of corneal shape parameters on corneal deformation responses was evaluated using multivariate regression models. RESULTS Multivariate regression analyses showed that six, five, four, and three corneal deformation parameters were significantly correlated with anterior CCR, posterior CCR, anterior Q-value, and posterior Q-value, respectively. Steeper anterior corneal curvature was associated with faster velocity during ingoing applanation and greater deformation during outgoing applanation. Steeper posterior corneal curvature was correlated with faster velocity during outgoing applanation and greater deformation during ingoing applanation. Eyes that had steeper corneal curvatures were associated with less stiff corneas. More negative anterior Q-value corresponded with faster velocity and greater deformation during ingoing applanation. Eyes that had more prolate posterior corneal surfaces showed more resistance to corneal deformation at the highest concavity. However, corneal diameter was not selected in any corneal deformation parameters models. CONCLUSION Corneal deformation response is significantly influenced by anterior and posterior corneal curvature and corneal asphericity, but not corneal diameter.
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Vincent SJ, Cho P, Chan KY, Fadel D, Ghorbani-Mojarrad N, González-Méijome JM, Johnson L, Kang P, Michaud L, Simard P, Jones L. CLEAR - Orthokeratology. Cont Lens Anterior Eye 2021; 44:240-269. [DOI: 10.1016/j.clae.2021.02.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Accepted: 02/01/2021] [Indexed: 12/25/2022]
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Alsaqr A, Fagehi R, Abu Sharha A, Alkhudair M, Alshabrami A, Muammar AB, Abdulwahed S, Alshehri A. Ethnic Differences of Corneal Parameters: A Cross-Sectional Study. Open Ophthalmol J 2021. [DOI: 10.2174/1874364102115010013] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Purpose:
To investigate the ethnic differences of corneal parameters in Arabs and other ethnicities.
Methods:
This study recruited 250 Saudi Arabian participants, 18–45 years of age. The McMonnies questionnaire was used to exclude participants with dry eye. The KR8800 auto refractometer (Topcon, Japan) was used to measure the refractive error. Oculus Keratograph 4 topography was used to assess 16 corneal parameters, including the k-readings, horizontal visible iris diameter, mean eccentricity index, asphericity, corneal shape factor, corneal flattening factor, sagittal height, sagittal curvature, and vertical palpebral aperture.
Results:
A statistically significant difference was found between male and female participants. Corneal parameters were compared to other ethnicities, including Caucasians and Asians, and those of Mongoloid origin. The horizontal visible iris diameter was wider in Saudi Arabians than in Asians but similar to Caucasians. The sagittal height was deeper and the corneal shape factor was higher than in the other ethnicities, and the eccentricity index was lower than that in Caucasians and Asians of Mongoloid origin.
Conclusion:
Our data provided normative corneal parameters of Saudi Arabians that may be useful for ophthalmic clinicians and designers of contact lenses. Furthermore, the parameters suggest that the corneal characteristics of Arabians are distinct from those of major ethnicities.
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Correlation Between Anterior Corneal Elevation Differences in Main Meridians and Corneal Astigmatism. Eye Contact Lens 2020; 46:99-104. [DOI: 10.1097/icl.0000000000000613] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Rouimi F, Ouanezar S, Goemaere I, Bayle AC, Borderie V, Laroche L, Bouheraoua N. Presbyopia management with Q-factor modulation without additive monovision: One-year visual and refractive results. J Cataract Refract Surg 2019; 45:1074-1083. [PMID: 31126780 DOI: 10.1016/j.jcrs.2019.02.039] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 02/20/2019] [Accepted: 02/23/2019] [Indexed: 01/19/2023]
Abstract
PURPOSE To analyze refractive results after hyperopic presbyopia surgery by Q-factor modulation without additive monovision. SETTING Quinze-Vingts National Ophthalmology Hospital, Paris, France. DESIGN Prospective nonrandomized study. METHODS Forty-five hyperopic presbyopic patients not tolerating monovision were included. The target for the dominant eye was emmetropia, whereas that for the nondominant eye was emmetropia associated with a target Q factor of -0.8. The postoperative follow-up included assessments of spherical equivalent (SE) refraction, monocular and binocular corrected and uncorrected (UDVA) distance visual acuities, and binocular corrected and uncorrected (UNVA) near visual acuities. Corneal pachymetry, topography, aberrometry and an analysis of patient satisfaction were performed at the 12-month examination. RESULTS The study comprised 90 eyes of 45 consecutive patients. The mean age at surgery was 53.8 years ± 4.99 (SD). The mean preoperative SE was +2.33 ± 1.16 diopters (D) in the dominant eyes and +2.26 ± 1.17 D in the nondominant eyes. At 12 months postoperatively, 42 patients (93%) had a binocular UDVA of Snellen 20/20 and 37 patients (82%) had a binocular UNVA of Jaeger 2 (Parinaud 3). The mean SE at 12 months was -0.22 ± 0.35 D in the dominant eyes (P < .0001) and -0.83 ± 0.50 D in the nondominant eyes (P < .0001). Two eyes required retreatment. Overall, 39 patients (87%) said that they were satisfied and would recommend the intervention. CONCLUSION The Q-factor modulation without additive monovision aims to compensate for presbyopia by changing the Q factor of the nondominant eye to generate a greater depth of field in hyperopic presbyopic patients who are unable to tolerate monovision. The visual outcomes and quality of vision were satisfactory, and only a few patients required additional correction.
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Affiliation(s)
- Fabien Rouimi
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France
| | - Sofiane Ouanezar
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France
| | - Isabelle Goemaere
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France
| | - Anne Charlotte Bayle
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France
| | - Vincent Borderie
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France; Institut de la Vision, INSERM UMR S 968, UPMC - Sorbonne Université, Paris, France
| | - Laurent Laroche
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France; Institut de la Vision, INSERM UMR S 968, UPMC - Sorbonne Université, Paris, France
| | - Nacim Bouheraoua
- Quinze-Vingts National Ophthalmology Hospital, UPMC - Sorbonne Université, Paris, France; Institut de la Vision, INSERM UMR S 968, UPMC - Sorbonne Université, Paris, France.
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Analysis of planning strategies in primary eyes gaining a line or more of visual acuity after topography-guided laser in situ keratomileusis. J Cataract Refract Surg 2019; 45:321-327. [PMID: 30733106 DOI: 10.1016/j.jcrs.2018.10.040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Revised: 09/17/2018] [Accepted: 10/10/2018] [Indexed: 11/20/2022]
Abstract
PURPOSE To analyze planning strategies for eyes that gained 1 or more lines of corrected distance visual acuity (CDVA) after topography-guided custom treatment (TCAT). SETTING Refractive Surgery Clinic, Cleveland Clinic, Ohio, USA. DESIGN Retrospective case series. METHODS Eyes having TCAT by the same surgeon between February 2016 and June 2017 were enrolled. The corneal shape was captured with the Wavelight Allegretto Topolyzer diagnostic device coupled with refraction, generating an ablation profile. The cylinder magnitude and axis of laser entry were decided by the surgeon based on the manifest and measured values, assisted by additional data from the Pentacam Scheimpflug tomographer and Ladarwave ocular wavefront aberrometer. RESULTS The study comprised 256 eyes. At 3 months, uncorrected distance visual acuity was 20/20 or better in 95.7% and 20/15 or better in 81.4%; 25.6% gained 1 or more lines of CDVA. The measured and manifest axes differed by less than 15 degrees in 59%, between 15 degrees and 30 degrees in 18%, and by more than 30 degrees in 23%. When it differed by at least 5 degrees, the measured axis was treated in 79%, 75%, and 73% of eyes, respectively. In eyes with higher measured cylinder, 75% were treated between the manifest and measured values, with 7% at full measured value. When the manifest value was greater, 60% were treated at the total measured value and 40% in between. Whole-eye aberrometry showed a small increase in coma, spherical aberration and the total root mean square (all P < .001). CONCLUSIONS The TCAT procedure achieved visual acuity better than the preoperative CDVA in more than 25.0% of eyes. Tomography and wavefront aberrometry assisted in the selection process to achieve optimum visual outcomes.
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Nasrin F, Iyer RV, Mathews SM. Simultaneous Estimation of Corneal Topography, Pachymetry, and Curvature. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:2463-2473. [PMID: 29994760 DOI: 10.1109/tmi.2018.2836304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Identification of objective criteria to correctly diagnose ectatic diseases of the cornea or to detect early stages of corneal ectasia is of great interest in ophthalmology and optometry. Metrics for diagnosis typically employed are curvature maps (axial/sagittal, tangential); elevation map of the anterior surface of the cornea with respect to a reference sphere; and pachymetry (thickness) map of the cornea. We present evidence that currently used curvature maps do not represent the actual curvatures (principal or mean) in a human cornea. A novel contribution of this paper is the computation of the true mean curvature over every point of a central region of the cornea. We show that the true mean curvature can accurately identify the location of the ectasia. We present a quartic smoothing spline algorithm for the simultaneous computation of elevation maps for anterior and posterior corneal surfaces, pachymetry, and true mean curvature. The input to the algorithm is data from a single measurement from imaging devices such as an anterior segment optical coherence tomographer or a Scheimpflug imager. We show that a different combination of metrics is useful for the diagnosis of existing ectasia (true mean curvature and anterior elevation map) as opposed to subclinical ectasia (pachymetry and posterior elevation map). We compare our results with existing algorithms, and present applications to a normal cornea, a forme fruste keratoconic cornea, and an advanced keratoconic cornea.
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Abstract
PURPOSE Corneal front-surface asphericity is directly related with the optical quality of the eye and with contact lenses fitting. The purpose of this study was to evaluate the corneal asphericity as a function of age, sex, and refractive error measured with autokeratometry and corneal topography and its long-term changes (5- to 10-year period). METHODS The asphericity and corneal curvature were obtained with the autorefractometer/autokeratometer NIDEK ARK-700A and with the videokeratoscope MODI 2.0 and compared. Corneal asphericity was retrospectively analyzed with NIDEK ARK-700A. The longitudinal study of asphericity was conducted with the same device between 2 appointments within an interval of 5 to 10 years. RESULTS NIDEK ARK-700A showed agreement of asphericity values with those of MODI 2.0 (P=0.172) for a 7-mm diameter chord. The mean Q value of 1,484 right eyes (58.6% female), with a mean age of 40.2±18.4 years, was -0.24±0.12. No differences were found for Q value between sexes (P=0.424), age groups (P=0.268), and refractive error groups (P=0.107). The longitudinal analysis of corneal asphericity in 190 eyes (62.1% female) over a mean period of 5.9±1.4 years showed no significant differences in the Q value (0.00±0.08, P=0.813) over time. However, 14% showed asphericity changes of ±0.10 or higher while 86% of the subjects showed a change below ±0.10. CONCLUSIONS The mean Q value observed in this study agrees with the average values of a white population and contributes to slightly reduce the positive spherical aberration of the eye. For the large majority of this population, the asphericity did not show significant changes within a period of 5 to 10 years, but significant changes can be observed in some patients.
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Rodriguez-Vallejo M, Montagud D, Monsoriu JA, Ferrando V, Furlan WD. Relative Peripheral Myopia Induced by Fractal Contact Lenses. Curr Eye Res 2018; 43:1514-1521. [PMID: 30089428 DOI: 10.1080/02713683.2018.1507043] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
PURPOSE To assess the peripheral refraction induced by Fractal Contact Lenses (FCLs) in myopic eyes by means of a two-dimensional Relative Peripheral Refractive Error (RPRE) map. MATERIALS AND METHODS This study involved 26 myopic subjects ranging from -0.50 D to -7.00 D. FCLs prototypes were custom-manufactured and characterized. Corneal topographies were taken in order to assess correlations between corneal asphericity and lens decentration. Two-dimensional RPREs were measured with an open-field autorefractor at 67 points, covering the central 60 × 30 degrees of the visual field. The bidimensional RPRE vector components: M, J0 and J45 of the difference between the values obtained with and without the FCLs in the eye were obtained. Additionally, the FCL-induced peripheral refraction in tangential and sagittal planes was computed along the horizontal meridian. RESULTS Induced by the FCLs, significant differences for all vector components were found in the peripheral retina. FCLs were decentered a mean of 0.7 ± 0.19 mm to the temporal cornea. The two-dimensional RPRE maps manifested the FCLs decentration. In particular, M varied asymmetrically between nasal and temporal retina after fitting the FCLs with a significant increment of the myopic shift beyond 10º (p < 0.05). No correlations were found between the amount of lens decentration and the asphericity of the cornea along temporal and nasal sides. However, significant correlations were found between the corneal asphericity and vector components of the RPRE in naked eyes. FCLs produced an increasing myopic shift in tangential and sagittal power errors along the horizontal meridian. CONCLUSIONS As predicted by ray-tracing simulations, FCLs fitted in myopic eyes produce a myopic shift of the RPRE. The two-dimensional RPRE maps show information about the lens performance that is hidden in the conventional one-dimensional meridional representations.
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Affiliation(s)
| | - Diego Montagud
- b Centro de Tecnologías Físicas , Universitat Politècnica de València , Valencia , Spain
| | - Juan A Monsoriu
- b Centro de Tecnologías Físicas , Universitat Politècnica de València , Valencia , Spain
| | - Vicente Ferrando
- c Departamento de Óptica , Universitat de València , Burjassot , Spain
| | - Walter D Furlan
- c Departamento de Óptica , Universitat de València , Burjassot , Spain
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Short-Term and Long-Term Changes in Corneal Power Are Not Correlated With Axial Elongation of the Eye Induced by Orthokeratology in Children. Eye Contact Lens 2018; 44:260-267. [DOI: 10.1097/icl.0000000000000313] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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Chen J, Jing Q, Tang Y, Qian D, Lu Y, Jiang Y. Corneal Curvature, Astigmatism, and Aberrations in Marfan Syndrome with Lens Subluxation: Evaluation by Pentacam HR System. Sci Rep 2018; 8:4079. [PMID: 29511238 PMCID: PMC5840414 DOI: 10.1038/s41598-018-22358-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/21/2018] [Indexed: 11/25/2022] Open
Abstract
Marfan syndrome (MFS) is associated with abnormalities of corneal biometric characteristics. We conducted a retrospective case-control study including 55 eyes of the MFS patients with lens subluxation and 53 normal eyes of the control subjects to evaluate the corneal curvature, astigmatism and aberrations using a rotating Scheimpflug camera (Pentacam HR). Compared with the control group, the anterior, posterior, and total corneal curvature were flatter in the MFS group. The anterior and total corneal astigmatism were higher in the MFS patients, whereas the posterior corneal astigmatism was not significantly different between the two groups. Regarding the total corneal aberrations, the root mean square (RMS) aberrations, RMS higher-order aberrations and RMS lower-order aberrations increased, whereas the spherical aberration decreased in the MFS patients. Corneal parameters had potential diagnostic values for MFS patients with lens subluxation and the more reasonable cutoffs were the values of corneal curvature <41.35 D, corneal astigmatism >0.85 D and spherical aberration <0.188 μm. Corneal biometric characteristics of MFS patients with lens subluxation include decreased corneal curvature, higher corneal astigmatism, larger corneal aberrations, and lower spherical aberration. Corneal curvature, corneal astigmatism, and spherical aberration are better diagnostic tools for suspicious 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.,Key Laboratory of Myopia of State Health Ministry, and 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.,Key Laboratory of Myopia of State Health Ministry, and 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.,Key Laboratory of Myopia of State Health Ministry, and Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China
| | - Dongjin Qian
- Department of Ophthalmology and Vision Science, Eye Ear Nose and Throat Hospital of Fudan University, Shanghai, China.,Key Laboratory of Myopia of State Health Ministry, and 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.,Key Laboratory of Myopia of State Health Ministry, and 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. .,Key Laboratory of Myopia of State Health Ministry, and Key Laboratory of Visual Impairment and Restoration of Shanghai, Shanghai, China.
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Dai ML, Wang QM, Lin ZS, Yu Y, Huang JH, Savini G, Zhang J, Wang L, Xu CC. Posterior corneal surface differences between non-laser in situ keratomileusis (LASIK) and 10-year post-LASIK myopic eyes. Acta Ophthalmol 2018; 96:e127-e133. [PMID: 29064187 DOI: 10.1111/aos.13532] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Accepted: 06/25/2017] [Indexed: 11/27/2022]
Abstract
PURPOSE To evaluate the posterior corneal surface differences between non-laser in situ keratomileusis (LASIK) and 10-year post-LASIK myopic eyes. METHODS The study included 130 eyes from 65 patients, who were treated with myopic LASIK 10 years ago. In addition, 130 eyes from 65 unoperated myopic patients of matching present age and preoperative refraction were divided into control group. Data on the posterior corneal surface and anterior chamber were obtained from Pentacam software and compared between the groups. Postoperative visual acuity (VA) and refractive error were also analysed. RESULTS The mean preoperative spherical equivalent (SE) was -6.99 ± 1.78 dioptre (D) in the LASIK group. Ten years after surgery, the mean SE was -0.45 ± 1.22 D, the efficacy index was 0.98, and the safety index was 1.01. The posterior corneal elevations of the LASIK group at 2 mm corneal diameter were significantly lower than those of the control group. However, posterior corneal elevations at 6 mm corneal diameter were higher in the LASIK group than the controls (p < 0.01 for all). The mean Q-values of posterior corneal surface demonstrated significant positive direction compared to that of control eyes at 6 and 7 mm corneal diameters (p < 0.05 for both). At the thinnest point of the cornea, the anterior chamber depths were shallower in the LASIK group than in controls. Meanwhile, the anterior chamber volumes (ACV) were smaller in the LASIK group than in the control group. CONCLUSION Our results demonstrated that the posterior corneal surface tends to show signs of central flattening and peripheral steepening 10 years after myopic LASIK surgery compared to that of non-operated myopic eyes.
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Affiliation(s)
- Ma-Li Dai
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | - Qin-mei Wang
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | - Zu-Shun Lin
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | - Ye Yu
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | - Jin-hai Huang
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | | | - Jia Zhang
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | - Ling Wang
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
| | - Chen-chen Xu
- School of Ophthalmology and Optometry and Eye Hospital; Wenzhou Medical University; Wenzhou Zhejiang China
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Arba Mosquera S, de Ortueta D, Verma S. The art of nomograms. EYE AND VISION 2018; 5:2. [PMID: 29417088 PMCID: PMC5784507 DOI: 10.1186/s40662-018-0096-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Accepted: 01/08/2018] [Indexed: 11/10/2022]
Abstract
Background To retrospectively analyse strategies for adjusting refractive surgery plans with reference to the preoperative manifest refraction. Methods We constructed seven nomograms based on the refractive outcomes (sphere, cylinder, axis [SCA]) of 150 consecutive eyes treated with laser in situ keratomileusis for myopic astigmatism. We limited the initial data to the SCA of the manifest refraction. All nomograms were based on the strategy: if for x diopters (D) of attempted metric, y D is achieved; we can reverse this sentence and state for achieving y D of change in the metric, x D will be planned. The effects of the use of plus or minus astigmatism notation, spherical equivalent, sphere, principal meridians notation, cardinal and oblique astigmatism, and astigmatic axis were incorporated. Results All nomograms detected subtle differences in the spherical component (p < 0.0001). Nomograms 5 and 7 (using power vectors) and 6 (considering axis shifts) detected significant astigmatic differences (nomogram 5, p < 0.001; nomogram 6, p < 0.05; nomogram 7, p < 0.005 for cardinal astigmatism, p = 0.1 for oblique astigmatism). We observed mild clinically relevant differences (~ 0.5 D) in sphere or astigmatism among the nomograms; differences of ~ 0.25 D in the proposals for sphere or cylinder were not uncommon. All nomograms suggested minor improvements versus actual observed outcomes, with no clinically relevant differences among them. Conclusions All nomograms anticipated minor improvements versus actual observed outcomes without clinically relevant differences among them. The minimal uncertainties in determining the manifest refraction (~ 0.6 D) are the major limitation to improving the accuracy of refractive surgery nomograms.
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Affiliation(s)
- Samuel Arba Mosquera
- 1Recognized Research Group in Optical Diagnostic Techniques, University of Valladolid, Valladolid, Spain.,SCHWIND eye-tech-solutions, Mainparkstr. 6-10, D-63801 Kleinostheim, Germany.,3Department of Ophthalmology and Sciences of Vision, University of Oviedo, Oviedo, Spain
| | | | - Shwetabh Verma
- SCHWIND eye-tech-solutions, Mainparkstr. 6-10, D-63801 Kleinostheim, Germany.,5Experimental Radiation Oncology, University Medical Center Mannheim, Heidelberg University, Heidelberg, Germany.,6Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Heidelberg, Germany.,7Central Institute for Computer Engineering (ZITI), Heidelberg University, Heidelberg, Germany
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Visual outcomes following Descemet stripping automated endothelial keratoplasty for corneal endothelial dysfunction. Eur J Ophthalmol 2017; 27:513-519. [PMID: 28574139 DOI: 10.5301/ejo.5000958] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/08/2017] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To assess objective and subjective visual outcomes achieved by patients with corneal endothelial dysfunction who have undergone surgical treatment with Descemet stripping automated endothelial keratoplasty (DSAEK). METHODS A total of 40 eyes of 36 patients with corneal endothelial dysfunction underwent DSAEK. All were followed up for 1 year. Visual acuity (VA; logMAR), mean endothelial cell density (MCD; via noncontact specular microscopy), and topography assessment were performed at baseline (preoperatively). Visual acuity and topography measurement were repeated at postoperative year 1. Subjective assessment of visual quality was evaluated using the National Eye Institute Visual Function Questionnaire (NEI-VFQ). RESULTS Preoperative best-corrected VA (BCVA) was 1.29 ± 0.53 logMAR with mean optical correction of -0.33 ± 1.74 D. Postoperative BCVA, assessed after a mean of 10.8 ± 2.1 months, showed mean line gain of 7.11 ± 4.8 logMAR, with optical correction of +1.17 ± 1.54 D. Mean 6-month postoperative pachymetry was 598.2 ± 72.3 µm. Three patients experienced premature graft detachment, requiring repositioning via injection of a sterile air bubble. No other adverse events were observed. Significant improvement (p<.05 for all) in general, near, and far vision, ocular pain, difficulty in carrying out daily tasks, dependency, social life, and mental health were reflected by NEI-VFQ scores at 10.4 ± 2.1 months postoperatively versus preoperatively. No significant correlation was noted between postoperative VA line gain and NEI-VFQ-25 questionnaire score (p>0.05). CONCLUSIONS Descemet stripping automated endothelial keratoplasty treatment may restore corneal clarity, improve VA, and increase vision-related quality of life in patients with advanced endothelial dysfunction. Further large-scale study is needed to corroborate these findings.
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Savini G, Hoffer KJ, Barboni P, Schiano Lomoriello D, Ducoli P. Corneal Asphericity and IOL Power Calculation in Eyes With Aspherical IOLs. J Refract Surg 2017; 33:476-481. [DOI: 10.3928/1081597x-20170504-05] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2017] [Accepted: 04/28/2017] [Indexed: 11/20/2022]
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Aberration-free intraocular lenses - What does this really mean? Z Med Phys 2017; 27:255-259. [PMID: 28476316 DOI: 10.1016/j.zemedi.2017.03.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 03/29/2017] [Indexed: 11/20/2022]
Abstract
BACKGROUND So-called aberration-free intraocular lenses (IOLs) are well established in modern cataract surgery. Usually, they are designed to perfectly refract a collimated light beam onto the focal point. METHODS We show how much aberration can be expected with such an IOL in a convergent light beam such as that found anterior to the human cornea. Additionally, the aberration in a collimated beam is estimated for an IOL that has no aberrations in the convergent beam. The convergent beam is modelled as the pencil of rays corresponding to the spherical wavefront resulting from a typical corneal power of 43m-1. The IOLs are modelled as infinitely thin phase plates with 20m-1 optical power placed 5mm behind the cornea. Their aberrations are reported in terms of optical path length difference and longitudinal spherical aberration (LSA) of the marginal rays, as well as nominal spherical aberration (SA) calculated based on a Zernike representation of the wavefront-error at the corneal plane within a 6mm aperture. RESULTS The IOL designed to have no aberrations in a collimated light beam has an optical path length difference of -1.8μm, and LSA of 0.15m-1 in the convergent beam of a typical eye. The corresponding nominal SA is 0.065μm. The IOL designed to have no aberrations in a convergent light beam has an optical path length difference of 1.8μm, and LSA of -0.15m-1 in the collimated beam. CONCLUSIONS An IOL designed to have no aberrations in a collimated light beam will increase the SA of a patient's eye after implantation.
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Comparison of Corneal Power and Astigmatism between Simulated Keratometry, True Net Power, and Total Corneal Refractive Power before and after SMILE Surgery. J Ophthalmol 2017; 2017:9659481. [PMID: 28421140 PMCID: PMC5381197 DOI: 10.1155/2017/9659481] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Accepted: 02/16/2017] [Indexed: 11/25/2022] Open
Abstract
Purpose. To compare the mean corneal power (Km) and total astigmatism (Ka) estimated by three methods: simulated keratometry (simK), true net power (TNP), and total corneal refractive power (TCRP) before and after femtosecond laser small incision lenticule extraction (SMILE) surgery. Methods. A retrospective, cross-sectional study. SimK, TNP, and TCRP from a Scheimpflug analyzer were obtained from 144 patients before and 6 months after SMILE surgery. Km and Ka were recorded as the mean of individual paracentral rings of 1.0 to 8.0 mm (R1 to R8). The surgically induced changes in Km (delta-simK, delta-TNP, and delta-TCRP) and Ka (delta-simKa, delta-TNPa, and delta-TCRPa) were compared to the changes in spherical equivalent of the cycloplegic refraction (delta-SE) and astigmatism (delta-RA). Results. Preoperatively, astigmatism values were greatest with simKa from R1 to R5 and greatest with TCRPa from R6 to R8. Astigmatism values were smallest with TNPa from R1 to R7. Postoperatively, astigmatism values were greatest with simKa from R1 to R5 and greatest with TCRPa from R6 to R8. Delta-TCRP3 and Delta-TCRP4 matched delta-SE most closely, and delta-TCRPa3 matched delta-RA most closely. Conclusions. TCRP proved to be the most accurate method in estimating corneal power and astigmatism both before and after SMILE surgery.
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Damian A, Seitz B, Langenbucher A, Eppig T. Optical coherence tomography-based topography determination of corneal grafts in eye bank cultivation. JOURNAL OF BIOMEDICAL OPTICS 2017; 22:16001. [PMID: 28055053 DOI: 10.1117/1.jbo.22.1.016001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 12/05/2016] [Indexed: 06/06/2023]
Abstract
Vision loss due to corneal injuries or diseases can be treated by transplantation of human corneal grafts (keratoplasty). However, quality assurance in retrieving and cultivating the tissue transplants is confined to visual and microbiological testing. To identify previous refractive surgery or morphological alterations, an automatic, noncontact, sterile screening procedure is required. Twenty-three corneal grafts have been measured in organ culture with a clinical spectral-domain optical coherence tomographer. Employing a biconic surface fit with 10 degrees of freedom, the radii of curvature and conic constants could be estimated for the anterior and posterior corneal surfaces. Thereupon, central corneal thickness, refractive values, and astigmatism have been calculated. Clinical investigations are required to elaborate specific donor–host matching in the future.
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Affiliation(s)
- Angela Damian
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Street 100, Building 22, 66421 Homburg/Saar, Germany
| | - Berthold Seitz
- Saarland University Medical Center (UKS), Department of Ophthalmology, Kirrberger Street 100, Building 22, 66421 Homburg/Saar, Germany
| | - Achim Langenbucher
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Street 100, Building 22, 66421 Homburg/Saar, Germany
| | - Timo Eppig
- Saarland University, Institute of Experimental Ophthalmology, Kirrberger Street 100, Building 22, 66421 Homburg/Saar, Germany
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Maier F, Wahl S, Schaeffel F. Off-axis astigmatism in the isolated chicken crystalline lens. Vision Res 2016; 129:61-68. [PMID: 27923771 DOI: 10.1016/j.visres.2016.10.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 10/26/2016] [Accepted: 10/26/2016] [Indexed: 11/30/2022]
Abstract
The chicken eye was previously found to have little off-axis astigmatism which is not explained by its special corneal shape but rather by the optical properties of the crystalline lens. To learn more about lens design, we studied off-axis astigmatism in the chicken lens in situ and compared it to a glass lens of similar power but with homogenous refractive index. After euthanasia, enucleated eye balls were cut in the equatorial plane right behind the scleral ossicles. The anterior segment was placed in a water-filled chamber. Several thin laser beams were projected in two perpendicular meridians through the lens under various eccentricities and the focal lengths were determined. Off-axis astigmatism across the horizontal visual field was determined as the differences in power in the two meridians. The same procedure was used for the glass lens. On-axis, the chicken crystalline lens had slightly more power in the vertical than in the horizontal meridian (-2.8±0.7D (SEM)). Astigmatism flipped sign and increased with eccentricity to reach +6.1±2.1D (SEM) at 33.5deg off-axis, as expected from off-axis astigmatism. Even though this value appears high, it was still 2.5 times lower than in the glass lens. A ZEMAX model of a lens with a homogeneous index and with surface profiles taken of the natural chicken lens revealed even higher levels of off-axis astigmatism. Obviously, the natural chicken lens displays much less off-axis astigmatism than a glass lens with similar power. Since its shape does not explain the low off-axis astigmatism, it must be due to a refined internal refractive index structure.
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Affiliation(s)
- Felix Maier
- Section of Neurobiology of the Eye, Ophthalmic Research Institute, Elfriede-Aulhorn-Straße 5-7, 72076 Tübingen, Germany
| | - Siegfried Wahl
- ZEISS Vision Science Lab, Ophthalmic Research Institute, Elfriede-Aulhorn-Straße 5-7, 72076 Tübingen, Germany
| | - Frank Schaeffel
- Section of Neurobiology of the Eye, Ophthalmic Research Institute, Elfriede-Aulhorn-Straße 5-7, 72076 Tübingen, Germany.
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Yazdani N, Shahkarami L, OstadiMoghaddam H, Ehsaei A. Topographic determination of corneal asphericity as a function of age, gender, and refractive error. Int Ophthalmol 2016; 37:807-812. [PMID: 27600511 DOI: 10.1007/s10792-016-0334-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Accepted: 08/30/2016] [Indexed: 11/30/2022]
Abstract
The aim of the study is to evaluate corneal asphericity in three diameters of 5, 6, and 7 mm, and to assess the effect of age, refractive error, and gender on asphericity. The study included 500 healthy subjects with a mean ± SD age of 29.51 ± 11.53 years. All analyses were based on the right eyes of the patients. Topographic data were analyzed using Oculus Keratograph 4. Mean ± SD corneal asphericity values of the study population in 5, 6, and 7 mm diameters were -0.21 ± 0.11, -0.24 ± 0.10, and -0.27 ± 0.11, respectively. The anterior corneal surface asphericity showed no correlation with either age, gender, or refractive error. The corneal asphericity shows a tendency for an increase with diameter and asphericity does not have a significant correlation with any factors of age, gender, and refractive error.
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Affiliation(s)
- Negareh Yazdani
- Department of Optometry, Mashhad University of Medical Sciences, Parastar 2, Ahmadabad Avenue, Mashhad, Iran
- Refractive Errors Research Center, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Leila Shahkarami
- Department of Optometry, Mashhad University of Medical Sciences, Parastar 2, Ahmadabad Avenue, Mashhad, Iran
| | - Hadi OstadiMoghaddam
- Department of Optometry, Mashhad University of Medical Sciences, Parastar 2, Ahmadabad Avenue, Mashhad, Iran
- Refractive Errors Research Center, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Asieh Ehsaei
- Department of Optometry, Mashhad University of Medical Sciences, Parastar 2, Ahmadabad Avenue, Mashhad, Iran.
- Refractive Errors Research Center, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.
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Changes in posterior corneal elevations after combined transepithelial photorefractive keratectomy and accelerated corneal collagen cross-linking: retrospective, comparative observational case series. BMC Ophthalmol 2016; 16:139. [PMID: 27502494 PMCID: PMC4977714 DOI: 10.1186/s12886-016-0320-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 08/01/2016] [Indexed: 12/03/2022] Open
Abstract
Background To compare the changes in anterior and posterior corneal elevations after combined transepithelial photorefractive keratectomy (PRK) and accelerated corneal collagen cross-linking (CXL) and after PRK. Methods Medical records of 82 eyes of 44 patients undergoing either combined transepithelial PRK and CXL (PRK-CXL group) or transepithelial PRK (PRK group) were examined retrospectively. Changes in anterior and posterior corneal elevations were calculated by fitting an 8.0-mm diameter best-fit sphere and best-fit toric ellipsoid (BFTE) to the corneal shape with a fixed eccentricity of 0.4 using Scheimpflug tomography (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany) preoperatively and 6 months postoperatively. Results In anterior corneal elevation, both groups demonstrated a similar trend of a forward displacement of peripheral anterior corneal surface and a backward displacement of central anterior corneal surface. In posterior corneal elevation, a forward displacement of peripheral posterior corneal surface was induced in both groups, along with a backward displacement of central posterior corneal surface, regardless of the calculation method. The magnitudes of displacement of peripheral and central posterior corneal surfaces were significantly smaller in the PRK-CXL group than in the PRK group. Moreover, the PRK-CXL group showed a backward displacement of posterior corneal surface at maximum corneal elevations when the BFTE was used as the reference surface. Conclusions Transepithelial PRK combined with prophylactic CXL significantly reduced the magnitudes of displacement of peripheral and central posterior corneal surfaces, with the radius of the BFTE was set to 8.0-mm on the Scheimpflug tomography system.
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Zocher MT, Rozema JJ, Oertel N, Dawczynski J, Wiedemann P, Rauscher FG. Biometry and visual function of a healthy cohort in Leipzig, Germany. BMC Ophthalmol 2016; 16:79. [PMID: 27268271 PMCID: PMC4895813 DOI: 10.1186/s12886-016-0232-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 05/05/2016] [Indexed: 11/23/2022] Open
Abstract
Background Cross-sectional survey of ocular biometry and visual function in healthy eyes across the life span of a German population aged 20 to 69 years (n = 218). Subject number in percent per age category reflected the percentage within the respective age band of the population of Leipzig, Germany. Methods Measurements obtained: subjective and objective refraction, best-corrected visual acuity, accommodation, contrast sensitivity, topography and pachymetry with Scheimpflug camera, axial length with non-contact partial coherence interferometry, and spectral-domain optical coherence tomography of the retina. Pearson correlation coefficients with corresponding p-values were given to present interrelationships between stature, biometric and refractive parameters or their associations with age. Two-sample T-tests were used to calculate gender differences. The area under the logarithmic contrast sensitivity function (AULCSF) was calculated for the analysis of contrast sensitivity as a single figure across a range of spatial frequencies. Results The results of axial length (AL), anterior chamber depth (ACD) and anterior chamber volume (ACV) differed as a function of the age of the participants (rho (p value): AL −0.19 (0.006), ACD −0.56 (< 0.001), ACV-0.52 (< 0.001)). Longer eyes had deeper ACD (AL:ACD 0.62 (< 0.001), greater ACV (AL:ACV 0.65 (< 0.001) and steeper corneal radii (AL:R1ant; R2ant; R1post; R2post 0.40; 0.35; 0.36; 0.36 (all with (< 0.001)). Spherical equivalent was associated with age (towards hyperopia: 0.34 (< 0.001)), AL (−0.66 (< 0.001)), ACD (−0.52 (< 0.001)) and ACV (−0.46 (< 0.001)). Accommodation was found lower for older subjects (negative association with age, r = −0.82 (< 0.001)) and contrast sensitivity presented with smaller values for older ages (AULCSF −0.38, (< 0.001)), no change of retinal thickness with age. 58 % of the study cohort presented with a change of refractive correction above ±0.50 D in one or both eyes (64 % of these were habitual spectacle wearers), need for improvement was present in the young age-group and for older subjects with increasing age. Conclusion Biometrical data of healthy German eyes, stratified by age, gender and refractive status, enabled cross-comparison of all parameters, providing an important reference database for future patient-based research and specific in-depth investigations of biometric data in epidemiological research. Trial registration ClinicalTrials.gov # NCT01173614 July 28, 2010
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Affiliation(s)
- Maria Teresa Zocher
- Department of Ophthalmology, Leipzig University Hospital, Liebigstrasse 10-14, 04103, Leipzig, Germany
| | - Jos J Rozema
- Department of Ophthalmology, Antwerp University Hospital, Wilrijkstraat 10, 2650, Edegem, Belgium.,Department of Medicine and Health Science, University of Antwerp, Universiteitsplein 1, 2610, Wilrijk, Belgium
| | - Nicole Oertel
- Department of Ophthalmology, Leipzig University Hospital, Liebigstrasse 10-14, 04103, Leipzig, Germany
| | - Jens Dawczynski
- Department of Ophthalmology, Leipzig University Hospital, Liebigstrasse 10-14, 04103, Leipzig, Germany
| | - Peter Wiedemann
- Department of Ophthalmology, Leipzig University Hospital, Liebigstrasse 10-14, 04103, Leipzig, Germany
| | - Franziska G Rauscher
- Department of Ophthalmology, Leipzig University Hospital, Liebigstrasse 10-14, 04103, Leipzig, Germany.
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Relationship of corneal asphericity to intraocular lens power calculations after myopic laser in situ keratomileusis. J Cataract Refract Surg 2016; 42:703-9. [DOI: 10.1016/j.jcrs.2016.01.050] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 01/23/2016] [Accepted: 01/26/2016] [Indexed: 11/18/2022]
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Savini G, Hoffer KJ, Schiano-Lomoriello D, Ducoli P. Estimating the Preoperative Corneal Power With Scheimpflug Imaging in Eyes That Have Undergone Myopic LASIK. J Refract Surg 2016; 32:332-6. [DOI: 10.3928/1081597x-20160225-03] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/15/2016] [Indexed: 11/20/2022]
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An Analysis of Factors Influencing Quality of Vision After Big-Bubble Deep Anterior Lamellar Keratoplasty in Keratoconus. Am J Ophthalmol 2016; 162:66-73.e2. [PMID: 26589583 DOI: 10.1016/j.ajo.2015.11.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 11/09/2015] [Accepted: 11/09/2015] [Indexed: 11/24/2022]
Abstract
PURPOSE To identify causes of reduced visual acuity and contrast sensitivity after big-bubble deep anterior lamellar keratoplasty (DALK) in keratoconus. DESIGN Prospective interventional case series. METHODS This study included 36 eyes in 36 patients with keratoconus who underwent DALK using the big-bubble technique. A bare Descemet membrane was achieved in all cases. Univariate analyses and multiple linear regression were used to investigate recipient-, donor-, and postoperative-related variables capable of influencing the postoperative quality of vision, including best spectacle-corrected visual acuity (BSCVA) and contrast sensitivity. RESULTS The mean patient age was 27.7 ± 6.9 years, and the patients were followed for 24.6 ± 15.1 months postoperatively. The mean postoperative BSCVA was 0.17 ± 0.09 logMAR. Postoperative BSCVA ≥20/25 was achieved in 14 eyes (38.9%), whereas a BSCVA of 20/30, 20/40, or 20/50 was observed in 15 eyes (41.7%), 6 eyes (16.6%), and 1 eye (2.8%), respectively. Preoperative vitreous length was significantly associated with postoperative BSCVA (β = 0.02, P = .03). Donor-recipient interface reflectivity significantly influenced scotopic (β = -0.002, P = .04) and photopic (β = -0.003, P = .02) contrast sensitivity. The root mean square of tetrafoil was significantly negatively associated with scotopic (β = -0.25, P = .01) and photopic (β = -0.23, P = .04) contrast sensitivity. Recipient age, keratoconus severity, donor-related variables, recipient trephination size, and graft and recipient bed thickness were not significantly associated with postoperative visual acuity or contrast sensitivity. CONCLUSION Large vitreous length, higher-order aberrations, and surgical interface haze may contribute to poor visual outcomes after big-bubble DALK in keratoconus.
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Arba Mosquera S. Influence of corneal asphericity on refractive outcomes after cataract surgery. J Cataract Refract Surg 2015; 41:1797-8. [PMID: 26432156 DOI: 10.1016/j.jcrs.2015.05.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 05/19/2015] [Indexed: 10/23/2022]
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Molchan RP, Taylor KR, Panday VA, Caldwell MC, Reilly CD. Retrospective Analysis Comparing the Preoperative and Postoperative "Q" Values for 2 Different Lasers in Refractive Surgery. Cornea 2015; 34:1437-40. [PMID: 26356749 DOI: 10.1097/ico.0000000000000611] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To compare the presurgical and postsurgical corneal asphericity, or "Q value," between VISX Wavefront-guided treatment and Allegretto Wave Wavefront-optimized treatment in photorefractive keratectomy for the correction of myopia. METHODS This is a retrospective database analysis performed at the Joint Warfighter Refractive Surgery Center, Lackland Air Force Base, TX. All data were accessed through the Institutional Review Board-approved Joint Warfighter Refractive Surgery Center database. Fifty-one patient records (102 eyes) were reviewed to determine the change in the Q value after photorefractive keratectomy for the correction of myopia. RESULTS The average change in the Q value per diopter of treatment sphere over the entire study population was 0.12 (±0.04) for Allegretto and 0.14 (±0.04) for VISX (P = 0.004). There was no statistical difference among the preoperative and postoperative best-corrected visual acuities (BCVAs), low-contrast BCVA (BCVA 5%), or quality of vision complaints between both platforms. CONCLUSIONS Low to moderate myopic correction with the Allegretto laser was associated with a smaller change in the Q value per diopter of treatment and therefore more closely maintained the original prolate shape of the cornea when compared with VISX. No difference in the postoperative visual outcome between both groups was detected.
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Affiliation(s)
- Ryan P Molchan
- *Joint Warfighter Refractive Surgery Center, Lackland AFB, TX; and †14th Medical Operations Squadron, Columbus AFB, MS
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Abstract
PURPOSE To characterize and compare the corneal shapes and monochromatic aberrations in Chinese myopic adults with and without astigmatism. METHODS Forty-six Hong Kong Chinese aged 50 to 70 years with compound against-the-rule myopic astigmatism (n = 18) or simple myopia (n = 28) were recruited. Corneal shapes were measured by a Scheimpflug-based corneal topographer: the semimeridian corneal shape factors at the nasal, temporal, inferior, and superior corneal quadrants measured from the corneal apex to 3 mm midperiphery were analyzed. The ocular aberrations were measured by the COAS (Complete Ophthalmic Analysis System) Shack-Hartmann wavefront aberrometer; the corneal aberrations were computed using the corneal topographic map data measured by the Medmont E300 corneal topographer; and the internal aberrations were calculated from the ocular and corneal aberrations. RESULTS Compared with simple myopia, myopic astigmatism had more oblate nasal and temporal corneal shapes and showed significantly more negative Y trefoil and more positive vertical coma. The asymmetry in corneal shape along the vertical principal meridian (inferior - superior) was significantly associated with the Y trefoil and vertical coma of the cornea, suggesting that this regional asymmetry in corneal shape may contribute to the ocular aberrations. CONCLUSIONS The significant relationships found between astigmatism, corneal shapes, and monochromatic aberrations underscore the importance of taking corneal shape into account when correcting the optical defects in myopic Chinese adults with astigmatism.
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Bolaños-Jiménez R, Navas A, López-Lizárraga EP, de Ribot FM, Peña A, Graue-Hernández EO, Garfias Y. Ocular Surface as Barrier of Innate Immunity. Open Ophthalmol J 2015; 9:49-55. [PMID: 26161163 PMCID: PMC4484240 DOI: 10.2174/1874364101509010049] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 04/06/2015] [Accepted: 04/13/2015] [Indexed: 01/08/2023] Open
Abstract
Sight is one of the most important senses that human beings possess. The ocular system is a complex structure equipped with mechanisms that prevent or limit damage caused by physical, chemical, infectious and environmental factors. These mechanisms include a series of anatomical, cellular and humoral factors that have been a matter of study. The cornea is not only the most powerful and important lens of the optical system, but also, it has been involved in many other physiological and pathological processes apart from its refractive nature; the morphological and histological properties of the cornea have been thoroughly studied for the last fifty years; drawing attention in its molecular characteristics of immune response. This paper will review the anatomical and physiological aspects of the cornea, conjunctiva and lacrimal apparatus, as well as the innate immunity at the ocular surface.
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Affiliation(s)
- Rodrigo Bolaños-Jiménez
- Research Unit, Institute of Ophthalmology, Conde de Valenciana Foundation, Chimalpopoca 14, Obrera, CP 06800, Mexico City, México ; Ophthalmology Department, Regional Hospital, Adolfo López Mateos, ISSSTE, México City, México
| | - Alejandro Navas
- Research Unit, Institute of Ophthalmology, Conde de Valenciana Foundation, Chimalpopoca 14, Obrera, CP 06800, Mexico City, México ; Department of Cataract and refractive surgery, Institute of Ophthalmology, Conde de Valenciana Foundation, Mexico City, México
| | - Erika Paulina López-Lizárraga
- Department of Cataract and refractive surgery, Institute of Ophthalmology, Conde de Valenciana Foundation, Mexico City, México
| | - Francesc March de Ribot
- Department of Retina, Institute of Ophthalmology, Conde de Valenciana Foundation, Mexico City, México
| | - Alexandra Peña
- Ophthalmology Department, Regional Hospital, Adolfo López Mateos, ISSSTE, México City, México
| | - Enrique O Graue-Hernández
- Research Unit, Institute of Ophthalmology, Conde de Valenciana Foundation, Chimalpopoca 14, Obrera, CP 06800, Mexico City, México ; Department of Cataract and refractive surgery, Institute of Ophthalmology, Conde de Valenciana Foundation, Mexico City, México
| | - Yonathan Garfias
- Research Unit, Institute of Ophthalmology, Conde de Valenciana Foundation, Chimalpopoca 14, Obrera, CP 06800, Mexico City, México ; Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México, 04510. Mexico City, Mexico
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The Effect of Silicone Hydrogel Bandage Soft Contact Lens Base Curvature on Comfort and Outcomes After Photorefractive Keratectomy. Eye Contact Lens 2015; 41:77-83. [DOI: 10.1097/icl.0000000000000067] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Gatinel D, Azar DT, Dumas L, Malet J. Effect of anterior corneal surface asphericity modification on fourth-order zernike spherical aberrations. J Refract Surg 2014; 30:708-15. [PMID: 25291755 DOI: 10.3928/1081597x-20140903-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2014] [Accepted: 06/18/2014] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the theoretical influence of the change in corneal asphericity (ΔQ) on the change in fourth-order Zernike spherical aberration coefficient (ΔC(4)0) with customized aspheric refractive correction of myopia and hyperopia. METHODS The initial anterior corneal surface profile was modeled as a conic section of apical radius of curvature R0 and asphericity Q₀. The postoperative corneal profile was modeled as a conic section of apical curvature R1 and asphericity Q1, where R1 was computed from defocus D, and Q₁ selected for controlling the postoperative asphericity. The corresponding change in fourth-order spherical aberration (ΔC(0)4) was computed within a 6-mm optical zone using inner products applied to the incurred optical path changes. These calculations were repeated for different values of D, R₀, Q₀, and various intended ΔC(4)0 values. RESULTS Increasing negative spherical aberration (ΔC(4)(0) < 0) requires a change toward more negative values of asphericity (increased prolateness; ΔQ < 0) for hyperopic and low myopic corrections, but more positive values (ΔQ < 0) for high myopic correction. The larger the intended change in corneal spherical aberration (ΔC(4)(0)), the more myopic the threshold value for which the required change in asphericity, ΔQ, becomes positive. The influence of the magnitude of paraxial defocus correction is less pronounced when larger changes in C(4)(0) are intended. CONCLUSIONS These results provide a basis for controlling the direction (sign) and the magnitude of spherical aberration changes when using customized aspheric profiles of ablation.
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Abstract
PURPOSE To search for differences in corneal asphericity on the basis of ethnicity between African-American and white populations. METHODS A prospective cohort design was used to analyze corneal asphericity (Q value) data obtained by Pentacam HR (Oculus, Wetzlar, Germany) on right eyes from African-American (n = 80) and white (n = 80). Subjects were stratified by ethnicity, age, and spherical equivalent (SE) refractive error. Q values were obtained from each quadrant (superior, nasal, inferior, and temporal) and two meridians (horizontal and vertical). RESULTS The mean Q values were African-Americans -0.26 ± 0.19 and whites -0.20 ± 0.12, indicating that the eyes of African-Americans were significantly more prolate (p = 0.003) than those of whites. There was a significant difference between mean Q values for ethnic groups only in the 30- to 39-year olds (p = 0.01) and there was a lack of correlation with age in both ethnic groups. Q value contrasts by gender were only significant between males (p = 0.01). There was a lack of correlation between Q value and SE for either ethnic group. Age group contrasts between ethnic groups found significant differences for those with SE greater than 0.00 D to -3.00 D (p = 0.05) and greater than 0.00 D to +3.00 D (p = 0.05). Comparison of mean Q values in opposing meridians within and across ethnic groups were significant, although neither group showed significant differences between horizontal and vertical meridians. CONCLUSIONS Corneal asphericity as represented by mean Q value varies significantly between African-Americans and whites. The greatest differences are evident in opposing quadrants and appear to be little influenced by age, gender, or SE.
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Abstract
PURPOSE Myopia and astigmatism are highly prevalent in the Hong Kong Chinese. This study aimed to determine the effects of age and myopic astigmatism (MA) on the corneal shape factors in the Hong Kong Chinese. METHODS One hundred subjects with compound MA or emmetropia (EM) were recruited from three age groups: 10 to 15 years (n = 32), 20 to 25 years (n = 37), and 40 to 45 years (n = 31). Refractive errors were measured by noncycloplegic subjective refraction. Corneal astigmatism and corneal shape factors were measured by the Scheimpflug-based Pentacam. The effects of age and refractive errors on the whole corneal shape (mean-P) and the semimeridian corneal shapes (semi-Ps) at the nasal, temporal, superior, and inferior corneal quadrants (from corneal apex to 3 mm peripheral cornea) were analyzed. RESULTS Age had significant effects on the mean-P and semi-Ps (both p < 0.001), with both EM and MA showing less prolate corneal shapes in older age groups. Partial correlation analyses adjusted for age showed that mean-P and semi-Ps were correlated with multiple refractive-error components (Pearson r = -0.30 to -0.78, all p < 0.05), with higher correlations found along the horizontal semi-Ps in MA (Pearson r = +0.37 to -0.78, all p < 0.01). Compared with EM, MA had more prolate temporal semi-Ps in all the three age groups (p < 0.05). Strikingly, age and refractive errors also had significant impacts on the asymmetry of the corneal shape along the horizontal meridian. CONCLUSIONS Corneal shapes were influenced by age and MA in the Hong Kong Chinese. These results highlight the importance of controlling these factors when designing a study on corneal shape.
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Abstract
PURPOSE To assess the changes of the surfaces and optical properties of the cornea as a function of age. METHODS The corneal shape of 407 normal eyes of 211 subjects with ages ranging from 4 to 79 years old was determined by means of Scheimpflug imaging. These data were analyzed by fitting their elevation topographies to a general surface model, which consists of a biconic plus a Zernike polynomial expansion. The analysis includes the computation of the position and orientation of the model in the three-dimensional space to determine the orientation of the optical axis and the apex coordinates. RESULTS Both average corneal surfaces show negative conic constant plus higher order aspheric terms Z(0)(4) and Z(0)(6) are significant). These surfaces are misaligned between them and with the line of sight. Such misalignment increases with age as the cornea seems to rotate as a solid body. The apex curvature and the magnitude of the conic constant along the most curved meridian increase as well, but the largest change with age correspond to the aspheric terms Z(0)(4) and Z(0)(6). As a result, the spherical aberration (SA) of the average cornea increases with age at a rate similar to the total SA of the eye. CONCLUSIONS The average corneal surfaces are misaligned general aspheres. Corneal SA is higher than total SA, but both SAs increase with age at a similar rate. This confirms that the lens is partially compensating SA and that such compensation is preserved with aging. Misalignment and solid body rotation seem to reduce astigmatism and coma for young and middle-aged corneas.
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