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Ding L, Niu L, Shi W, Zhou X, Qian Y. Influence of corneal diameter on the accuracy of corneal tomography in patients with forme fruste keratoconus or thin corneas. Clin Exp Optom 2024:1-7. [PMID: 38227767 DOI: 10.1080/08164622.2023.2300297] [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: 10/19/2022] [Accepted: 12/22/2023] [Indexed: 01/18/2024] Open
Abstract
CLINICAL RELEVANCE The detection of subclinical ectasia is important in preoperative screening for laser-refractive surgery. Previous studies have confirmed the impact of corneal diameter on the diagnostic accuracy of several ectasia indices in tomographically normal eyes. BACKGROUND This study aimed to investigate the influence of corneal diameter on the diagnostic accuracy of Pentacam tomographic indices in eyes with forme fruste keratoconus (FFKC) and thin corneas. METHODS One hundred and one eyes of 101 patients with FFKC (FFKC group), 104 eyes of 104 patients with a corneal thickness <490 μm (thin cornea group), and 200 eyes of 200 normal subjects (normal group) were analysed in the study. Pentacam ectasia indices were compared between the groups. RESULTS The results of multiple linear regression analysis showed that the standardised coefficients for corneal diameter and overall deviation of normality (BAD-D) were -0.386, -0.552, and -0.552 for the FFKC, thin cornea, and normal groups, respectively (p < 0.001). Comparing for the classifications (normal versus abnormal) of the individual indices demonstrated that for corneal diameters ≤11.9 mm, the rates of abnormal cases were significantly higher in the FFKC group than in the normal group for seven indices and in the thin cornea group than normal group for nine indices. For corneal diameters >11.9 mm, the rates of abnormal cases were higher in the FFKC than normal group for three indices and higher in the thin cornea group than normal group for seven indices. CONCLUSION Belin/Ambrosio Enhanced Ectasia display indices may underestimate the risk of ectasia in patients with large corneas, especially those with FFKC.
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Affiliation(s)
- Lan Ding
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University and NHC Key Laboratory of Myopia (Fudan University), Shanghai, China
| | - Lingling Niu
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University and NHC Key Laboratory of Myopia (Fudan University), Shanghai, China
| | - Wanru Shi
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University and NHC Key Laboratory of Myopia (Fudan University), Shanghai, China
| | - Xingtao Zhou
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University and NHC Key Laboratory of Myopia (Fudan University), Shanghai, China
| | - Yishan Qian
- Department of Ophthalmology, Eye and ENT Hospital, Fudan University and NHC Key Laboratory of Myopia (Fudan University), Shanghai, China
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Jiménez-Santos M, Sáenz-Francés F, Rodríguez-Quet O, Cerván-Lopez I, Santos-Bueso E, Martinez-de-la-Casa JM, Jañez-Escalada L. Dependence of corneal hysteresis on non-central corneal thickness in healthy subjects. J Fr Ophtalmol 2023; 46:866-872. [PMID: 37085371 DOI: 10.1016/j.jfo.2022.12.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/18/2022] [Accepted: 12/20/2022] [Indexed: 04/23/2023]
Abstract
OBJECTIVE To evaluate the dependence of corneal hysteresis (CH) on non-central corneal thickness. METHODS Cross-sectional study of 1561 eyes of 1561 healthy volunteers with IOP less than 21mmHg, open angles on gonioscopy and no prior eye surgeries or local or systemic diseases. Pentacam-Scheimpflug technology was employed to segment the cornea into 6 circular zones centered on the apex (zones 1-6) and to determine the mean corneal thickness of these areas. CH was measured with ORA. Univariate and multivariate linear regression models adjusted for age and sex were created to model the dependence of CH on corneal thickness in zones 1 to 6. RESULTS In the univariate linear regression models, we found that CH was dependent on mean corneal thickness of zone 1 (B=0,004; R2=0.95%; P<0.001), zone 2 (B=0,004; R2=0.57%; P=0.002), zone 4 (B=0,005; R2=1.50%; P<0.001) and zone 6 (B=0,003; R2=0.92%; P<0.001). Similar results were obtained in the multivariate model (R2=3.46%; P<0.001). CONCLUSION This study suggests a significant dependence of CH on non-central corneal thickness. The model of corneal thickness segmentation into circular zones centered on the corneal apex is able to explain 3.47% of the variation in CH measurements.
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Affiliation(s)
- M Jiménez-Santos
- Ophthalmology Department, Hospital Clinico San Carlos, Madrid, Spain
| | - F Sáenz-Francés
- Ophthalmology Department, Hospital Clinico San Carlos, Madrid, Spain
| | - O Rodríguez-Quet
- Ophthalmology Department, Hospital Clinico San Carlos, Madrid, Spain.
| | - I Cerván-Lopez
- Centre d'ophthalmologie, Jardin des Buis, Carpentras, France
| | - E Santos-Bueso
- Ophthalmology Department, Hospital Clinico San Carlos, Madrid, Spain
| | | | - L Jañez-Escalada
- Instituto de Tecnología del Conocimiento, Universidad Complutense de Madrid, Madrid, Spain
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Eliasy A, Lopes BT, Wang J, Abass A, Vinciguerra R, Vinciguerra P, Bao FJ, Elsheikh A. Introduction and Clinical Validation of an Updated Biomechanically Corrected Intraocular Pressure bIOP (v2). Curr Eye Res 2022; 48:382-391. [PMID: 36581595 DOI: 10.1080/02713683.2022.2162087] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
PURPOSE To improve the stability of the Corvis ST biomechanically-corrected intraocular pressure measurements (bIOP) after refractive surgery and its independence of corneal biomechanics. METHODS A parametric study was carried out using numerical models simulating the behavior of the eye globe under the effects of IOP and Corvis ST external air pressure and used to develop a new algorithm for bIOP; bIOP(v2). It was tested on 528 healthy participants to evaluate correlations with CCT and age. Its ability to compensate for the geometrical changes was tested in 60 LASIK and 80 SMILE patients with six months follow up. The uncorrected Corvis ST IOP (CVS-IOP) and the two versions of biomechanically corrected IOP; bIOP(v1) and bIOP(v2), were compared. RESULTS In the healthy dataset, bIOP(v2) had weak and non-significant correlation with both CCT (R = -0.048, p = .266) and age (R = 0.085, p = .052). For bIOP(v1), the correlation was non-significant with CCT (R = -0.064, p = .139) but significant with age (R = -0.124, p < .05). In both LASIK and SMILE groups, the median change in bIOP(v2) following surgery was below 1 mmHg at follow-up stages and the interquartile range was smaller than both bIOP(v1) and CVS-IOP. CONCLUSION The bIOP(v2) algorithm performs better than bIOP(v1) and CVS-IOP in terms of correlation with CCT and age. The bIOP(v2) also demonstrated the smallest variation after LASIK and SMILE refractive surgeries indicating improved ability to compensate for geometrical changes.
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Affiliation(s)
- Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, UK
| | - Bernardo T Lopes
- School of Engineering, University of Liverpool, Liverpool, UK.,Department of Ophthalmology, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Junjie Wang
- Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Ahmed Abass
- School of Engineering, University of Liverpool, Liverpool, UK.,Department of Production Engineering and Mechanical Design, Faculty of Engineering, Port Said University, Egypt
| | - Riccardo Vinciguerra
- School of Engineering, University of Liverpool, Liverpool, UK.,Department of Opthalmology, Humanitas San Pio X Hospital, Milan, Italy
| | - Paolo Vinciguerra
- Department of Biomedical Sciences, Humanitas University, Milan, Italy.,Humanitas Clinical and Research Center, IRCCS, Rozzano, Italy
| | - Fang-Jun Bao
- Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK.,Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China.,NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, UK
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Jóźwik A, Przeździecka-Dołyk J, Wałek E, Czerniak M, Asejczyk M. Corneal Behavior during Tonometer Measurement during the Water Drinking Test in Eyes with XEN GelStent in Comparison to Non-Implanted Eyes. J Clin Med 2022; 11:jcm11112962. [PMID: 35683350 PMCID: PMC9181234 DOI: 10.3390/jcm11112962] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Revised: 05/15/2022] [Accepted: 05/18/2022] [Indexed: 11/16/2022] Open
Abstract
Biomechanics of the cornea have significant influences on the non-contact measurement of the intraocular pressure. The corneal behaviour during tonometry is a fundamental factor in estimating its value. The aim of the study was to analyse the behaviour of the cornea during tonometric measurement with the forced change in intraocular pressure during the water drinking test. Ocular Response Analyser (Reichert) was used to the measurement. Besides four basic parameters connected with intraocular pressure (IOPg, IOPcc) and biomechanics (corneal hysteresis CH and corneal resistance factor (CRF), other parameters representing the behaviour of the cornea during a puff of air were analysed. There were 47 eyes included in the study, including 27 eyes with a XEN GelStent implanted and 20 without it. The eyes of people with monocular implementation were the reference group. The values of analysed parameters were compared before and after 10, 25, 40, and 55 min after drinking the water. The intraocular pressure increased by 2.4 mmHg (p < 0.05) for eyes with a XEN stent and 2.2 mmHg for eyes without a stent (p < 0.05) in the tenth minute after drinking of water. This change caused a decreasing of corneal hysteresis (p < 0.05) without significant changes in the corneal resistance factor (p > 0.05). Corneal hysteresis changed similarly in the reference group and the group with a XEN GelStent. The analysis of additional parameters showed a difference in the behaviour of the cornea in eyes with a XEN GelStent in comparison to the corneas of eyes without a stent. This was particularly visible in the analysis of the cornea’s behaviour during the second applanation, when the cornea returns to its baseline state after deformation caused by air puff tonometry.
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Affiliation(s)
- Agnieszka Jóźwik
- Department of Optics and Photonics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland; (A.J.); (M.C.); (M.A.)
| | - Joanna Przeździecka-Dołyk
- Department of Optics and Photonics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland; (A.J.); (M.C.); (M.A.)
- Department of Ophthalmology, Wroclaw Medical University, Borowska 213, 50-556 Wrocław, Poland;
- Correspondence:
| | - Ewa Wałek
- Department of Ophthalmology, Wroclaw Medical University, Borowska 213, 50-556 Wrocław, Poland;
| | - Magdalena Czerniak
- Department of Optics and Photonics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland; (A.J.); (M.C.); (M.A.)
| | - Magdalena Asejczyk
- Department of Optics and Photonics, Wrocław University of Science and Technology, Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland; (A.J.); (M.C.); (M.A.)
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Razeghinejad MR, Farsiani AR, Salout R, Owji N, Masoumpour M, Kharmandar A, Zamani M. Corneal biomechanical properties in hyperthyroidism and thyroid eye disease. Saudi J Ophthalmol 2021; 34:251-255. [PMID: 34527867 PMCID: PMC8409357 DOI: 10.4103/1319-4534.322605] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 04/21/2020] [Accepted: 07/06/2020] [Indexed: 11/17/2022] Open
Abstract
PURPOSE: The purpose of this study is to compare the corneal biomechanical properties of hyperthyroids without ophthalmopathy (HWO), thyroid eye disease (TED), and euthyroid participants. METHODS: In this prospective comparative study, one eye per patient included in the analysis and according to exclusion criteria, 38 eyes of 40 HWO patients, 31 eyes of 40 TED patients, and 150 eyes of 160 age- and sex-matched euthyroid participants were enrolled. All participants were evaluated by an endocrinologist and oculoplastic surgeon for evaluation of thyroid function and orbitopathy, respectively. Measurements of corneal biomechanical properties were performed using ocular response analyzer and Corvis ST tonometers. RESULTS: In the HWO group, applanation-1 length (A1 L), applanation-2 velocity (A2V) (P < 0.001), and corneal resistant factor (P = 0.043) were higher than the control group and corneal hysteresis (CH) was lower (P = 0.018). In the TED group, A1 L, A2V (P < 0.001), and highest concavity radius (HCR) (P = 0.027) were higher than the control group, and the CH (P = 0.007) and highest concavity deformation amplitude (HCDA) (P = 0.001) were lower. Furthermore, the level HCDA in the TED group was lower than HWO group (P = 0.011). The level of upper scleral show and palpebral fissure had a negative correlation with CH and HCDA. The amount of exophthalmos level had a positive correlation with HCR. CONCLUSION: Corneal biomechanical properties in the HWO and TED groups were different from the normal euthyroid individuals and may be taken into account in managing situation like glaucoma and refractive surgeries.
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Affiliation(s)
- M Reza Razeghinejad
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Glaucoma Research Center, Wills Eye Hospital, Philadelphia, PA, USA
| | - Amir R Farsiani
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Department of Ophthalmology, School of Medicine, Zanjan University of Medical sciences, Zanjan, Iran
| | - Ramin Salout
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran.,Salouti Eye Research Center, Salouti Eye Clinic, Shiraz, Iran
| | - Naser Owji
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Masoumeh Masoumpour
- Poostchi Ophthalmology Research Center, Department of Ophthalmology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Alireza Kharmandar
- Endocrine and Metabolism Research Center, Shiraz University of Medical Sciences, Shiraz, Iran
| | - Mohammad Zamani
- Salouti Eye Research Center, Salouti Eye Clinic, Shiraz, Iran
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Ding L, Wang J, Niu L, Shi W, Qian Y. Pentacam Scheimpflug Tomography Findings in Chinese Patients With Different Corneal Diameters. J Refract Surg 2020; 36:688-695. [PMID: 33034361 DOI: 10.3928/1081597x-20200730-02] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2020] [Accepted: 07/30/2020] [Indexed: 01/01/2023]
Abstract
PURPOSE To investigate the Pentacam (Oculus Optikgeräte) Scheimpflug tomography findings in Chinese patients with different corneal diameters. METHODS This prospective cross-sectional study included candidates for correction of myopia with normal tomography (ABCD keratoconus grading system, stage 0). The participants were grouped according to their horizontal corneal diameters. Pentacam ectasia detection indices were compared between different corneal diameter-based groups. RESULTS A total of 643 eyes were included (corneal diameter ⩽ 11 mm, n = 206; 11 to 12 mm, n = 219; ⩾ 12 mm, n = 218). The corneal powers and the thinnest pachymetry were negatively correlated with corneal diameter (linear regression analysis, P < .001). However, the corneal astigmatism was positively correlated with corneal diameter (R2 = 0.03, P < .001). Both the front (FE) and back (BE) elevations were negatively correlated with corneal diameter (FE: R2 = 0.027, P < .001; BE: R2 = 0.274, P < .001). The three pachymetric progression indices (PPI) (minimum, maximum, and average) were negatively correlated with corneal diameter (PPImin: R2 = 0.164, P < .001; PPImax: R2 = 0.06, P < .001; PPIavg: R2 = 0.158, P < .001). The maximum Ambrósio's relational thickness (ARTmax) also was positively correlated with corneal diameter (R2 = 0.031, P < .001). Five normalized indices were negatively correlated with corneal diameter (deviation of normality of the front elevation [Df]: R2 = 0.122, P < .001; deviation of normality of the back elevation [Db]: R2 = 0.47, P < .001; deviation of normality of pachymetric progression [Dp]: R2 = 0.159, P < .001; deviation of normality of relational thickness [Da]: R2 = .031, P < .001; Belin/Ambrósio Enhanced Ectasia display: R2 = 0.32, P < .001) and Dt was positively correlated with corneal diameter (R2 = 0.015, P = .002). Additionally, it was noted that corneal diameter had the greatest influence on Db, Belin/Ambrósio Enhanced Ectasia display (BAD-D), and BE. CONCLUSIONS Corneal diameter has an influence on the BAD parameters, especially Db, BAD-D, and BE, and therefore should be incorporated as an additional variable in BAD analysis. The analytical dimensions should be individualized for eyes with individual corneal diameter. [J Refract Surg. 2020;36(10):688-695.].
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Maklad O, Eliasy A, Chen KJ, Wang J, Abass A, Lopes BT, Theofilis V, Elsheikh A. Fluid-Structure Interaction Based Algorithms for IOP and Corneal Material Behavior. Front Bioeng Biotechnol 2020; 8:970. [PMID: 32984273 PMCID: PMC7483485 DOI: 10.3389/fbioe.2020.00970] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Accepted: 07/27/2020] [Indexed: 01/31/2023] Open
Abstract
Purpose: This paper presents and clinically validates two algorithms for estimating intraocular pressure (IOP) and corneal material behavior using numerical models that consider the fluid-structure interaction between the cornea and the air-puff used in non-contact tonometry. Methods: A novel multi-physics fluid-structure interaction model of the air-puff test was employed in a parametric numerical study simulating human eyes under air-puff pressure with a wide range of central corneal thickness (CCT = 445-645 μm), curvature (R = 7.4-8.4 mm), material stiffness and IOP (10-25 mmHg). Models were internally loaded with IOP using a fluid cavity, then externally with air-puff loading simulated using a turbulent computational fluid dynamics model. Corneal dynamic response parameters were extracted and used in development of two algorithms for IOP and corneal material behavior; fIOP and fSSI, respectively. The two algorithms were validated against clinical corneal dynamic response parameters for 476 healthy participants. The predictions of IOP and corneal material behavior were tested on how they varied with CCT, R, and age. Results: The present study produced a biomechanically corrected estimation of intraocular pressure (fIOP) and a corneal material stiffness parameter or Stress-Strain Index (fSSI), both of which showed no significant correlation with R (p > 0.05) and CCT (p > 0.05). Further, fIOP had no significant correlation with age (p > 0.05), while fSSI was significantly correlated with age (p = 0.001), which was found earlier to be strongly correlated with material stiffness. Conclusion: The present study introduced two novel algorithms for estimating IOP and biomechanical material behavior of healthy corneas in-vivo. Consideration of the fluid structure interaction between the cornea and the air puff of non-contact tonometry in developing these algorithms led to improvements in performance compared with bIOP and SSI.
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Affiliation(s)
- Osama Maklad
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Kai-Jung Chen
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - JunJie Wang
- Eye Hospital and The Institution of Ocular Biomechanics, Wenzhou Medical University, Wenzhou, China
| | - Ahmed Abass
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | | | - Vassilis Theofilis
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, United Kingdom
- Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, China
- NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, United Kingdom
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Vinciguerra R, Rehman S, Vallabh NA, Batterbury M, Czanner G, Choudhary A, Cheeseman R, Elsheikh A, Willoughby CE. Corneal biomechanics and biomechanically corrected intraocular pressure in primary open-angle glaucoma, ocular hypertension and controls. Br J Ophthalmol 2019; 104:121-126. [PMID: 30923134 PMCID: PMC6922012 DOI: 10.1136/bjophthalmol-2018-313493] [Citation(s) in RCA: 63] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 02/06/2019] [Accepted: 02/26/2019] [Indexed: 11/03/2022]
Abstract
AIMS To compare the biomechanically corrected intraocular pressure (IOP) estimate (bIOP) provided by the Corvis-ST with Goldmann applanation tonometry (GAT-IOP) in patients with high-tension and normal-tension primary open-angle glaucoma (POAG; HTG and NTG), ocular hypertension (OHT) and controls. Moreover, we compared dynamic corneal response parameters (DCRs) of the Corvis-ST in POAG, OHT and controls, evaluated the correlation between global visual field parameters mean deviation and pattern SD (MD and PSD) and DCRs in the POAG group. METHODS 156 eyes of 156 patients were included in this prospective, single-centre, observational study, namely 41 HTG and 33 NTG, 45 OHT cases and 37 controls. Central corneal thickness (CCT), GAT-IOP and bIOP were measured, GAT-IOP was also adjusted for CCT (GATAdj). DCRs provided by Corvis-ST were evaluated, MD and PSD were recorded by 24-2 full-threshold visual field. To evaluate the difference in DCRs between OHT, HTG and NTG, a general linear model was used with sex, medications and group as fixed factors and bIOP and age as covariates. RESULTS There was a significant difference between GAT-IOP, GATAdj and bIOP in NTG and HTG, OHT and controls. NTG corneas were significantly softer and more deformable compared with controls, OHT and HTG as demonstrated by significantly lower values of stiffness parameters A1 and highest concavity and higher values of inverse concave radius (all p<0.05). There was a significant correlation (p<0.05) between MD, PSD and many DCRs with POAG patients with softer or more compliant corneas more likely to show visual field defects. CONCLUSIONS Corneal biomechanics might be a significant confounding factor for IOP measurement that should be considered in clinical decision-making. The abnormality of corneal biomechanics in NTG and the significant correlation with visual field parameters might suggest a new risk factor for the development or progression of NTG.
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Affiliation(s)
- Riccardo Vinciguerra
- Birmingham and Midland Eye Centre, Sandwell and West Birmingham Hospitals, Birmingham, UK
| | - Salwah Rehman
- St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK
| | - Neeru A Vallabh
- St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK
| | - Mark Batterbury
- St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK
| | - Gabriela Czanner
- Department of Biostatistics, University of Liverpool, Liverpool, UK
| | - Anshoo Choudhary
- St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK
| | - Robert Cheeseman
- St Paul's Eye Unit, Royal Liverpool University Hospital, Liverpool, UK
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK
| | - Colin E Willoughby
- Biomedical Sciences Research Institute, University of Ulster, Coleraine, UK
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Lee SH, Moon JI, Jung YH. Comparison of Intraocular Pressures Measured by the Corvis ST and Other Tonometers in Normal Eyes. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2019. [DOI: 10.3341/jkos.2019.60.12.1250] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Seung-hoon Lee
- Department of Ophthalmology, College of Medicine, The Catholic University, Seoul, Korea
| | - Jung-il Moon
- Department of Ophthalmology, College of Medicine, The Catholic University, Seoul, Korea
| | - Youn Hea Jung
- Department of Ophthalmology, College of Medicine, The Catholic University, Seoul, Korea
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10
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Souza MB, de Medeiros FW, Villela FF, Alves MR. Relationship between the biomechanical properties of the cornea and anterior segment measurements. Clinics (Sao Paulo) 2018; 73:e491. [PMID: 30281681 PMCID: PMC6137613 DOI: 10.6061/clinics/2018/e491] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/26/2018] [Indexed: 01/26/2023] Open
Abstract
OBJECTIVE To evaluate the relationship of biomechanical properties, corneal hysteresis and corneal resistance factor with age, sex and various corneal parameters measured with a Pentacam in normal subjects. METHODS A total of 226 eyes from 113 patients were enrolled in this study. The subjects underwent Ocular Response Analyzer and Pentacam evaluations. A varying-intercept multilevel regression was implemented using Bayesian inference. The predictor variables were age, sex, central corneal thickness, corneal volume at a 7-mm diameter, anterior chamber angle and volume, anterior chamber depth, mean radius of the corneal curvature and corneal astigmatism. RESULTS Corneal hysteresis ranged from 5.5 to 14.8 mmHg (mean 10.42±1.74 mmHg), and the corneal resistance factor ranged from 5.7 to 15.5 mmHg (mean 10.23±1.88 mmHg). No predictor variable other than gender and central corneal thickness had a significant correlation with either corneal hysteresis or corneal resistance factor. Corneal hysteresis was positively associated with female sex and with central corneal thickness, and corneal resistance factor was positively associated with central corneal thickness. CONCLUSION Despite the associations found, only a small fraction of the variance in biomechanical measurements could be explained by the descriptors that were evaluated, indicating the influence of other corneal aspects on the biomechanical characteristics.
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Affiliation(s)
- Murilo Barreto Souza
- Divisao de Oftalmologia, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, BR
- *Corresponding author. E-mail:
| | - Fabricio Witzel de Medeiros
- Divisao de Oftalmologia, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, BR
| | - Flavio Fernandes Villela
- Divisao de Oftalmologia, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, BR
| | - Milton Ruiz Alves
- Divisao de Oftalmologia, Hospital das Clinicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, BR
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Gobeka H, Barut Selver Ö, Palamar Onay M, Eğrilmez S, Yağcı A. Corneal Biomechanical Properties of Keratoconic Eyes Following Penetrating Keratoplasty. Turk J Ophthalmol 2018; 48:171-177. [PMID: 30202612 PMCID: PMC6126104 DOI: 10.4274/tjo.79664] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 01/03/2018] [Indexed: 12/01/2022] Open
Abstract
Objectives To investigate the corneal biomechanical properties of keratoconic eyes following penetrating keratoplasty (PKP). Materials and Methods Thirty-five patients (70 eyes) were enrolled to this prospective study. Operated and contralateral keratoconic eyes were defined as Group 1 and 2, respectively. All patients underwent ophthalmological examination and measurements of corneal biomechanical properties by Ocular Response Analyzer (ORA), intraocular pressure (IOP) by Goldmann applanation tonometry, and central corneal thickness (CCT) by Pentacam. Shapiro-Wilk W test was performed to test normality of the data. The statistical significance was evaluated with the paired t-test and Wilcoxon signed ranks test. Pearson correlation and Spearman rho tests were used for correlation analysis. Results The average age and male/female ratio were 31.34±11.65 (15-60) years and 21/14, respectively. The mean values of the data obtained from Group 1 and 2 respectively were: corneal hysteresis (CH): 9.35±1.66, 8.18±1.84 mmHg (p=0.013), corneal resistance factor (CRF): 9.48±1.96, 7.14±2.05 mmHg (p<0.001), IOPcc: 16.90±4.32, 14.26±3.69 mmHg (p=0.004), IOPg: 15.45±4.61, 10.91±3.97 mmHg (p<0.001), IOPapl: 14.26±3.11, 13.09±2.54 mmHg (p=0.046), and central corneal thickness (CCT): 545.64±60.82, 442.60±68.14 μM (p<0.001). The positive correlation between CH and CRF was moderate (r=0.444) in Group 1 and strong (r=0.770) in Group 2. There was a moderate negative correlation between CH and IOPcc in both groups (r=-0.426, r=-0.423), but CH was not correlated with IOPg or IOPapl in either group. There were weak to strong positive correlations between CRF and all IOP values in both groups. There was no correlation between CRF and CCT in Group 1 (r=0.075) and a very weak correlation in Group 2 (r=0.237). Only IOPcc and IOPg were strongly correlated in both groups. Conclusion Better understanding of corneal biomechanical properties is essential for elucidating the pathophysiology and diagnosis of several corneal pathologies such as keratoconus. The biomechanical properties of keratoconic eyes seem to be closer to normal values after PKP.
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Affiliation(s)
- Hamidu Gobeka
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
| | - Özlem Barut Selver
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
| | - Melis Palamar Onay
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
| | - Sait Eğrilmez
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
| | - Ayşe Yağcı
- Ege University Faculty of Medicine, Department of Ophthalmology, İzmir, Turkey
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Eliasy A, Chen KJ, Vinciguerra R, Maklad O, Vinciguerra P, Ambrósio R, Roberts CJ, Elsheikh A. Ex-vivo experimental validation of biomechanically-corrected intraocular pressure measurements on human eyes using the CorVis ST. Exp Eye Res 2018; 175:98-102. [PMID: 29908883 DOI: 10.1016/j.exer.2018.06.013] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2018] [Revised: 05/30/2018] [Accepted: 06/14/2018] [Indexed: 11/17/2022]
Abstract
The purpose of this study was to assess the validity of the Corvis ST (Oculus; Wetzlar, Germany) biomechanical correction algorithm (bIOP) in determining intraocular pressure (IOP) using experiments on ex-vivo human eyes. Five ex-vivo human ocular globes (age 69 ± 3 years) were obtained and tested within 3-5 days post mortem. Using a custom-built inflation rig, the internal pressure of the eyes was controlled mechanically and measured using the CorVis ST (CVS-IOP). The CVS-IOP measurements were then corrected to produce bIOP, which was developed for being less affected by variations in corneal biomechanical parameters, including tissue thickness and material properties. True IOP (IOPt) was defined as the pressure inside of the globe as monitored using a fixed pressure transducer. Statistical analyses were performed to assess the accuracy of both CVS-IOP and bIOP, and their correlation with corneal thickness. While no significant differences were found between bIOP and IOPt (0.3 ± 1.6 mmHg, P = 0.989) using ANOVA and Bonferroni Post-Hoc test, the differences between CVS-IOP and IOPt were significant (7.5 ± 3.2 mmHg, P < 0.001). Similarly, bIOP exhibited no significant correlation with central corneal thickness (p = 0.756), whereas CVS-IOP was significantly correlated with the thickness (p < 0.001). The bIOP correction has been successful in providing close estimates of true IOP in ex-vivo tests conducted on human donor eye globes, and in reducing association with the cornea's thickness.
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Affiliation(s)
- Ashkan Eliasy
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK.
| | - Kai-Jung Chen
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK
| | - Riccardo Vinciguerra
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK; St Paul's Eye Unit, Royal Liverpool and Broadgreen University Hospital, Liverpool, UK
| | - Osama Maklad
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK
| | - Paolo Vinciguerra
- Department of Biomedical Science-Humanitas University, Via Manzoni 56, Rozzano, MI, Italy; Eye Center, Humanitas Clinical and Research Center, Via Manzoni 56, Rozzano, MI, Italy
| | - Renato Ambrósio
- Rio de Janeiro Corneal Tomography and Biomechanics Study Group, Rio de Janeiro, Brazil; Department of Ophthalmology, Federal University of São Paulo (UNIFESP), São Paulo, Brazil; Department of Ophthalmology, Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, Brazil
| | - Cynthia J Roberts
- Department of Ophthalmology & Visual Science, Department of Biomedical Engineering, The Ohio State University, Columbus, OH, USA
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, L69 3GH, UK; NIHR Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, UK
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Nemeth G, Szalai E, Hassan Z, Lipecz A, Flasko Z, Modis L. Corneal biomechanical data and biometric parameters measured with Scheimpflug-based devices on normal corneas. Int J Ophthalmol 2017; 10:217-222. [PMID: 28251079 DOI: 10.18240/ijo.2017.02.06] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 09/27/2016] [Indexed: 12/19/2022] Open
Abstract
AIM To analyze the correlations between ocular biomechanical and biometric data of the eye, measured by Scheimpflug-based devices on healthy subjects. METHODS Three consecutive measurements were carried out using the corneal visualization Scheimpflug technology (CorVis ST) device on healthy eyes and the 10 device-specific parameters were recorded. Pentacam HR-derived parameters (corneal curvature radii on the anterior and posterior surfaces; apical pachymetry; corneal volume; corneal aberration data; depth, volume and angle of the anterior chamber) and axial length (AL) from IOLMaster were correlated with the 10 specific CorVis ST parameters. RESULTS Measurements were conducted in 43 eyes of 43 volunteers (age 61.24±15.72y). The 10 specific CorVis ST data showed significant relationships with corneal curvature radii both on the anterior and posterior surface, pachymetric data, root mean square (RMS) data of lower-order aberrations, and posterior RMS of higher-order aberrations and spherical aberration of the posterior cornea. Anterior chamber depth showed a significant relationship, but there were no significant correlations between corneal volume, anterior chamber volume, mean chamber angle or AL and the 10 specific CorVis ST parameters. CONCLUSIONS CorVis ST-generated parameters are influenced by corneal curvature radii, some corneal RMS data, but corneal volume, anterior chamber volume, chamber angle and AL have no correlation with the biomechanical parameters. The parameters measured by CorVis ST seem to refer mostly to corneal properties of the eye.
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Affiliation(s)
- Gabor Nemeth
- Department of Ophthalmology, Borsod-Abaúj-Zemplén County Hospital and University Teaching Hospital, Miskolc 3526, Hungary
| | - Eszter Szalai
- Department of Ophthalmology, University of Debrecen, Debrecen 4032, Hungary
| | - Ziad Hassan
- Orbi-Dent Refractive Surgery and Medical Centre, Debrecen 4032, Hungary
| | - Agnes Lipecz
- Department of Ophthalmology, University of Debrecen, Debrecen 4032, Hungary
| | - Zsuzsa Flasko
- Department of Ophthalmology, University of Debrecen, Debrecen 4032, Hungary
| | - Laszlo Modis
- Department of Ophthalmology, University of Debrecen, Debrecen 4032, Hungary
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Evaluation of Corneal Biomechanical Properties in Patients With Thyroid Eye Disease Using Ocular Response Analyzer. J Glaucoma 2016; 25:269-73. [PMID: 26020688 DOI: 10.1097/ijg.0000000000000254] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To assess variations in the corneal biomechanical properties in thyroid eye disease (TED) patients using ocular response analyzer (ORA). PATIENTS AND METHODS In this observational cross-sectional study, 75 patients with TED and 57 healthy subjects were enrolled. The mean age of the patients and healthy subjects were 47.50±1.55 and 43.6±1.23 years, respectively (P=0.06). All study participants underwent comprehensive ophthalmologic examination, Goldmann applanation tonometry (GAT), corneal pachymetry, and corneal biomechanical analysis using ORA. Corneal hysteresis (CH), corneal resistance factor (CRF), cornea-compensated IOP value (IOPcc), and Goldmann-corrected IOP value (IOPg) were measured with ORA. RESULTS Central corneal thickness (CCT) in patients group (536.18±36.20 μm) and control group (539.22±28.83 μm) were not significantly different (P=0.1). In TED group, the IOPcc (20.23±0.54 mm Hg) was significantly higher than both IOP-GAT (17.54±0.49 mm Hg, P<0.001) and IOPg (18.35±0.52, P<0.001). CH in TED patients (9.01±0.20) was significantly lower compared with CH in healthy subjects (10.45±0.21) (P<0.001). Although CRF was lower in TED patients (10.06±0.16) in comparison with normal subjects (10.42±0.29), this difference was not statistically significant (P=0.25). Both CH and CRF were positively correlated with CCT (r=0.52, P<0.001 and r=0.62, P<0.001, respectively) in TED group. CONCLUSIONS In TED patients, CH seems to be lower than in normal subjects. GAT might underestimate the IOP due to differences in corneal properties of cornea in TED patients.
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Zheng X, Bao F, Geraghty B, Huang J, Yu A, Wang Q. High intercorneal symmetry in corneal biomechanical metrics. EYE AND VISION 2016; 3:7. [PMID: 26949709 PMCID: PMC4779259 DOI: 10.1186/s40662-016-0037-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Accepted: 02/20/2016] [Indexed: 12/02/2022]
Abstract
Backgroud To evaluate the symmetry of corneal biomechanical metrics, measured using an ocular response analyzer (ORA) and self-built corneal inflation test platform, in bilateral rabbit corneas and to investigate their relationship with physical intraocular pressure (IOPp). Methods Twenty fresh enucleated eyes from ten rabbits were used for ex vivo whole ocular globe inflation. IOP was increased from 7.5 to 37.5 mmHg with 7.5 mmHg steps and biomechanical metrics were acquired using the ORA. At least 3 examinations were performed at each pressure stage. Two biomechanical metrics, corneal hysteresis (CH) and corneal resistance factor (CRF) were recorded and analyzed as a function of IOPp. Corneal specimens were then excised from the intact ocular globe and tested under inflation conditions up to 45.7 mmHg posterior pressure. The experimental pressure-deformation data was analyzed using an inverse modeling procedure to derive the stress-strain behavior of the cornea. Results A comparison of corneal shape parameters showed no statistically significant difference (P > 0.05) between bilateral eyes. Similarly, there were no statistically significant differences in values of CH, CRF and corneal stiffness (as measured by the tangent modulus, Et) between bilateral eyes (CH: F = 0.94, P = 0.54; CRF: F = 4.42, P = 0.35; Et: F = 3.15, P = 0.12) at different pressure levels. IOPp was highly correlated with CRF while the relationship with CH was less pronounced. Conclusions An obvious interocular symmetry in biomechanical metrics is found in this research. IOP has been shown to have important influences on the value of CRF provided by ORA.
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Affiliation(s)
- XiaoBo Zheng
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province 325027 China ; The Institution of Ocular Biomechanics, Eye Hospital, Wenzhou Medical University, No. 270# Xueyuan West Road, Wenzhou City, Zhejiang Province 325027 China
| | - FangJun Bao
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province 325027 China ; The Institution of Ocular Biomechanics, Eye Hospital, Wenzhou Medical University, No. 270# Xueyuan West Road, Wenzhou City, Zhejiang Province 325027 China
| | - Brendan Geraghty
- School of Engineering, University of Liverpool, Liverpool, L69 3GH UK
| | - JinHai Huang
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province 325027 China ; The Institution of Ocular Biomechanics, Eye Hospital, Wenzhou Medical University, No. 270# Xueyuan West Road, Wenzhou City, Zhejiang Province 325027 China
| | - Ayong Yu
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province 325027 China ; The Institution of Ocular Biomechanics, Eye Hospital, Wenzhou Medical University, No. 270# Xueyuan West Road, Wenzhou City, Zhejiang Province 325027 China
| | - QinMei Wang
- The Affiliated Eye Hospital of Wenzhou Medical University, Wenzhou, Zhejiang Province 325027 China ; The Institution of Ocular Biomechanics, Eye Hospital, Wenzhou Medical University, No. 270# Xueyuan West Road, Wenzhou City, Zhejiang Province 325027 China
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The biomechanical properties of the cornea and anterior segment parameters. BMC Ophthalmol 2013; 13:49. [PMID: 24083664 PMCID: PMC3852860 DOI: 10.1186/1471-2415-13-49] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 09/25/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To investigate the biomechanical properties of the cornea measured with the Ocular Response Analyzer (ORA) and their association with the anterior segment parameters representing the geometric dimensions including the corneal volume and anterior chamber volume. METHODS A retrospective review of 1020 patients who visited the BGN Eye Clinic was done. The mean radius of the corneal curvature, corneal astigmatism, corneal volume, anterior chamber depth, and anterior chamber volume were measured with an anterior segment tomographer. The central corneal thickness (CCT) was measured with an ultrasonic pachymeter. The corneal diameter was measured with an Orbscan as White to White. Cornea hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOPg), and cornea-compensated IOP (IOPcc) were measured with an ORA. Multiple linear regression models were constructed with CH and CRF as the dependent variables and age, gender, and the anterior segment parameters as the covariates. RESULTS 958 eyes from 958 patients (mean age 26.7 years; male 43.4%) were included in this study after excluding some eyes according to the exclusion criteria. The mean CH and CRF were 10.1 and 9.9 mmHg, respectively. The mean IOPg and IOPcc were 14.8 and 15.8 mmHg. The multivariate analysis showed that CH was negatively associated with the mean radius of the cornea curvature (regression coefficient = -0.481, p = 0.023) and positively associated with CCT (regression coefficient = 0.015, p < 0.001) and corneal volume (regression coefficient =0.059, p = 0.014). The association between CH and the corneal diameter, anterior chamber depth, and anterior chamber volume were not statistically significant. The evaluation of CRF showed that CRF was negatively associated with the mean radius of the cornea curvature (regression coefficient = -0.540, p = 0.013), and positively associated with CCT (β = 0.026, p < 0.001). The association between CRF and the corneal diameter, corneal volume, anterior chamber depth, and anterior chamber volume were not statistically significant. CONCLUSION The CH was shown to be positively associated with the corneal volume and the association between CH and the anterior chamber volume were not significant. The associations of CRF with the corneal volume or anterior chamber volume were not significant.
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Bouhéraoua N, Hamard P, Iordanidou V, Brasnu E, Dupond-Monod S, Baudouin C, Labbé A. Analyse de l’architecture du segment antérieur par OCT après sclérectomie profonde non perforante. J Fr Ophtalmol 2012; 35:760-7. [DOI: 10.1016/j.jfo.2011.11.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2011] [Revised: 10/24/2011] [Accepted: 11/04/2011] [Indexed: 12/01/2022]
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Lopez-De La Fuente C, Sanchez-Cano A, Ferreras A, Fuertes-Lazaro I. Comparison of Keeler Pulsair EasyEye tonometer and Ocular Response Analyzer for measuring intraocular pressure in healthy eyes. JOURNAL OF OPTOMETRY 2012; 5:139-146. [PMCID: PMC3861132 DOI: 10.1016/j.optom.2012.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 06/10/2012] [Indexed: 06/10/2023]
Abstract
Purpose To evaluate the relationship between intraocular pressure (IOP) measurements obtained with Pulsair EasyEye (PEE) and Ocular Response Analyser (ORA) in healthy patients. Methods Sixty-five eyes from 65 patients underwent a full optometric examination, including central corneal thickness (CCT), and IOP measured with PEE and ORA. Differences between IOP measurements between both tonometers were analyzed. Pearson correlation coefficients between IOP values and ORA corneal biomechanics parameters were also obtained. Results Statistically significant differences were found between IOP of PEE (IOPk) and Goldmann-corrected IOP of ORA (IOPg; p = 0.001). IOPk and corneal resistance-corrected IOP of ORA (IOPcc) were also found to differ significantly (p = 0.025). Mean differences between IOPg-IOPk, IOPcc-IOPk and IOPg-IOPcc were 0.71 ± 1.66, 0.70 ± 2.46 and 0.01 ± 1.54 mmHg (mean ± standard deviation), respectively. Pearson correlation coefficients indicated that IOPk, IOPg, and IOPcc were significantly correlated among them (p < 0.001): r = 0.816 for IOPk-IOPg, r = 0.826 for IOPcc-IOPg and r = 0.587 IOPcc-IOPk. IOPk and IOPg were linearly associated with corneal resistance factor (CRF; r = 0.626 and r = 0.619, respectively) and with CCT (r = 0.531 and r = 0.579, respectively). IOPcc had a linear relationship with corneal hysteresis (CH) (r = −0.482) and similar results were found between CRF and CH (r = 0.841), CRF and CCT (r = 0.681) or between CH and CCT (r = 0.466). Conclusions Differences between mean values of IOP measured with PEE and ORA are statistically significant, with ORA tonometer taking higher IOP values than PEE in most of the cases. IOPk, IOPcc and IOPg have, al least, moderate positive linear correlations and ORA biomechanics parameters CRF, CH and CCT have a linear positive relation between them.
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Affiliation(s)
| | - Ana Sanchez-Cano
- Applied Physics Department, University of Zaragoza, Zaragoza, Spain
| | - Antonio Ferreras
- Department of Ophthalmology, Miguel Servet University Hospital, Aragon Health Sciences Institute, Zaragoza, Spain
- Department of Surgery, Ginecology and Obstetrics, University of Zaragoza, Zaragoza, Spain
| | - Isabel Fuertes-Lazaro
- Department of Ophthalmology, Miguel Servet University Hospital, Aragon Health Sciences Institute, Zaragoza, Spain
- Department of Surgery, Ginecology and Obstetrics, University of Zaragoza, Zaragoza, Spain
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Alhamad TA, Meek KM. Comparison of factors that influence the measurement of corneal hysteresis in vivo and in vitro. Acta Ophthalmol 2011; 89:e443-50. [PMID: 21457485 DOI: 10.1111/j.1755-3768.2011.02150.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE The purpose of this study was to compare measurements of corneal hysteresis (CH) obtained in vivo, with similar measurements from excised human eyes and from excised human corneas mounted in an artificial anterior chamber. METHODS Corneal hysteresis was measured using an ocular response analyser (Reichert Ophthalmic Instruments) from three groups: 53 healthy normal corneas of fifty-three patients, six excised eyes and 17 excised corneas. RESULTS In vivo, it was found that CH was independent of gender, age and mean spherical equivalent, but has a significant inverse relationship with intraocular pressure (IOP(cc)) (r = 0.53; p < 0.0001). However, there was no correlation between CH and IOP(G) (r = 0.10; p = 461). The same inverse relationship with IOP(cc) was recorded in intact, excised eyes (r = 0.74; p < 0.0001), with no significant differences between the behaviour each individual eye. Excised corneas also showed an inverse relationship between CH and trans-corneal pressure (r = 0.72; p < 0.0001), but the measured values of CH were lower than those recorded in vivo and from intact globes. In both excised eyes and excised corneas, we found a significant correlation between CH and central corneal thickness [r = 0.86; p < 0.0001 and r = 0.611; p < 0.0005 (respectively)]. CONCLUSION The in vitro results indicate that every normal human eye at physiological hydration shows an identical dependence of CH on IOP(cc) , the same dependence as is observed in vivo. This therefore would appear to be an intrinsic response of the tissue to a change in IOP. However, it is possible that the lower values of CH recorded from excised corneas reflect the influence of the artificial chamber replacing the eye globe, so in vivo values of CH may be influenced to some extent by the presence of the other components of the eye.
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Affiliation(s)
- Tariq A Alhamad
- School of Optometry and Vision Sciences, Cardiff University, Cardiff, UK
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Évaluation des facteurs biomécaniques cornéens mesurés à l’Ocular Response Analyzer dans l’hypertension intraoculaire, le glaucome primitif à angle ouvert et chez le sujet normal. Étude prospective sur 329 yeux. J Fr Ophtalmol 2008; 31:953-60. [DOI: 10.1016/s0181-5512(08)74740-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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