David A Atchison1, W Neil Charman. 1. Queensland University of Technology, Kelvin Grove, Queensland, Australia. d.atchison@qut.edu.au
Abstract
PURPOSE: To determine likely errors in estimating retinal shape using partial coherence interferometric instruments when no allowance is made for optical distortion. METHODS: Errors were estimated using Gullstrand no. 1 schematic eye and variants which included a 10 diopter (D) axial myopic eye, an emmetropic eye with a gradient-index lens, and a 10.9 D accommodating eye with a gradient-index lens. Performance was simulated for two commercial instruments, the IOLMaster (Carl Zeiss Meditec) and the Lenstar LS 900 (Haag-Streit AG). The incident beam was directed toward either the center of curvature of the anterior cornea (corneal-direction method) or the center of the entrance pupil (pupil-direction method). Simple trigonometry was used with the corneal intercept and the incident beam angle to estimate retinal contour. Conics were fitted to the estimated contours. RESULTS: The pupil-direction method gave estimates of retinal contour that were much too flat. The cornea-direction method gave similar results for IOLMaster and Lenstar approaches. The steepness of the retinal contour was slightly overestimated, the exact effects varying with the refractive error, gradient index, and accommodation. CONCLUSIONS: These theoretical results suggest that, for field angles ≤30°, partial coherence interferometric instruments are of use in estimating retinal shape by the corneal-direction method with the assumptions of a regular retinal shape and no optical distortion. It may be possible to improve on these estimates out to larger field angles by using optical modeling to correct for distortion.
PURPOSE: To determine likely errors in estimating retinal shape using partial coherence interferometric instruments when no allowance is made for optical distortion. METHODS: Errors were estimated using Gullstrand no. 1 schematic eye and variants which included a 10 diopter (D) axial myopic eye, an emmetropic eye with a gradient-index lens, and a 10.9 D accommodating eye with a gradient-index lens. Performance was simulated for two commercial instruments, the IOLMaster (Carl Zeiss Meditec) and the Lenstar LS 900 (Haag-Streit AG). The incident beam was directed toward either the center of curvature of the anterior cornea (corneal-direction method) or the center of the entrance pupil (pupil-direction method). Simple trigonometry was used with the corneal intercept and the incident beam angle to estimate retinal contour. Conics were fitted to the estimated contours. RESULTS: The pupil-direction method gave estimates of retinal contour that were much too flat. The cornea-direction method gave similar results for IOLMaster and Lenstar approaches. The steepness of the retinal contour was slightly overestimated, the exact effects varying with the refractive error, gradient index, and accommodation. CONCLUSIONS: These theoretical results suggest that, for field angles ≤30°, partial coherence interferometric instruments are of use in estimating retinal shape by the corneal-direction method with the assumptions of a regular retinal shape and no optical distortion. It may be possible to improve on these estimates out to larger field angles by using optical modeling to correct for distortion.
Authors: Pavan K Verkicharla; Marwan Suheimat; James M Pope; Farshid Sepehrband; Ankit Mathur; Katrina L Schmid; David A Atchison Journal: Biomed Opt Express Date: 2015-08-05 Impact factor: 3.732
Authors: James M Pope; Pavan K Verkicharla; Farshid Sepehrband; Marwan Suheimat; Katrina L Schmid; David A Atchison Journal: Biomed Opt Express Date: 2017-04-05 Impact factor: 3.732
Authors: Jan-Willem M Beenakker; Teresa A Ferreira; Karina P Soemarwoto; Stijn W Genders; Wouter M Teeuwisse; Andrew G Webb; Gregorius P M Luyten Journal: MAGMA Date: 2016-02-25 Impact factor: 2.310