Estimation of the full shape of the crystalline lens from optical coherence tomography images using Eigenlenses.

Abstract

Purpose : Estimating the full 3-D biometry of the crystalline lens is important for understanding its changes with aging, accommodation or myopia development, and for improving intraocular lens calculations. In Martinez-Enriquez IOVS 2016, we proposed a 2-region parametric model (2RM) to estimate the full lens shape ex vivo and in vivo from optical coherence tomography (OCT) images. Martinez-Enriquez BOE 2020 described a novel method for the representation of the full shape of the lens ex vivo (Eigenlenses). Here we demonstrate the use of Eigenlenses to estimate the full shape of the lens in vivo, in comparison with the 2RM method.

Methods : OCT images were obtained on one eye of 17 human subjects (26±2 y/o; unaccommodated; 5 repetitions) using a custom-developed swept source OCT system (200K A-scans/s, axial depth=16 mm, pixel size=8.3 μm). Surface segmentation and distortion correction were performed to obtain 3-D models of the lens within the pupil. From these models, the full shape of the lens represented by 6 Eigenlenses coefficients was estimated using multiple linear regression. The following parameters were quantified: diameter (DIA), volume (VOL), equatorial plane position (EPP) and lens surface area (LSA). Results from the two methods (2RM and Eigenlenses) were compared in terms of repeatability (standard deviation of repeated measurements) and Pearson coefficient (ρ).

Results : The mean values of lens parameters across subjects were DIA=8.86±0.12/8.70±0.25 mm, VOL=140±7/136±9 mm³, LSA=152±4/150±7 mm², and EPP=1.43±0.03/1.56±0.08 mm, for Eigenlenses/2RM, respectively. Repeatability was DIA_SD=0.06/0.11 mm, VOL_SD=2.3/3.3 mm³, LSA_SD=1.8/3.1 mm² and EPP_SD=0.029/0.041 mm for Eigenlenses/2RM, respectively. The correlation between the parameters calculated with both methods were ρDIA=0.89, ρVOL=0.94, ρLSA=0.92 and ρEPP=0.88. R² from multiple linear regression between the first two Eigenlenses coefficients, which are related with the size and aspect ratio of the lens, and the DIA and VOL were R²=0.98 and R²=0.997 respectively. Using just these two coefficients only reduced the accuracy of DIA by 0.017 mm and VOL by 0.3 mm³.

Conclusions : 2RM and Eigenlenses are both robust methods to estimate the full lens shape parameters in vivo. However, the Eigenlenses method is more repeatable and efficient, requiring only two coefficients for an accurate estimation of lens volume and diameter.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.