3D OCT-based geometrical changes of human crystalline lenses during simulated accommodation in a lens stretcher

Abstract

Purpose : Quantifying human crystalline lens geometry as a function of age and accommodation is essential for understanding disorders such as cataract and presbyopia. We estimated the geometry of the full shape of crystalline lens at different levels of accommodation simulated by a lens stretcher using optical coherence tomography (OCT).

Methods : 15 human donor globes (28-54 y/o) were dissected to preserve lens with its accommodating framework. The tissue was mounted in a motorized miniature lens-stretcher system and immersed in a cuvette filled with BSS. The system simulated disaccommodation by radial stretching of sclera. 3-D OCT images were acquired at 0, 1 and 2 mm of radial displacements, and full shape models were obtained after segmentation of the images and fan and optical distortions correction. For each lens, the average refractive index (n), calculated from the cuvette optical distortion, was considered. Lens volume (VOL), surface area (LSA), thickness (LT), diameter (DIA), radius of curvature of anterior (RAL) and posterior surfaces (RPL), and LT/DIA were quantified. A custom laser ray tracing system coupled with the OCT was used to measure the lens wavefront aberrations and power. Geometrical changes with stretching were analyzed as a function of age using linear regression.

Results : In the maximally accommodated state (0 mm stretching), DIA, VOL, LSA and RAL increased linearly with age at rates of 0.015 mm/yr (r=0.65,p=0.02), 1.55 mm³/yr (r=0.74,p=0.006), 0.93 mm²/yr (r=0.77,p=0.003) and 0.078 mm/yr (r=0.58,p=0.04) respectively. The 2 mm scleral stretch produced changes in lens power that were equivalent to physiological disaccommodation in most of the lenses, ranging from -6.5D (30-35y/o) to 0D (ages above 45y/o). Stretching changes (parameter @2 mm- parameter @0 mm) were higher for younger lenses. Specifically, for ages below 45 y/o:-1.15+0.027yr (r=0.74,p=0.03) for LT, 5.82-0.13yr (r=-0.62,p=0.04) for RAL, and -0.15+0.003yr (r=0.74, p=0.03) for LT/DIA. We did not find significant stretching changes of VOL (mean=0.60±1.90 mm³) or n with age, or of any parameter after 45y/o.

Conclusions : 3-D OCT measurements coupled to a stretcher allow ex vivo quantification of the full shape of the crystalline lens while simulating physiological disaccommodation. Deformations were larger in younger lenses compared to older ones. The lens volume remained constant with stretching at all ages.

This is a 2020 ARVO Annual Meeting abstract.