Contributed Session II: Ex-vivo human crystalline lenses geometrical changes during simulated disaccommodation.

The young crystalline lens changes its shape to focus targets at different distances, a capability (accommodation) that is lost with age. Quantifying crystalline lens morphology during accommodation and aging is essential for understanding basic mechanisms of function and disease (presbyopia and cataract). We studied the geometrical changes of the ex-vivo human crystalline lens while simulating different levels of physiological disaccommodation using a motorized lens-stretcher system designed for this purpose. 14 human lenses (11-54 y/o) from donor eyes were radially stretched mounted in the lens-stretcher and immersed in a cuvette filled with balanced salt solution for preservation purposes. Lens geometry and power were characterized using custom-developed high resolution 3-D optical coherence tomography (OCT) and laser ray tracing system coupled with the OCT. The lens thickness decreased linearly 81 microns/diopter (D) of simulated disaccommodation (-r=0.87, p<0.001), the diameter increased 76 microns/D (r=0.84, p<0.01), the radius of curvature of the anterior surface increased 0.63 mm/D (r=0.92, p<0.001), the lens surface area increased 1.9 mm2/D (r=0.62, p<0.01) and the lens volume remained constant. The same stretching displacement produced larger deformations in younger than in older lenses. Simultaneous high resolution optical and geometrical measurements of stretched lenses therefore match results in vivo and support the Helmholtz theory of accommodation.