Development of an improved eye model for optical path visualization of native and artificial lens characterization under physiological conditions

Abstract

Purpose: Apart from mathematical simulations, only the optical path visualization of native lenses and IOLs enable a qualitative characterization of their imaging properties. Published setup’s for optical path visualization have taken into account all refracting elements but not an adequate beam profile. Our approach addressed this deficit and focused on the characterization of lens properties concerning the focusing position, transmission properties, misalignment and tilt.

Methods: A laser based optical setup was developed which included a customized artificial cornea. The beam profile of a semiconductor laser (λ = 532 nm) was used to create a laser line with a flat-top intensity profile, which was generated by an inverted beam expander (10x) and a Powell lens as a line generator (45°). During the measurement the lenses are localized in balanced salt solution containing fluorescein to visualize the optical path captured by a Nikon D3S camera in combination with a 60mm lens. For setup verification, the optical path of a dedicated artificial and native porcine lenses (n=5) were examined regarding the focal length and compared to literature data.

Results: The used flat-top intensity profile improves the imaging quality of the artificial eye model significantly. The focal length of both artificial and native lenses can be visualized. Using the plano-convex lens a focal length of 22.3 ± 0.2 mm was determined experimentally compared to a calculated focal length of 22.5 mm. For porcine lenses we found a mean focal length of 24.05 ± 1.99 mm compared to ray-tracing simulations based on the GRIN-lens model of de Castro (focal length 23.67mm) and the experimental data of Vilupuru (23 to 33 mm).

Conclusions: The developed instrument enables the optical path visualization of native and artificial lenses under physiological conditions. In combination with WinLens3D simulations and a ray-tracing analysis a qualitative optical path characterization is possible to analyze the optical performance of new IOL designs.