Comparison of histology and a non–contact optical system to measure lens capsule thickness.

Abstract

Abstract: : Purpose: To compare lens capsule thickness measured in cadaver eyes by light microscopy (LM) and with a non–contact optical system (NCO). Methods: The NCO uses a 670nm laser beam delivered to a single–mode fiber coupler. The output of the sensing arm of the fiber coupler is focused on the tissue surface using an aspheric lens (NA=0.68) mounted on a translation stage with a motorized actuator. Light reflected from the sample surface is collected by the fiber coupler and sent to a photodiode. The photodiode and translation stage are computer–controlled. Signal peaks are detected when the aspheric lens is focused on the capsule boundaries. The capsule thickness is proportional to the distance traveled between two peaks. Anterior and posterior capsule thickness was measured on 10 human, 7 monkey, and 28 New Zealand white rabbit lenses. The cadaver eye was prepared by bonding a PMMA ring on the slera after removal of conjunctiva, adipose, and muscle tissues. The posterior pole was sectioned, excess vitreous was removed, the eye was placed on a teflon slide, and the cornea and iris were sectioned. After the NCO measurements, all lenses were prepared for LM. The capsule thickness was measured on digital images of the histological section recorded at 40x magnification. Measurements were performed at the anterior and posterior capsule center. A t–test was performed to determine if the differences between LM and NCO measurements were statistically significant. Results: See table. 

Conclusions: This study shows that the anterior capsule thickness in intact cadaver lenses can be measured accurately using a non–contact optical system. The relative error between optical and histological thickness measurements was larger for the posterior lens capsule.

Keywords: microscopy: confocal/tunneling • optical properties • laser