Confocal reflectance microscopy for mapping collagen fiber organization in the vitreous gel of the eye

Abstract

Vitreous collagen structure plays an important role in ocular mechanics. However, capturing this structure with existing vitreous imaging methods is hindered by the loss of sample position and orientation, low resolution, or a small field of view. The objective of this study was to evaluate confocal reflectance microscopy as a solution to these limitations. Intrinsic reflectance avoids staining, and optical sectioning eliminates the requirement for thin sectioning, minimizing processing for optimal preservation of the natural structure. We developed a sample preparation and imaging strategy using ex vivo grossly sectioned porcine eyes. Imaging revealed a network of uniform diameter crossing fibers (1.1 ± 0.3 µm for a typical image) with generally poor alignment (alignment coefficient = 0.40 ± 0.21 for a typical image). To test the utility of our approach for detecting differences in fiber spatial distribution, we imaged eyes every 1 mm along an anterior-posterior axis originating at the limbus and quantified the number of fibers in each image. Fiber density was higher anteriorly near the vitreous base, regardless of the imaging plane. These data demonstrate that confocal reflectance microscopy addresses the previously unmet need for a robust, micron-scale technique to map features of collagen networks in situ across the vitreous.