Purpose:
In central primate retina the multitiered vasculature leads to nonuniform gradients of oxygen along radial retinal profiles (Yu &Cringle,2001). In the far periphery, vasculature is reduced and spread out into a non-overlapping monolayered plexus with alternating cascades of arterioles, venules and a mediating capillary zones. This compartmentalization may create microenvironments with different metabolic profiles. We therefore developed a procedure for studying possible effects of such vascular domains on the spatial distribution of retinal cell classes. In particular, it is applied to detect eventual biases in the overlying short wavelength sensitive (S-) cone mosaic.
Methods:
A statistical framework has been designed and implemented in Matlab. In a set of iterations applied to binary maps of vascular elements (collagen IV labeled) and S-cones (S-opsin labeled) in peripheral sectors from an Orang Utan (6yrs,f) and a Human (76 yrs,f) retina, we obtained the percentage of cones located within increasing domains along a vessel network and compare the results with data from Monte Carlo (MC) simulations.
Results:
The comparisons suggest differential positioning of S-cones with respect to the type of underlying vasculature (Fig.). For 90% of S-cones a significant positive correlation to retinal capillaries (c) was found. For arterioles (a), a small circumferential "aura" (~2 x 115 μm) of lower than expected S-cone densities was detected. No significant correlation was found along underlying venules (v) for S-cones within 300 µm domains. The pattern of peripheral S-cone mosaic itself is random (Chi-Square, 95%).
Conclusions:
Peripheral S-cone positioning appears influenced by vicinitiy to underling vessels types, although the timing and specific catalysts for the shaping of these correlation are yet unclear. The inferred tiling of peripheral retina could also demarcate sites, predisposed for initial manifestation of progressive pathologic conditions as from retinitis pigmentosa, diabetes or from aging.
Keywords: photoreceptors • topography • oxygen