Macular photoreceptor organization
A precondition for maximum acuity and other optimizations of human and primate photopic visual function is the high density of the retinal foveolar cones. Spatial packing is near optimum in the all-cone foveal center but always deviations from ideal hexagonal order remain. Pattern analysis has allowed to demonstrate the presence of serially arranged lattice defects separating crystalline patches sharing similar axial orientation . The present study demonstrates similar patchwork-like organizations in the initial portion of cone axons. It is proposed that these patterns are correlated with the batch-wise descendence and sequential stacking of cone cell bodies during mosaic condensations. The multitiered relocation of the primarily monolayered macular sensory epithelium compensates the diameter difference between somata and slender inner segments. Induced by the arrangement of somata this modular organization is projected upon the two dimensional aspects on both sides of the ONL: distally it appears as the inner/outer segment patches and proximally it leads to the bundling of cone axons below the nuclear layer. Thus discontinuities are an inherent element of fovea) microarchitecture and may be sites of increased vulnerability to mechanical/osmotic stress and retinoschisis.
KeywordsOuter Nuclear Layer Human Retina Modular Organization External Limit Membrane Axon Bundle
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