Microvascular Density Is Associated With Retinal Ganglion Cell Axonal Volume in the Laminar Compartments of the Human Optic Nerve Head.

Purpose: To quantify associations between microvascular density and retinal ganglion cell (RGC) axonal volume in the laminar compartments of the human optic nerve head (ONH).

Methods: Eleven normal human ONHs were evaluated. Antibodies were used to label the vascular endothelium (factor VIII-related antigen/von Willebrand factor antibody) and RGC axons (neurofilament heavy antibody). Three-dimensional analysis of confocal scanning laser microscope images was used to study microvascular density and RGC axonal volume in the prelaminar, anterior lamina cribrosa, posterior lamina cribrosa, and retrolaminar compartments.

Results: Microvascular volume was significantly different between laminar compartments (P < 0.0083) and was greatest in the prelaminar region, occupying 11.7% of tissue volume. Microvascular volume per RGC axonal volume and cumulative capillary length per RGC axonal volume were significantly different between laminar compartments (all P < 0.0083). Both were significantly greater in the posterior laminar cribrosa (27.4% and 2.28 × 10-3 μm/μm3, respectively).

Conclusions: Microvascular density is closely coupled to RGC axonal volume in the ONH. The posterior laminar cribrosa is a site of high blood supply as evidenced by a greater ratio of microvascular density to RGC axonal volume. The greater percentage of tissue volume occupied by microvasculature in the prelaminar region may implicate it as a site where significant connections between the central retinal artery and short posterior ciliary arteries occur.