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Bryn Brazile, Bin Yang, Alexandra Gogola, Po Lam, Andrew Voorhees, Ian A Sigal; One beam-one vessel is not true: lamina cribrosa vessel and collagen beam networks have distinct topologies. Invest. Ophthalmol. Vis. Sci. 2019;60(9):4275. doi: https://doi.org/.
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It is often stated that each lamina cribrosa collagen beam contains a vessel and that all vessels are contained in a beam. We analyzed the spatial interrelation between the lamina cribrosa microvasculature and collagen beams. Specifically, we quantified the percentage of collagen beams that contain a vessel, and the number of vessels that are inside/outside of a collagen beam
The vasculature of six normal monkey eyes was labeled by perfusing lipophilic carbocyanine dyes through the carotid artery. Eyes were enucleated, and coronal cryosections through the lamina cribrosa were imaged using fluorescence and polarized light microscopy to visualize the vessels and collagen beams, respectively. The images were registered to form 3D volumes, and the beams and vessels segmented for visualization and analyzed to quantify their spatial interrelationship
On average, only 22% of the collagen beams contained a vessel within (individual eyes ranged from 14% to 32%). On average, 21% of the vessels within the LC were located outside of a collagenous beam (range 13% to 36%). Thus, on average, 79% of the LC vessels were inside a beam (range 64% to 87%). Individual monkeys differed significantly in the fraction of vessels outside a beam (p<0.01 by linear mixed effect analysis), but not in the fraction of beams containing a vessel (p>0.05). Contralateral eyes were not significantly different in the fraction of beams with a vessel and vessels outside of beams (p>0.05)
The laminar vascular and collagenous networks are clearly distinct. The widespread notions that every lamina beam has a vessel, and all vessels are within beams are inaccurate. Up to a third of the beams did not have a vessel within. Similarly, up to a third of the lamina vessels are outside beams. We postulate that vessels outside beams may be particularly sensitive to elevated IOP
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
A) Lamina vasculature (red) and collagen (green) in a 32um thick projection. Collagen beams with no vessels (pink arrows), vessel outside beams (white arrow), vessel along the side of the beam (blue arrow), and the expected vessel through the center of a beam (yellow arrows). B) Percentage of beams with a vessel within. C) Percentage of vessels outside a beam. Bars: mean over lamina depth; error bars: SD
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