Abstract
Purpose :
Advances in ocular imaging have made it possible to assess aspects of the choriocapillaris in vivo. However, establishing a link between its structure and its capacity for metabolite transfers to the RPE/retina has remained elusive. Using a robust mathematical framework developed to predict choriocapillaris function based upon its structure, we have identified key anatomical determinants of these transfers. We sought to estimate these parameters in the human macula and to assess their variability in the population.
Methods :
Six-millimeter-diameter, 1 µm thick sections were derived from the macula of 81 eyes obtained from the Steele Center for Translational Medicine, University of Utah (mean age: 68.9; range: 31-93). These sections were stained with Richardson’s stain, imaged, and manually segmented using ImageJ. Confocal microscopy volume scans of 3 wholemounts of human maculas obtained from the Moorfields Eye Bank, University College London, and stained with Ulex Europaeus Agglutinin I were segmented using an in-house validated protocol. Estimates of choriocapillaris thickness and vascular density, their spatial variation and their association with age were determined. Point-pattern analyses of maps of arteriolar and venular insertions into the choriocapillaris were performed using the R package spatstat.
Results :
The thickness of the choriocapillaris ranged from 6.14 µm to 15.34 µm (mean: 8.82 µm) and did not vary significantly with distance from the foveal center or with age. The vascular density of the choriocapillaris did not vary significantly with distance from the foveal center. Median density corrected for sampling region size and location ranged from 0.38 to 0.72 (mean: 0.47) and decreased significantly with age (p = 0.007). The location of arteriolar and venular insertions was probabilistically dependent, with venular openings clustering around arteriolar ones. The median distance between these insertions ranged from 96.0 µm (IQR 60 µm) to 135.3 µm (IQR 195µm).
Conclusions :
The quantification of structural determinants of mass transfers between choriocapillaris and retina will allow for in-depth analyses of its function and how it varies with age and in disease. The distribution of arteriolar and venular insertions into the choriocapillaris display clustering patterns at multiple levels, highlighting a partition into sectors supplied by distinct arterioles.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.