The effect of myopia on retinal string vessels and vascular branchpoint density is exacerbated by age

Abstract

Purpose : The retinal vasculature supplies nutrition to the retina and is crucial for optimal retinal function. The mechanical elongation of the globe induced by myopic eye growth may affect the retinal vasculature and predispose the eye to ocular complications. Here, we studied how the effect of age interacts with myopia on the retinal microvascular template in an established non-human primate (NHP) model of myopia, the common marmoset (Callithrix Jacchus).

Methods : Five six-month-old control (6mC), six six-month-old myopic (6mM), and three twelve-month-old myopic (12mM) retinal whole mounts (6mC average refraction, Rx: -0.7±0.4D, age: 232.2±32.9 days; 6mM average Rx: -7.0±-1.8D, age: 200.3±14.2 days; 12mM average Rx: -4.1±2.1D, age: 388.0 ±0.0 days) were labeled with isolectin-488 to visualize the retinal vasculature at the cellular level and assess string vessel and vessel branchpoint density in the parafoveal, peripapillary, and peripheral retinal regions using confocal microscopy. Statistical analysis was performed using student t-test at a confidence level of 95%.

Results : 6mM retinas had increased string vessels/mm² in the radial peripapillary (RPC) and superficial (SCP) vascular plexi compared to 6mC, and the increase was even greater in 12mM (RPC; 6mC: 23.5 ± 8.6; 6mM: 65.3 ± 11.4; 12mM: 182.2 ± 23.6; p<0.01; SCP: parafovea 6mC: 35.2 ± 8.4; 6mM: 85.42 ± 25.7; 12mM: 198.89 ± 49.1; p<0.05. SCP: Peripapillary 6mC: 36.6 ± 14.6; 6mM 74.0 ± 17.7; 12mM: 155.0 ± 37.2, p<0.01). Capillary branchpoints (branchpoints/mm²) in the parafovea SCP increased, but decreased in the peripapillary SCP in 12mM compared to 6mM and 6mC (parafovea 6mC: 147.8 ± 24.1; 6mM 121.5 ± 27.6; 12mM 271.1 ± 38.6; p<0.05; peripapillary 6mC 157.5 ± 43.2; 6mM 111.8 ± 27.4; 12mM 227.2 ± 67.8; p<0.05). String vessels and capillary branchpoint density increased with aging (R² = 0.13, p<0.001), axial length (R² = 0.83, p<0.001) and refractive error (R² = 0.69, p<0.001).

Conclusions : Experimental myopic eyes without pathology exhibit increased string vessel formation and changes to capillary branchpoint numbers in all four vascular plexi pan-retinally, which is exacerbated by age. The combined effect of myopia and aging on the architectural template of the retinal microvasculature at the cellular level in primate eyes might be adaptation mechanisms that could serve as early cellular markers of myopic degeneration.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.