Retinal and Choroidal Vascular Biomarkers Are Correlated With the Degree of Myopia

To investigate adaptive changes in retinal and choroidal vasculature with increasing retinal surface area in myopia.

Widefield optical coherence tomography angiography and enhanced depth imaging (EDI)-OCT images of the retina were used to acquire digital images of the choroidal and retinal vasculature in 32 eyes with axial myopia and 14 emmetropic control population eyes. Retinal vessel density was calculated using Otsu's method and used for quantitative comparison of retinal vascular architecture and perfusion ability with increasing retinal surface area. The choroidal vascularity index was also calculated from skeletonized 15 × 9 mm swept-source EDI-OCT images. Correlations were sought between increasing myopia and the retinal vessel density and choroidal vascularity index.

Increased axial myopia was negatively correlated with retinal vessel density (r2 = 0.35, P < 0.001) and positively correlated with choroidal vascularity index (r2 = 0.31, P < 0.001).

Increased retinal surface area in myopia results in decreased retinal vascular surface coverage. The inadequacy of retinal vascular coverage is compensated for by increased choroidal vascularity index in high myopes. This adaptive change may enable oxygen diffusion from choroidal vessels to the relatively thinner retina, thereby supplementing the oxygen needs of the inner retinal neurons.

Adaptive changes in the choroidal vessels to supply more oxygen to the inner retina can explain why myopic patients exhibit a decreased risk of diabetic retinopathy and its vision-threatening complications despite being vulnerable due to inadequate retinal vascular coverage.