Myopia-related stepwise and quadrant retinal microvascular alteration and its correlation with axial length

To investigate the characteristics of retinal vascular alterations in patients with varying degrees of myopia, and to determine correlated variables and alteration patterns over different retinal zones.

A total of 208 right eyes of 208 patients with myopia were enrolled and divided into mild, moderate, high, and extreme myopia groups. The macular vasculature in superficial, deep, and whole retinal layers was imaged with optical coherence tomography angiography (OCTA). The vessel densities over the whole annular zone, four quadrants, and six annuli were quantified as fractal dimension using a customized software. Simple linear regressions and ridge regression were used to determine and compare explanatory variables of microvascular density.

The microvascular density within the superficial, deep and whole retinal layers was highest in mild myopia group, second highest in moderate myopia group, second lowest in high myopia group and lowest in extreme myopia group. Within the same layer, differences between any two groups were significant (all p < 0.05). Among the four quadrants, only the inferior nasal (IN) quadrant showed no difference in microvascular density between mild and moderate groups. Ridge regression indicated that microvascular density values in all three layers were more strongly correlated with axial length (AL) (scaled estimates -0.139, -0.103, -0.154; all p < 0.001) than with spherical equivalent (SE) (scaled estimates -0.052, -0.096, -0.057; all p < 0.05).

We characterized a stepwise and quadrant alteration of retinal microvascular density from mild to extreme myopia, which was more strongly affected by axial elongation, although both AL and SE were meaningful indicators.