Evaluation of Optic disc vascular density in high myopia with optical coherence tomography angiography

Abstract

Aim This study aimed to investigate the correlation between the optic nerve (ON) vascular density (VD) and myopia severity as estimated by the spherical equivalent (SE) and the axial length (AL) in high myopia (HM) compared with normal eyes using optical coherence tomography angiography (OCTA). Patients and methods This prospective, cross-sectional study included 20 eyes of 10 patients having nonpathological HM (SE ≥ −6.0 diopters) and 20 eyes of 10 normal individuals as a control group (SE=±0.5 diopter). OCTA was used to measure the average capillary VD of the optic disc (OD) at the radial peripapillary capillary (RPC) and the entire disc volume (ONH) which was correlated with AL and SE. Results The mean SE was −11.25±4.55 diopters (D) in the myopic group compared with −0.04±0.28 D in the control group with a statistically significant difference (P < 0.001), while the mean AL was 27.37±1.65 mm in the myopic group and 22.87±0.58 mm in the control group, a statistically significant difference (P < 0.001). The average capillary VD of the RPC and the ONH in the myopic group (44.36±4.65 and 49.6±4.28, respectively) was significantly less compared with the control group (49.51±1.60 and 55.49±1.86, respectively) (P < 0.001). There was a highly significant negative correlation between the optic nerve VD both RPC and ONH and axial length (r =−0.755, P < 0.001). On the other hand, there was no statistically significant correlation between the SE and best corrected visual acuity and the ON VD. Conclusion The decrease in ON VD could be attributed to ocular axial elongation that occurs with high myopia. So, the AL elongation must be considered, rather than the SE.