Characteristics of Retinal Oxygen Kinetics and Blood Flow in Myopia of Different Degrees.

PURPOSE: To investigate the characteristics of retinal oxygen kinetics and blood flow across varying degrees of myopia and to explore associated factors.

METHODS

This study included 146 eyes from 132 participants with varying refractive errors, classified by spherical equivalent (SE) into nonmyopia (NM; SE > -0.25 D, n = 45), mild-to-moderate myopia (MM; -0.25 D ≥ SE > -6.00 D, n = 48), and high myopia (HM; SE ≤ -6.00 D, n = 53). Retinal oxygen kinetics and blood flow were assessed in an optic-disc-centered annulus using a Multimodal Eye Functional Imaging and Analysis System. Group differences and correlation were evaluated with generalized estimating equations (GEEs), and nonlinear associations were examined using restricted cubic spline analysis.

RESULTS

The mean age was 27.35 ± 8.61 years, and 47 participants were male (35.6%). Arterial and venous retinal external diameters decreased significantly and progressively from NM to HM (all P < 0.05). Compared with NM, both MM and HM groups exhibited reduced venous blood flow velocity (BFVv) and venous retinal blood flow (RBFv). Significant reductions in arterial oxygen saturation (SaO2) were observed only in the HM group (NM, 90.38% ± 3.65%; MM, 91.60% ± 3.85%; HM, 86.30% ± 4.90%; all P < 0.05). Hierarchical multivariable regression identified axial length (AL) as an independent factor associated with SaO2, BFV, and venous vascular diameters. Restricted cubic spline analysis revealed a nonlinear relationship between AL and SaO2, with an inflection point at 25.45 mm, beyond which SaO2 declined markedly.

CONCLUSIONS

Reductions in retinal vessel diameter and blood flow velocity were evident even at the mild-to-moderate myopia stage, whereas significant declines in arterial oxygen saturation occurred only when AL reached ≥25.45 mm. These results offer new insights into the mechanisms of fundus vascular complications in high myopia. Further longitudinal investigations are warranted to fully elucidate the underlying pathophysiological processes.