Retinal vessel oxygen saturation and vessel diameter in high myopia.

Purpose: To investigate changes in retinal vessel oxygen saturation and diameter in high myopia.

Methods: Relative oxygen saturation was measured in the retinal blood vessels of 54 participants with high myopia and compared to a control group of 54 individuals with emmetropia with the Oxymap T1 retinal oximeter. The participants with high myopia were further divided into two groups according to the grade of myopic retinopathy: Group A (grade < M2 ) and Group B (grade ≥ M2 ). One-way anova was used to analyse the mean saturation and diameter of retinal arterioles and venules and the mean difference in arterio-venous saturation among the four groups. Further analysis of multiple comparisons was performed with the Bonferroni test. Linear regression was used to analyse the correlation of ocular perfusion pressure or best corrected visual acuity with other variables.

Results: For all of the high myopia patients, retinal arteriole saturation (92.3 ± 5.6%) and the difference in arterio-venous saturation (30.8 ± 5.0%) were significantly lower than in normal individuals (96.0 ± 5.8%, 35.4 ± 6.2%; p = 0.006, p < 0.001, respectively). In Group A, only the difference in arterio-venous saturation (31.0 ± 4.7%) was significantly lower than in the control group (p = 0.011). In Group B, retinal arteriole saturation (92.2 ± 5.3%) and the difference in arterio-venous saturation (30.7 ± 5.3%) were also lower than the control group (p = 0.02, p = 0.001, respectively). Both retinal arteriole diameter and retinal venule diameter were narrower than in participants with high myopia than the control group (p < 0.001). No statistically significant correlations were found between ocular perfusion pressure or best corrected visual acuity with any other variables.

Conclusions: The study demonstrated decreased retinal arteriole saturation and decreased difference in arterio-venous saturation as well as narrowing retinal vessel diameter in highly myopic eyes. Further studies are needed to determine if such changes play a role in the development of high myopia and its complications or occur as a consequence of tissue remodelling during axial elongation.