High myopia is protective against diabetic retinopathy via thinning retinal vein: A report from Fushun Diabetic Retinopathy Cohort Study (FS-DIRECT).

Purpose: To investigate the association between high myopia and diabetic retinopathy, and its possible mechanism, in a northeastern Chinese population with type 2 diabetic mellitus.
Methods: Patients were included from Fushun Diabetic Retinopathy Cohort Study. High myopia was defined as spherical equivalent of autorefraction less than -5D.
Results: A total of 1817 patients [688 (37.9%) diabetic retinopathy, 102 (5.6%) high myopia] were included. Compared to eyes without high myopia, the frequency of diabetic retinopathy and non-proliferative diabetic retinopathy was significantly less in eyes with high myopia (23.5% vs 38.7%, p  = 0.002; 22.5% vs 35.3%, p  = 0.005). Eyes with high myopia were less likely to have diabetic retinopathy (multivariate odds ratio, 95% confidence interval: 0.39, 0.22-0.68) or non-proliferative diabetic retinopathy (odds ratio, 95% confidence interval: 0.40, 0.23-0.70). High myopia was negatively associated with central retinal venular equivalent (multivariate β, 95% confidence interval: -37.1, -42.3 to -31.8, p  < 0.001). Furthermore, central retinal venular equivalent (per 10 μm increase) had a significant association with diabetic retinopathy (odds ratio, 95% confidence interval: 1.24, 1.17-1.31) as well as non-proliferative diabetic retinopathy (odds ratio, 95% confidence interval: 1.24, 1.18-1.31).
Conclusions: High myopia was negatively associated with both diabetic retinopathy and non-proliferative diabetic retinopathy in this northeastern Chinese population. This protective effect may have been partially achieved via thinning retinal veins.