Association of Myopia with Peripapillary Retinal Nerve Fiber Layer Thickness in Diabetic Patients Without Diabetic Retinopathy.

Purpose: To investigate the association between myopia and peripapillary retinal nerve fiber layer (pRNFL) thickness in diabetic patients without diabetic retinopathy (DR). Methods: A total of 271 eyes of 271 participants were included. They were divided into four groups according to the presence of myopia (≤ -3 diopters [D]) and diabetes without DR: (1) control group (n = 76), (2) myopia group (n = 57), (3) diabetes group (n = 82), and (4) diabetes + myopia group (n = 56). The peripapillary average and sector RNFL thicknesses were measured and compared among the four groups to determine the effects of myopia and diabetes. Covariates were adjusted using analyses of covariance. Linear regression analyses were fitted to evaluate the factors associated with pRNFL. Results: Spherical equivalents were 0.12 ± 1.31 D in the control group, -4.00 ± 1.47 D in the myopia group, 0.00 ± 1.05 D in the diabetes group, and -4.33 ± 1.70 D in the diabetes + myopia group (P < 0.001). The respective axial lengths (ALs) were 23.91 ± 0.99 mm, 25.16 ± 0.94 mm, 23.68 ± 0.77 mm, and 25.34 ± 1.33 mm (P < 0.001). The average pRNFL showed a progressive decrease from the control group (97.16 ± 8.73 µm) to the myopia group (94.04 ± 9.13 µm) to the diabetes group (93.33 ± 9.07 µm) to the diabetes + myopia group (91.25 ± 9.72 µm) (P = 0.009). Age, diabetes, hypertension, and AL were significantly correlated with the pRNFL. The rate of reduction of pRNFL with increasing age was higher in the diabetes + myopia group than in the other groups, and pRNFL in the diabetes groups decreased more steeply with increasing AL compared to the non-diabetic groups. Conclusions: Myopia and diabetes are important factors affecting pRNFL thickness, and the simultaneous presence of diabetes and myopia results in greater pRNFL damage than observed with either pathology alone.