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purpose. To determine whether type 1 diabetes preferentially affects the inner retinal layers by comparing the thickness of six retinal layers in type 1 diabetic patients who have no or minimal diabetic retinopathy (DR) with those of age-and sex-matched healthy controls.

methods. Fifty-seven patients with type 1 diabetes with no (n= 32) or minimal (n= 25) DR underwent full ophthalmic examination, stereoscopic fundus photography, and optical coherence tomography (OCT). After automated segmentation of intraretinal layers of the OCT images, mean thickness was calculated for six layers of the retina in the fovea, the pericentral area, and the peripheral area of the central macula and were compared with those of an age-and sex-matched control group.

results. In patients with minimal DR, the mean ganglion cell/inner plexiform layer was 2.7 μm thinner (95% confidence interval [CI], 2.1–4.3 μm) and the mean inner nuclear layer was 1.1 μm thinner (95% CI, 0.1–2.1 μm) in the pericentral area of the central macula compared to those of age-matched controls. In the peripheral area, the mean ganglion cell/inner plexiform layer remained significantly thinner. No other layers showed a significant difference.

conclusions. Thinning of the total retina in type 1 diabetic patients with minimal retinopathy compared with healthy controls is attributed to a selective thinning of inner retinal layers and supports the concept that early DR includes a neurodegenerative component.