Diabetic macular morphology changes may occur in the early stage of diabetes

Background: The purpose of this study was to observe whether invisible morphological changes are presented in the two types of diabetes mellitus patients without diabetic retinopathy. Methods: Twenty-six type 1 diabetes mellitus (T1DM) patients and 34 type 2 diabetes mellitus (T2DM) patients without diabetic retinopathy (DR) were recruited for this study. They underwent complete examinations that included stereoscopic color fundus photography and optical coherence tomography (OCT). The OCT patterns were used to measure the macular retinal thickness (RT), the ganglion cell and inner plexiform layer (GC-IPL) complex thickness, the inner nuclear layer (INL) thickness, the outer nuclear layer (ONL) thickness and the subfoveal choroidal thickness (SFCT) using the enhanced depth imaging (EDI) patterns and the retinal fiber layer (RNFL) thickness around the optic disc. All results were compared to those of age-and sex-matched control groups. Results: In the patients with T1DM, the mean RT and GC-IPL complex thicknesses were significantly thinner than those of the control group (p < 0.05). The RNFL was found to be thinner at the 9 o'clock position around the optic disc in the patients compared with the control group. The SFCTs were similar in the controls and subjects. The INL and ONL were decreased in parts of the pericentral and peripheral areas in the T1DM patients (p < 0.05) and increased in the T2DM patients (p < 0.05). Conclusions: This study demonstrated that in short-duration T1DM patients, the layers of the retina are affected and that the neural tissue has begun to be lost. As diabetes develops, neurodegeneration may cause vascular permeability, which causes thickening of the retinal layers.