Purpose The aim was to assess early functional and structural changes in the neural retina in type 2 diabetic patients with no clinical signs of diabetic retinopathy (DR). Patients and methods A total of 92 eyes of 48 patients were included, which were divided into the following groups: 30 eyes of 16 participants with type 2 diabetes mellitus without clinical DR, with a mean age of 48.75±3.09 years, as group 1; 30 eyes of 16 participants with type 2 diabetes mellitus with DR, with a mean age of 51.75±2.86 years, as group 2; and a control group of 32 eyes of 16 healthy age-matched and sex-matched participants, with a mean age of 49.88±4.26 years. After full ophthalmologic examination, spectral-domain optical coherence tomography scans, multifocal electroretinogram (Mf-ERG), pattern electroretinogram (PERG), and photonegative response (PhNR) were tested for all participants. Statistical analysis was performed to compare ganglion cell complex (GCC) thicknesses, multifocal electroretinogram, PERG, and phNR values between the groups. Results There were no statistically significant differences between the studied groups regarding age, sex, refraction, or intraocular pressure (P=0.056,0.72, 0.16, and 0.35, respectively). There were significant differences of total GCC thickness values among group 1 (107.13±7.04 μm), group 2 (97.27±10.97 μm), and control group (113.81±5.26 μm) (P