['To study retinal function in asymptomatic Type 1 and Type 2 diabetic patients with nonproliferative diabetic retinopathy (NPDR) and no clinical signs of diabetic macular edema.', 'Thirty-six consecutive Type 1 and Type 2 diabetic patients with nonproliferative diabetic retinopathy and no diabetic macular edema and 28 healthy controls underwent a complete ophthalmologic examination, including spectral domain optical coherence tomography and microperimetry.', 'Seventy-one eyes (17 patients with Type 1 and 19 with Type 2 diabetes) were tested, and data from 36 (17 Type 1 and 19 Type 2) eyes were analyzed. Mean best-corrected visual acuity was 0.00 ± 0.01 logMAR and 0.00 ± 0.02 logMAR for Type 1 and Type 2 diabetic patients, respectively (P = 0.075). Mean central foveal thickness was 234.5 ± 13.7 μm and 256.3 ± 12.7 μm for Type 1 and Type 2 diabetic patients, respectively (P = 0.04); the central foveal thickness was statistically different compared with the control groups (P = 0.04 and P = 0.01, respectively). Mean retinal sensitivity was 18.9 ± 0.5 dB and 17.7 ± 0.4 dB for Type 1 and Type 2 diabetic patients, respectively; it was statistically different compared with control groups (P < 0.0001 and P < 0.0001, respectively).'] Is macular dysfunction common in both type 1 and type 2 diabetic patients without macular edema?