2Baskent University, Faculty of Medicine, Department of Physiology, Ankara, Türkiye DOI : 10.37845/ret.vit.2026.35.10 Objective: To evaluate color contrast sensitivity, dark adaptation (DA), and full-field electroretinography (ffERG) parameters in patients with mild nonproliferative diabetic retinopathy (NPDR) and to compare these findings with those of healthy individuals to identify early functional changes related to retinal neurodegeneration.
Methods: This cross-sectional study included patients with mild NPDR and healthy controls. Color contrast sensitivity along the protan and tritan axes was assessed using the ChromaTest. DA maximum sensitivity and ffERG parameters, including photopic negative response, were recorded using a Ganzfeld system in accordance with ISCEV standards. All participants had best-corrected visual acuity of 0.0 logMAR and no clinically significant cataract or other ocular pathology.
Results: Both protan and tritan color contrast thresholds were significantly higher in the NPDR group compared with controls (p < 0.001). The maximum sensitivity threshold for DA was significantly reduced in patients with NPDR (p = 0.032). In ffERG measurements, rod response b-wave implicit time was significantly longer (p = 0.005), whereas maximal response b-wave implicit time was shorter (p < 0.001) and maximal response a-wave amplitude was higher (p = 0.002) in the NPDR group compared with controls. No significant differences were observed in other ffERG parameters.
Conclusion: Patients with mild NPDR exhibit impaired color contrast sensitivity and DA despite relatively preserved ffERG responses. These findings suggest that functional alterations related to retinal neurodegeneration may precede overt vascular changes in diabetic retinopathy. Psychophysical measures such as color contrast sensitivity and DA may represent accessible tools for detecting early functional retinal involvement in diabetes.
Keywords : Color vision, Dark adaptation, Diabetic retinopathy, Electroretinography