Macular function assessed with mfERG before and after panretinal photocoagulation in patients with proliferative diabetic retinopathy

Abstract

Purpose: To examine macular function and its correlation to macular thickness before and after panretinal photocoagulation for proliferative retinopathy in diabetic patients. Methods: Ten diabetic patients (aged 57 ± 10 years, diabetes duration 21 ± 10 years) treated with panretinal photocoagulation outside the great vascular arcade underwent multifocal electroretinography (mfERG) and optical coherence tomography (OCT) before and 6 months after treatment. When focal treatment in the macular region was performed prior to panretinal photocoagulation the investigations took place 3 weeks after this treatment but before the panretinal photocoagulation. One eye per patient was examined. Amplitudes and implicit times of the mfERG response were analyzed within the four innermost (27°) of the six concentric rings registered by the mfERG, which corresponds to the area measured by the OCT (Ø 3.5 mm). Results: Visual acuity was similar before and after photocoagulation, 1.0; 0.7–1.0 (md, range) versus 1.0; 0.6–1.0 (md, range). The mean values of the ring average amplitudes were reduced in the first and second, third and fourth concentric rings from foveola after photocoagulation, p= 0.001, p= 0.011 and p= 0.004, respectively. No change was seen in implicit time after treatment. OCT values were similar before and after photocoagulation. There was no correlation between retinal thickness assessed with OCT and amplitudes measured by the mfERG. Conclusion: In spite of unchanged values of retinal thickness and visual acuity, panretinal photocoagulation seems to cause a functional impairment in the adjacent untreated macula, shown by reduced amplitudes measured by the mfERG.