Retinal function and morphology of severe non-proliferative diabetic retinopathy before and after retinal photocoagulation

Purpose: The purpose of this project was to investigate the changes in macular function and macular morphology of severe non-proliferative diabetic retinopathy (NPDR), due to photocoagulation, using the multifocal electroretinogram (mfERG) and optical coherence tomography (OCT). Methods: Thirty-five volunteers were in the control group, with one eye per person examined with the mfERG. Both the mfERG and OCT were conducted on 30 patients with diabetes who had severe NPDR before, and two, seven and 14-days after, treatment with photocoagulation. Results: Compared with the control group, the P1 and N1 response densities in the patients with NPDR appeared to decrease significantly at rings 2-3 and rings 3-4, respectively, whereas no difference was seen in the implicit times. At two days after photocoagulation, the P1 and N1 response densities decreased significantly in ring 1 and they were still lower than the pre-photocoagulation values at 14-days after photocoagulation. In addition, no change was found in the implicit times before and after photocoagulation. There was no obvious difference in the macular thickness after treatment. At two days after treatment, the P1 response density in ring 1 negatively correlated with the corresponding macular thickness. Conclusion: The para-macular function was significantly impaired in those patients with severe NPDR and photocoagulation reduced the central macular function. Even after 14-days, the central macular function had not returned to pre-photocoagulation levels.