Assessment of Macular Function by Multifocal Electroretinography and Optical Coherence Tomography before and after Panretinal Photocoagulation in Diabetic Retinopathy

We evaluated macular function before and after panretinal photocoagulation (PRP) in diabetic retinopathy using a multifocal electroretinogram (mfERG) and optical coherence tomogram (OCT). In mfERGs, the 1st positive wave (P1) minus the 1st negative wave (N1) amplitude (P1 ? N1 amplitude), the P1 peak latency and the response density were measured in 7, 19, 37 and 103 hexagonal areas or elements (Areas 1, 2, 3 and 4) within a central radius of 5, 7, 10 and 20 degrees, respectively. The mean retinal thickness was estimated from 9 calculation points at the foveal region within 5 degrees; the central and each of the other 4 points at a distance of 250 ?m and 500 ?m from the central por tion on horizontal and vertical sections on OCT. The P1 peak latencies from the 4 areas were remarkably prolonged in 14 eyes of 9 patients with preproliferative or early proliferative diabetic retinopathy showing no clinically significant macular edema before PRP as compared with those in 15 normal control eyes, without a tendency of recovery throughout the course after PRP except for area 1. The P1-N1 amplitudes and the mean response density levels from the 4 areas were remarkably decreased in the diabetic eyes before PRP as compared with those in the control eyes, followed by a maximum decrease in both parameters at 3 months after PRP. However, remarkable recoveries were detected in both decreased parameters from the 4 areas at 6 months after PRP. The mean foveal retinal thickness on OCT was remarkably increased in the diabetic eyes before PRP as compared with the thickness in 16 normal control eyes. Most remarkably, a transient increase in thickness was detected in diabetic eyes 1 month after PRP, followed by a tendency of recovery 3 to 6 months after PRP. These results indicate that mfERG and OCT examinations are useful in the assessment of macular function before and after PRP in diabetic retinopathy, especially within 5 degrees of the central portion, and that the effects of PRP on macular function in this entity seem to be reversible at the foveal region, although we need to do further investigation in relation to the outcome of visual acuity.