Prognostic prediction ability of postoperative multifocal ERG after vitrectomy for diabetic macular edema.

PURPOSE: Diabetic macular edema (DME) causes visual loss in diabetic patients. Multifocal electroretinograms (mfERGs) have been used to assess macular function pre- and postvitrectomy for DME.

METHODS: A standard three-port pars plana vitrectomy with peeling of inner limiting membrane was performed in 25 eyes of 21 patients (13 male, 8 female) with DME. For each patient, visual acuity examination, measure of retinal thickness (using optical coherence tomography), and mfERGs were performed before and 1 week, 1 month, 3 months, and 6 months after vitrectomy.

RESULTS: Mean postoperative visual acuity was significantly improved (p<0.05, t test), with mean increase of 0.17 logMAR units; mean retinal thickness was significantly (p<0.001) decreased after surgery (from 537 microm to 298 microm). The increase of normalized amplitude of central ring was not significant; the mean P1 wave-amplitude increased from 0.33 to 0.40 mV; mean P1 wave-implicit time decreased 2.88 ms. We divided the patients into two groups: Group 1 (13 eyes), in which the visual recovery was less than 0.20 logMAR, and Group 2 (12 eyes), in which the visual recovery was greater than 0.20 logMAR. ERG results were statistically significantly different between the groups (p<0.025), when we consider the response recorded from the central ring. In Group 2 there is a marked reduction in implicit time of both ERGs waves, which was statistically significant for N1 wave (p=0.01). The changes of parameters of mfERG observed 6 months after surgery were consistent with those recorded just 1 week after surgery.

CONCLUSIONS: Multifocal electroretinogram can be useful to predict functional prognosis in patients with diabetes who underwent vitrectomy for diabetic macular edema.