Background: To evaluate quantification of metamorphopsia before and after the removal of unilateral epiretinal membrane (ERM).
Methods: One hundred and four consecutive patients with unilateral ERM scheduled for membrane peeling were prospectively enrolled. A complete ophthalmologic examination was performed. Metamorphopsia was evaluated, with standard Amsler grids and a laser grid generated with a scanning laser ophthalmoscope (SLO). The SLO procedure determined the area of distortion and was performed twice at a 30-minute interval to evaluate its reproducibility. The result was considered to be reliable when the area of distortion was identical in both SLO test sessions. One year after surgery, a complete ophthalmologic examination was performed. Metamorphopsia was again quantified with the SLO procedure.
Results: Before surgery, a reliable quantification of metamorphopsia (defined as area of distortion) could be performed in 98 patients (94%). Among these patients, 85 completed the follow-up of 12 months after surgery. Of these 85 patients, visual distortions had been detected preoperatively in 48 patients (56%). One year after surgery, visual distortions were detected in only 11 patients (13%). In 48 patients with preoperative distortions, the decrease of the area of distortion correlated with the change in visual acuity (r = -0.460, p = 0.011).
Conclusions: SLO-based evaluation of metamorphopsia made it possible to provide a fast and reliable method for preoperative and post-operative quantification of visual distortion in patients undergoing ERM removal.