Quantification of metamorphopsia in patients with epiretinal membranes before and after surgery

To evaluate quantification of metamorphopsia before and after the removal of unilateral epiretinal membrane (ERM).

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.

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).

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.