Time course of changes in aniseikonia and foveal microstructure after vitrectomy for epiretinal membrane.

PURPOSE: To quantify aniseikonia in patients undergoing vitrectomy for epiretinal membrane (ERM) and to investigate the relationship between the aniseikonia and the foveal microstructure by spectral-domain (SD) optical coherence tomography (OCT).

DESIGN: Prospective, consecutive, interventional case series.

SUBJECTS: This study included 44 eyes of 44 patients undergoing vitrectomy for idiopathic ERM.

METHODS: We examined visual acuity and aniseikonia using the New Aniseikonia Test and SD-OCT before and 3 and 6 months after surgery. On the basis of the obtained OCT image, we divided the 1.0 × 1.0-mm area centered on the fovea into 9 sections at 0.25-mm intervals and quantified the following parameters using an image-processing program: central foveal thickness and mean thickness of the ganglion cell layer, inner nuclear layer (INL), and outer retinal layer (outer nuclear layer + outer plexiform layer). The status of the photoreceptor inner segment/outer segment junction, external limiting membrane, and cone outer segment tips also was evaluated.

MAIN OUTCOME MEASURES: Amount of aniseikonia 6 months after surgery.

RESULTS: Of 44 patients, 39 (89%) had macropsia, 1 (2%) had micropsia, and 4 (9%) had no aniseikonia preoperatively. Mean preoperative aniseikonia was 6.2% ± 4.5%. Vitrectomy significantly improved visual acuity in patients with ERM but did not change the amount of aniseikonia. Multiple regression analysis revealed that preoperative aniseikonia at 6 months was significantly related to preoperative INL thickness, whereas postoperative aniseikonia at 6 months was associated with postoperative INL thickness at 6 months. Preoperative INL thickness was found to be of significant prognostic value for postoperative aniseikonia at 6 months.

CONCLUSIONS: Most of the patients with ERM had macropsia. Aniseikonia was not reduced after surgery. The amount of aniseikonia was associated with INL thickness.