Visual outcomes of primary versus secondary epiretinal membrane following vitrectomy and cataract surgery

Purpose To compare visual outcomes, incidence of cystoid macular edema (CME), and rate of repeat epiretinal membrane (ERM) surgery following phacovitrectomy for primary and secondary ERM. Methods Retrospective review of 178,856 cataract surgeries from 2003 to 2015. Eyes that underwent cataract surgery combined with ERM peel were included (n = 708). Eyes were divided into primary (n = 538) and secondary (n = 170) ERM groups. Patient demographics, visual acuity (VA), and postoperative CME were recorded. Results Patients with secondary ERM had worse preoperative VA, 0.9 +/- 0.6 logMAR (20/160 Snellen equivalent) as compared to patients with primary ERM, 0.6 +/- 0.3 (20/80), respectively (p < 0.0001). There was no difference between the secondary and primary ERM groups in postoperative vision (0.5 +/- 0.4 logMAR vs. 0.5 +/- 0.3; p = 0.9962) or proportion with VA >= 20/40 (46.4% vs. 43.1%; p = 0.6744) at 12-24 weeks. Postoperative CME was twice as likely in the secondary ERM group (16.5%) compared to the primary ERM group (7.8%) (p = 0.0018). There was no difference in the rate of repeat ERM surgery between the secondary ERM group (1.8%) and the primary ERM group (1.5%) (p = 0.7308). Conclusion Eyes with secondary ERM had significant postoperative improvement in VA. They had worse preoperative VA and had a twofold increase in postoperative CME than primary ERM.