Retinal outer layer thickness increases after vitrectomy for epiretinal membrane, and visual improvement positively correlates with photoreceptor outer segment length

Purpose To investigate postoperative thickness changes in the retinal layers in eyes with epiretinal membrane (ERM). Correlations between these changes and visual outcomes were also examined. Methods Retrospective review of 25 eyes (24 patients) that had undergone pars plana vitrectomy for ERM and had a postoperative follow-up period ≥6 months. Optical coherence tomography (6 × 6 mm macular thickness map) was used to measure mean thickness of the inner and outer retinal layers 1 week and 1, 3, and 6 months following surgery. Photoreceptor outer segment (PROS) length was evaluated manually, and used to assess the association between best-corrected visual acuity (BCVA) and retinal layer thickness at the fovea. Results At 1 week and 1, 3, and 6 months, retinal layer thickness was 388, 377, 362, and 352 μm for the whole layer; 133, 115, 107, and 101 μm for the inner layer; 138, 145, 147, and 148 μm for the outer layer; and 28, 35, 36, and 40 μm for the PROS length, respectively. In comparison to 1-week data, the inner layers were significantly thinner at 1 month and later, as was the thickness of the entire retina. Outer layer thickness and PROS length were also significantly thicker at these time points. Six months following surgery, BCVA was significantly correlated with an elongated PROS length ( R = 0.49, P = 0.01). Conclusion Retinal outer layer thickness significantly increased following pars plana vitrectomy for ERM. Visual improvement was positively correlated with PROS length recovery.