Purpose: Epiretinal membranes (ERMs) are a common cause of visual impairment for patients over the age of 50 years. Predicting visual outcome is essential for counselling and weighing the risks against the benefits of surgery. Although the predictive value of outer retinal integrity in patients with ERM has been investigated thoroughly, the role of inner retinal changes remains unknown. Disorganization of the retinal inner layers (DRIL) has emerged as a novel predictor of visual acuity in eyes with inner retinal pathology. The aim of this study is to correlate pre-operative inner retinal morphology with anatomical and functional outcomes after ERM surgery. 
Methods: Charts and spectral-domain optical coherence tomography (OCT) images of 191 patients who underwent treatment for fovea-involving idiopathic ERM between 2014 and 2018 at the Ottawa Eye Institute were reviewed. The main outcome measure included the correlation of pre-operative DRIL on OCT with best-corrected visual acuity at baseline, 3 and 6 months after ERM surgery. DRIL was defined as the loss of distinction between the ganglion cell–inner plexiform layer complex (GC-IPL), inner nuclear layer, and outer plexiform layer. DRIL grading was based on its extent within the central 2mm region of a transfoveal B-scan (mild:<1/3, moderate: 1/3-1/2 and severe: >1/2 horizontal width). Secondary outcome measures included the correlation of DRIL with the integrity of outer retinal OCT structures (ellipsoid zone and external limiting membrane).
Results: Of the 191 patients reviewed, 77% had available 3-month follow-up data. Preliminary analysis of 74 pseudophakic eyes, showed presence of moderate/severe DRIL in 36% and absence or mild DRIL in 64%. Pre-operatively, greater extent of DRIL and central retinal thickness were associated with worse baseline VA (p=0.0028 and p<0.001, respectively). DRIL status at baseline did not affect median change in VA at 3 months (0.12 vs. 0.09 log MAR; mild vs. severe DRIL). Disruption of the ellipsoid zone and DRIL with GC-IPL thinning temporal to the fovea were found commonly among eyes that lost VA at 3-months.
Conclusion: Presence of DRIL correlates with worse baseline visual acuity in ERM patients. However, outer retinal disruption and post-operative DRIL /GC-IPL thinning appear to be stronger predictors of long-term visual outcomes in ERM surgery.

Inner retinal morphology and visual outcomes in idiopathic epiretinal membrane surgery: A retrospective OCT study

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