Case Report

Epiretinal membrane is a common macular pathology known to cause morphologic changes observed on macular optical coherence tomography (OCT) and retinal nerve fiber layer (RNFL) OCT. However, the longitudinal effect of epiretinal membrane progression on RNFL OCT morphology is not well studied.This report documents a case of epiretinal membrane progression with associated quantifiable changes to the RNFL OCT over time.A 63-year-old man initially presented in 2014 with a grade 0 epiretinal membrane in his left eye and low suspicion of glaucoma in both eyes. Over the next 6 years, his left eye's epiretinal membrane gradually worsened. Along with this change, the RNFL OCT started to show areas of adjacent suspected RNFL thickening and thinning compared with baseline per guided progression analysis (GPA). Despite this, clinical suspicion for actual glaucomatous progression was low. Closer retrospective analysis suggested that the RNFL was continuously dragged temporally toward the macula over this period. Because of traction, values such as the angular location, width, and peak thickness of the inferior RNFL bundles changed. This dynamic shift of a typically stationary structure contributed to an inability to rely on the RNFL OCT GPA to correctly stratify concern for glaucomatous progression.Both macular and RNFL OCT allow us to observe morphologic changes to the retina caused by epiretinal membrane. Other authors have described this phenomenon, but this case demonstrates the continual change over time, suggestive of a dynamic process that requires continuous awareness and monitoring. Clinicians should be especially aware of this phenomenon when a patient is also suspicious of glaucoma. These RNFL changes can make it more problematic to rely on the OCT GPA to determine early progressive glaucomatous changes to the RNFL.