Evaluation of Foveal Cone and Mller Cells in Epiretinal Membrane using Adaptive Optics OCT

Objective: To investigate cellular-level morphological alterations in the retinal neuroglia in eyes with epiretinal membrane (ERM).Design: Prospective cross-sectional, observational study (November 2020-May 2022).Subjects and Controls: We included 41 eyes with unilateral idiopathic ERM and 33 healthy eyes of healthy volunteers.Methods: We examined the foveal microstructures in all eyes using adaptive optics OCT (AO-OCT) with axial and lateral resolutions of 3.4 and 3.0 mu m, respectively. Adaptive optics OCT images were acquired for a 2.5 degrees (728 mu m) area at the foveal center.Main Outcome Measures: Foveal microstructures on AO-OCT images, best-corrected visual acuity (BCVA) in logarithm of the minimum angle of resolution units, and associations between these parameters.Results: Adaptive optics OCT imaging of healthy eyes and eyes with ERM revealed sharp hyperreflective lines of the external limiting membrane (ELM), accompanied by hyporeflective gaps, individual nuclei of the foveal cone photoreceptors, and M & uuml;ller cell bodies. The arrangement of M & uuml;ller cell bodies was more vertical in eyes with ERM than in normal eyes. Epiretinal membranes adhered to foveal M & uuml;ller cells via the internal limiting membrane (ILM), exerting vertical traction that pulled the foveal cones anteriorly. Adaptive optics OCT also enabled visualization of outer segment (OS) discs. Hyperreflective changes in the OS discs were observed beneath the vertically thickened ellipsoid zone (EZ) in 15 eyes (36.6%) with ERM. For eyes with ERM, multiple regression analysis showed that the length from ILM to the inner border of the outer nuclear layer and the EZ thickness were significantly associated with BCVA (beta = 5.3 x 10(-4) and 82.7 x 10(-4), respectively), with associated 95% confidence intervals of 1.3 x 10(-4) to 9.3 x 10(-4) (P = 0.011) and 39.0 x 10(-4) to 126.5 x 10(-4) (P < 0.001), respectively. The EZ thickness was significantly and positively associated with the length from ELM to the retinal pigment epithelium (beta = 23.9 x 10(-2), 95% confidence interval: 4.8 x 10(-2) to 42.9 x 10(-2); P = 0.015).Conclusions: Cellular imaging of retinal neuroglia by AO-OCT may suggest possible mechanisms associated with visual impairment in patients with ERM, which could potentially contribute to the growing body of knowledge on its pathophysiology. However, these insights require further validation through extensive studies to fully ascertain their significance.