Inner Nuclear Layer Thickness, a Biomarker of Metamorphopsia in Epiretinal Membrane, Correlates With Tangential Retinal Displacement

Abstract

Purpose: To examine correlations of inner nuclear layer (INL) thickness with metamorphopsia and tangential retinal displacement in epiretinal membrane (ERM).

Design: Retrospective, consecutive, interventional case series.

Methods: Setting: Institutional study.

Patient population: Fifty eyes of 50 patients undergoing epiretinal membrane surgery.

Observation procedures: M-CHARTS were used to measure metamorphopsia. Inner nuclear layer (INL) thickness and outer retinal layer (ORL) thickness in the macula and distances between the intersections of 2 sets of retinal vessels situated vertically or horizontally were measured in Spectralis optical coherence tomography and infrared images.

Main outcome measures: Correlations of INL and ORL thicknesses with M-CHARTS scores and distances of retinal displacement.

Results: Preoperative INL thickness significantly correlated with preoperative and postoperative metamorphopsia scores at 3 months (Spearman correlation coefficient: P = .036 and P = .003, respectively). The baseline INL thickness and its change at 3 months significantly correlated with the postoperative vertical retinal displacements at 3 months (P < .001 for both). Preoperative and postoperative ORL thicknesses were not correlated with preoperative and postoperative metamorphopsia scores at any periods.

Conclusions: INL thickness is a useful biomarker to evaluate metamorphopsia and appears to be determined by tangential retinal displacement in ERM. Structural changes of the inner retinal layer, which cause Müller cells to be distorted, play a more important role for generation of metamorphopsia than outer retina. Our results provide evidence for the theory that Müller cell functions as an optic fiber in humans.