Correlation between OCT Findings and Visual Acuity in Patients with Epiretinal Membrane

Abstract

Purpose: : With the introduction of spectral domain optical coherence tomography (SD-OCT), higher resolution of the disease changes in the retinal layers is possible. The aims of this study are (1) to determine which anatomical features of the retina seen on SD-OCT correlated with visual acuity (VA) in patients with epiretinal membrane (ERM), and (2) to compare certain retinal features between ERM patients and normal patients.

Methods: : Spectralis SD-OCT images were analyzed for 23 patients (23 eyes) with ERM and 21 control patients (21 eyes). The presence or absence of the following anatomical features at the fovea on OCT images were assessed: retinal pigment epithelium (RPE), inner segment/outer segment (IS/OS) junction, external limiting membrane (ELM), foveal depression (FD), RPE detachment, and subretinal fluid (SRF). ImageJ software was used to manually measure the thickness of the following retinal layers: fovea, outer nuclear layer (ONL), ELM to RPE, RPE, ELM, IS/OS, and photoreceptor layer (PRL). Central macular thickness (CMT), central volume thickness (CVT), and central foveal thickness (CFT) were extracted from a macula thickness map generated by the OCT machine. Best corrected visual acuity (VA) at the time of OCT image was obtained from the patients’ charts.

Results: : There was a significant difference in CMT (p=0.000116), CVT (p=0.000298), CFT (p=0.000001), and PRL (p<0.00001) between ERM patients and normal patients. The expected distribution of patients with and without normal FD differed significantly between control and ERM patients (p<0.0001). For ERM patients, no relevant correlations were seen between VA and the presence or absence of SRF (p=0.54) and IS/OS junction abnormality (p=0.32). A significant difference was seen between the VA of ERM patients who have and who do not have a normal FD (p=0.043). Among ERM patients, VA correlated significantly with CFT (p=0.0001, r²=0.51) and PRL (p=0.031, r²=0.20). Of the factors (SRF, IS/OS abnormality, FD, CFT, PRL), CFT was most predictive of VA in ERM patients (p=0.002, r²=0.60).

Conclusions: : ERM patients had a thicker central macula, volume, fovea, and photoreceptor layer than normal patients. In ERM patients, those with a normal foveal depression had significantly better visual acuity than those without. Visual acuity declined significantly with increased thickness of central fovea and photoreceptor layer. Central foveal thickness was most predictive of visual acuity in ERM patients with moderate correlation.

Keywords: imaging/image analysis: clinical • retina • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)