Morphologic and functional association of retinal layers beneath the epiretinal membrane with spectral-domain optical coherence tomography in eyes without photoreceptor abnormality

To access the differential thickening of retinal layers in the epiretinal membrane (ERM) and to determine their correlation with visual acuity. Prospective and comparative case series of 22 patients, each of whom has one unilateral ERM eye and one normal eye. The eyes with abnormal photoreceptor layer by OCT images were excluded. Spectral-domain optical coherence tomography (SD-OCT) images were generated with Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany). The thicknesses were obtained by a volume scan program using manual segmentation of the total retina, inner retina, inner nuclear layer (INL), outer plexiform layer (OPL), and outer nuclear layer (ONL) in the fovea (1.0 mm diameter) and the parafovea (3.0 mm diameter). The thickness and the proportion of each retinal layer and their relationship with visual acuity were analyzed. All retinal layers of ERM eyes were thicker than the patients’ normal eyes (P < 0.05). In the fovea, the levels of thickness difference of inner retina (240.38%) and INL (266.26%) were significantly higher than total retina (126.7%). Visual acuity was not correlated with the retinal thickness in both ERM eyes and normal eyes (P > 0.05). However, significant correlations between visual acuity difference with retinal thickness difference were found in the total retina (rho = 0.450, P = 0.046) and the inner retina (rho = 0.602, P = 0.005) of the fovea, as well as in the inner retina (rho = 0.468, P = 0.037) and the INL (rho = 0.466, P = 0.039) of the parafovea. When we convert each retinal thickness into a proportion, in the foveal area, the percentages of thickness of the inner retina and the INL of ERM eye were significantly higher than that of the normal eye (P < 0.05), whereas that of the ONL was significantly lower (P < 0.05). In the parafoveal area, the percentage of thickness of the inner retina of the ERM eye was significantly higher than that of the normal eye (P < 0.05), whereas that of ONL was significantly lower (P < 0.05). Idiopathic ERM affects the volume of all retinal layers. Inner retina had the most variability of thickness and is strongly associated with visual acuity changes in the case of intact photoreceptor layer.