Epiretinal membrane. Optical coherence tomography (OCT) scan of a section through the retina of the eye of a patient with an epiretinal membrane. An epiretinal membrane is a layer of scar tissue that grows across the macula (centre) and distorts the retinal tissue as it contracts and thickens. The macula (centre) is the central area of the retina that contains the highest density of rod and cone cells. This impairs sight by distorting the central area of vision, but does not cause total blindness. Treatment is by removing the membrane in a procedure known as a vitrectomy.