Epiretinal membrane

Overview
Epiretinal membrane is a disease of the eye in response to changes in the vitreous humor or more rarely, diabetes. It is also called macular pucker. Sometimes, as a result of immune system response to protect the retina, cells converge in the macular area as the vitreous ages and pulls away in posterior vitreous detachment (PVD). PVD can create minor damage to the retina, stimulating exudate, inflammation, and leucocyte response. These cells can form a transparent layer gradually and, like all scar tissue, tighten to create tension on the retina which may bulge and pucker (e.g. macular pucker), or even cause swelling or Macular edema. Often this results in distortions of vision that are clearly visible as bowing and blurring when looking at lines on chart paper (or an Amsler grid) within the macular area, or central 1.0 degree of visual arc. Usually it occurs in one eye first, and the distortions create binocular diplopia or double vision. The distortions can make objects look different in size (usually larger = macropsia), especially in the central portion of the visual field, creating a localized or field dependent aniseikonia that cannot be fully corrected optically with glasses. Partial correction often improves the binocular vision considerably though. In the young (under 50 years of age), these cells occasionally pull free and disintegrate on their own; but in the majority of sufferers (over 60 years of age) the condition is permanent. The underlying photoreceptor cells, rod cells and cone cells, are usually not damaged unless the membrane becomes quite thick and hard; so usually there is no macular degeneration.

Surgery for epiretinal membrane
Surgeons can remove or peel the membrane through the sclera and improve vision by 2 or more Snellen lines. Usually the vitreous is replaced at the same time with clear fluid, in a vitrectomy. Surgery is not usually recommended unless the distortions are severe enough to interfere with daily living, since there are the usual hazards of surgery, infections, and a possibility of retinal detachment. A more common complication is high intraocular pressure, bleeding in the eye, and Cataract, which is the most frequent complication of vitrectomy surgery. Many patients will develop a cataract within the first few years after surgery. In fact, the visual distortions and diplopia created by cataracts may sometimes be confused with epiretinal membrane.

Prevention
There is no good evidence for any preventative actions to take, since it appears this is a natural response to aging changes in the vitreous that happen to everyone. It is important to remember that posterior vitreous detachment PVD has been estimated to have occurred in over 75 per cent of the population over 65, that PVD is essentially a harmless condition although with some disturbing symptoms and that it does not normally threaten sight. However, since epiretinal membrane appears to be a protective response to PVD, where inflammation, exudative fluid, and scar tissue is formed,  it is possible that NSAIDS may reduce the inflammation response, so taking NSAIDS may be helpful. Usually there are flashing light experiences and the emergence of floaters in the eye that herald changes in the vitreous before the epiretinal membrane forms.

Science background
This ocular pathology was first described by Iwanoff in 1865, and it has been shown to occur in about 7% of the population. It can occur more frequently in the older population with postmortem studies showing it in 2% of those aged 50 years and 20% in those aged 75 years.

The source of the cells in epiretinal membranes (ERM) has been found to comprise glial cells, retinal pigment epithelial (RPE) cells, macrophages, fibrocytes, and collagen cells. These cells are found in varying proportions. Those from retinal breaks, previous retinal detachments, or cryopexy are composed mainly of dispersed RPE cells, while cells of glial origin predominate in idiopathic pathology.

The incidence of associated PVD range from 75-93%, and PVD is present in virtually all eyes with retinal breaks or retinal detachments and subsequent ERM formation. PVD can lead to retinal breaks that may liberate RPE cells that initiate membrane formation. Small breaks in the ILM after PVD also may provide retinal astrocytes access to the vitreous cavity, where they may subsequently proliferate. Finally, vitreous hemorrhage, inflammation, or both associated with a PVD also may stimulate ERM formation.

Both sexes appear to be affected in relatively equal percentages.

Synonyms
Macular pucker, preretinal membrane, cellophane maculopathy, retina wrinkle, surface wrinkling retinopathy, premacular fibrosis, and internal limiting membrane disease.