Epiretinal Membranes (Macular Pucker)
An epiretinal membrane (ERM) is a fine piece of "scar tissue" that grows on the surface of the retina that may contract and cause retinal wrinkling. It may also be referred to as macular pucker, surface wrinkling retinopathy, and cellophane maculopathy due to its appearance. The membrane itself is a thin sheet of transparent or translucent tissue thought to be derived from cells originally under the retina that migrate onto the retinal surface and settle in the central macular region. Proliferation with subsequent contraction of the tissue results in various degrees of retinal distortion. In most cases, the vitreous gel has partially or completely detached which may allow for such cellular migration. This condition is most often idiopathic (cause unknown) or associated with other conditions such as retinal tears or detachments, diabetes mellitus, retinal vein occlusions, and chronic post-operative cystoid macular edema.
There is a wide spectrum of severity and, hence, clinical findings. Mild disease shows an abnormal sheen to the retinal surface of the macula without retinal distortion or symptoms. If this progresses, mild retinal striae formation are often accompanied by subtle visual acuity change or metamorphopsia. The most severe disease shows frank distortion of macular anatomy with more severe visual acuity change or metamorphopsia than surface wrinkling retinopathy. The ERM is usually easily visible on the retinal surface as a gray, sometimes dense fibrous-like tissue which can often obscure underlying retinal details.
Other clinical findings include straightening or zigzagging of retinal vessels in the macula, a central defect in the membrane or pseudo-macular hole, retinal thickening/edema with leakage evident on fluorescein angiography, and a posterior vitreous detachment.
The clinical course is variable and unpredictable. The condition may remain stable if the membrane has fully contracted or may progress if full contraction has yet to occur. Most patients remain at 20/70 or better, and less than 5% progress to 20/200 or worse. Very rarely, vision may improve if the membrane spontaneously separates.
|OCT of a patient with severe epiretinal membrane with significant retinal distortion. This patient eventually underwent a vitrectomy with removal of the membrane|
|OCT of the same patient three months after vitrectomy surgery. Note the significant reduction in retinal thickness.|
With idiopathic epiretinal membranes, early stages are generally observed for progression. Generally, serial fundus photography and/or OCT imaging are used in conjunction with clinical exams to monitor the progression of the disease. Vitrectomy with peeling of the membrane is the only treatment option for patients who develop significant visual symptoms. Current drops, injections, and medications do not treat the disease. The decision to proceed with surgery depends primarily on patient complaints, although surgery is usually reserved for patients with vision worse than 20/40.
|Fundus photographs of a second patient before [top] and three months after [bottom] vitrectomy surgery for epiretinal membrane. Note the tortuosity of the blood vessels before surgery and the straightening of the blood vessels after the membrane is removed.|
It is generally felt that patients can expect to double their Snellen visual acuity or regain half of the vision that they had lost after surgical removal of the membrane. The length of postoperative recovery is variable. Patients generally have some wrinkling of the retina for months to years before surgery and the retina may take a few months to settle back down into a more normal position. Some patients have improved, but still abnormal anatomy. A small percentage will develop recurrent membrane, some even requiring additional surgery.