Ophthalmology – Epiretinal Membranes

Epiretinal membrane (ERM), also called macular pucker, cellophane maculopathy, or surface-wrinkling retinopathy, is a thin fibrocellular membrane that develops along the inner surface of the retina, usually over the macula. Contraction of this membrane can distort the underlying retina, resulting in metamorphopsia and decreased central vision. ERM is frequently associated with abnormal vitreous separation and may coexist with vitreomacular traction.

ERM occurs predominantly in older adults and is uncommon as a primary disorder in children. Approximately 2% of eyes are affected around age 50, increasing to approximately 20% by age 75. The condition is bilateral in approximately 20–30% of patients, although the severity is often asymmetric. Most ERMs are mild, asymptomatic, and do not require treatment. In pregnancy, evaluation and intervention can usually be deferred when clinically appropriate.

Risk factors include increasing age, female sex, diabetes, retinal vascular disease, previous retinal laser treatment, ocular surgery or trauma, vitreous hemorrhage, and intraocular inflammation. There is no established genetic predisposition.

Pathophysiology and Etiology

ERM develops through proliferation of cells along the retinal surface, including fibrous astrocytes, Müller cells, fibrocytes, myofibroblasts, macrophages, and hyalocytes. These cells commonly gain access to the retinal surface following a posterior vitreous detachment (PVD), although proliferation may occur before complete vitreous separation.

As the cellular membrane develops myofibroblastic properties, it can contract and exert tangential traction on the retinal surface. This produces retinal wrinkling, displacement of retinal structures, vascular tortuosity, and sometimes macular edema, ultimately causing visual distortion and reduced visual acuity.

ERM may be primary (idiopathic) when it develops without an identifiable underlying ocular disorder, or secondary when associated with conditions such as retinal vascular disease, diabetes, intraocular inflammation, ocular trauma, or previous surgery.

Diagnosis

Many patients are asymptomatic, particularly during the early stages. Symptomatic patients usually describe a gradual reduction in central vision and metamorphopsia, in which straight lines appear bent, curved, or distorted. Patients may have difficulty reading because of blurred or distorted letters. Less commonly, monocular diplopia or central photopsias may occur.

Funduscopic or biomicroscopic examination may demonstrate a subtle shiny or cellophane-like reflex over the macula. With increasing contraction, retinal folds or striae become apparent. Retinal vessels may become distorted or tortuous because of traction. Macular edema may develop, while retinal hemorrhages or cotton-wool spots can occasionally be present depending on associated disease.

Optical coherence tomography (OCT) is the most useful imaging modality for evaluating an ERM. It demonstrates the hyperreflective membrane along the retinal surface and provides detailed assessment of retinal distortion, macular thickness, cystic changes, vitreomacular traction, and photoreceptor integrity. Significant cystoid macular edema or disruption of the outer retinal layers may indicate a less favorable visual prognosis.

The Amsler grid is useful for identifying and monitoring metamorphopsia. Patients can use it at home to recognize progression of distortion.

Fluorescein angiography is not routinely required for an uncomplicated idiopathic ERM but can help identify associated retinal vascular disease, macular leakage, or capillary nonperfusion. Significant vascular abnormalities may limit visual recovery following surgery. Routine laboratory testing is generally unnecessary.

The differential diagnosis includes vitreomacular traction or an incomplete posterior vitreous detachment with adherent posterior hyaloid, as well as fibrovascular membranes associated with proliferative diabetic retinopathy or ischemic retinal vein occlusion.

Treatment

Most asymptomatic or minimally symptomatic ERMs require observation rather than treatment. The presence of a membrane alone is not an indication for surgery. Patients should undergo periodic examination and OCT monitoring, particularly when there is evidence of progressive retinal distortion.

Medication generally has no role in eliminating the membrane itself. When associated macular edema has another treatable cause, therapy should be directed toward that underlying disorder. Associated conditions such as diabetes, retinal vascular disease, inflammation, or age-related macular degeneration should be appropriately managed.

Patients with significant metamorphopsia, progressive visual impairment, or substantial structural distortion on OCT should be referred to a vitreoretinal surgeon. Surgical decisions are based on the patient’s symptoms, functional limitations, visual acuity, OCT findings, and expected benefit rather than a single visual-acuity threshold.

The definitive treatment is pars plana vitrectomy with epiretinal membrane peeling. The internal limiting membrane (ILM) may also be peeled to reduce the likelihood of ERM recurrence. Surgery releases traction on the macula and allows gradual remodeling of the retinal architecture.

Follow-up and Prognosis

Asymptomatic patients can usually be observed with periodic examinations. ERMs may remain stable for many years. Patients should monitor their vision, often with an Amsler grid, and seek reassessment if they develop new or increasing distortion, blurred central vision, or other visual symptoms.

The prognosis for an asymptomatic, stable ERM is generally excellent. In appropriately selected symptomatic patients, surgery frequently improves visual acuity and substantially reduces metamorphopsia. Visual recovery is usually gradual and may continue for several months. The degree of recovery depends partly on the preoperative visual acuity and integrity of the macular photoreceptor layers.

Potential complications of vitrectomy and membrane peeling include cataract progression, retinal tears, retinal detachment, recurrent ERM, retinal phototoxicity, and, rarely, endophthalmitis. Cataract progression is particularly common following vitrectomy in phakic older adults.