Macular pucker, also referred to as epiretinal membrane, is a condition in which a thin, membranous tissue grows over the surface of the retina. Contraction of this membrane or 'scar tissue' causes wrinkling of the retina and may result in subsequent swelling of the retina (macular edema). Just as one would prefer to view a movie on a flat, smooth movie screen, clear vision depends on a smooth retina to accurately receive visual information from our environment. Wrinkling of the retina results in distorted images, while swelling of the retina produces blurred vision.
Macular pucker typically occurs in those over age 50, and there is a slightly higher incidence in females. In most cases, the cause is unknown but predisposing conditions include retinal vascular disease (e.g. diabetic retinopathy), retinal tear, prior retinal detachment, and uveitis (ocular inflammation). The condition is mild in most cases and affects both eyes in approximately 25% of cases.
Clinical Appearance & Symptoms
Most epiretinal membranes are clinically insignificant and produce no symptoms or very mild visual disturbances. These membranes are often discovered on routine eye examination and present with a glistening or subtle sheen on the retinal surface. No treatment other than periodic monitoring is required, as approximately 70% of these will remain stable without intervention.
When macular pucker starts to cause symptoms, the membrane is more clearly visualized on the surface of the retina (Figure 1, 2). Definite wrinkling or striae of the retina are observed; the retinal blood vessels appear tortuous where the membrane is contracting and straightened or stretched in the surrounding areas. This produces symptoms of varying degrees of distortion depending upon the degree and location of traction induced by the epiretinal membrane. Careful examination will often reveal retinal swelling, or macular edema, which is responsible for blurred vision. Patients often describe their condition as 'looking through a fish tank.
When an epiretinal membrane is discovered, certain diagnostic tests may be requested by your retinal specialist. The purpose of these tests is to evaluate a possible underlying cause of the epiretinal membrane, determine the degree of traction or macular edema caused by the membrane, and plan possible treatment.
The simplest technique is photographic documentation of the epiretinal membrane. Color and red-free photographs provide a valuable baseline for following the progress of membrane formation through time or evaluating a response to treatment.
Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the epiretinal membrane and its effect on the retina. This technology uses laser light to scan the retina and construct an accurate cross-sectional image, non-invasively. The epiretinal membrane can be visualized along with its attachments to the retina, traction and distortion of the retinal architecture, and degree of macular edema (Figure 3). This is very helpful in guiding decisions for treatment.
Fluorescein angiography may be employed in the diagnosis of epiretinal membrane. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the retinal circulation. This technique is very useful for evaluating possible underlying causes of epiretinal membrane due to retinal vascular diseases such as diabetic retinopathy and retinal vein occlusion. The dye also highlights the retinal blood vessels, and depicts the tortuosity often seen in areas of retina under significant traction (Figure 4, 5). Leakage of dye into the retina also provides an indication of the presence and degree of retinal swelling, or macular edema.
When a macular pucker, or epiretinal membrane, causes significant visual loss or symptoms that affect an individual's ability to adequately perform their activities of daily living, consideration is given to surgical intervention. Surgery is the only definitive treatment for effectively removing the membrane and alleviating the symptoms. The procedure is called vitrectomy with membrane peeling and involves removal of the vitreous gel from the eye through tiny openings, followed by peeling of the membrane from the surface of the retina using fine instruments such as micro-forceps. Following removal of the membrane, the retinal architecture usually returns to a more normal state with relief of traction and distortion and resolution of edema (Figure 6).
Visual recovery after vitrectomy with membrane peeling usually occurs over several weeks. Approximately 80-90% of patients report significant improvement in blurred vision and distortion, although many are left with some degree of residual visual loss or symptoms. The cause, duration, baseline vision, and severity of the original macular pucker all play a role in the ultimate prognosis following surgical intervention.