What is an Epiretinal Membrane (ERM)?
Epiretinal Membranes are also often referred to as cellophane maculopathy or macular pucker. They are semi-translucent, fibro-cellular membranes that form on the inner surface of the retina. Most often they cause minimal symptoms, but in some cases can result in severe vision loss and distorted vision. ERMs are most symptomatic if they affect the macula, the most central portion of the retina, which we use to distinguish fine detail.
What causes an ERM to form?
An ERM is formed when cells migrate through the surface layer of the retina and start to grow in a membranous sheet on the retinal surface. This membrane can appear like “cellophane” and over time may contract and cause traction (pulling) of the retina, leading to decreased vision and distortion.
The most common cause of an ERM is an age-related condition called posterior vitreous detachment, where the gel-like substance in the back of the eye, the vitreous, separates from the retina. ERMs can also be associated with a variety of other ocular conditions such as prior retinal tear or retinal detachment, retinal vascular diseases such as diabetic retinopathy, post-trauma, post-surgical, or inflammation occurring inside the eye.
Risk Factors:
Increasing age
Posterior Vitreous Detachment (PVD)
Retinal tear
Recent eye trauma
Recent eye surgery
Diabetes
Vein Occlusions
Inflammatory eye conditions
Symptoms:
Blurry or decreasing vision
Distortion, ie. straight lines can look wavy
Central flashes
Double vision in the affected eye
Objects appear slightly larger than normal
Diagnosis:
Most of the time an ERM is diagnosed during a dilated eye examination. A test known as an Ocular Coherence Tomography (OCT) is useful to gauge the severity of the ERM and to monitor for progression. Fluorescein angiography (FA) is often used to determine if there is an underlying etiology for the ERM formation.
Treatment:
ERMs can enlarge or grow over time. It is hard to predict how quickly an ERM will grow or how large it will become. Since most ERMs are mild and only affect vision slightly, they can simply be monitored. In rare instances, the membrane will spontaneously release from the retina, relieving the traction and clearing up the vision. However, if examination shows significant progression, or worsening of vision which affects daily activities, surgical intervention may be needed.
There are no eye drops, medications or nutritional supplements to treat ERMs. A surgical procedure called vitrectomy is the only option when treatment is necessary. During a vitrectomy the natural vitreous gel is drained from the eye and replaced with saline. This allows the surgeon to gently peel the membrane from the surface of the eye. After the tissue is removed, the macula flattens and vision slowly improves, though it usually does not return all the way to normal.
Risk involved with this procedure is small, however those with their natural lens may have an increase in the rate of cataract development. Occasionally the ERM can grow back, but this is rare.
Factors affecting Visual Outcome:
Cause of the ERM
Degree of traction
Length of time ERM has been present
Surgery to repair an ERM is a very delicate procedure. In most cases, vision is improved, but does not usually return to normal. On average, about half of the vision lost from an ERM is restored with surgery. Some are more successful, some less. In most cases, visual distortion is significantly reduced. Vision recovery after surgery can take up to three months.
There is no known way to prevent the formation of an ERM, or to slow the growth of an ERM. It is important to have regular eye examinations to monitor the progression of the disease.
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