Epiretinal Membrane
What is an Epiretinal Membrane?
An epiretinal membrane (ERM) is a thin film of scar tissue that grows on the surface of the macula. The scar tissue contracts and wrinkles the macula. It is also known as cellophane maculopathy, macular pucker, and premacular fibrosis. Epiretinal membrane affects the macula, but it is not the same condition as macular degeneration.
What Causes an Epiretinal Membrane to form?
The inside of the eye, behind the lens, is filled with a clear jelly-like material called the vitreous. With normal ageing, the vitreous jelly becomes more liquid and eventually separates from the retina. This process is known as posterior vitreous detachment (PVD). In some people this process releases cells that lead to scar tissue growing on the surface of the macula. This is the most common cause of epiretinal membrane.
Other causes of epiretinal membrane include retinal tear, retinal detachment, inflammation, trauma, bleeding within the eye, and retinal vascular diseases such as diabetic retinopathy.
What are the Symptoms of an Epiretinal Membrane?
Epiretinal membranes can cause blurred vision, distortion, difficulty with reading or judging distances and double vision. Mild epiretinal membranes however often cause no symptoms.
Because epiretinal membranes only affect the centre of vision, and the peripheral (side) vision remains normal, some people will not be aware of a problem unless they cover the other eye.
How is Epiretinal Membrane Diagnosed?
An epiretinal membrane is seen during a dilated retinal exam. Optical coherence tomography (OCT) can confirm the diagnosis and monitor the condition. Fluorescein angiography may be needed in a small number of cases to assess the extent of damage to the macula and to check for any other problems with the retina.
How is Epiretinal Membrane Treated?
Mild epiretinal membranes do not require treatment and can be monitored.
More marked epiretinal membranes that cause symptoms require vitreoretinal surgery (pars plana vitrectomy) which is performed in hospital. Using microsurgical techniques, the vitreous jelly in the eye is removed and the epiretinal membrane is then peeled from the surface of the retina and removed. The vitreous gel is not required for normal function of the eye and is replaced with a saline solution similar to the eye’s natural fluid. Occasionally it is necessary to temporarily replace the vitreous fluid with a gas bubble. The gas is absorbed by the eye and replaced with the eye’s natural fluid. Vitrectomy surgery is usually done under local anaesthesia, as a day only procedure.
At least 80% of patients will experience improvement in their vision (reading more letters on the chart, and/or having less distortion) with this surgery. Even with significant improvement, vision will not be “perfect”, and it is common to have some residual distortion or blurring of vision. The chance of feeling that the vision is worse after the operation is 5% or less.
What If Epiretinal Membrane Is Untreated?
If the epiretinal membrane is mild and not causing any visual problem it can safely be observed without surgery.
Some patients decide not to have an operation despite blurred vision or distortion. In such cases surgery can be considered if the symptoms get worse in the future.
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