Epiretinal membrane, or ERM, is a condition where a film develops over the macula, or center of the retina. The retina is the fragile, light-sensitive membrane at the back of the eyeball. This is where images are focused and sent to the brain via the optic nerve.
ERM is not life threatening and, in most cases, the patients have no symptoms. The condition is often discovered when they go to their eye doctor for something else. However, ErM can progress to the point where patients notice lines that should be straight are somewhat wavy or crooked. The effect is most pronounced when the person closes their healthy eye. This article covers the causes, symptoms, and treatment of epiretinal membrane.
What Is Epiretinal Membrane?
The film that covers the macula is very thin and made of fibrous tissue. It is avascular, which means it has no blood supply. It comes about because of changes in the cells between the vitreous gel and the macula. Glial cells from the retina, white blood cells, fibrocytes, bits of collagen, retinal pigment epithelial cells and laminocytes fall back onto the macula, where they accumulate until a membrane forms. Often, the membrane is so slight that it doesn’t affect the person’s vision. But sometimes it puckers and pulls like a scar, which leads to visual distortions.
ERM does not progress to the point where the person goes blind in that eye. Even if their central vision is distorted, their peripheral, or side vision, is unaffected. The membrane doesn’t affect the person’s color vision unless it becomes very hard and thick. The risk of contracting ERM becomes more pronounced as people age, and studies show that about 2 percent of people over 50 and 20 percent over 75 have ERM. However, most don’t need treatment. The condition is painless.
What Causes Epiretinal Membrane?
Some diseases and conditions of the eye increase the risk of epiretinal membrane. They include posterior vitreous detachment. This is where the gel that fills the eyeball pulls away from the retina, which results in floaters and flashes of light. Other conditions include damage done to the retina as a complication of diabetes. This is called diabetic retinopathy. It happens when the blood vessels in the retina are damaged because the patient’s diabetes is not in control. Other conditions that damage the blood vessels in the eye increase the risk for ERM. Sometimes, the disease has no cause and is called “idiopathic.”
Epiretinal membrane can appear after eye surgery, such as that for cataracts. An inflammation of the eye such as uveitis also places a person at greater risk for ERM. Uveitis causes pain in the eye and sensitivity to light. The eye turns red, the patient sees dark floaters and has blurred vision.
Epiretinal Membrane Treatment
Since ERM tends to stabilize after a while, most ophthalmologists adopt an attitude of watchful waiting. There are some cases where the condition resolves when the membrane just pulls away from the retina, and the body absorbs it. This is often the case in younger patients. In cases where the ERM is badly affecting the patient’s vision, the ophthalmologist may recommend epiretinal membrane surgery to remove the membrane. There are no eye drops or noninvasive treatments that can completely cure ERM though there are some treatments that make it tolerable.
Though doctors can discover ERM during a regular eye exam, the eye doctor might want to order an ocular coherence tomography, or OCT, to determine how severe the membrane is. This is a non-invasive technique that produces a three-dimensional image of the patient’s eye. The doctor may also order a fluorescein angiography. First, the patent is given eyedrops that dilate their pupil, and the eye doctor uses a camera to take pictures of the inside of the eye. After that, a dye called sodium fluorescein is introduced into the patient’s vein, where it makes its way to the blood vessels in the retina. As the yellow dye enters, the doctor continues to photograph the patient’s eye.
The operation to remove the membrane is called a vitrectomy. During the operation, the doctor makes tiny incisions in the white of the eye behind the cornea and replaces the vitreous humor with saline, or sterile salt water. Then, the doctor uses a microscope to see inside the eye and specialized forceps to remove the membrane. Sometimes the surgical incisions close up by themselves and don’t require sutures, which causes less pain and a faster recovery time for the patient. The doctor then places a patch over the eye, which the patient wears for about a day. After that, the patient uses ointment or eye drops for a few weeks to help the eye heal and prevent infection. The patient can usually return to their non-strenuous daily tasks the day after the surgery, and their vision usually improves over a period of months.
Complications are rare, but they include retinal detachment and infection. If a person is at risk for cataracts, cataracts tend to get worse. Some patients have cataract surgery at the same time they have their vitrectomy.
The success of the surgery also depends on whether the ERM is the result of a disease or an unknown cause, how much pulling the membrane has done at the macula and how long the membrane has been present.
ERM relates to the age of the patient, and many cases are idiopathic. Consequently, there’s no way to prevent it. However, if the person is diabetic, it is important for them to keep their diabetes under control to avoid the retinopathy that can lead to ERM.
Some eye doctors prescribe NSAIDS, or non-steroidal anti-inflammatory drugs to reduce the swelling of the membrane. In some cases, this can help the patient avoid surgery. Other doctors prescribe sub-Tenon’s steroid injections to treat this swelling. Studies have also shown that removing the ILM, or inner limiting membrane, the clear layer between the retina and the vitreous humor, produces a better outcome for people with ERM and does not adversely affect the patient’s vision.