What is the macula
The back of the eye is lined with a thin layer of tissue called the retina. The retina is like the film in a camera. It is the “seeing” tissue of the eye. When light hits the retina, a picture is taken. This picture is then sent to the brain through the optic nerve. This is how we see.
The retina has two parts: the peripheral retina and the macula. The macula is used to see very fine detail straight ahead, to read small print, and to recognise faces. The peripheral retina gives you your side vision.
What is an epiretinal membrane?
An epiretinal membrane (or macular pucker) is an abnormal wrinkling of the retina that overlies the macula. Scar tissue can grow on the surface of the retina, directly over the macula. This scar tissue contracts and causes the retina to wrinkle. This membrane can cause visual loss, as well as distortion or double vision. Vision loss can vary from barely noticeable to severe. It is only the central vision that is affected. The peripheral vision remains normal.
What causes an epiretinal membrane?
Epiretinal membranes may be caused by a variety of eye problems. In most patients, the membrane forms because of a posterior vitreous detachment, which occurs with ageing.
In some people, the vitreous is attached very firmly to the macula. As the vitreous starts to contract and separate, it can irritate and damage the macula area. This irritation causes cells to migrate and clump over the macula in an attempt to heal the area of damage. These cells form a thin layer of scar tissue known as an epiretinal membrane. It is this scar that results in the wrinkling and distortion of the macula.
Epiretinal membranes can sometimes occur following retinal detachment surgery, laser treatment or cryotherapy (freezing treatment) for retinal tears.
The membrane can also be associated with retinal blood vessel problems such as diabetes, retinal vein occlusion or inflammation.
What tests will be needed to determine if I have an epiretinal membrane?
Your ophthalmologist can diagnose an epiretinal membrane by looking inside your eye with a special instrument called an ‘ophthalmoscope’.
An Optical Coherence Tomography (OCT) may also be performed to examine a cross section of your retina.
You may require photographs to be taken of your eye to confirm the diagnosis. The ‘Red Free’ photograph on the right shows an epiretinal membrane, as does the colour photograph (above right).
A special photographic study called an angiogram may be performed to determine the extent of damage to the macula, as well as checking that there are no other problems with your retina.
How is an epiretinal membrane treated?
The only treatment for visual loss caused by an epiretinal membrane is vitrectomy surgery to remove the membrane. Vitrectomy surgery is performed under local anaesthesia. You will be given a small amount of anaesthetic whilst your eye is put to sleep. This takes approximately five minutes. The surgery takes approximately 45 minutes in total.
Using 23-gauge microsurgical instruments, the vitreous gel is removed from the centre of the eye. The membrane is gently peeled, and the scar tissue removed from the surface of the retina, relieving the traction, and reducing the distortion to the retinal surface. During the surgery, a fluid, which is similar to the fluid naturally produced by cells inside of the eye, is used to replace the vitreous.
This surgery is sutureless. The benefits of sutureless surgery include minimal conjunctival scarring, faster visual recovery, decreased discomfort in the eye, and overall increased patient satisfaction.
In most cases, air or gas is injected into the eye to help hold the retina in place. You may need to posture in a face down position between 1 to 5 days after the surgery so the gas can exert pressure on the macula. There is equipment available to hire to make this position more comfortable. If gas is used during surgery, vision will be poor until the gas bubble is absorbed by your body.
What happens to an untreated epiretinal membrane?
Not all patients choose to have an epiretinal membrane treated. Some patients are not bothered by the distortion and find the symptoms very mild.
If left untreated, the membrane may cause permanent and irreversible damage to the retina. This can affect your ability to perform daily tasks such as driving or reading.
If I do have surgery, what type of vision improvement can be expected??
Patients can expect an average of 50% improvement in vision. Recovery does vary from patient to patient. Even though some patients may only achieve a small improvement on the vision chart, the degree of distortion is significantly improved.
The improvement in vision following this type of surgery occurs gradually as the eye heals. Usually, there is a significant amount of improvement in the first six weeks, but the eye can slowly keep improving for a further twelve months after the surgery.
Once the macula has had a chance to heal, a prescription for new glasses will be recommended.
What are the risks associated with surgery?
As with all surgical procedures, there are potential complications and side effects associated with repair of an epiretinal membrane. These include the potential to develop retinal tears during the procedure or post-operatively. This only occurs in a very small percentage of people. During the course of the operation, careful inspection for retinal tears is performed. If a tear is found, laser treatment or freezing treatment is applied to these areas.
There are more serious complications that can occur, such as infection, retinal detachment, increased intra-ocular pressure, or haemorrhage. These complications are rare.
In patients who have not undergone cataract surgery, development of a cataract may occur more rapidly following vitrectomy surgery.
Is there anything I should not do following surgery?
Avoid heavy lifting, swimming or very strenuous exercise for the first three weeks after surgery. You are allowed to read, watch television, and walk. If air or gas is used during the surgery, do not fly in an airplane or travel to high altitudes until you are told the gas bubble is gone. A rapid increase in altitude may cause a dangerous rise in eye pressure. You will be given a wrist bracelet to warn Medical Staff against giving nitrous oxide whilst gas remains in the eye.
Can the membrane grow back?
In a very small number of cases, the epiretinal membrane can recur or grow back as a result of reactivation of the healing process. The reason for this is still not fully understood. Fortunately, instances of regrowth are very uncommon.
Above: Normal OCT image of macula (top) and OCT image showing epiretinal membrane (bottom)