Dr. Bueno Palacín, an expert in the diagnosis of any pathology related to the retina, is the director of the Vitreoretinal Unit at Innova Ocular IOA MADRID. In the following article he explains what the epiretinal membrane is and how it is treated.
The macula is the central area of the retina, which occupies a few central millimeters of the retina. The light rays that penetrate the eye fall directly on it, which is why it is the area that achieves the best vision. This area allows us to identify fine details, read, thread a needle or recognize faces, among others.
The peripheral retina serves to expand the field of vision, aiding spatial orientation. This allows us to know what is to our right and what is to our left, but not precisely. For example, if we have our eyes fixed on the TV, we will be able to see that there is furniture next to it, but if a text is placed next to the TV, we will not be able to read it. This is because the peripheral retina does not have the capacity for detailed vision.
The epiretinal membrane or epimacular membrane is a thin layer of fibrous tissue that grows on the surface of the macula. Over time, this membrane tends to contract little by little and causes a progressive deformation of this central area of the retina.
What causes the appearance of the epiretinal membrane?
Most of the time, the appearance of the epiretinal membrane has no definite cause but is related to the patient’s age. It is usually rare to see an epiretinal membrane below the age of 50 years, being diagnosed more frequently in the 70s.
A small percentage of these epiretinal membranes may be inflammatory in origin, arising as a reaction to trauma, surgery, intraocular inflammation, laser treatment or in relation to vascular or tumor diseases. This type of epiretinal membranes can occur at any age.
What are the symptoms of epiretinal membrane?
When the membrane is recent, it is not very contracted and deforms the macula very little, so it may not cause any symptoms. The patient may have good vision and, because the membrane is so thin, it may even go unnoticed by the physician in a routine fundus examination. We have a device known as OCT, which performs a small scan of the macula and is very sensitive in detecting the presence of these membranes even in these early stages.
As the membrane contracts, the deformation of the macula becomes greater and greater and the symptoms it produces are mainly two:
- The first and most important is decreased central vision. This is easy to identify in an examination because the affected eye, even if it is well graduated, is able to see fewer letters than the healthy eye when a visual acuity test is performed.
- The second is the appearance of metamorphopsia, which is the appearance of vision deformity. The patient refers to this by saying that in one eye he sees objects crookedly, if he compares it with the good eye.
Can epiretinal membrane be prevented?
The epiretinal membrane can be prevented only when its origin is inflammatory, and it can be prevented with treatment. In the vast majority of cases the membrane usually arises spontaneously, so it cannot be prevented.
How is epiretinal membrane treated?
Currently there are devices that help in the early diagnosis of these membranes. Many of them do not need to be treated since they do not cause great visual alterations and the treatment can be limited to a follow-up. In addition, their evolution is usually very slow and an annual check-up, or two, is usually enough to keep them under control.
When these membranes clearly affect the patient’s visual acuity, either because of loss of vision or because the distortion they cause is great, the only solution is to perform an intervention called posterior vitrectomy. This intervention basically consists of entering the eye and eliminating a gelatinous liquid inside it, known as vitreous, in order to access the macula. Once there is free access to the macula, a dye is used that stains the membrane blue and allows it to be better identified. Then, with very small forceps, an attempt is made to separate the membrane of the macula little by little in order to detach it without damaging the underlying retina.
If we have a macula deformed by the existence of a membrane on its surface and we manage to successfully remove this membrane, the aim is to stop the process of progressive deformity of the macula and, at the very least, to slow down the loss of vision. In addition, once the macula is freed from traction, we increase the likelihood that the macula will tend to regain its normal shape and improve vision and distortion.
In general, the results are better in patients who have not lost much vision prior to surgery. This is logical, since if a patient has a severe visual impairment it means that the membrane has been evolving for a long time, with a deformed macula for a long time and, therefore, with less capacity to recover its original shape and improve vision. There is no fixed rule as to when an epiretinal membrane should be operated, nor is there a limit of vision loss beyond which it is mandatory to operate. Nevertheless, as a general rule, it is important to know that the better the vision before surgery, the greater the possibility of a good visual recovery and vice versa. If we observe that in successive revisions the patient remains stable, it would not be necessary to do anything, but if the loss of vision is progressive, it would not be advisable to wait too long to operate.