Macular epiretinal membrane causes a slow and progressive visual loss lasting months or years, and affecting one or both eyes. Generally, it causes image distortion, and undulation of straight lines. Numbers and letters can appear to be in another line, and perception of colors may be decreased.
The typical sign is a semitransparent membrane that covers the rear surface of the retina, known as macula, which is the area responsible for detailed vision necessary to read. This membrane obscures and creases the retina in a greater or lesser degree, depending on its thickness and its capacity to contract.
In some cases, retinal cysts are detected, as a result of the leakage of fluid from blood vessels, which are subject to the membrane’s pulling effect. This disturbance is known as cystoid macular edema and implies a higher visual loss.
Types of membrane
- Stage 0: It is known as cellophane maculopathy. A semi-transparent membrane that does not cause distortion on the retina nor obscures the underlying blood vessels.
- Stage 1: A membrane that causes distortion on the retina but allows to see the underlying blood vessels.
- Stage 2: A membrane that causes a prominent distortion on the retina and obscures the underlying blood vessels. The membrane is opaque and has a whitish color.
It appears in healthy patients without any evidence of other intraocular diseases.
- Eye surgery: retinal detachment surgery or treatment of retinal tears by means of laser argon or cryotherapy.
- Intraocular inflammation (for example, uveitis).
- Vascular diseases of the retina (venous obstruction).
- Eye trauma.
- Intraocular tumors.
- Degenerative eye diseases (such as retinitis pigmentosa).
Management of patients with macular epiretinal membrane
First of all, it’s important to determine whether any of the abovementioned causes are responsible for the macular epiretinal membrane. If so, the first thing to do is to treat the underlying disease.
In idiopathic epiretinal membranes and, once resolved, in secondary epiretinal membranes, it is necessary to evaluate whether its removal can improve the visual acuity of the patient and reduce the vision distortion.
Before removing the epiretinal membrane, it is necessary to assess the patient’s degree of cataract. In patients who have cataracts, a combined surgical procedure consisting in the removal of the cataract and epiretinal membrane surgery is recommended, so as to avoid the need of a second intervention.
Personal history: drugs, systemic diseases, injuries, and eye diseases.
Full eye examination has to include:
- Distant and near vision, pupil examination and refraction.
- Biomicroscopy under pupil dilation, with direct lighting and backlighting, in order to study the cornea, the anterior chamber, and the possible presence of cataracts, as well as to rule out an eye inflammation.
- Tonometry to determine the intraocular pressure.
- Examination of the eye fundus, with special care on the macula, in order to determine the stage of epiretinal membrane. It is also very important to rule out any vitreous inflammation or retinal diseases that can cause epiretinal membranes.
- Macular OCT to confirm the diagnosis, determine the shape and thickness of the epiretinal membrane, rule out a cystoid macular edema and assess the status of the different retinal layers. All this information is very important to determine if the removal of the membrane can improve the patient’s vision.
- Fluorescein angiography. In some patients, it may be necessary to complete the study with this test in order to rule out other retinal diseases.
- Ultrasound or interferometry biometry: when a cataract surgery is considered, keratometric data becomes necessary and the measurement of the axis by means of type A ultrasound or laser is used to calculate the power of the intraocular lens that the patient will need.
- The evaluation is required of the corneal endothelium, usually through the slit lamp and sometimes through a count of endothelial cells.
Extraction of macular epiretinal membrane is performed in order to:
- improve the vision and reduce image distortion in patients with symptomatic visual disturbances.
- avoid progressive visual loss that typically suffer over time patients with macular epiretinal membrane.
Cataract extraction is performed to:
- improve the vision of the patient.
- avoid the need for a second intervention due to the cataract development later in time, something very common in patients with cataract and over 60 years old.
Cataract extraction allows us to correct any refractive errors that the patient may have.
Patients who do not require surgery should undergo an examination every 6 months and should carry out self-monitoring at home with the Amsler grid in order to determine if there have been any changes in distortion.
Patients should go the clinic before the scheduled date in case there is a symptomatic decrease in vision or an increase of distortion.
In every examination, patient’s vision loss will be assessed, as well as any increase in image distortion. A macular OCT will also be performed in order to assess whether there has been progression in macular epiretinal membrane.