EPIRETINAL MEMBRANES (aka, Macular Pucker)
Epiretinal membranes are also known as "macular pucker".
An epiretinal membrane is a sheet of proliferative tissue, on the order of translucent or transparent scar tissue that grows on the surface of the retina.
This tissue is similar to Saran Wrap in the way that it first tends to lay down a smooth, relatively clear layer on the surface of the retina, but later may contract and become wrinkled. When this epiretinal membrane is on the surface of the macula, the part of the retina that is responsible for reading and fine vision, it can distort or reduce the vision.
When the effect of the epiretinal membrane (macular pucker) interferes with the patient's vision, surgical intervention is a practical option.
Who gets an Epiretinal Membrane?
There is no one group of patients who get epiretinal membranes. These phenomena are known as 'idiopathic' because we often do not know who will get one or wh
Some people who have had other eye disease, like uveitis, trauma or retinal tears may be more predisposed to epiretinal membranes, but for the most part, their development is unpredictable as is their course.
How does an Epiretinal Membrane form?
The vitreous jelly fills most of the eye. It is the substance that occupies the 'posterior segment' which comprises 80% of the eye's volume.
The vitreous jelly is somewhat denser around its perimeter, and sends tiny fibrils onto the retinal surface. With age, and sometimes trauma or inflammation, the vitreous will contract and pull away from its attachment to the retina.
While this "vitreous detachment' is relatively benign, it can be associated with flashing lights and floaters. Sometimes, when the retina is thin in certain spots, or the attachment of the vitreous to the retina is particularly strong, the pulling away of the vitreous can lead to a torn retina. A torn retina is potentially more serious, which is why all patients who see flashing lights or floaters should be examined. by an ophthalmologist. (Please see the retinal detachment section)
When the vitreous pulls away from the retina, on a much more microscopic scale, the retina can be injured by these focal areas of traction. The eye may elaborate reparative 'scar' tissue that grows into the region to repair the damage. This reparative scar tissue may form an epiretinal membrane.
Epiretinal membranes are myocontractile, that is, they can assume the characteristics of muscle and contract. When this happens, the transparent, virtually invisible sheet of Saran Wrap becomes wrinkled and even cloudy.
This diagramtic representation illustrates the change in the appearance and topography of a macula due to the development of an epiretinal membrane
What are the symptoms of an Epiretinal Membrane?
The patient who has an epiretinal membrane may have anywhere from no symptoms at all to reduced vision and metamorphopsia (distortion of images). The primary indication to treat an epiretinal membrane is to restore vision, or to prevent more severe compromise to the macula.
Can an Epiretinal Membrane be treated?
There are two basic approaches to epiretinal membranes:
If the vision is not significantly affected, or the compromise in vision does not unduly interfere with the individual's vision, no intervention is mandatory.
The surgical approach consists of performing a vitrectomy (removing the vitreous humor (or fluid)) and mechanically 'peeling' off the membrane. [Pars Plana Vitrectomy with Membrane Segmentation]
Surgery is performed on an outpatient basis at a hospital or ambulatory surgery center.
Unlike cataract surgery, an injection of anesthetic is placed behind the eye while the patient is sedated and the patient is discharged home with a patch that remains on until the patient is seen by the ophthalmologist.
The surgery is not painful, but the vision may be blurry for some time after the surgery, initially from the surgery itself, and more protractedly from the need for the retina that was distorted by the membrane to recover its normal pattern. (see diagram above)
Patients can resume most activity shiortly after surgery, but tasks that require higher levels of depth perception may not be advisable until more substantial visual recovery has occurred.
What are indications for surgery?
The indications for surgery are fairly individual; while one person may be significantly impaired by an epiretinal membrane, another person may not be aware of its presence.
These may include (but are not limited to):
Surgical removal of the membrane allows the retinal surface to return to its normal contour, but this is a gradual process, and the ability of the retina to achieve full recovery dependes on the duration of the distortion, associated edema (swelling of the tissues with fluid) and compromise to the integrity of the macula.
Reduced Vision: Just as it can cause metamorphopsia, a macular pucker (or epiretinal membrane) can interfere with the function of the retina's photoreceptors and reduce the individual's ability to see. This may result in reduced visual acuity - inability to see smaller letters on the chart or to read small print, increased difficulty seeing in certain, usually reduced, lighting.
Impending macular hole: Traction on the macula can thin out the tissue or cause a piece of the macula to become avulsed. The loss of tissue in this section of the retina can result in significant reduction in vision, or the development of a scotoma (a defect in the visual field).
In the process of pulling on the macula, the tissue that is under stress may accummulate fluid, resulting in cystic changes or macular edema. Because this fluid and cystic change can permanently damage the tissue, early intervention in the form of surgery is a consideration.