Cystoid Macular Edema
How does the Eye Function
The human eye is like a camera where a system of lenses focuses a picture on a sensitive film. The cornea and crystalline lens, together, are the lenses that focus the picture onto the retina. The retina corresponds to the camera’s film. It reacts to light through a chemical process that sends nerve impulses directly to the brain where the ‘picture’ is registered. The sclera, or white of the eye, is a tough, protective container like the box of the camera. The iris is the colored circle in the front of the eye. In the center of the iris is the black pupil, which enlarges and contracts to regulate the amount of light coming into the eye. The choroid is a system of blood vessels which covers the outer surface of the retina and provides it with nourishment. The vitreous body is a transparent jelly filling the space between the lens and the retina. It maintains the shape of the eyeball and helps to hold the retina in place. The macula is the small specialized area of the retina which is utilized for reading vision.
What is Cystoid Macular Edema?
The healthy retina is a very thin, semitransparent tissue which lines the back of the eye. When the central portion of the retina (the macula), becomes swollen and accumulates fluid, it tends to swell like a sponge. This swelling occurs in grape-like clusters and looks like cysts, hence the name cystoid macular edema.
Who gets Cystoid Macular Edema?
Cystoid macular edema can occur in different conditions and is seen commonly in patients who have had previous eye surgery. Only a small percentage of people who have had cataract or other eye surgery will develop cystoid macular edema. The swelling may develop many months or even years after the surgery. It can occur with all types of cataract surgery (intracapsular, extracapsular, phacoemulsification) and with any type of lens implant (anterior chamber or posterior chamber intraocular lens). Cystoid macular edema may occur despite perfect surgery without any complications.
What are the Symptoms of Cystoid Macular Edema?
Patients with cystoid macular edema frequently notice their reading vision is blurred. The peripheral or side vision remains unchanged. Frequently, distortion of objects is noted as well as dimness to the vision. In addition, eyes with cystoid edema may appear irritated and red, may water a great deal and may be tender to the touch.
How do we prove the diagnosis?
If cystoid edema is suspected, an intravenous fluorescein angiogram may be performed. During the test, photographs are taken of the retina and a red dye is injected into the arm vein. Photographs of the retina following dye injection indicate pooling of dye in the macula confirming the diagnosis of cystoid macular edema. Sometimes the cystoid edema can be seen without the need for angiography.
What treatments are available for Cystoid Macular Edema
There is no known magical cure for this retinal swelling. Several different treatments may be helpful for different patients. Non-steroidal anti-inflammatory medication is frequently prescribed. Patients with arthritis usually take this medication and it has specific anti-inflammatory effects in the eye. After many weeks of taking this medicine by mouth, some people will notice an improvement in their vision. It is important to take the pills after meals because they can irritate an empty stomach.
If non-steroidal and anti-inflammatory medicine is not helpful in improving vision in patients with macular edema, other treatments, including other drugs, might be available. In selected patients, the YAG laser can be used to cut adherent strands of jelly within the eye if they appear to be contributing to the problem. The YAG laser treatment is done as an outpatient procedure and is painless. Treatment is indicated only in a minority of patients and your surgeon will advise you about the appropriateness of this form of therapy.
In patients who do not respond to medication and who are not candidates for YAG laser treatment, vitrectomy surgery may be considered. This is a surgical operation that involves removing the inflamed jelly of the eye (vitreous) under microscopic control. In some patients this can cause dramatic improvement in the vision, but the results of this type of surgery are variable and it is saved only for the most difficult cases.
Summary
Cystoid macular edema is a swelling in the central part of the retina causing visual problems especially for reading. The exact cause is unknown, but it is frequently seen in patients who have had previous eye surgery or ocular inflammation. It is a very frustrating problem both for the patient and the surgeon since there is not a simple cure. It is particularly frustrating since no one has been able to demonstrate the exact mechanism that accounts for the retinal swelling and, therefore, a specific cure is not available.
The condition is of particular concern for those people undergoing cataract surgery where a perfect operation has been performed. Both the patient and surgeon have high hopes for normalization of the vision only to have cystoid macular edema compromise an otherwise perfect result. Many people with cystoid macular edema will respond to therapy and the edema will disappear within weeks to months following the appearance. With current forms of therapy, at least 50% of the patients can expect to have resolution of the problem within one year with improvement in vision.
