Cystoid macular edema, commonly called CME, is a painless disorder which affects the retina, the light-sensitive inner lining of the eye. When this condition is present, multiple cyst-like (cystoid) formations appear in the portion of the retina responsible for central or “straight-ahead” vision and cause retinal swelling or edema.
Although the exact causes of CME are not known, it may accompany a variety of diseases such as retinal vein occlusion, uveitis or diabetes. It most commonly occurs after cataract surgery. About three percent of those who have cataract extractions will experience decreased vision due to CME in the first year, usually from two to four months after surgery. If the disorder appears in one eye, there is an increased risk–as high as 50%–that it will also affect the second eye. However, most people recover their vision after some time.
The most common symptom of cystoid macular edema is blurred or decrease central vision (CME does not affect peripheral or side vision). There may also be painless retinal inflammation or swelling. However, the condition may be present even when no visual loss occurs. In these cases it is diagnosed after a thorough medical eye examination, usually using a photographic test called an OCT or Ocular Coherence Tomography.
Since many factors can lead to CME, it is not possible to say which treatment, if any, will prove effective. Signs of retinal inflammation are usually treated with anti-inflammatory medications, in either eye-drop, oral, or injected forms. Diuretics such as Diamox may help to reduce the swelling in some cases.
In instances where the retina begins to be pulled or starts to develop a tear, laser surgery may be recommended. A more common option in this situation is to perform a vitrectomy, which is removal of the clear gel-like substance in the eye and then replacing it with new fluid.