The most common conditions that lead to macular edema are macular degeneration, diabetic retinopathy, and retinal vein occlusion [internal links here]. There are other common, but less well-known causes for macular edema, including hypertension, cataract surgery inflammation and uveitis. With these three conditions, the swelling that occurs is called cystoid macular edema (CME).
When a patient experiences extended periods of extremely high blood pressure, the retinal vessels can leak fluid. This would be analogous to the leakage that would occur if an old garden hose were put under too much water pressure. Sometimes the blood vessel wall protrudes, called a macroaneurysm.
CME is one of the most frequent side effects of eye surgery, particularly cataract surgery. Ophthalmologists currently believe that this retinal leakage occurs due to post-surgical inflammation that causes macular vessels to leak. It typically appears a few weeks following cataract extraction, notable to the patient as an unexplained worsening of central vision. Up to 50% of patients experience cystoid macular edema after cataract surgery, but only a handful require extended treatment by a retina specialist. In most cases, CME resolves over time with or without treatment.
Another cause for cystoid macular edema is uveitis, a generic term for inflammation in the eye. There are many countless reasons for an eye to be inflamed, but most fall under the category of infections or autoimmune conditions, where the body’s immune system attacks its own tissue. Uveitis is a complex process requiring lab work-up and other specialized testing to determine the proper diagnosis and treatment.
Rarely, cystoid macular edema can occur without infection or inflammation. This so called ‘non-leaking’ CME may be due to inherited retinal disorders, epiretinal membranes, or too much vitamin (niacin) supplementation.
What Are the Symptoms of Macular Edema?
Macular edema causes painless blurring of central vision in one or both eyes. In some cases, the eye may be red or sensitive to light. The symptoms may fluctuate over time. Macular edema does not cause transient loss of vision, double vision, or eye irritation. The condition may be associated with a history of autoimmune disease or recent eye surgery.