Macular edema is swelling of the macula, the small area of the retina responsible for central vision, of which the central 5% of the retina is most critical to vision. The edema is caused by fluid leaking from retinal blood vessels. Blood leaks out of the weak vessel walls into a very small area of the macula which is rich in cones, the nerve endings that detect color and from which daytime vision depends. Blurring occurs in the middle or just to the side of the central visual field, It can appear like one is looking through cellophane. Visual loss may progress over a period of months, and can be very annoying because of the inability to focus clearly.
Because the macula is surrounded by many tiny blood vessels, anything affecting them, such as a medical condition affecting blood vessels elsewhere in the body or an abnormal condition originating in the eye can cause macular edema.
Retinal blood vessel obstruction, eye inflammation, and age-related macular degeneration have all been associated with macular edema. The macula may also be affected by swelling following cataract extraction, though typically this resolves itself naturally.
ME rarely causes a permanent loss of vision, but the recovery is often a slow, gradual process. The majority of patients recover in 2 to 15 months.
