Macular edema is a condition where leaky blood vessels cause swelling in the macula, which is the area of the central retina responsible for fine and detailed vision such as reading.  The leaky blood vessels result from a variety of conditions including diabetes, inflammatory eye diseases (uveitis), cataract surgery, and retinal detachment to name a few.  Typically, patients will notice a central graying or central blurry vision.  There are various treatments available to treat the swelling including eye drops, lasers, and injections.