Macular edema is a medical condition in which there is a swelling of the macula (yellow central part of the retina of the eye). It occurs when fluid and protein deposits collect on or under the macula, causing it to thicken and swell. The swelling may distort a person's central vision, as the macula is near the center of the retina at the back of the eyeball. This area holds tightly packed cones that provide sharp, clear central vision to enable a person to see form, color, and detail that is directly in the line of sight.
Macular edema can also occurs a few days or weeks after cataract surgery, but most such cases can be successfully treated with NSAID or cortisone eye drops. Until recently there were no good treatments for macular edema caused by central retinal vein occlusion (CRVO). Laser photocoagulation has been used for macular edema caused by branch retinal vein occlusion.
Cystoid Macular Edema
Cystoid macular edema is also a thickening of the macula of the eye and is usually associated with blurred or distorted vision. It is frequently associated with various ocular conditions, such as cataract surgery, age-related macular degeneration (ARMD), uveitis, eye injury, diabetes, retinal vein occlusion, or drug toxicity. The primary cause of cystoid macular edema depends on the underlying disease process, but most pathways eventually lead to vascular instability and breakdown of the blood-retinal barrier. The Müller cells in the retina become overwhelmed with fluid leading to their lysis. This results in an accumulation of fluid in the outer plexiform and inner nuclear layers of the retina. Diabetes and retinal vein occlusion can both lead to cystoid macular edema by causing vascular instability directly (vascular endothelial cell damage).