A range of problems can affect macula. Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in adults. It is caused by changes in the blood vessels of the retina. In some people with diabetic retinopathy, blood vessels may swell and leak fluid. In other people, abnormal new blood vessels grow on the surface of the retina. Retinal vein occlusion is a blockage of the small veins that carry blood away from the retina. The retina is the layer of tissue at the back of the inner eye that converts light images to nerve signals and sends them to the brain. Proliferative retinopathy and retinal vein occlusion are treated with laser photocoagulation. Laser photocoagulation uses the heat from a laser to seal or destroy abnormal, leaking blood vessels in the retina. One of two approaches may be used when treating diabetic retinopathy: focal photocoagulation or grid photocoagulation. Focal treatment is used to seal specific leaking blood vessels in a small area of the retina, usually near the macula. The ophthalmologist identifies individual blood vessels for treatment and makes a limited number of laser burns to seal them off. Grid laser treatment helps to shrink the abnormal blood vessels. 1,000 to 2,000 laser burns are placed in the areas of the retina away from the macula, causing the abnormal blood vessels to shrink. Because a high number of laser burns is necessary, two or more sessions usually are required to complete treatment. Although you may notice some loss of your side vision, grid laser treatment can save the rest of your sight. Scatter laser treatment may slightly reduce your color vision and night vision.