Macular edema most common cause is -
Macular edema occurs when there is abnormal leakage and accumulation of fluid in themacula from damaged blood vessels in the nearby retina. A common cause of macular edema is diabetic retinopathy, a disease that can happen to people with diabetes. Other common cause is, as a complication of cataract surgery. Ref AK khurana 6/e p 280
Secondary glaucoma
Cataract surgery
Retinitis pigmentosa
Uveitis
Vitreous and retina