General pathophysiology of macular edema.

Macular edema represents a common final pathway for many ocular diseases. Related ocular disorders include diabetic retinopathy, vascular occlusions, postsurgical situations, and uveitic diseases. The key pathophysiologic process is a breakdown of the blood-retinal barrier, normally preventing water movement in the retina, thus allowing fluid to accumulate in the retinal tissue via special water fluxes. Inflammatory processes and an increase in vascular permeability play a central role. Different mechanisms, complicated by ischemic conditions, interact in a complex network. Key factors are angiotensin II, prostaglandins, and the vascular endothelial growth factor. The various pathogenetic mechanisms and their contribution to the edema process are described in detail in this article.