Macular edema is a nonspecific but very common final pathway for many ocular diseases and not a specific entity. Related ocular disorders include diabetic retinopathy, vascular occlusions, post surgical situations and inherited disorders. The retinal fluid accumulation could be intracellular or an extracellular. Extra cellular fluid accumulation, which is more frequent and more clinically evident, is directly associated with an alteration of the blood-retinal barrier (BRB). Intracellular fluid accumulation leads to a cellular damage because of cytotoxic alterations of the cellular ionic distribution. These mechanisms may be complicated by the release of various cytokines, significant inflammation and/or ischemic processes. The influence fluid from the retinal origin should be illustrated with various diseases. Examples for typical findings of diagnostic tools like fluorescein angiography (FA) and optical coherence tomography (OCT) were given for each entity and described. We will discuss the different mechanisms of occurrence, the various clinical forms of fluid accumulation and the mechanisms of action.