Macular edema is defined as swelling of the layers of the neurosensory retina within the macula. Although the classic presentation of macular edema is termed “cystoid macular edema” (CME), which represents the collection of excess fluid in “cysts” within the neurosensory retina, it is more broadly defined as extracellular accumulation of fluid within the outer plexiform layer of the retina. Thus, CME should be referred to as a subtype of macular edema with specific characteristics on imaging studies (e.g., fluorescein angiography and optical coherence tomography [OCT]). The most common clinical manifestation of macular edema is a reduction in central visual acuity. However, it is now recognized that macular edema may exist without impairing visual acuity but detectable on sophisticated retinal imaging. Thus, reliance on visual acuity to exclude the presence of macular edema is not sufficient, nor is it appropriate to rely on vision to suggest resolution of macular edema in response to treatment. Other clinical manifestations of macular edema include micropsia, in which objects appear smaller than they really are, as well as metamorphopsia. Although macular edema is reversible through both medical and surgical intervention, the development of chronic macular edema may eventually result in irreversible photoreceptor damage with a constant central scotoma. Other functional indications of the presence of macular edema include decreased reading speed, as well as reduced contrast sensitivity.