Diagnosis of macular edema.

Macular edema may be intracellular or extracellular. Intracellular accumulation of fluid (cytotoxic edema) is an alteration of the cellular ionic distribution. Extracellular accumulation of fluid is more frequent and clinically more relevant, and is directly associated with an alteration of the blood-retinal barrier. Fluorescein angiography has been critical for detecting macular edema and currently remains the 'gold standard' for its diagnosis by identifying the characteristic stellar pattern of cystoid macular edema, also providing a qualitative assessment of vascular leakage essential for identifying treatable lesions. The clinical diagnosis of macular edema, recognition of its main etiologies and its treatment have greatly improved due to multiple and remarkable advances in modern imaging technologies. By correlating results from fluorescein angiography and optical coherence tomography (OCT), fluid accumulation within and under the sensory retina can be confirmed and located. We are now able to measure changes in retinal thickness and use noninvasive instrumentation in a clinical setting to identify macular edema. Moreover, spectral-domain OCT can characterize the presence and integrity of the external limiting membrane and the photoreceptor inner and outer segments, which is useful information for prognosis as well as a guide for treatment. The diagnosis of macular edema and its clinical forms is now based primarily on the correlation of these imaging techniques.