Macular edema is defined as an abnormal thickening of the macula associated with the accumulation of excess fluid in the extracellular space of the neurosensory retina. Intracellular edema involving Müller cells has also been observed histopathologically in some cases.
DME results from retinal microvascular changes, thickening of the basement membrane and reduction in the number of pericytes are believed to lead to increased permeability and incompetence of the retinal vasculature. This compromise of the BRB leads toleakage of plasma constituents into the surrounding retina, with subsequent retinal edema. Hypoxia induced by this mechanism can also stimulate VEGF production. There is evidence that VEGF is up-regulated in DME and proliferative diabetic retinopathy.
Ranibizumab was approved by the FDA in June 2006 for the treatment of all subtypes of neovascular AMD and was approved in 2010 for the treatment of macular edema associated with retinal vein occlusion and diabetic retinopathy.
Optical coherence tomography is a non-invasive diagnostic method for the high-resolution imaging of ocular tissues. OCT is very helpful in the diagnosis and follow-up of DME,and OCT also analyzes the vitreomacular relationship.