Continuing education CET

M acular oedema refers to the accumulation of fluid in retinal layers around the fovea, usually as a result of blood-retina barrier dysfunction. Macular oedema is not a specific entity, but rather a non-specific response to an abnormal retinal environment. Vision is impaired due to disruption of the normal cellular relationships in the retina, mechanical stress, and a mild inflammatory response. The process begins with diffuse swelling of the outer retinal layers, and may advance to form the typical cyst-like spaces (termed ‘cystoid macular oedema’ – CMO) most often in the outer plexiform (Henle’s) and inner nuclear layers (Figure 1). With increasing severity and duration, the cysts may enlarge, coalesce, and extend to involve all retinal layers from the retinal pigment epithelium to the internal limiting membrane (Figure 2). Uncommonly, the cysts may rupture, resulting in a type of macular hole.1,2