Macular oedema: the role of soluble mediators

Extracellular accumulation of fluid resulting in oedema is well tolerated in most tissues of the body, but in the retina, it results in dysfunction of retinal neurons. Collection of fluid in the macula is called macular oedema and when the fovea is involved, it results in decreased visual acuity. Macular oedema occurs in a wide variety of ocular diseases and is one of the most prevalent causes of vision loss in developed countries. It is the most common cause of vision loss in patients with diabetic retinopathy1 and in other ischaemic retinopathies such as branch and central retinal vein occlusion.2 3 Macular oedema is also a major cause of decreased vision following intraocular surgery. In the literature, the term cystoid macular oedema (CMO) is often used to describe oedema occurring after surgery,4 because collection of fluid in the macula often results in cystic changes that are visible by ophthalmoscopy. However, cystic changes can occur with any type of macular oedema, and therefore the term post-surgical macular oedema is preferred when referring to oedema occurring after any type of intraocular procedure. Macular oedema is also a frequent complication of uveitis regardless of aetiology5 and is commonly seen in patients with retinitis pigmentosa.6 Thus, macular oedema is a component of many different types of pathological conditions and is an enormous clinical problem.