[Retinal manifestations of infectious diseases]

The retina and the choroids are richly vascularised structures and can therefore be colonised by germs via the haematogenous route in the course of a systemic infectious disease. The germs responsible for this type of infection can be fungi, viruses, bacteria and parasites. Ocular candidiasis is outstanding amongst these colonisations because of its frequency; it can manifest itself as an endophthalmitis with a slow and hidden course. The so-called ocular histoplasmosis syndrome, although it is infrequent in our setting, is an important cause of choroidal neovascularisation. The viruses that most frequently affect the retina are of the herpes type and can produce devastating symptoms in immunoincompetent patients, named acute retinal necrosis syndrome. Retinitis due to cytomegalovirus is more frequent in immunodepressed patients, as in the case of AIDS, but it must also be contemplated in patients with lymphoma and immunomodulatory treatment. The most frequent bacterial diseases that affect the retina are syphilis and tuberculosis. Disease due to cat scratches, caused by a borrelia, can produce a neuroretinitis. Toxoplasmosis is the most common of the infectious diseases caused by a parasite and gives rise to chorioretinitis. Toxocariasis, also caused by a parasite, is second in importance, giving rise to choroidal granulomas and retinal tractions.