Lymphatic filariasis (LF) is a severe form of filariasis (see this term), caused by the parasitic worms <i>Wuchereria bancrofti</i>, <i>Brugia malayi</i> and <i>Brugia timori</i>, and the most common cause of acquired lymphedema worldwide. LF is endemic to tropical and subtropical regions. The vast majority of infected patients are asymptomatic but it can also cause a variety of clinical manifestations, including limb lymphedema, genital anomalies (hydrocele, chylocele), elephantiasis in later stages of the disease (frequently in the lower extremities), and tropical pulmonary eosinophilia (nocturnal paroxysmal cough and wheezing, weight loss, low-grade fever, adenopathy, and pronounced blood eosinophilia). Renal involvement (hematuria, proteinuria, nephritic syndrome, glomerulonephritis), and mono-arthritis of the knee or ankle joint have also been reported.

Blindness is the condition of lacking visual perception defined as visual perception below 3/60 and/or a visual field of no greater than 10 degress in radius around central fixation.