Ocular involvement in patients infected by the West Nile virus.

West Nile virus (WNV), a mosquito-borne RNA virus for which there is no treatment, began emerging as a threat to health in the United States in 1999. Since then, its frequency and apparent clinical severity have increased. Patients with severe disease may experience ocular complications that include pain, vitreous inflammation, nonrelapsing chorioretinitis, retinal vasculitis, chorioretinal scarring, optic neuritis, and retinal hemorrhages. Age appears to be a risk factor for the development of ocular symptoms. Most patients with ocular involvement report floaters or decreased vision. Many ocular inflammatory conditions with an associated underlying systemic cause often present with chorioretinitis. However, the characteristic distribution and linear array or scattered pattern of the chorioretinal lesions seen in WNV is distinctive. The foregoing notwithstanding, other multifocal choroidopathies must be considered including syphilis, ocular histoplasmosis, multifocal choroiditis, tuberculosis, and sarcoid. Although topical steroids were reported to resolve WNV-induced uveitis and its associated keratic precipitates, most cases resolved irrespective of treatment, and relapses were uncommon. It is important for the eye care professional to be alert to the possible presence of WNV, particularly in older patients who present with ocular symptoms during mosquito season. Thus, a thorough ocular evaluation should include a dilated fundus examination and, when indicated, fluorescein angiography should be performed in patients suspected of being infected with WNV.