Diffuse Unilateral Subacute Neuroretinitis Syndrome in Canada

Diffuse unilateral subacute neuro-retinitis (DUSN) is a clinical syndrome characterized by unilateral visual loss and associated in the early stages with vitritis, papillitis, retinal vasculitis, and recurrent crops of gray-white outer retinal lesions. With time, visual loss may be progressive, with secondary development of optic atrophy, retinal vessel narrowing, and retinal pigment epithelium (RPE) degeneration.1-3Evidence suggests that DUSN is caused by an intraretinal nematode of 2 different sizes. The smaller nematode, measuring 400 to 700 μm in length, appears to be endemic to the southeastern United States, the Caribbean islands, and Brazil. The larger nematode, measuring 1500 to 2000 μm in length, has been described in the northern midwestern United States.3,4 In this report, we describe 3 cases of DUSN in Canada that represent different stages along the clinical spectrum of early to late DUSN. In the first 2 cases, both from Vancouver, British Columbia, subretinal nematodes