Diffuse Unilateral Subacute Neuroretinitis
Diffuse unilateral subacute neuroretinitis (DUSN) is a rare condition that typically occurs in otherwise healthy, young patients and is caused by the presence of a mobile subretinal nematode. Prompt diagnosis and treatment of the condition can help prevent vision loss, which can be severe. The clinical findings in DUSN can be divided into acute and endstage manifestations. In the acute phase, patients frequently have decreased visual acuity, vitritis, papillitis, and clusters of gray-white or yellow-white outer retinal and choroidal lesions. The clustering of the lesions is important because it often helps localize the causative nematode. The degree of vision loss is often greater than might be expected from the clinical examination. Left untreated, late sequelae ultimately develop, which include optic atrophy, retinal arterial narrowing, and diffuse RPE disruption with severe vision loss. The late findings can be misinterpreted as unilateral retinitis pigmentosa.
The causative nematodes in DUSN have yet to be definitively established, although Toxocara species, Baylisascaris procyonis, and Ancylostoma caninum have all been implicated. Raccoon exposure appears to be common in patients in North America. The characteristic lesions are believed to result from a single nematode migrating within the subretinal space. If the nematode can be observed, which occurs in less than half of cases, it should be destroyed using laser photocoagulation. After the worm is killed, vision usually stabilizes.
de Amorim Garcia Filho CA, Gomes AH, de A Garcia Soares AC, de Amorim Garcia CA. Clinical features of 121 patients with diffuse unilateral subacute neuroretinitis. Am J Ophthalmol. 2012;153(4):743–749.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.