Diffuse unilateral subacute neuroretinitis. Report of transvitreal surgical removal of a subretinal nematode.

BACKGROUND: The precise identification of nematodes which cause diffuse unilateral subacute neuroretinitis (DUSN) has been unsuccessful. Shape and size are useful in the initial stages of identification, but histopathologic examination usually is necessary for accurate classification. Intact nematodes recovered from patients with DUSN have been mentioned scarcely in the literature. The authors report the first case of DUSN in which a viable nematode was removed successfully via a transvitreal surgical approach and recovered for parasitologic study.

METHODS: Bimanual pars plana vitrectomy was performed in a 9-year-old Brazilian boy with typical DUSN in its late stage. During surgery, a motile subretinal nematode was confirmed temporal to the macular area. A retinotomy was created adjacent to the nematode. The subretinal material then was aspirated with a 20-gauge soft-tip needle, and parasitologic examination was performed.

RESULTS: Based on length (630 m x 10(-6)) and width (30 m x 10(-6)) of the nematode and other features such as a small buccal capsule, an esophagus one third of body length, and tapered tail, a morphologic identification of the nematode was made as a third-stage Toxocara larva. Histopathologic examination could not be performed for confirmation because of subsequent deterioration of the specimen.

CONCLUSIONS: Although direct laser photocoagulation of the nematode is the treatment of choice for DUSN, surgical transvitreal removal of the nematode may be indicated in selected cases. This method for treatment allows removal of the nematode for parasitologic identification.