Diagnosis of ocular toxocariasis by establishing intraocular antibody production.

PURPOSE To investigate the role of Toxocara canis in posterior uveitis of undetermined origin. DESIGN Retrospective case-study. METHODS Paired ocular fluid (47 aqueous humor [AH] and two vitreous fluids) and serum samples of 37 adults and 12 children with undetermined posterior uveitis were retrospectively analyzed for intraocular IgG antibody production against Toxocara canis by enzyme-linked immunosorbent assay and Goldmann-Witmer coefficient (GWC) determination. Previous diagnostic investigation by polymerase chain reaction and GWC for Herpes simplex virus, Varicella zoster virus, and Toxoplasma gondii had not provided a cause of the posterior uveitis. RESULTS Three of 12 (25%) children showed intraocular IgG production against Toxocara canis. One child had vitritis, one presented with a low-grade uveitis and a peripheral retinal lesion, and the third had posterior uveitis and a chorioretinal scar. All three children had AH IgG titers exceeding those of the corresponding serum. In fact, two children had low Toxocara serum IgG titers (<1:32) and would have been considered seronegative upon routine serology screening. Intraocular antibody production against Toxocara canis was absent in all 37 adults, including five seropositive patients. CONCLUSIONS Our results indicate that ocular toxocariasis is mainly a pediatric disease. Serological screening is not informative for the diagnosis of intraocular Toxocara infection. Toxocara GWC analysis, however, can be of value when diagnosing patients with posterior focal lesions or vitritis of unknown etiology.