Analysis of Aqueous Humor in Ocular Toxoplasmosis

Abstract

We report the results of our use of the polymerase chain reaction to identify Toxoplasma gondii in the aqueous humor of patients with presumed ocular toxoplasmosis. Currently, the diagnosis of ocular toxoplasmosis is based clinically on the observation of a necrotizing lesion in the fundus.¹ However, in cases of atypical retinitis or when the fundus is masked by vitreal inflammation, aqueous-humor analysis may be used as a diagnostic tool. Intraocular production of antitoxoplasmic antibodies can be assessed by the C coefficient: antibody titer (aqueous humor/serum) × immunoglobulin (serum/aqueous humor).² We analyzed samples of aqueous humor obtained from 17 Brazilian patients with clinical presentations consistent with ocular toxoplasmosis. Ocular inflammation was present for a minimum of two weeks at the time of anterior-chamber paracentesis. The C coefficient ranged between 0.5 and 808, with a median of 2.50. Local production of anti-toxoplasmic antibodies was considered certain for C values of more than 3 (six patients)³ and probable for values of 2 to 3 (four patients). Serum titers of antitoxoplasmic IgG were positive for all patients.