Risk of visual impairment in children with congenital toxoplasmic retinochoroiditis

PURPOSE: Reliable information is needed to counsel parents of children with congenital toxoplasmosis regarding the long,term risk of visual impairment resulting from ocular toxoplasmosis. DESIGN: Prospective cohort study of children with congenital toxoplasmosis identified by prenatal or neonatal screening. METHODS: After three years of age, ophthalmologists reported the site of retinochoroidal lesions and visual acuity and parents reported visual impairment. An ophthalmologist predicted the child's vision based on the last retinal diagram. Selection biases were minimized by prospective enrollment and data collection, high rates of follow,up, and exclusion of referred cases. RESULTS: Two hundred and eighty-one of 284 infected children who underwent ophthalmic examinations were followed up to a median age of 4.8 years. One in six children (49/281; 17%) had at least one retinochoroidal lesion, two,thirds of whom (32/49; 65%) had a lesion at the posterior pole. In children with retinochoroiditis who had visual acuity measured after 3 years of age, 94% (31/33) had normal vision in the best eye (6/12 Snellen or better), as did 91% of those with a posterior pole lesion (21/23). Analyses based on affected eyes showed that 42% (29/69) had a posterior pole lesion, of which just more than half (15/29, 52%) had normal vision, as did 84% (16/19) of eyes with a peripheral lesion alone. Vision predicted by the ophthalmologist was moderately sensitive (59%) but overestimated impairment associate with posterior pole lesions. Of 44 children with information on acuity, four (9%) had bilateral visual impairment worse than 6/12 Snellen. CONCLUSIONS: Severe bilateral impairment occurred in 9% of children with congenital toxoplasmic retinochoroiditis. Half the children with a posterior pole lesion and one in six of those with peripheral lesions alone were visually impaired in the affected eye.