Is ocular toxoplasmosis caused by prenatal or postnatal infection?

Ocular toxoplasmosis is commonly attributed to prenatally acquired (congenital) infection unless there is clear evidence that infection was acquired postnatally. We challenge this view by comparing the risks of ocular disease caused by prenatal and postnatal toxoplasmosis. As the history, clinical appearances, and serological findings associated with the two aetiologies are frequently indistinguishable, we summarise the available information on the risks of ocular disease caused by prenatal and postnatal toxoplasmosis. We conclude that there is no evidence to suggest that the majority of cases are the result of prenatal infection. On balance, the available evidence suggests that at least two thirds of ocular toxoplasmosis is caused by postnatal infection. This information is relevant for counselling patients and for the development of strategies to prevent ocular toxoplasmosis.