Which ocular sign is virtually pathognomonic for trachoma caused by chlamydia?

The presence of superior tarsal follicles is considered virtually pathognomonic for trachoma, which is caused by the bacterium Chlamydia trachomatis. These follicles are characterized by the formation of small, raised lesions in the upper tarsal conjunctiva and often signify an active inflammatory response associated with trachoma.

When examining patients with trachoma, the identification of these superior tarsal follicles is crucial because they are indicative of the chronic conjunctival inflammation that occurs with repeated Chlamydia infections. This finding helps differentiate trachoma from other conjunctival conditions, providing essential clues for diagnosis and appropriate management.

The other options may be associated with trachoma or other conjunctival conditions, but they do not specifically indicate a history of chlamydial infection in the same definitive manner. Thus, the presence of superior tarsal follicles stands out as a key diagnostic feature for trachoma, reinforcing its importance in clinical practice.