We report a case of a male with bilateral tonic pupils associated with syphilis, that partially improved after syphilis treatment.

A 27-year-old male presented with a 2-month history of near vision impairment. The right and left pupils were 5.5 mm and 6.5 mm in diameter, respectively, in the dark and 5.3 mm and 6.1 mm, respectively, in the light. Both pupils demonstrated light-near dissociation, slow constriction and redilation when looking at near, and constriction after instillation of 0.0625% pilocarpine. Serological tests were positive for syphilis, while cerebrospinal fluid testing was negative. Two months after treatment with intramuscular injection of benzathine penicillin G, his near vision subjectively improved and the right and left pupils were 5.9 mm and 6.4 mm, respectively, in the dark and 4.8 mm and 5.3 mm, respectively, in the light. The size of both pupils decreased and the pupillary light responses partially improved in both eyes.

Patients with bilateral tonic pupils should have serological tests for syphilis. Recovery of tonic pupils can be expected after early treatment with effective antibiotics.