Introduction <p>Ocular syphilis is an uncommon but important complication of syphilis, most often presenting as posterior or panuveitis in latent syphilis of unknown duration. If left untreated, ocular syphilis can result in permanent vision loss, which underscores the importance of appropriate evaluation and treatment of ocular syphilis.</p> Case presentation <p>A unique case, involving a 32-year-old Irish man who presented with sudden-onset deterioration in his right-sided visual acuity, is presented. This man reported significant deterioration in his right-sided visual acuity from a previous baseline of 6/6 vision to “counting fingers.” His ophthalmic history was unremarkable up until that event, but his medical history encompassed psoriatic arthritis, managed by sustained monoclonal antibody therapy in the form of adalimumab.</p> Clinical findings <p>The clinical findings at initial presentation included painless monocular right-sided visual loss with gradual onset and discomfort associated with active eye movement alongside frank scalp tenderness. Further examination findings demonstrated a grossly swollen right optic nerve, right-sided visual acuity diminished to “counting fingers” amid normal intraocular pressure measurements. The patient was admitted to hospital and initially managed with intravenous steroid therapy. Subsequent serologic testing revealed an underlying diagnosis of syphilis. Targeted antibiotic therapy was commenced thereafter with further ophthalmic reviews to follow.</p> Conclusion <p>Syphilis may go undetected without a high index of clinical suspicion owing to its often nonspecific presentation. All patients with ocular inflammation should have syphilis testing as a part of their infectious workup with both treponemal and nontreponemal testing.</p>