Lens siderosis resulting from a tiny missed intralenticular foreign body.

We report a patient with clinical ocular siderosis at the time of presentation but undetectable intraocular foreign body on computed tomography (CT) and ultrasonography. A 24-year-old man suffered from right ocular injury when hammering metal on metal. Slit-lamp examination revealed a small corneal perforating wound and an iris hole, but no intraocular foreign body was found under fundus examination. There was also no evidence of intraocular foreign body on ultrasonography and orbital CT scan. About 1 month later, lens siderosis with cataract formation developed, and the patient received lens extraction with intraocular lens implantation. During the operation, a small (< 1 x 1 x 1 mm in size) intralenticular foreign body of metal material was found and removed. The patient's visual acuity improved from 6/20 to 6/6 on the next day. A patient suspected to have intraocular foreign body should be followed-up closely; it is better to remove the foreign body before siderosis bulbi occurs.