Demystifying the role of magnetic resonance in identifying intraocular foreign bodies: a case of ocular siderosis

Background: Ocular siderosis (OS) is a significant cause of visual loss due to retained ferrous intraocular foreign bodies (IOFB). Despite its rarity, OS can lead to severe visual impairment if not promptly diagnosed and treated. This case is notable due to the occult nature of the IOFB, which was undetected by standard imaging modalities, emphasizing the critical role of magnetic resonance imaging (MRI) in such scenarios. Case presentation: A 51-year-old Caucasian male presented with progressive vision loss in his right eye over 20 days. Best corrected visual acuity (BCVA) was 20/1000 in the right eye and 20/20 in the left eye. Intraocular pressure (IOP) was 9 mmHg in both eyes. Slit-lamp examination revealed a small linear corneal wound and an iris defect in the right eye, along with a cataract featuring brownish deposits on the anterior capsule. The left eye was normal. Fundus examination of the right eye was hindered by media opacities. Ultrasonography showed a flat retina and choroid with no detectable IOFB. Despite a strong clinical suspicion of OS, computed tomography (CT) did not detect any IOFB. MRI subsequently identified an artifact in the inferior sectors of the right eye, indicative of a metallic IOFB. Surgical intervention involved a 23-gauge vitrectomy, phacoemulsification, IOFB removal and silicon oil (SO) tamponade resulting in a fully restored VA of 20/20 and normal IOP one month post-operation. SO was removed 2 months later. The retina remained adherent with no PVR development, and optical coherence tomography (OCT) scans showed a normal macula. Conclusions: This case underscores the importance of considering OS in patients with unexplained vision loss and history of ocular trauma, even when initial imaging fails to detect an IOFB. MRI proved crucial in identifying the IOFB, highlighting its value in the diagnostic process. Early detection and surgical removal of IOFBs are essential to prevent irreversible visual damage. This case demonstrates that MRI should be employed when CT and ultrasonography are inconclusive, ensuring accurate diagnosis and timely intervention to preserve vision.