A case of siderosis bulbi without a radiologically detectable foreign body

Abstract

A 29-year-old locksmith presented with anisocoria that he had noticed a few days ago. Anterior segment examination revealed anisocoria, iris heterochromia, and a corneal foreign body channel in the left eye with intracorneal rust and a dustlike rust layer on the anterior surface of the lens (Fig. 1). Visual acuity was 20/20 for both eyes. The patient’s medical history did not reveal any corresponding injury. However, considering the typical clinical findings and the patient’s occupation, a working diagnosis of developing siderosis bulbi was made. Suspecting a retained metallic foreign body, we performed screening tests including x-ray and computed tomography of the orbit, ultrasound biomicroscopy, and extensive funduscopy of the dilated pupil. We also tested the electroretinography (ERG) response to detect possible toxic retinal damage. X-ray and computed tomography of the orbit and ultrasound biomicroscopy did not yield any intraocular metallic foreign body. Initially, ERG results were normal and bilaterally equal. At the follow-up examination 2 months later, the patient complained of vision loss to 20/35 and night blindness. Electrophysiology revealed marked amplitude loss in the ERG, electro-oculography, and multifocal ERG (Fig. 2). Under the assumption of siderosis bulbi caused by residual particles of iron in the intracorneal space, precise corneal rust removal was performed under the microscope using an electric drill, and the anterior chamber of the left eye was irrigated. Six weeks postoperatively, visual acuity had recovered to 20/20, and full-field ERG had improved slightly after anterior chamber washout. Four months later, the patient presented with progressive vision decline (best corrected visual acuity 20/100) in the left eye. Examination of the fully dilated pupil revealed advanced lens opacification. No intraocular foreign body (IOFB) was identified after repeated thorough examinations. One day after phacoemulsification and intraocular lens implantation, visual acuity improved to 20/32 in the left eye. Siderosis bulbi may result from a sequence of unremoved ferrous IOFBs. Clinical signs of siderosis bulbi are iris heterochromia, mydriasis, deposits on the anterior capsule of the lens with cataract, and retinal degeneration with ERG changes. Removal of the foreign body is an adequate therapy.1Weiss M.J. Hofeldt A.J. Behrens M. Fisher K. Ocular siderosis. Diagnosis and management.Retina. 1997; 17: 105-108Crossref PubMed Scopus (47) Google Scholar Siderosis bulbi with no radiologically detectable foreign body is rare and has been described as a result of intralenticular2Klemen U.M. Freyler H. [Siderosis bulbi et lentis produced by intralenticular rust (author's transl)].Klin Monatsbl Augenheilkd. 1978; 172 (German): 258-261PubMed Google Scholar, 3Wu T.T. Kung Y.H. Sheu S.J. Yang C.A. Lens siderosis resulting from a tiny missed intralenticular foreign body.J Chin Med Assoc. 2009; 79: 42-44Abstract Full Text PDF Scopus (19) Google Scholar or intrascleral4Fineman M.S. Sharma S. Shah G.K. Brown G.C. Eagle Jr., R.C. Ultrasound biomicroscopic diagnosis of an occult intrascleral foreign body: an unusual case of ocular siderosis.Retina. 2001; 21: 265-267Crossref PubMed Scopus (16) Google Scholar rust residue. Wu et al.3Wu T.T. Kung Y.H. Sheu S.J. Yang C.A. Lens siderosis resulting from a tiny missed intralenticular foreign body.J Chin Med Assoc. 2009; 79: 42-44Abstract Full Text PDF Scopus (19) Google Scholar and DeAngelis et al.5DeAngelis D. Howcroft M. Aslanides I. Siderosis bulbi with an undetectable intraocular foreign body.Can J Ophthalmol. 1999; 34: 341-342PubMed Google Scholar also described radiologically undetectable foreign bodies; but in their cases, metallic IOFBs were detected during intralenticular and epiretinal surgeries, respectively. To the best of our knowledge, the present case is the only case of siderosis bulbi caused by intracorneal residual rust with no radiologically detectable foreign body to be reported.