From the Yüzüncü Yıl University (AK, ST, AG, AC, TY), Faculty of Medicine, Department of Ophthalmology; and Yüzüncü Yıl University (SA), Faculty of Medicine, Department of Radiology, Van, Turkey.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Adil Kiliç, MD, Hafıziye M. Kazımbey 5. Sok. No 24 Saraykent Sitesi A Blok D 4 65100 Van, Turkey.
Magnetic resonance imaging (MRI) is a widely used imaging technique in cross-sectional imaging of the eye. MRI employs electro-magnetic waves combined with the reception of weak radio signals in order to record the concentration or density of hydrogen or other nuclei in the human body.1 On contrary to routine X-rays or computerized tomography (CT), MRI does not cause health risks of ionising radiation. Assessment of eye traumas via imaging techniques is of great importance. X-rays, CT, B-scan ultrasonography, and MRI are the common techniques used for the examination of a traumatized eye, though CT is the top choice. A probability of radiopaque or radiolucent foreign bodies should be paid attention while performing MRI in cases with a traumatized eye. A metallic intraorbital foreign body can move, and thus, can cause morbidity in the tissue during MRI. Therefore, a possibility of a metallic intraorbital foreign body is a contraindication for MRI.
A 50-year-old man presented to the out-patient clinic because of a sudden pain in his left eye just after lumbal MRI examination was started. Therefore, the imaging process was ended. MRI examination was performed with 1,5 Tesla MR unit (Siemens Symphony, Erlangen, Germany). The ophthalmological examination of the right eye revealed normal findings. Best-corrected visual acuity in the left eye was 20/40 (ETDRS line). Intraocular pressure was 32 mm Hg in the left eye on the day the patient presented. Slit-lamp biomicroscopic examination of the left eye revealed an inferiorly located foreign body and ++ inflammatory cells in the anterior chamber (Fig. 1). Figure 2 reveals the image of the superior anterior chamber angle including the iris portion, in which the foreign body was stuck prior to the MRI examination and the localized lens opacity at the previous localization of the foreign body. The scleral entrance site of the foreign body was observed (Fig. 3). The funduscopic examination and the ultrasonographic evaluation of the eye revealed normal findings. The eye was otherwise healthy. His history revealed an accidental penetrating eye trauma of the shotgun pellet of 28 years ago.
Figure 1. Preoperative Image of Metallic Foreign Body in the Anterior Chamber Angle of the Left Eye.
Figure 2. Image of the Superior Anterior Chamber Angle Including the Iris Portion, in which the Foreign Body was Stuck Prior to the MRI Examination and the Localized Lens Opacity at the Previous Localization of the Foreign Body.
Figure 3. Peroperative Image of the Left Eye After Removal of the Foreign Body from the Anterior Chamber Angle. Note the Black Arrow that Indicates the Entrance Site of the Metallic Foreign Body at 1-o’clock Position.
Medical treatment included topical dexamethasone sodium phosphate 0.1%, cyclopentolate hydrochlorure 1%, and brimonidine tartrate 0.2%. Intraocular pressure decreased to 22 mm Hg, and 12 mm Hg in the left eye 1 and 2 days after the admission, respectively.
A probable endothelial deficiency that might result from chronic irritation by the foreign body necessiated a surgical intervention. The patient underwent a surgical procedure. Subtenon anesthesia was employed for the surgical intervention. Surgical asepsis and antisepsis were obtained. Thereafter, access into the anterior chamber was gained through a clear corneal incision. Miosis was obtained using carbachol 0.01% intraocular solution (Miostat®, Alcon, Switzerland) to prevent any accidental tearing of the anterior lens capsule, or any trauma to the lens. After the anterior chamber was filled by viscoelastic substance, the foreign body was easily removed using a forceps (Fig. 3). At the end of the operation, viscoelastic substance was removed and a single 10-0 nylon suture was used for closure of the corneal and traumatic incisions. Two weeks postoperatively, slit-lamp examination revealed + inflammatory cells. Therefore, the eye was administered topical 0.1% dexamethasone sodium phosphate eyedrops five times a day. The corneal suture was removed. No complication was detected during the first two postoperative weeks.
The foreign body that caused pain in the left eye during MRI examination was defined as a ferromagnetic foreign body postoperatively.
Eye trauma represents about 3% of all emergency deparment visits in the States.2 Rapid assessment following eye trauma is crucial.2 Besides routine ophthalmoscopic examination, MRI is also a widely used imaging technique employed in assessment. MRI is successfully employed in locating intraspinous, paraspinous, intramyocardial, intrathoracic, intracranial, and intraorbital ballistic foreign bodies.3 MRI is useful in evaluation of gunshot wounds, particularly in the presence of a star artifact that a dense metallic bullet caused limits the usefulness of CT.4
Important queries arise regarding the safety of MRI in the presence of retained metallic ballistic fragments in the sensitive tissues, such as the orbit. Teitelbaum et al. concluded that caution should be exercised with MRI in the presence of metallic foreign bodies, especially if they are located near vital neural, vascular, or soft tissue structures, and determining the composition of a bullet in an anatomically sensitive area before MRI is attempted is crucial. The main risk of MRI in ferromagnetic bullets is the injury that rotation of the object causes due to magnetic torque, such as vitreous hemorrhage and blindness.3
Fortunately, neither vitreous hemorrhage nor blindness was observed in our patient.
Practically, each case of trauma to the orbit should be approached with a suspicion for probable intraorbital foreign body. In patients with penetrating eye injury, the nature of the foreign body determines the clinical behaviour; inert objects, such as steel and glass, may not warrant removal, because they usually do not cause significant inflammation, abscess, or fistula formation.5
The probable source of foreign body in our case was suggested as penetrating eye trauma by shotgun pellet 28 years ago, which was described by the patient in his history.
Some bullets and airgun pellets containing steel, copper, or copper-nickel-jacketed lead bullets were reported to produce marked MRI artifacts and image distortion due to their ferromagnetism.3 Gunenc et al. concluded that metallic foreign bodies they had placed into fresh bovine eyes produced beam-hardening MRI artifacts, which did not cause any problem in localizing the foreign bodies.6
Intraocular steel particles can result from head and neck shrapnel wounds.3 Hence, the presence of an intraocular foreign body should warn the practitioners about the probable coexistence of wounds in other parts of the body.
Before attempting an MRI examination, detailed patient history about previous penetrating accidents, such as exposure to metallic foreign bodies, should be obtained to prevent the potential harm the device can give to the vital structures. In case of a previous penetrating injury to the body, X-rays, CT, or B-scan ultrasonography should be employed prior to MRI to exclude the presence of a metallic foreign body, even if the patient denies any symptom. If the presence of a metallic foreign body is excluded, then MRI can be safely performed. In a case that a metallic foreign body, particularly one located near vital neural, vascular, or soft tissue structures, is detected via X-rays, CT, or B-scan ultrasonography, the risks benefits of MRI should be weighted carefully before attempting it. For a safer examination, we suggest to perform MRI with ultra-low-field-strength units in such cases. Any subjective discomfort of the patient should be paid attention during MRI examination and the process should be interrupted to further question the patient about history of exposure to metallic foreign bodies in order not to harm the patient.
- Frame AJ, Undrill PE, Cree MJ, Olson JA, McHardy KC, Sharp PF, et al. A comparison of computer-based classification methods applied to the detection of microaneurysms in ophthalmic fluorescein angiograms. Comput Biol Med. 1998;28:225–238. doi:10.1016/S0010-4825(98)00011-0 [CrossRef]
- Bord SP, Linden J. Trauma to the globe and orbit. Emerg Med Clin North Am. 2008;26:97–123. doi:10.1016/j.emc.2007.11.006 [CrossRef]
- Teitelbaum GP, Yee CA, Van Horn DD, Kim HS, Colletti PM. Metallic balistic fragments: MR imaging safety and artifacts. Radiology. 1990;175:855–859.
- Ebraheim NA, Savolaine ER, Jackson WT, Andreshak TG, Rayport R. Magnetic resonance imaging in the evaluation of a gunshot wound to the cervical spine. J Orthop Trauma. 1989;3:19–22. doi:10.1097/00005131-198903010-00004 [CrossRef]
- Karcioglu ZA, Nasr AM. Diagnosis and management of orbital inflammation and infections secondary to foreign bodies: a clinical review. Orbit. 1998;17:247–269. doi:10.1076/orbi.220.127.116.1137 [CrossRef]
- Gunenc U, Maden A, Kaynak S, Pirnar T. Magnetic resonance imaging and computed tomography in the detection and localization of intraocular foreign bodies. Doc Ophthalmol. 1992;81:369–378. doi:10.1007/BF00169098 [CrossRef]