Retained Intraocular Iron Foreign Body Leading to Late-Onset Siderotic Glaucoma: A Challenging Case Report

Background

Secondary glaucoma after ocular trauma is a complex complication involving inflammation, angle regression, or retained intraocular iron [1]. Retained iron may cause ocular siderosis by a direct or indirect pathway [2]. The direct pathway is caused by iron-binding proteins that cause lysosome breakdown and degeneration of photoreceptor and retinal pigment epithelium [3]. The indirect pathway is caused by damage to retinal vessels [4]. In addition, the iron may cause iron deposits in the trabecular meshwork and glaucoma [5,6]. Early detection of the intraocular foreign body (IOFB) is particularly important for diagnosis and therapy. Here, we present a case of redness in the right eye after ocular trauma with good visual acuity but high intraocular pressure (IOP) for a long time, despite a normal fundus examination. Upon further inspection, the foreign body was detected by CT scan and ultrasound biomicroscopy (UBM). The patient was successfully managed with vitrectomy. The present report presents the case of a 58-year-old man with a retained iron intraocular foreign body and late-onset siderotic glaucoma.

Case Report

A 58-year-old man presented with redness and eye pain in the right eyes for 1 month after ocular trauma. He had a history of ocular blunt contusion when working as a mechanic in a garage. His visual acuity was good. First, he went to the regional hospital and accepted a B-scan ultrasound and dilated fundus examination, the results of which did not show abnormal findings. After getting eyedrops of tobramycin and dexamethasone, the redness resolved but the IOP increased for 2 weeks, and the doctor suggested that he visit the senior hospital.

On examination, his best corrected vision acuity was 20/20 in both eyes. The IOP was 53.0 mmHg in the right eye and 14.6 mmHg in the left eye. There was a moderate grade II relative afferent pupillary defect in the right eye. The cornea was transparent and there existed a small cataract in both eyes (Figure 1). The angle was opened by ultrasound biomicroscope (Figure 1). The IOFB was not detected by the fundus and B-scan ultrasound examination (Figure 2A, 2B). The fundus examination showed a deep-sized optic disc with an optic disc pit-like shape with a cup-disc ratio of 0.8 in the right eye and 0.3 in the left eye. Macular optical coherence tomography indicated no inner or outer retinal layer schisis, and there was no connection between the retina and optic regions (Figure 2D). The retina was normal, without changes in the retinal pigment epithelium or sclerosed retinal vessels (Figure 2A). Given these results, a diagnosis of secondary glaucoma was made, since the patient had a history of ocular trauma 1 month earlier. CT scan and color Doppler ultrasonography were used to exclude IOFB. However, these results showed a tiny IOFB around the pars plana ciliaris (Figure 2C, 2E, 2F). The perimetry and retinal nerve fiber layer of the right eye was destroyed (Figure 3A, 3B). Vitrectomy was carried out to remove the IOFB and the IOP returned to normal. The patient’s visual acuity was maintained at a good level of 20/20 and the IOP decreased to 13.5 mmHg at 3 months after therapy. The revised diagnosis was ocular siderosis.

Discussion

Although the visual acuity was good, with a normal fundus, the possible presence of an IOFB cannot be ignored in a patient being seen after ocular trauma. The high IOP may be caused by ocular siderosis disease. Therefore, a suitable examination is needed to find the IOFB. CT scan and Doppler ultrasound assist in the diagnosis of an IOFB. Timely removal of the IOFB is effective in reducing the risk of ocular siderosis.

Many patients do not suffer from vision lost after ocular trauma, so the examinations should be conducted carefully and thoroughly [7,8]. In this case, the doctor did not ask the patient to get a CT scan in the initial visit since the B-scan was normal. In actuality, only 45% of IOFBs are detected in clinical practice by slit-lamp, but the accuracy of detecting IOFBs by CT scan is 96% [9]. A choice of thin-section axial CT of 1 mm achieves excellent accuracy in detecting foreign bodies compared with a thin-section axial CT of 0.05 mm [10]. In our study, color Doppler was first used to detect the IOFB, and this method showed excellent accuracy compared with B-ultrasound. MRI is recommended when a metallic IOFB is ruled out. MRI with a metallic IOFB may cause damage to ocular structures even with small quantities of metal [11]. However, a very small-size (0.5 mm or smaller) intraocular ferromagnetic material can be safely visualized by MRI [12].

Secondary glaucoma is common after ocular trauma, angle recession, lens dislocation, trabecular meshwork injuries, and inflammation [13]. In our patient, the anterior was normal, and the high IOP was caused by siderotic glaucoma, which is a rare and challenging scenario. The reason for the glaucoma is related to iron deposits in the trabecular meshwork or an increase in albuminous aqueous by the ciliary body and trabecular fibrosclerosis [14]. The IOP may decrease after removal of the IOFB. Alternatively, the IOP may increase and necessitate glaucoma therapy in the future for the pre-existing trabecular fibrosclerosis [15]. A gonio-scope is necessary to examine the patient after trauma. Long-term monitoring of the IOP is necessary for the patient.

The harm caused by the IOFB in our patient was the formation of siderosis bulbi. Iron can produce oxidants within the ocular microenvironment which destroys cells and causes lipid peroxide generation [16]. The main evidence for this etiology of the disease were retinal pigment epithelium changes, sclerosed retinal vessels, pigmentation in the lens, and angles. The electroretinogram results indicated extinguished scotopic and photopic responses with an electronegative b wave [14]. In this case, we did find pigmentations in the lens and retina surfaces. Electroretinogram is the gold standard to monitor the toxicity of ocular siderosis in cases showing a normal fundus [17].

Although secondary glaucoma is common after ocular trauma, ocular siderosis is rare and challenging. The patient complained about red eyes for a long time, but showed a normal fundus. A CT scan or color Doppler ultrasound is recommended for a patient after trauma. Removal of the IOFB is an effective method for controlling the IOP.

Conclusions

This report has highlighted that a retained IOFB can be challenging to diagnose and that cases associated with siderotic glaucoma require multiple methods of investigation. In our case, visual acuity, slit-lamp examination, measurement of IOP, a CT scan, and color Doppler ultrasound assisted in the diagnosis, and the patient was successfully treated by vitrectomy.