Ocular siderosis caused by a subretinal iron foreign body masquerading as a blood clot: a case report

Abstract

Purpose: We report a case of ocular siderosis caused by a subretinal iron foreign body.

Observations: A 30-year-old male construction worker injured by a small piece of shrapnel while working visited an eye clinic for decreased vision in left eye on day X, and was subsequently referred to our hospital with a diagnosis of vitreous hemorrhage on day X+1. Although a penetrating foreign body was suspected, no obvious wound or intraocular foreign body was found even after the hemorrhage subsided. On X+3 months, a rhegmatogenous retinal detachment was found and a lens-sparing vitrectomy was performed. A black elevated subretinal lesion was noted intraoperatively but not removed because it was considered to be a blood clot. The postoperative course was stable with best corrected visual acuity (BCVA) recovering to 20/16. However, the BCVA decreased to 20/30 on X+11 months with the subretinal lesion turning reddish brown. The electroretinogram also showed a significant attenuation of all stimuli. Siderosis was considered to have developed due to the subretinal foreign body. On X+14 months, we performed a combined phaco-vitrectomy to remove the foreign body. Analysis revealed iron as the main component of the foreign body. However, the postoperative electroretinogram remained unchanged, and the BCVA was 20/63 without improvement.

Conclusions and importance: We experienced a case of a subretinal iron foreign body being mistaken for a blood clot. Even if the vision stays stable, ocular siderosis may occur over the long term if a subretinal iron foreign body remains. Therefore, surgical removal should be actively considered when a subretinal iron foreign body is suspected.

Keywords: Electroretinogram; Intraocular foreign body; Ocular siderosis; Vitrectomy.

Fig. 1

Fundus images before retinal detachment surgery. On day X+1, the fundus was difficult to observe due to vitreous hemorrhage (A). After X+1 month, the vitreous hemorrhage spontaneously subsided (B). After X+3 months, a rhegmatogenous retinal detachment from 2 o'clock to 9 o'clock was observed (C).

Fig. 2

Fundus image during retinal detachment surgery. A black elevated lesion under the retina below the macula was observed. Retrospectively, an iron foreign body lurking under the peripheral retina is thought to have migrated to the posterior pole due to gravity when the retinal detachment occurred.

Fig. 3

Fundus images and optical coherence tomography (OCT) after retinal detachment surgery. Two months after retinal detachment surgery, no change was observed in the subretinal black lesion, and there appeared to be blurring of the retinal layer structure (A). Eight months after retinal detachment surgery, the subretinal lesion changed from black to reddish brown (B). Ten months after retinal detachment surgery, the subretinal lesion changed from reddish brown to brown, and OCT showed no remarkable changes (C). (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

Anterior segment image at the start of phaco-vitrectomy surgery. Multiple yellowish brown, irregular, minute dots were observed on the lens, which were thought to be rust materials. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5

Goldmann perimeter results. An absolute scotoma above the retina was observed, corresponding to the presence of a foreign body in the macula. Loss of sensitivity on the nasal side due to superior NFLD was also observed after peripheral retinal detachment (A). The upper visual field defect in the macula, corresponding to the location of the foreign body, expanded (B).

Fig. 6

Electroretinogram results. Preoperative electroretinogram showed loss of rod response, attenuation of a-wave and b-wave to flash stimulation, loss of OP wave, and marked attenuation of cone response, suggesting widespread retinal damage (A). Postoperative electroretinogram showed no significant changes compared to preoperative results in any of the responses (B).

Fig. 7

Simple quantitative analysis results (Weight %) and chart using electron microscope X-ray microanalysis. A large amount of iron (Fe) was detected in the sample (Table). The spectrum showed characteristic X-rays representative of Fe (Figure, horizontal axis as energy (kiloelectronvolts), vertical axis as number of detected photons (count number)).