診断に苦慮した眼内鉄片異物の1例

Protracted diagnostic procedure in a case of retained intraocular iron foreign body

要約　目的：眼内に異物が18か月間滞留し，MRI検査で発見された1症例の報告。

症例：44歳男性が9か月前から徐々に進行した右眼の視力低下と夜盲で受診した。

所見：矯正視力は右0.6，左1.5で，右眼に求心性視野狭窄があり，網膜電図は陰性型であった。眼窩内を精査するために頭部MRIを実施しようとした際に右眼痛を訴えた。問診で，受診する17か月前にハンマーを使った作業中に，右の下眼瞼に約1 mmの鉄片が刺さり，除去されたとの経緯が判明した。頭部CTで右の眼内に異物があった。手術で長径5 mmの鉄片を摘出した。

結論：長期間滞留した眼内異物が，片眼性の夜盲，視野狭窄，網膜電図の減弱の原因になりうることを本症例は示している。

Abstract　Purpose: To report a case of retained intraocular iron foreign body detected by MRI.

Case: A 44-year-old male presented with gradually progressive impaired right vision and night blindness that started since 9 months before.

Findings: Corrected visual acuity was 0.6 right and 1.5 left. The right eye showed concentric contraction of visual field and negative ERG. The patient complained of pain in the right eye when MRI was attempted. Further inquiry showed that a piece of iron pierced the right lower eyelid while working with a hammer. The iron piece was removed and was 1 mm in size. Computed tomography showed a foreign body in the right eye. Surgery was performed to remove an iron piece of 5 mm in length.

Conclusion: This case illustrates that retained intraocular iron foreign body may induce unilateral night blindness, visual field constriction, and negative ERG.