観察できない虹彩下の磁性眼内異物の摘出に眼内マグネットが有用であった症例

A case of the foreign body under the iris removed by intraocular magnet

要約　目的：眼内マグネットを用いて，虹彩下にあり観察できなかった磁性眼内異物を摘出できた症例を経験し，眼内マグネットの新たな有用性を報告する。

症例：45歳，男性。金属片をハンマーで叩いている際に異物が左眼に当たったことを自覚しA眼科を受診したが，異物，眼球穿孔の所見はなかった。受傷翌日にB病院を紹介され受診したが，異物，眼球穿孔の所見はなく，左眼外傷性虹彩炎と診断された。受傷2日後，自覚症状と虹彩炎の悪化を認めたため，眼内異物が疑われ頭部CTを撮影したところ，眼内異物が検出されたため滋賀医科大学医学部附属病院を紹介され受診となった。

　初診時の左視力は（0.2）で，左眼圧は18mmHg，角膜浮腫，前房内細胞（＋＋＋），フィブリン析出，軽度白内障を認めた。眼底は観察不能であった。異物，穿孔創は観察できなかった。頭部CTで左眼5時方向の虹彩と水晶体の間に磁性異物を疑う高輝度の異物を認めた。

所見：手術では，角膜輪部の11時方向に幅2.4mmの角膜創を作製し，虹彩と水晶体の間を粘弾性物質で拡張し，眼内マグネットを角膜創より虹彩の下に挿入し眼内異物を吸着させ，異物を角膜創より摘出した。粘弾性物質を吸引後，抗菌薬の硝子体内注射を施行した。術後，炎症は軽快し，1年後の左視力は（1.5）であった。

結論：細隙灯顕微鏡検査や手術顕微鏡で観察できない虹彩下の磁性眼内異物の摘出に眼内マグネットは有用である。

Abstract　Purpose：Here, we report a case in which a magnetic intraocular foreign body invisible under the iris was successfully removed using an intraocular magnet.

Case：A 45-year-old man noticed a foreign body affecting his left eye while hammering a metal piece. Clinic A found no signs of a foreign body or glob perforation. The patient was referred to Hospital B the following day, in which no foreign body or globe perforation was detected, and diagnosed with traumatic iritis in the left eye. Two days post-injury, worsening subjective symptoms and iritis led to the suspicion of an intraocular foreign body. Head computed tomography（CT） was performed, and a foreign body was detected, resulting in the patient being referred to Shiga University of Medical Science Hospital. Upon presentation, his left best-corrected visual acuity was 0.2, and intraocular pressure was 18 mmHg. He presented with corneal edema, anterior chamber cells（＋＋＋）, fibrin formation in the anterior chamber, and mild cataracts. The fundus is unobservable. No foreign bodies or wounds were visible. CT revealed a highly reflective intraocular foreign body, suspected to be magnetic, located between the iris and lens at the 5 o'clock position in the left eye.

Findings：Intraoperatively, a 2.4-mm corneal incision was made at the 11 o'clock limbus. The space between the iris and lens was expanded using a viscoelastic substance. An intraocular magnet was inserted through the corneal incision under the iris, and attracted and removed the foreign body. After aspiration of the viscoelastic substance, an intravitreal injection of antibiotics was administered. Postoperatively, the inflammation subsided, and the patient's left best-corrected visual acuity was 1.5 after one year.

Conclusion：An intraocular magnet can remove a magnetic intraocular foreign body located under the iris that cannot be observed by slit-lamp examination or surgical microscopy.