釣り竿の眼窩深部への刺入によって生じた外傷性視神経症の1例

A case of traumatic optic neuropathy caused by a fishing rod puncture deep into the orbita

要約　目的：外傷性視神経症（TON）は，眉毛部外側の鈍的外傷によるものや視神経乳頭離断の介達性と，開放性損傷に基づく視神経断裂による直達性とに分類されるが，臨床で遭遇する頻度は介達性がほとんどである。今回，釣り竿の眼窩内への刺入によって生じたTONの1例を経験したので報告する。

症例：61歳，女性。先端直径5mmの釣り竿で左眼を受傷した。受傷直後から視力が低下したため近医眼科を受診し，精査・加療目的で川崎医科大学附属病院眼科に紹介され受診となった。初診時，視力は右1.5，左 光覚なし，左眼の相対的瞳孔求心路障害（RAPD）は陽性で，瞳孔記録計RAPDx^®によるRAPD振幅（log units）は9.62であった。細隙灯顕微鏡で左眼の鼻側結膜裂傷がみられたが，眼底や光干渉断層計で異常所見はなかった。頭部・眼窩CTでは左眼窩内に視神経まで続く気泡がみられたため，釣り竿が視神経まで到達したと考えられた。以上の結果，左眼TONと診断し，即日入院のうえ，ステロイドパルス療法を1クール行った。初診時から1か月後，左視力は光覚弁，RAPD振幅は5.82，OCTで網膜内層の菲薄化がみられた。初診から1年後の左視力は指数弁，視野検査では耳側下方のみ残存した。

結論：釣り竿が眼窩深部まで刺入することでTONを生じる可能性があり，急性期TONの診断にはRAPD検出による他覚的所見が重要でRAPDx^®による客観的かつ定量的な評価が有用である。

Abstract　Purpose：Traumatic optic neuropathy（TON）is classified as either indirectly caused by blunt trauma to the eyebrow, avulsion of optic nerve head, or directly caused by optic nerve rupture due to open injury. Among these, posterior indirect TON is most frequently encountered in clinical practice. Here we present a TON case caused by a fishing rod puncture in the orbit.

Case：A 61-year-old woman was injured in her left eye by a fishing rod with a 5 mm tip diameter. Her vision worsened immediately, therefore, she visited an ophthalmologist and was referred to our department on the same day for further examination and treatment.

Observations：At initial examination, her visual acuity was 1.5 in the right eye, whereas the left eye had no light perception and a relative afferent pupillary defect（RAPD）was observed in the left eye. RAPD amplitude（log units）by RAPDx^® was 9.62. Slit-lamp microscopy revealed a nasal conjunctival tear in the left eye, however, no abnormal findings were found on fundus examination and optical coherence tomography（OCT）. Head and orbital computed tomography（CT）showed a bubble in the left orbit extending to the optic nerve, suggesting that the fishing rod had reached the optic nerve. The patient was hospitalized on the same day and underwent one course of steroid pulse therapy. One month post-initial visit, the visual acuity of the left eye was light perception, RAPD amplitude was 5.82, and OCT showed thinning of the inner retinal layer. One year post-initial visit, the visual acuity of the left eye was counting fingers, and a visual field test showed residuals only in the inferior region.

Conclusion：Objective findings with RAPD detection are essential for diagnosing acute TON, and objective and quantitative evaluation using RAPDx contributes to diagnoses. In this TON case, the patient was treated with steroid pulse therapy, which slightly improved visual acuity and visual field；however, the prognosis of visual function was poor.