眼窩減圧術による外直筋断裂の1例

A case of external rectus muscle tear due to orbital decompression

要約　目的：眼窩減圧術で右眼の外直筋断裂をきたし，斜視手術により良好な眼位を得た症例を経験したので報告する。

症例：33歳，女性。X年1月にBasedow病と診断され，同年6月に複視と視力低下を自覚して当院を受診した。両眼に全外眼筋の腫脹，全方向性の眼球運動障害を認めた。視力は右0.04（0.7×−4.75D），左0.08（1.5×−4.00D），限界フリッカ値は右31.5Hz，左41.9Hzであり，右眼は甲状腺眼症による圧迫性視神経症をきたしていると判断した。ステロイドパルスを施行したが，視力は悪化傾向にあったため，同年9月に両眼眼窩減圧術を施行した。術中に右眼外直筋を断裂し，術後は右眼に外転制限と高度の内斜視を生じた。眼位整復のため，術後3日目に右眼の外直筋縫合を施行したが改善は得られず，2か月後に両内直筋大量後転および右眼上・下直筋外方移動術を追加した。術後3か月では外転制限は残存したものの，遠見2prism diopter（PD）内斜位となった。また矯正視力は両眼とも1.5，限界フリッカ値は40.4Hz/40.2Hzであった。

結論：外傷性の外眼筋完全断裂を伴う麻痺性斜視では，損傷筋の修復のみで治療できた報告などを散見する。しかし，本症例のように甲状腺眼症に伴い拘縮，線維化した筋においては，筋縫合が難しく，損傷筋の整復のみでは眼位改善が得られなかった可能性がある。このような症例には拮抗筋の後転や筋移動術が有効と考える。

Abstract　Purpose：We report a case in which the external rectus muscle of the right eye was ruptured by orbital decompression surgery, and a good eye position was obtained by strabismus surgery.

Case：A 33-year-old female patient was diagnosed with Graves' disease in January and came to our hospital in June of the same year with diplopia and decreased visual acuity. Visual acuity was 0.15 logMAR in the right eye and −0.18 logMAR in the left eye, with flicker values of 31.5 Hz in the right eye and 41.9 Hz in the left eye. The right eye was judged to have compressive optic neuropathy caused by thyroid ophthalmopathy, and steroid pulses were performed, but the patient continued to deteriorate. During the surgery, the external rectus muscle of the right eye was ruptured, resulting in limited abduction of the right eye and severe internal strabismus after the surgery. The right lateral rectus muscle was sutured on the third postoperative day to correct the eye position, but there was no improvement. Two months later, massive recession of both medial rectus muscles and external shift of the right superior and inferior rectus muscles were performed. At 3 months postoperatively, although abduction restriction remained, the eye position was 2 PD esotropia in distance. Corrected visual acuity was −0.18 logMAR in both eyes with flicker values of 40.4 Hz/40.2 Hz.

Conclusion：In this case, the paralytic strabismus was not completely repaired. However, in the case of fibrosis associated with thyroid ophthalmopathy, as in the present case, muscle suture was difficult, and it is possible that eye position could not be improved only by repair of the injured muscle. In such cases, recession of the antagonist muscle or muscle transportation may be effective.