片眼性強度近視例における患眼と僚眼の眼球形態の比較検討

Comparison of eye morphology between the affected eyes and the contralateral eyes in patients with unilateral high myopia

要約　目的：片眼性強度近視例における患眼と僚眼の前眼部から後眼部の眼球形態を比較し，病態背景を検討した。

対象と方法：今回，片眼の眼軸長が26.5mm以上で，その僚眼の眼軸長が26mm未満かつ眼軸長差が1mm以上（平均眼軸長差3.77mm）ある片眼性強度近視31例を対象とした。前眼部は，前眼部OCTを用いて中心角膜厚・角膜屈折力・前房深度を計測し，患眼と僚眼で比較した。後眼部は，超広角眼底カメラ画像とOCTの3D解析を用いて，後部ぶどう腫（ぶどう腫）の有無を判定し，患眼と僚眼のぶどう腫の割合とCurtin分類に沿ってタイプ別に分類した。また，僚眼のぶどう腫の有無からみた背景と患眼の眼底所見からみた僚眼の背景を検討した。

結果：前眼部では，患眼と僚眼で中心角膜厚・角膜屈折力・前房深度に有意差はなかった。後眼部は，患眼でぶどう腫を全例に認め，type Ⅰ＋type Ⅱで約85％占めていた。一方，僚眼でも全体の約60％にぶどう腫を認め，そのうち同一症例でも患眼とタイプが違う症例が約60％にみられた。僚眼にぶどう腫を伴うと，高齢（p＜0.01）・僚眼の視力低下（p＜0.01）・眼疾患（p＝0.04）・萎縮病変（p＝0.03）の割合が有意に高かった。また，患眼の眼底所見が限局性萎縮病変まで進行している症例では，僚眼の萎縮病変（41％）・ぶどう腫（83％）・合併疾患（50％）の割合が高い傾向にあった。

結論：片眼性強度近視例では，患眼と僚眼の前眼部形態に有意差はなく，後眼部の構造変化が大きい。また，病的近視眼は強度近視でない症例にも起こりうる。

Abstract　Purpose：To compare the ocular morphology of the anterior to posterior portions of the affected eyes and the contralateral eyes in patients with unilateral high myopia and to examine the pathological background.

Subjects and Methods：In this study, 31 cases of unilateral high myopia with an axial length of 26.5 mm or more in one eye, an axial length of less than 26 mm in the contralateral eye, and an axial length difference of 1 mm or more（mean axial length difference 3.77 mm）were included. Corneal thickness, corneal refractive power, and anterior chamber depth were measured using anterior segment optical coherence tomography（OCT）and compared between the affected eye and the contralateral eye. In the posterior segment, the presence or absence of staphylomas was determined using Optos images and 3D analysis of OCT（Avanti）, and we examined the percentage of staphyloma in the affected eye and the contralateral eye and classified staphyloma's types according to the Curtin classification. In addition, we examined the background of the contralateral eyes based on the presence or absence of staphyloma and in the affected eyes, based on the fundus findings of the affected eye.

Result：In the anterior segment, no significant difference was seen in corneal thickness, corneal refractive power, or anterior chamber depth between the affected eye and the contralateral eye. In the posterior segment, staphylomas were seen in all affected eyes, and type Ⅰ＋type Ⅱ accounted for about 85％ of the cases. Conversely, about 60％ of the affected eyes also had staphyloma, and about 60％ of the affected eyes had different type of staphyloma from the contralateral eye in the same case. The proportions of old age（p＜0.01）, decreased visual acuity（p＜0.01）, ocular disease（p＝0.04）, and atrophic lesions（p＝0.03）were significantly higher when the contralateral eye had staphyloma. In addition, patients with fundus findings in the affected eye progressing to localized atrophic lesions had a higher percentage of atrophic lesions（41％）, staphyloma（83％）, and other diseases（50％）in the contralateral eye.

Conclusion：In cases of unilateral high myopia, no significant difference was observed in the anterior segment morphology between the affected eye and the contralateral eye, and structural changes in the posterior segment were greater. Pathological myopia can occur even in cases without high myopia.