角膜移植後の乱視矯正角膜切開術の効果

Astigmatic keratotomy after keratoplasty

　角膜移植術後の強度乱視に，オプチカルゾーン7ミリの弧状切開による乱視矯正角膜切開術（AK）を施行した12眼（16回）の術後成績につき検討した。屈折乱視は術前6.47±2.10Dから3.77±2.28D，角膜乱視は7.67±1.92Dから3.64±2.00Dと有意に減少した。7例でベクトル解析による惹起乱視度数と目標度数とのずれが2D以内に収まったが，残りは過矯正となっていた。矯正視力は，2段階以上の改善7例，不変6例，悪化3例であった。結論として，角膜移植後のAKは乱視軽減に有効であったが，予測性が低く，その他の手段では矯正不能な強度乱視例に限定して，低矯正を目標に行われるべきであると考えられた。

We reviewed the results of astigmatic keratotomy in 12 eyes after keratoplasty. Penetrating keratoplasty had been performed in 11 eyes and lamellar keratoplasty in one. Arcuate keratotomy with 7mm in optical zone was performed. The procedure was repeated twice in 4 eyes. Following keratotomy, manifest astigmatism decreased from 6.47±2.10 D to 3.77±2.28 D and the keratometric astigmatism from 7.67±1.92 D to 3.64±2.00 D. The changes were significant. The differences between the intended and the induced astigmatism as calculated by vector analysis were within ±2 diopters in only 7 eyes, 47%. Overcorrections resulted in the other 5 eyes including 3 eyes of severe overcorrection. Two of the 3 eyes needed further surgical correction. The findings show that astigmatic keratotomy is effective for reducing astigmatism in eyes after keratoplasty but that predictability is relatively poor. We advocate the procedure to eyes with high astigmatism with severely impaired visual function following keratoplasty. It is also advised to aim at an undercorrection.