乱視矯正角膜切開後の不正乱視の定量的検討

Quantitation of irregular corneal astigmatism after astigmatic keratotomy

　矯正角膜切開術後の17症例20眼で，術前後の角膜不正乱視を定量的に検討した。術前と術後1，4,12,24週に角膜形状解析装置で測定し，光学領域の3本のマイヤーリング上の屈折力分布を正弦曲線に近似し，その回帰残差を不正乱視量の指標とした。術前の角膜不正乱視量は正常人の値と同様であった。術後1週で不正乱視量がやや上昇し，その後次第に減少していく傾向があったが，どの時点でも術前値と有意差はなかった。乱視矯正角膜切開術は，光学領域内の角膜不正乱視に大きな影響を与えないと考えられた。

We quantitated the irregular corneal astigmatism in 20 eyes treated by astigmatic keratotomy. Computed corneal topography was performed before and after surgery at 1, 4, 12 and 24 weeks. The refractive power on a mire ring was approximated to a sine curve and the calculated final loss served as parameter for the irregular astigmatism. Preoperative values for irregular astigmatism were similar to those in normal controls. Postoperatively, the irregular astigmatism failed to show significant changes during the period of observation from the preoperative values. The findings show that astigmatic keratotomy does not influence the amount of corneal irregular astigmatism within the optical zone.