放射状角膜切開術後の白内障手術における眼内レンズ度数決定

Refraction following cataract surgery with insertion of intraocular lens in an eye after radial keratotomy

要約　目的：近視眼に対して放射状角膜切開術（RK）後の白内障手術における眼内レンズ（IOL）度数決定に際して，術前角膜屈折値および術後屈折誤差を，検討する。症例：両眼RK施行歴のある61歳女性。今回，右眼に白内障手術を施行。IOL度数決定には，眼軸長をIOLマスター^®を用い，術前角膜屈折力はPentacam^®を用いたTrue Net Power（TNP）法，計算式はSRK/T式を使用した。術後屈折度数誤差は術後等価球面度数と予測屈折度数の差とした。ほかの方法でも術後屈折誤差を推測した。結果：術後屈折誤差は，IOLマスター^®が0.25D，ring 3法が−0.72D，TNP法が0.04D，Haigis-L式が−2.49Dであった。結論：RK術後の眼内レンズ度数決定は，TNP法とSRK/T式を用いることで，屈折誤差が減少した。

Abstract.　Purpose：To report the state of refraction following cataract surgery with intraocular lens（IOL）implantation in an eye that had received radial keratotomy before. Case：A 61-year-old female presented with impaired vision in the right eye. She had received radial keratotomy in both eyes for myopia at the age of 30 years. She had received cataract surgery in the left eye 2 years before. Refraction after surgery showed an error by −02.54 diopters after determination of IOL after Haigis-L formula. Findings：Corrected visual acuity was 0.4 right and 0.7 left. Eight radial scars were present in either eye. The right eye received cataract surgery. Axial length was measured by IOL Master^® and corneal curvature by Pentacam^® True Net Power method. IOL power was calculated after SRK/T formula. Error of refraction from predicted value was 0.25D after IOL Master, −7.2D after ring 3 method, −0.04D after True Net Power method, and −2.49D after Haigis-L formula. Conclusion：Error of refraction from the predicted value was minimum when the power of IOL was calculated after True Net Power and SRK/Y formula.