IOLマスターによる眼軸長値を用いた眼内レンズパワー計算式の検討

Calculation of intraocular lens power using the axial length obtained by IOL MasterTM

　白内障手術における眼軸長を超音波式眼軸長測定器Aモード，光学式眼軸長測定器IOLマスターによりそれぞれ測定し，4つの眼内レンズパワー計算式（Holladay, SRK/T, Hoffer Q, SRKⅡ式）の予想屈折度精度を比較検討した。対象は白内障手術例118眼である。その結果，予想屈折度と術後屈折度の差が±1D未満におさまった症例の割合は，IOLマスターの術前眼軸長値を用いた場合Holladay式86％，SRK/T式83％，Aモードの眼軸長値を用いた場合Holladay式64％，SRK/T式68％で，IOLマスターの眼軸長値を用いた予想屈折度精度はAモードに比較し，有意に良好であった。

　Purpose：To compare laser inferometry and A-mode ultrasound for axial length inserted into formulas for power calculation of intraocular lens（IOL）. Cases and Methods：Cataract surgery with IOL implantation was performed on 188 eyes. Four formulas were used in power calculation：Holladay,SRK/T,SRKⅡ,Hoffer Q. The axial length was measured by laser inferometry（IOL Master,Zeiss）and by A-mode ultrasound（AL010,Tomey）. Results：By using the axial length obtained by laser inferometry,the postoperative refraction was within±1.0 diopter in 86％of eyes for Holladay formula,and in 83％of eyes for SRK/T formula. By using the axial length obtained by A-mode ultrasound,the postoperative refraction was within±1.0 diopter in 64％of eyes for Holladay formula,and in 68％of eyes for SRK/T formula. Conclusion：IOL power calculation by Holladay or SRK/T formula was more accurate when axial length value was measured by laser inferometry than A-mode ultrasound.