第3世代眼内レンズ計算式の精度

Accuracy of power calculation formulas for third-generation intraocular lens

　Holladay式，Hoffer Q式およびSRK／T式を従来からの各計算式のアクリルソフトレンズを用いた際の精度を検討した。超音波水晶体乳化吸引術，アクリルソフト眼内レンズ（MA30BA，アルコン社）嚢内挿入術を行い術後矯正視力がO．5以上であった111症例148眼の結果からpACD, SFを算出した。その値を同様の条件を満たす他の母集団304例390眼において，Holladay式，Hoffer Q式，SRK／T式，SRK式，SRKⅡ式，SRK修正式の精度を比較した。その結果，pACDは5.45±0.59mm,SFは1.69±0.44mmであった。誤差±1D未満の症例の割合はHoffer Q式84.9％，Holladay式84.1％，SRK／T式80.0％，SRK修正式75.9％，SRK式72.6％，SRKⅡ式70.3％であった。HOIIaday式，Hoffer Q式およびSRK／T式は，SRK,SRKⅡに比較して有意に精度が高かった（p＜0.05）。以上のように第3世代計算式は，アクリルソフトレンズを用いた小切開白内障手術においても高い精度であった。

Purpose:To evaliate the accuracy of three calculation formulas as applied to acryl soft intraocular lens (IOL). They were:SRK/T formula, personal anterior chamber depth (pACD) in Hoffer Q formula, including the surgeon factor (SF).

Cases and Method:pACD and SF were calculated in 148 eyes following small incision phacoemulsification and soft acrylic IOL implantation in the capsular bag. Another similarly treated group of 390 eyes were evaluated regarding the incidence of refraction within±1.00 diopter of the predicted value by Holladay and Hoffer Q formulas. Both groups were also evaluated regarding other formulas including SRK /T, SRK, SRK II and modified SRK.

Results: The value of pACD was 5.45±0.59 mm and SF was 1.69±0.44 mm. The incidence of eyes which resultrd in refraction within±1.00 diopter was 84.9% for Hoffer Q, 84.1% for Holladay, 80.0% for SRK/T, 75.9% for modified SRK, 72.6% for SRK, and 70.3% for SRK II formula. Formulas for third-generation IOL were significantly more accurate than earlier ones, SRK or SRK Ⅱ (p＜ 0.05).

Conclusion: Formulas for third-generation IOL showed good predictive value of postoperative refraction fol-lowing small incision phacomulsification and soft acrylic IOL implantation.