矫正角膜散光对人工晶状体计算的影响

目的:分析白内障术中矫正角膜散光对人工晶状体度数预测的影响。方法:选择老年性白内障患者35例35眼,行上方切口超声乳化联合PMMA人工晶状体植入术后角膜散光减少,测量术前和术后3mo的角膜曲率及屈光状态。比较SRKⅡ,SRK/T,HolladayⅠ公式在使用术前和术后角膜曲率值计算的绝对预测误差。结果:手术前后平均角膜曲率增加0.30±0.81D,角膜散光度数减少0.70±0.71D,都有统计学意义(P<0.05),两者的相关性为(r=-0.554,P<0.01)。SRKⅡ,SRK/T,HolladayⅠ使用术前角膜曲率计算的绝对预测误差中位数分别为0.85D,0.73D,0.78D,公式间无统计学差异(χ2=4.474,P>0.05);使用术后角膜曲率计算则分别为0.72D,0.54D,0.46D,有统计学差异(χ2=7.758,P<0.05);3代公式在两种计算方法下结果有有统计学差异(Z=-2.208,-2.273,P<0.05)。结论:矫正角膜散光会引起角膜屈光度变化,导致人工晶状体度数的预测误差增大,计算公式尤其是3代公式的准确性下降,有必要对公式进行相应调整优化。

Influence of correcting the corneal astigmatism on intraocular lens power formulas

· AIM:To analyse the influence of correcting corneal astigmatism on the accuracy of intraocular lens power prediction after cataract surgery.· METHODS:Thirty-five cases of age-related cataract 35 eyes were selected,the corneal astigmatism was reduced after phacoemulsification with superior incision and PMMA intraocular lens implantation.The keratometry was measured before operation and three months postoperatively,then the absolute forecast error of SRK Ⅱ,SRK/T,Holladay Ⅰ formula with preoperative and postoperative corneal curvature were compared.·RESULTS:The average corneal curvature was increased by 0.30±0.81D(t=-2.205,P<0.05),the corneal astigmatism was decreased by 0.70±0.71D after operation(t=5.846,P<0.01),there was correlation between them(r=-0.554,P<0.01).The absolute predict errors of SRKⅡ,SRK/T and Holladay Ⅰ formulas using preoperative curvature was respectively 0.85D,0.73D and 0.78D,there was no significant difference(χ2=4.474,P>0.05).The absolute predict error using postoperative curvature was respectively 0.72D,0.54D and 0.46D,SRKⅡ indicated statistical difference from other formulas(χ2=7.758,P<0.05).The third theoretical formula had statistical difference from using preoperative and postoperative curvature(Z=-2.208,-2.273,P<0.05).· CONCLUSION:Correcting the corneal astigmatism may cause the changes in corneal refraction,which leads to the error of the intraocular lens prediction increase,especially the accuracy of the third generation formula decrease,so it is necessary to adjust and optimize the formula accordingly.·