光线追踪技术测算人工晶状体度数的临床观察

Intraocular lens power calculation using ray-tracing technique

目的比较光线追踪技术与光学生物测量方法计算人工晶状体度数的准确性。方法选择可以用IOL-Master测量出角膜曲率和眼轴的白内障患者60例(81只眼),分为正常眼轴组(22 mm≤AL≤24 mm)和长眼轴组(AL>24 mm),行普通的同轴微切口白内障超声乳化加IOL植入术,植入人工晶状体度数按照IOL-Master测算结果,术前同时行角膜地形图检查及A超测量晶状体厚度,并应用Phaco-optics软件计算人工晶状体度数。术后1个月进行电脑验光。根据术后验光结果计算IOL理论度数,两种测算方法的屈光预测误差和绝对预测误差。用SPSS19.0软件进行比较分析。结果 (1)所有纳入患者应用角膜地形图所测量的K1、K2值均小于IOL Master的测量结果,有统计学差异(P<0.05),而两者测量的中央前房深度比较无明显差异(P>0.05)。(2)正常眼轴组应用IOL-Master测算方法和Phaco optics软件得到的预测屈光误差分别为(-0.182±0.762)D、(-0.244±0.967)D,比较无统计学差异(P>0.05),而长眼轴组分别为(-0.89±0.652)D、(0.47±1.575)D,比较有明显统计学差异(P<0.05)。(3)长眼轴组中应用Phaco optics软件测算的绝对误差与散光大小有明显正相关性(P<0.05),与眼轴无相关性(P>0.05),而以IOL Master计算公式为基础的LSW1公式的绝对误差与散光大小无明显相关(P>0.05),与眼轴有明显正相关性(P<0.05)。结论基于光线追踪技术的Phaco optics软件适用于散光较小的正常眼轴患者,对于长眼轴患者的计算结果有轻度远视倾向,但随眼轴长短的变异性较小。

Objective To compare the accuracy of ray-tracing technique and IOL Master for intraocular lens（ IOL） power calculation. Methods 81 eyes of 60 patients whose axial length and corneal curvature measured by IOL Master were collected and divided into two groups,normal axial length group（ 22mm≤AL≤24mm） and long axial length group（ AL24mm）. All patients accepted coaxial phacoemulsification cataract extraction through micro incision combined with IOL implantation. IOL Master decided the power of actual implanted IOL. Meanwhile,all patients were examined with corneal topography and type A ultrasound before operation,and IOL power was calculated with Phaco Optics software. The refractive errors at 1 month after surgery were measured by automatic refractor. Theoretical IOL degree,predictive error（ PE） and absolute predictive error（ AE） of the two calculation approaches were calculated based on the results of postoperative refraction. The results were analyzed by SPSS 19.0 software. Results 1） Among all the patients selected in this study,K1 and K2 measured by corneal topography were smaller than that measured by IOL Master（ P〈0.05）. Anterior chamber depth measured by two instruments had no significant difference（ P〉0.05）.2） PE of IOL Master and Phaco Optics software in the normal axial length group were-0.182±0.762 D and-0.244±0.967 D,and there was no significant difference（ P〉0.05）. PE in the long axial length group were-0.89±0.652 D and 0.47 ±1.575 D respectively,PE of IOL Master was significantly smaller than that of Phaco Optics software（ P〈0.05）.3） AE of Phaco Optics software in the long axial length group was positively correlated with astigmatism（ P〈0.05）,but not correlated with axial length. However,AE of LSW1 formula which based on IOL Master calculation formula was not correlated with astigmatism but positively correlated with axial length（ P〈0.05）. Conclusions Phaco Optics software based on ray-tracing technique is good for normal axial length patients with slight astigmatism. Our results showed a hyperopia tendency for patients with long axial length,but its correlation with axial length is weak.