Accuracy of intraocular power calculation formulas]

PURPOSE: We examined the accuracy of intraocular lens power calculation formulas, with special emphasis on the prediction of refraction in different axial lengths. MATERIAL AND METHODS: 786 cases were subdivided into four groups based on the axial length (short axial length < 22.0 mm, normal axial length = 22-24.4 mm, mid-range axial length = 24.5-26.9 mm and long axial length > 27 mm). Seven different formulas (Holladay, SRK, SRK II, SRK/T, S-SRK, M-SRK, L-SRK) were tested for their accuracy in predicting post-operative refraction. RESULT: The best results were obtained using the S-SRK formula in the short axial length group (n = 114), The SRK and Holladay formulas in the normal axial length group (n = 278). The Holladay and SRK/T formulas in the mid-range axial length group (n = 135), and the SRK/T and L-SRK in the long axial length group (n = 259). CONCLUSION: Our results emphasize the importance of using an intraocular lens formula specific for each range of axial length when calculating the predicted refraction.     

Accuracy of intraocular lens power calculation formulas in primary angle closure glaucoma

Purpose

To compare the accuracy of intraocular lens (IOL) power calculation formulas in eyes with primary angle closure glaucoma (ACG).

Methods

This retrospective study compared the refractive outcomes of 63 eyes with primary ACG with the results of 93 eyes with normal open angles undergoing uneventful cataract surgery. Anterior segment biometry including anterior chamber depth, axial length, and anterior chamber depth to axial length ratio were compared by the IOL Master. Third generation formulas (Hoffer Q and SRK/T) and a fourth generation formula (Haigis) were used to predict IOL powers in both groups. The predictive accuracy of the formulas was analyzed by comparison of the mean error and the mean absolute error (MAE).

Results

In ACG patients, anterior chamber depth and the anterior chamber depth to axial length ratio were smaller than normal controls (all p < 0.05). The MAEs from the ACG group were larger than that from the control group in the Haigis formula. The mean absolute error from the Haigis formula was the largest and the mean absolute error from the Hoffer Q formula was the smallest.

Conclusions

IOL power prediction may be inaccurate in ACG patients. The Haigis formula produced more inaccurate results in ACG patients, and it is more appropriate to use the Hoffer Q formula to predict IOL powers in eyes with primary ACG.     

Accuracy of 8 intraocular lens power calculation formulas in pediatric cataract patients

Graefe's Archive for Clinical and Experimental Ophthalmology - To compare the accuracy of the eight formulas for intraocular lens (IOL) power calculation in pediatric cataract patients. A...     

高度近视眼人工晶状体度数计算公式的准确性比较

目的　评价用ＩＯＬＭａｓｔｅｒ和ＳＲＫ-Ⅱ、ＳＲＫ-Ｔ、Ｈｏｌｌａｄａｙ-１和Ｈａｉｇｉｓ四种公式计算眼轴≥２７ｍｍ的高度近视眼人工晶状体（ｉｎｔｒａｏｃｕｌａｒｌｅｎｓ,ＩＯＬ）度数的准确性。方法　回顾性分析于我院行白内障超声乳化摘出联合ＩＯＬ植入术、眼轴≥２７ｍｍ的高度近视合并白内障患者１０５例（１４８眼）的临床资料,用ＩＯＬＭａｓｔｅｒ测量并用以上四种公式计算ＩＯＬ度数和预测术后屈光度。按照眼轴长度分组,从２７ｍｍ起每增加１ｍｍ为一组,分别计算各组术后３个月时实际术后等效球镜度（ａｃｔｕａｌｐｏｓｔｏｐｅｒａｔｉｖｅｓｐｈｅｒｉｃａｌｅｑｕｉｖａｌｅｎｃｅ,ＡＰＳＥ）与四种公式计算的预测术后等效球镜度（ｐｒｅｄｉｃｔｅｄｐｏｓｔｏｐｅｒａｔｉｖｅｓｐｈｅｒｉｃａｌｅｑｕｉｖａｌｅｎｃｅ,ＰＰＳＥ）的差值,即为预测屈光度误差值（ｐｒｅｄｉｃｔｉｖｅｅｒｒｏｒ,ＰＥ）。比较四种公式在不同眼轴长度区间ＰＥ的统计学差异,将眼轴组间ＰＥ没有统计学差异的组合并得到眼轴长区间,并计算出这四种ＩＯＬ计算公式在不同眼轴长度区间的ＰＥ。结果　１４８眼眼轴长度为（３１．０６±２．３２）ｍｍ,ＰＥ在ＳＲＫ-Ⅱ、ＳＲＫ-Ｔ、Ｈｏｌｌａｄａｙ-１和Ｈａｉｇｉｓ公式分别为（１．０１±１．５３）Ｄ、（０．７６±０．９６）Ｄ、（１．２４±０．８０）Ｄ和（０．７８±０．８４）Ｄ;四种公式计算的ＰＰＳＥ与ＡＰＳＥ间差异均有统计学意义（均为Ｐ＜０．０５）,ＳＲＫ-Ｔ和Ｈａｉｇｉｓ公式的ＰＥ差异无统计学意义（Ｐ＞０．０５）;Ｈｏｌｌａｄａｙ-１公式的ＰＥ与ＳＲＫ-Ｔ、Ｈａｉｇｉｓ公式的ＰＥ均有显著差异（均为Ｐ＜０．０５）。将眼轴组间ＰＥ没有统计学差异的组合并后得到２７～３０ｍｍ、３０～３２ｍｍ、３２～３４ｍｍ、≥３４ｍｍ四个眼轴长度区间,ＳＲＫ-Ｔ／Ｈａｉｇｉｓ公式在各区间的ＰＥ分别为（０．２１±０．６５）Ｄ／（０．４８±０．７１）Ｄ、（０．５８±０．５６）Ｄ／（０．５８±０．６１）Ｄ、（１．１８±０．６７）Ｄ／（０．９７±０．６１）Ｄ和（１．９７±１．４４）Ｄ／（１．７６±１．２６）Ｄ。结论　在眼轴≥２７ｍｍ的高度近视眼ＩＯＬ度数计算上ＳＲＫ-Ⅱ、ＳＲＫ-Ｔ、Ｈａｉｇｉｓ和Ｈｏｌｌａｄａｙ-１公式预测术后屈光度均为近视方向的过矫正。在不同眼轴长度区间用ＳＲＫ-Ｔ／Ｈａｉｇｉｓ公式计算时,适当向近视方向调整ＰＰＳＥ（－０．２～－２．０）／（－０．５～－１．８）Ｄ而得到的植入ＩＯＬ度数可以改善计算公式的准确性。     

IOLMaster测量眼人工晶状体计算公式准确性比较

目的比较由IOLMaster完成测量眼中临床常用各个人工晶状体计算公式（Haigis、SRKII、Hoffer Q、Holladay 1、SRK／T以及Holladay 2）的准确性。方法回顾性分析在温州医学院附属眼视光医院白内障专科行自内障超声乳化吸除联合人工晶状体植入术患者137例（191只眼）使用各个人工晶状体计算公式的准确性。结果Haigis公式的绝对预测误差中位数是0．38D,小于其他人工晶状体计算公式的绝对预测误差中位数,与SRKII、Hoffer Q、Holladay 1公式的差异有统计学意义。以跟轴分组对人工．晶状体计算公式分析,Haigis公式的绝对预测误差中位数始终是最小的。结论在临床眼科工作中,Haigis公式是IOLMaster测量下计算结果准确性最高的人工晶状体计算公式。超长眼轴下Haigis公式有明显的预测误差,而短眼轴下人工晶状体计算公式的准确性需要进一步的研究。     

Accuracy of the newer generation intraocular lens power calculation formulas in long and short eyes

The accuracy of two newer generation theoretical intraocular lens (IOL) power calculation formulas and of the empirical SRK I and II formulas was evaluated in a series of 500 IOL implantations including a series of unusually long and short eyes. The prediction error of the theoretical formulas was found to be largely unaffected by the variation in axial length and corneal power, while the prediction of the SRK I formula was less accurate in the short and long eyes. The prediction of the SRK II formula was more accurate than the SRK I in that no systematic offset error with axial length could be demonstrated. However, because of a relatively larger scatter in the long eyes and a significant bias with the corneal power, the absolute error of the SRK II formula was higher than that of the theoretical formulas in the long eyes. The higher accuracy of the newer generation theoretical formulas was attributed to their improved prediction of the pseudophakic anterior chamber depth.     

Influence of the invariant refraction assumption in studies of formulas for monofocal and multifocal intraocular lens power calculation

International Ophthalmology - To assess the influence in paired design studies of formulae comparison for intraocular lens (IOL) power calculation of using a single formula for deciding the...     

IOL—Master在人工晶状体屈光度计算中的精确性研究

目的 评价IOL-Master在人工晶状体屈光度计箅中的临床应用价值.方法 对160眼白内障分别运用IOL-Master与A型超声波测量眼轴,术后1月、3月行屈光检查.结果 IOL-Master测量眼轴:22＜L≤24.5 mm组平均轴长为(23.75±0.56)mm,24.5＜L≤26 mm组平均轴长为(25.21±0.61)mm,L＞26.0 mm组平均轴长为(28.87±0.58)mm.A型超声波测量眼轴,上述3个组平均轴长依次为:(23.68±0.81)mm,(25.01±0.90)mm,(29.33±1.02)mm.术后1月,L＞26.0 mm组,A超组和IOL-Master组的平均等效球镜屈光度误差为(1.449±0.723)D及(0.875±0.682)D(P<0.001).术后3月,L>26.0 mm组,A超组和IOL-Master组的平均等效球镜屈光度误差为(1.345±0.714)D及(0.865±0.683)D(P<0.001).结论 IOL-Master在人工晶状体屈光度计算方面具有极高的临床应用价值.     

Use of Scheimpflug corneal anterior‐posterior imaging in ray‐tracing intraocular lens power calculation

Purpose: To examine improvement with the use of Scheimpflug imaging of the anterior and posterior corneal surfaces in the accuracy of ray‐tracing intraocular lens (IOL) power calculation for normal cataractous eyes. Methods: Prospective case series comprised 136 eyes of 136 consecutive patients who had undergone cataract surgeries. Scheimpflug imaging of the cornea was included with routine preoperative examinations. Postoperative refractions were predicted using three methodologies; ray‐tracing calculation using Scheimpflug imaging and Placido topography, ray‐tracing calculations using Placido topography, and the SRK/T formula using autokeratometry. Prediction errors from the manifest refraction at 1 month postoperatively were compared between the methods. Influence of the posterior corneal curvature was also evaluated. Results: Mean prediction errors were 0.008, ?0.103 and ?0.042 D, respectively without significant difference between the three methods (p = 0.23). The prediction errors were significantly correlated with the posterior corneal curvature when the Scheimpflug imaging was not used (p < 0.03). Conclusion: Use of Scheimpflug imaging in ray‐tracing IOL power calculation was as accurate as the other calculations in normal cases, showing no bias in the posterior corneal curvature, as is the case with the other calculations.     

六种人工晶状体屈光度数计算公式的准确性比较

目的 比较六种人工晶状体（IOL）屈光度数计算公式（SRK-T，Haigis，Binkhorst-Ⅱ，Hoffer Q，Holladay-1，SRK-Ⅱ）在不同眼轴长中的准确性。设计 回顾对比临床分析。研究对象 169例（169眼）年龄相关性白内障患者。方法 将上述白内障患者按术眼眼轴长度（AXL）分成五组，即AXL≤22mm、22mm〈AXL≤24．5mm、24．5mm〈AXL≤27mm、27mm〈AXL≤28．4mm和AXL〉28．4mm，术前使用A型超声仪测量术眼的眼轴长及角膜屈光度，术后1个月用电脑验光与检影验光相结合的方法测量术眼获得最佳矫正远视力时的实际屈光度数，回输超声测量值及术眼所使用的IOL屈光度数，用SRK-T，Haigis，Binkhorst-Ⅱ，Hoffer Q，Holladay-1，SRK-Ⅱ这六种公式分别计算术眼的预期屈光度数。比较不同眼轴长度组中预期屈光度数和实际屈光度数的差值。主要指标 术后实际屈光度数与预期屈光度数差值的绝对值，即绝对预测误差值。结果 在各AXL长度组中，每组中除Binkhorst-Ⅱ公式外，其他5种公式所得出的绝对预测误差值均无统计学差异（P均〉0．05）；AXL〉28．4mm时，这6种公式间均无统计学差异（P均〉0．05），但Haigis、SRK-T公式的平均绝对预测误差值明显小于SRK-Ⅱ和Binkhorst-Ⅱ公式。结论 在目前的研究样本量下，除Binkhorst-Ⅱ公式外其他五种IOL屈光度数计算公式对术后屈光度的影响无明显差异，但在特长眼轴组（AXL〉28．4mm），Haigis、SRK-T公式显示一定的优势。     

儿童白内障手术人工晶状体度数计算准确性分析

目的 分析儿童眼人工晶状体度数计算的准确性.方法 回顾性研究37例(62只眼)行先天性白内障摘除加人工晶状体(IOL,intraocular lens)植入术患儿生物测量及屈光状态数据,应用SRKⅡ计算IOL度数.术后2个月行视网膜检影验光检测屈光状态.分析手术年龄,眼轴长度,IOL植入时机与IOL度数计算准确性关系.结果 全部平均绝对预测误差为(1.56±1.43)D.绝对预测误差低于1.0 D共32只眼,占总眼数52%.眼轴≤20 mm组绝对预测误差为(2.75±1.66)D,＞20 mm组为(1.06±0.93)D,2组间差异具有统计学意义(P＜0.01).年龄≤2岁组绝对预测误差为(2.38±1.65)D,＞2岁为(1.04±0.99)D,2组间差别具有统计学意义(P＜0.01).Ⅰ期IOL植入组绝对预测误差为(1.37±1.35)D,Ⅱ期IOL植入为(2.03±1.56)D,2组间差异无统计学意义(P=0.22).结论 全组植入的IOL度数安全有效.眼轴≤20 mm及年龄≤2岁患儿绝对预测误差明显增加.该研究证明,专门为儿童眼设计IOL计算公式是有必要的.

Abstract：

Objective To determine the accuracy of intraocular lens (IOL) power calculation in a group of pseudophakic children. Methods A relrospective analysis of biometric and refractive data was performed on 62 eyes of 37 infants and children, who successfully underwent cataract extraction and IOL implantation. SRKII were used to calculate the IOL power. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 2 months afier surgery by retinoscopy. The data were analyzed to assess the effects of age at the time of surgery, axial length, and primary or secondary intraocular lens implantation on the accuracy of calculation of IOL power. Results For the overall group the mean and median prediction errors were 1.56D (SD 1.43). There were 32 eyes'absolute predictions errors lower than 1D (52%). The mean absolute prediction errors in eyes with axial lengths≤20 mm were 2.75 D (SD 1.66), and in eyes ＞20 mm were 1.06 D (SD 0.93). The mean absolute prediction errors in eyes in children aged≤2 years were 2.38 D (SD 1.65), and in children aged ＞2 years were 1.04D (SD 0.99). The differences between the absolute prediction errors for both axial length and age were statistically significant (P ＜0.01). The mean-absolute prediction errors in eyes with primary IOL implantation were 1.37D (SD 1.35), and secondary intraocular lens implantation were 2.03D (SD 1.56). The differences between the absolute prediction errors primary or secondary intraocular lens implantation, were not statistically significant (P =.22). Conclusions For the overall group IOL power calculation is generally acceptable. In eyes with axial lengths less than 20 mm and in children younger than 2 years of age larger errors can arise, and the variations increase. This study demonstrates the need for an IOL formula specifically designed for pediatric use.     

白内障合并高度近视人工晶状体计算公式的选择

目的　比较SRK -Ⅱ和SRK -T公式 ,以提高高度近视白内障人工晶状体屈光度计算的准确性。方法　使用相同的生物参数和A常数 ,比较SRK -Ⅱ和SRK -T公式理论计算值的差异。对 2 3例 (2 6眼 )高度近视白内障行晶状体超声乳化吸出联合人工晶状体植入术 ,用SRK -T公式计算人工晶状体屈光度 ,记录SRK -T和SRK -Ⅱ两公式在实际植入人工晶状体屈光度下对应的预计术后屈光度 ,并比较两公式的预测偏差 ,评估测量的准确性。结果　按照SRK -T公式计算结果植入人工晶状体术后 ,按照两公式计算预计屈光度为SRK -Ⅱ(1.3 7± 0 .45 )D ,SRK -T(-0 43± 0 .15 )D。预计偏差有显著性差异。结论　SRK -T公式适用于眼轴长度 >2 7.0mm的高度近视白内障 ,其准确性明显优于SRK -Ⅱ公式。     

Accuracy of intraocular lens power calculation in paediatric cataract surgery

AIMS: To determine the accuracy of intraocular lens (IOL) power calculation in a group of pseudophakic children. METHODS: A retrospective analysis of biometric and refractive data was performed on 52 eyes of 40 infants and children, who successfully underwent cataract extraction and IOL implantation. The following parameters were included: age at the time of surgery, keratometry, axial length, estimated refraction, and the power of IOL implanted. The postoperative refractive outcome was taken as the spherical equivalent of the refraction at 3 months after surgery. The prediction error was taken as the absolute difference between the estimated and actual postoperative refraction. The data were analysed to assess the effects of age at the time of surgery, keratometry, and axial length on the accuracy of calculation of IOL power. RESULTS: For the overall group the mean and median prediction errors were 1.40 D and 0.84 D (SD 1.60). The mean and median prediction errors in eyes with axial lengths > or =20 mm were 1.07 D and 0.71 D (SD 0.98) and in eyes <20 mm were 2.63 D and 2.61 D (SD 2.65). The mean and median prediction errors in eyes in children aged > or =36 months were 1.06 D and 0.68 D (SD 1.02) and in children aged <36 months was 2.56 D and 2.29 D (SD 2.50). The differences between the prediction errors for both axial length and age were statistically significant (p<0.05). CONCLUSIONS: For the overall group IOL power calculation is satisfactory. In eyes with axial lengths less than 20 mm and in children less than 36 months of age larger errors can arise. This study demonstrates the need for an IOL formula specifically designed for paediatric use.     

Accuracy of optimized Sirius ray-tracing method in intraocular lens power calculation

AIM:To evaluate the accuracy and predictability of ray tracing-assisted intraocular lens(IOL) calculation function in Sirius internal software and further improve the accuracy by optimizing the calculation of predicted lens position(PLP).METHODS:This retrospective study recruited 52 eyes of 49 patients.All of the cases with cataract had undergone phacoemulsification combined with IOL implantation.SRK-T,Haigis formula,and Sirius ray-tracing method were all used for each eye’s IOL calculation.The mean absolute value of prediction error(prediction error=predicted refraction-postoperative refraction) was defined as mean absolute prediction error(MAPE) and was determined for each method.Calculation of PLP was optimized by effective lens position(ELP).Optimized PLP was entered to Sirius internal software again to verify whether the method was improved.RESULTS:Compared with SRK-T and Haigis formulas,less accuracy was shown in Sirius ray-tracing method(P=0.001).The ELP of the IOL moved forward compared to PLP(P<0.001).The MAPE of the ELP-inputted Sirius ray-tracing method was reduced.ELP and PLP were well correlated.Taking ELP as y and PLP given by Sirius soft as x,a linear regression formula y=0.1637 x+3.1741 was concluded(R²=0.1066,P=0.018).It was shown that the optimized Sirius ray-tracing method(optimized PLP entered),compared with SRK-T and Haigis formulas,worked with the same accuracy(P=0.038).CONCLUSION:The original Sirius ray tracing method is not satisfactory enough.However,in normal eyes,the optimized Sirius ray-tracing method in IOL calculation was as accurate as SRK-T and Haigis formulas.