| Purpose: To compare the accuracy of intraocular lens(IOL) power calculation methods for patients after corneal refractive surgeries by using the Holladay IOL Consultant Program(HICSOAP) and the American Society of Cataract and Refractive Surgery IOL Power Calculator(ASCRS-IPC).Methods: This prospective and retrospective case series comprised 64 patients(120 eyes) who had previous corneal refractive surgery and had uneventful phacoemulsification and IOL implantation from January 2011 to January 2013. According to the surgical procedure, all these patients were divided into three groups: group A(Myopic LASIK/PRK, A1 with clinical histroy data, A2 without clinical histroy data), group B(hyperopic LASIK/PRK, B1 with partial clinical histroy data, B2 without clinical histroy data) and group C(myopic RK without clinical histroy data). Over ten methods were used to calculate IOL power. Optimal IOL power corresponding to the target refraction was back-calculated using stable post-cataract surgery refraction(postop 3 months) and implanted IOL power. Using the optimal IOL power, the predicted IOL power error and the resultant refractive error with each method was calculated and compared. The accuracy of K value measured by three kinds of instruments( Pentacam, Lenstar, Atlas) also was evaluated in the same IOL power calculate method--Holladay II method. All statistical tests were performed using Graph Pad Prism Software(version 5.0).Results: 1. Comparison of the mean absolute refractive prediction errors and IOL power prediction errors calculated by different methods in HICSOAP and ASCRS-IPC software. 1.1 Myopia group with primary LASIK/PRK history Group A1(with clinical histroy data, 17eyes): Among these 13 IOL-calculation methods, there was statistically significant difference among the mean absolute error(MAE) in refraction and IOL power prediction of them(F=2.790,P=0.0017). The Holladay II-PK, Holladay II-Flat K, Holladay II-LK, ASCRS-AWH, Modified-Masket, ASCRS-Min, Holladay II-AK, Holladay II-His K and Wang-Koch-Maloney methodsproduced the lowest MAE in refraction and IOL power prediction, with no statistically significant difference seen among them(F=0.8201,P=0.5865), followed by the ASCRS-ANH, Shammas-no history, Haigis-L and ASCRS-Max, significant differences were found between the two groups(P<0.05),and there was no statistically significant difference among the latter 4 methods(F=0.6449,P=0.5905). Group A2(without clinical histroy data, 17eyes): Among these 10 IOL-calculation methods, Holladay IIFlat K produced the lowest MAE in refraction and IOL power prediction, and there was a statistically significant difference between the MAE results of Holladay IIFlat K and that of Holladay II-PK(t=1.989,P=0.0256). The Holladay II-PK,Holladay II-LK,ASCRS-Min and Wang- Koch-Maloney methods gave the second lowest MAEs with no statistically significant difference seen among them(F=0.2551,P=0.8577),followed by the ASCRS-ANH, Holladay II-AK, Shammas-no history and Haigis-L methods(F=0.8777,P=0.4532), and there was a statistically significant difference between the MAE results of Wang- Koch-Maloney and that of ASCRS-ANH(t=1.957,P=0.0275). The ASCRS-Max method gave the highest MAE among all 10 methods, and the difference between the MAE result of Haigis-L and that of ASCRS-Max methods was statistically different(t=3.491,P=0.0004). 1.2 Hyperopia group with primary LASIK/PRK history Group B1(with clinical history data): Among these 6 IOL-calculation methods, Holladay II-PK, Holladay II-Flat K, Holladay II-LK, Holladay II-AK, Modified-Masket and Haigis-L, there was no statistically significant difference among the MAEs in refraction and IOL power prediction of them(F=0.7482,P=0.5930). Group B2(without clinical history data): Among these 5 IOL-calculation methods, Holladay II-PK, Holladay II-Flat K, Holladay II-LK, Holladay II-AK and Haigis-L, there was also no statistically significant difference among the MAEs in refraction and IOL power prediction of them(F=1.658,P=0.1727). 1.3 Myopia group with primary RK history Group C(without clinical history data): Among these 5 IOL-calculation methods, Holladay II-LK, Holladay II-AK, Holladay II-PK, Holladay II-Flat K, and Atlas1-4, there was no statistically significant difference among the MAEs in refraction and IOL powerprediction of them(F=0.6736,P=0.6139). 2. General trend of the median arithmetic errors in refrective prediction of these different methods in HICSOAP and ASCRS-IPC software. The median arithmetic error in refractive prediction in group A shows positive values using the HICSOAP methods(excepting Holladay II-His K method), indicating a slight postoperative hyperopic shift. In contrast, the median arithmetic errors in refractive prediction shows negative values with all 8 ASCRS-IPC methods, indicating a slight postoperative myopic shift. The median arithmetic error in refractive prediction in group B shows negative values using the 4 HICSOAP methods(Holladay II-PK, Holladay II-Flat K, Holladay II-LK and Holladay II-AK) and Haigis-L method in ASCRS-IPC, indicating a slight postoperative myopic shift. In contrast, the median arithmetic errors in refractive prediction shows positive values using the Modified-Masket method in ASCRS-IPC, indicating a slight postoperative hyperopic shift. The median arithmetic error in refractive prediction in group C shows negative values using the 3 HICSOAP methods(Holladay II-LK, Holladay II-AK and Holladay II-Flat K) and one ASCRS-IPC method(Atlas1-4), indicating a slight postoperative myopic shift. While the Holladay II-PK method in the HICSOAP shows positive median arithmetic error in refractive prediction, indicating a slight postoperative hyperopic shift. 3. The difference of K readings measured with three instruments(Pentacam, Lenstar and Atlas) and the influence of it on the accuracy of the IOL power and refraction prediction in the Holladay II method. 3.1 Myopia group with primary LASIK/PRK history In the group A, especially in the group A2, the Pentacam EKR was the lowest one among that of the three measurements, there were statistical differences between the Pentacam EKR and Lenstar AKR(t=1.964,P=0.0271), and between the Pentacam EKR and Atlas(0~3mm)AKR(t=3.308,P=0.0008), the Atlas(0~3mm)AKR was the highest one among them with statistical differences between which and Lenstar AKR(t=2.873,P=0.0028). Among these three devices, the K reading provided by the Pentacam was chosen as the lowest K most frequently(33 times, 53.23%). Thedifferences of frequency of being chosen as the lowest K between the Pentacam and Lenstar and between the Pentacam and Atlas were statistically significant(Fisher’s exact test, P<0.01), with no statistically significant difference seen between the IOL-Master and Atlas(Fisher’s exact test, P >0.05). In the group A2, Holladay IIFlat K, which plugged the Flat K into it to calculate IOL power, produced the lowest MAE in refraction and IOL power prediction, and the Pentacam EKR was choosed as the Flat K among three measurements most frequently. 3.2 Hyperopia group with primary LASIK/PRK history In the group B1 and B2, there were no statistical differences among the Pentacam EKR, Lenstar AKR and Atlas(0~3mm)AKR(F1=1.183, P1=0.3353;F2=0.4654,P2=0.6327) and for the MAE in refraction and IOL power prediction, there was no statistical differences among the Holladay II-PK, Holladay II-LK and Holladay II-AK accordingly(P>0.05). 3.3 Myopia group with RK history In the group C, there were statistical differences between the Pentacam EKR and Lenstar AKR and between the Pentacam EKR and Atlas(0~3mm)AKR(t1=2.813,P1<0.05;t2=3.563,P2<0.05), there was no statistical differences between the Lenstar AKR and Atlas(0~3mm)AKR(t=1.050,P>0.05). Yet, for the MAE in refraction and IOL power prediction, there was no statistical differences among the Holladay II-PK, Holladay II-LK and Holladay II-AK(P>0.05).Conclusions: 1. It seems that in the HICSOAP and ASCRS-IPC softwares, those methods using primary clinical history data did not appear more advantages in the accuracy of refraction and IOL power prediction comparing with those without primary clinical history data. 2. The Holladay IIFlat K method seems to provide the most accurate result in IOL power prediction for the post-myopic LASIK/PRK patients without prior refractive data, when comparing with the ASCRS-IPC methods. Coupled with the result of IOL-calculation formula comparison, Pentacam appears to produce the most accurate K readings among the three popular K-measuring devices(Lenstar, Atlas and Pentacam).3. If the HICSOAP is unavailable, among the ASCRS-IPC methods, the ASCRS-Min and Wang-Koch-Maloney methods appear to provide the next best choice for IOL power prediction in eyes without prior myopic LASIK/PRK data. 4. For the hyperopic LASIK/PRK group and myopic RK group, because of the limited sample size, all these methods in the HICSOAP and ASCRS-IPC didn’t appear stitistical difference in the accuracy of refraction and IOL power prediction. 5. According to the corneal refractive surgery types, different trend of the median arithmetic errors in refrective prediction exsist in these different methods in HICSOAP and ASCRS-IPC software, which indicates a slight postoperative hyperopic shift or myopic shift. |
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