Reflection on refraction in multifocal intraocular lenses - Chapter 6: ASCRS calculator formula accuracy in multifocal intraocular lens implantation in hyperopic corneal refractive laser surgery eyes

Hele tekst

(1)CHAPTER 6 ASCRS calculator formula accuracy in multifocal intraocular lens implantation in hyperopic corneal refractive laser surgery eyes Violette Vrijman, MD Adi Abulafia, MD Jan Willem van der Linden, BOpt, PhD Ivanka J.E. van der Meulen, MD, PhD Maarten P. Mourits, MD, PhD Ruth Lapid-Gortzak, MD, PhD [J Cataract Refract Surg 2019; 45:582–586].

(2) Chapter 6. ABSTRACT Purpose: To evaluate the accuracy of different intraocular lens (IOL) power calculation formulas available on the American Society of Cataract and Refractive Surgery calculator in calculating multifocal IOL power in eyes with previous hyperopic corneal refractive laser surgery. Design: Retrospective case series. Setting: Amsterdam University Medical Center, University of Amsterdam, and Retina Total Eye Care, Driebergen, the Netherlands. Methods: This study compared the accuracy of 3 formulas using historical refractive data (ie, Masket, modified Masket, and BarrettTrue-K) and 3 formulas using no previous refractive data (ie, Shammas, Haigis-L, and Barrett True-K no-history). Results: Sixty-four eyes were included. The variance of the prediction error of the various formulas was similar and ranged from 0.27 D2 to 0.33 D2 (P = .99). The modified Masket formula had a significantly higher median absolute prediction error than the Masket formula, Barrett True-K formula, and mean value of all formulas (P < .001). Conclusion: All formulas showed comparable accuracy in predicting IOL power in eyes after hyperopic corneal refractive laser surgery except for the modified Masket formula, which performed less accurately than the Masket formula, Barrett True-K formula, and mean value of all formulas.. 76.

(3) IOL calculation formulas of the ASCRS calculator for eyes after hyperopic laser. INTRODUCTION Corneal refractive laser surgery is a safe and predictable procedure with good results for myopic and hyperopic refractions.1 It is known that after refractive laser surgery, the intraocular lens (IOL) power calculation is more difficult because of incorrect measurements of the corneal curvature by instruments, the change in corneal refractive index caused by surface flattening, and the error in formula estimation of the effective lens position.2-4 Different formulas have been developed to calculate IOL power in these specific patients; however, comparing those various formulas can be hard and time consuming. The American Society of Cataract and Refractive Surgery (ASCRS) developed an online calculator to facilitate these comparisons.A The surgeon enters the keratorefractive data in the online calculator, and it automatically generates an output with IOL power prediction of the available formulas. A variation in the predicted IOL power between the various formulas is often found, and few studies have compared the performance of different IOL power calculation formulas in eyes with previous hyperopic laser surgery.5-8 The purpose of this study was to evaluate the performance of different IOL power calculation formulas in calculating IOL power in eyes with previous refractive laser surgery for hyperopia.. 6. PATIENTS AND METHODS Study Group and Protocol This study included all eyes of patients with previous corneal refractive laser surgery for hyperopia (photorefractive keratectomy, laser in situ keratomileusis, or laser-assisted subepithelial keratectomy) that had multifocal IOL implantation at Retina Total Eye Care, Driebergen, the Netherlands, between March 2008 and March 2012. The study adhered to the tenets of the Declaration of Helsinki. Inclusion criteria were uneventful phacoemulsification with implantation of a ReSTOR SN6AD1 IOL (Alcon Laboratories, Inc.) and full keratorefractive data from before and after the refractive laser surgery and before and after phacoemulsification. Pre-laser keratometry data were obtained with the Orbscan (Bausch & Lomb, Inc.). Preoperative keratometric data were obtained with the IOLMaster 500 (version 2.0 and 5.1, Carl Zeiss MeditecAG). Postoperative refractions were performed by 2 staff optometrists (3 meters refractive lane). Refractions were then adjusted to a 6 meters lane according to the standard described by Hill et al.9 The ASCRS online post-refractive calculatorB was used for IOL power calculation, and IOL power was chosen based on the surgeon’s clinical judgment. Phacoemulsification was performed under local anesthesia by one of 2 surgeons (I.J.E. v.d.M., R.L.-G.) using the Infiniti OZil unit (Alcon Laboratories, Inc.) and a 2.2 mm near-clear corneal incision on a 100 degrees axis. To achieve a more myopic target for monovision purposes, some myopic eyes had a hyperopic ablation. 77.

(4) Chapter 6. METHODS Of the available formulas of the ASCRS online post-refractive IOL calculator, the Masket,10 modified Masket,C Barrett True-K,D,11 Shammas with regression analysis,12 Haigis-L,13 Barrett True-K no history,D,11 and the mean value of these formulas were included in this study. The formulas order follows the order of their appearance in the ASCRS calculator. The adjusted effective refractive power method, adjusted Atlas 0-3 method, and optical coherence tonometry–based IOL formula were not included because the data needed for those formulas were not available. The refractive prediction error was calculated for each formula as the difference between the actual postoperative refraction and the predicted postoperative refraction. The surgeons’ standard optimized IOL constants for the ReSTOR SN6AD1 IOL were used for the ASCRS online calculator (A-constant = 119.0; SF = 1.79; a0 = -0.523; a1 = 0.172; a2 = 0.211). For each formula, the mean prediction error, median absolute error (MedAE), mean absolute error, and percentage of eyes within ±0.50 diopter (D) and within ±1.00 D of the predicted refraction were calculated.14 Statistical Analysis A sample size of 42 eyes was calculated (power 80%) based on a 0.10 D mean of the difference and a 0.25 D standard deviation of the difference. The 1-sample signed-rank test was used to assess whether the mean numerical refraction prediction errors produced by the different formulas were significantly different from zero. The Levene test was used to analyze the variances of the mean numerical refractive prediction error, evaluating the consistency of the predictions’ performance. The absolute refractive prediction errors were compared using the Wilcoxon signed-rank test. The percentage of eyes within ±0.50 D and within ±1.00 D was compared with the McNemar test. The Bonferroni correction was applied for multiple tests, and differences were considered statistically significant when the P value was 0.002 or less (21 comparisons). Statistical analysis was performed using XLSTAT software (version 2014.2.03, Addinsoft) and SPSS for Windows software (version 22.0, IBM Corp.).. RESULTS The cohort comprised 64 eyes of 38 patients. Table 1 shows the patients’ demographics, including the mean manifest refraction spherical equivalent after cataract surgery.. 78.

(5) IOL calculation formulas of the ASCRS calculator for eyes after hyperopic laser Parameter. Mean ± SD. Range. Pre-laser MRSE (D). 1.65 ± 1.11. 4.63, -1.50. Post-laser MRSE (D). -0.52 ± 0.90. 1.38, -2.38. Axial length (mm). 22.99 ± 0.91. 21.26, 25.69. IOL power implanted (D). 20.98 ± 2.67. 14.5, 26.5. Anterior chamber depth (mm). 3.06 ± 0.28. 2.45, 3.70. Post-cataract MRSE (D). 0.02 ± 0.97. -3.00, 2.75. Table 1. Patient demographics. IOL = intraocular lens; MRSE = manifest refraction spherical equivalent.. Refractive Prediction Error The mean prediction errors ranged from -0.10 D to 0.42 D. All formulas had hyperopic mean prediction errors except the Shammas. All formulas had mean prediction errors that were not statistically different from zero except for the modified Masket (P < .001), which had the highest mean prediction error. The MedAE varied from 0.25 D to 0.38 D. The MedAE of the modified Masket was significantly higher than that of the Masket formula, BarrettTrue-K formula, and mean value of all formulas (P < .001) (Table 2 and Figure 1). Refractive prediction error (D) Numerical. Absolute Range. Variance (D2). 0.28. 0.01, 1.68. 0.29. 0.52 ± 0.47. 0.37. 0.01, 1.96. 0.31. -1.39, 1.52. 0.41 ± 0.39. 0.29. 0.00, 1.52. 0.28. -2.14, 1.17. 0.45 ± 0.36. 0.38. 0.01, 2.14. 0.33. 0.15 ± 0.52. -1.55, 1.36. 0.41 ± 0.35. 0.33. 0.01, 1.55. 0.27. Barrett True-K (No History). 0.12 ± 0.53. -1.57, 1.31. 0.41 ± 0.36. 0.33. 0.00, 1.57. 0.28. Average. 0.16 ± 0.52. -1.52, 1.43. 0.40 ± 0.37. 0.25. 0.01, 1.52. 0.27. Formula. Mean ± SD. Range. Mean ± SD Median. Masket. 0.21 ± 0.53. -1.39, 1.68. 0.42 ± 0.39. Modified Masket. 0.42 ± 0.56. -1.06, 1.96. Barrett True-K. 0.19 ± 0.53. Shammas. -0.10 ± 0.57. Haigis-L. Table 2. Refractive prediction errors and variances of prediction errors.. 79. 6.

(6) Chapter 6. Figure 1. Refractive prediction errors of the different methods.. The variance of the prediction error of the various formulas ranged from 0.27 D2 to 0.33 D2. None of the differences between formulas was statistically significant. Figure 2 shows the refractive accuracy histograms, including the percentage of eyes within ±0.50 D and within ±1.00 D of the predicted refraction. The percentage of eyes with a prediction error within ±0.50 D ranged from 59.4% to 73.4%. The percentage of eyes with a prediction error within ±1.00 D ranged from 85.9% to 92.2%. These differences were not statistically significant.. 80.

(7) IOL calculation formulas of the ASCRS calculator for eyes after hyperopic laser. 6. Figure 2. Spherical equivalent refractive accuracy.. 81.

(8) Chapter 6. DISCUSSION Calculating IOL power in eyes after refractive surgery is challenging. Several IOL calculation formulas have been developed, and the ASCRS post-refractive online calculatorB can assist the surgeon in comparing formulas and choosing the appropriate IOL for a specific patient. Previous studies of the accuracy of those formulas have been published. However, most reports included patients with previous myopic laser surgery,15-17 with only few evaluating their accuracy in eyes that had previous laser surgery for hyperopia.5-8 Also, those studies included a small number of eyes and focused on monofocal IOL implantation. Although multifocal IOL implantation in eyes after previous refractive laser surgery is controversial because of the proposition that visual acuity might deteriorate in such cases, previous studies18-20 report good visual acuity and refractive outcomes in these patients. The purpose of this study was to analyze and compare the IOL power calculation formulas of the ASCRS post refractive online calculatorB in eyes with previous refractive laser surgery for hyperopia. All formulas had a mean prediction error that was not significantly different from zero except the modified Masket formula. These results suggest that our center must adjust the IOL constants for the modified Masket formula. In cases of residual refractive error, laser enhancement was considered. All formulas had a comparable MedAE except for the modified Masket, which had a significantly higher MedAE than the Masket formula, Barrett True-K formula, and the mean value of all formulas (P < .001). This difference might be because the mean prediction error was not adjusted to zero. The variance of the arithmetic IOL prediction error shows the consistency of IOL prediction performance for each method. We found that all formulas - those using historical refractive data and those that do not - had similar variance. The percentages of eyes within ±0.50 D and within ±1.00 D of the predicted refraction ranged from 59.4% to 73.4% and from 85.9% to 92.2%, respectively, with no statistical difference between formulas. These results are comparable to the older benchmark standards for refractive outcomes after cataract surgery in virgin eyes;21,22 however, recent reports show higher accuracy23,24 and confirm that improvement of IOL calculation formulas for eyes after refractive surgery is still necessary. Compared with results in other studies of monofocal IOLs that used similar IOL calculation formulas in eyes after hyperopic laser, the percentages of eyes with a prediction error within ±0.50 D and within ±1.00 D in our study were comparable to the results of Shammas et al.7 except for the Haigis-L formula, which performed better in the present study. Our results were better than those of Hamill et al.8 (Table 3). These differences might be partly explained by the small number of eyes and variety in IOLs used in the other studies.. 82.

(9) IOL calculation formulas of the ASCRS calculator for eyes after hyperopic laser Eyes (%) Formula. Present (n=65). Hamill8 (n=21). Shammas7 (n=18). Masket. 68.8. 52.4. 66.7. Modified Masket. 59.4. 47.6. 55.6. Barrett True-K. 71.9. 57.1. -. Shammas. 64.1. 38.1. 66.7. Haigis-L. 70.3. 38.1. 44.4. Barrett True-K (No History). 73.4. 42.9. -. Masket. 89.1. 81.0. 83.3. Modified Masket. 85.9. 81.0. 66.7. Barrett True-K. 87.5. 81.0. -. Shammas. 92.2. 85.7. 83.3. Haigis-L. 92.2. 81.0. 77.8. Barrett True-K (No History). 92.2. 81.0. -. Within ±0.50. Within ±1.00. Table 3. Comparison of percentage of eyes within ±0.50 D and within ±1.00 D of predicted refraction between present study and Hamill et al8 and Shammas et al7.. One limitation of this study is its retrospective design. Stringent guidelines for the practice of refractive surgery demand data collection for audit purposes, which in this sense probably makes retrospective data more robust. Second, the modified Masket formula had a mean prediction error that was significantly different from zero and no adjustment of the IOL constant was done. However, not all surgeons have large numbers of patients with previous refractive surgery for hyperopia, making it hard to optimize the IOL constants. Thus, we believe our results represent real-life practice. Another limitation is that not all available formulas of the ASCRS post-refractive calculator were included in this study. We did not have access to the measurement devices needed for those formulas. Future studies should analyze those formulas and compare them with the others. Both eyes of 26 (68%) of 38 patients were included; thus, there might have been a type 1 error in the statistical analysis. However, adjusted analyses with nonparametric tests were used (Wilcoxon signed-rank test to compare the medians of the different formulas), as described in the literature.25-29 Another limitation is that we did not compare patients with different axial lengths and keratometry values. In conclusion, when our optimized IOL constants for normal eyes were used, all analyzed formulas of the ASCRS post-refractive online calculatorB except one had similar accuracy in calculating IOL power for eyes after previous hyperopic refractive laser. The. 83. 6.

(10) Chapter 6. exception was the modified Masket formula, which had lower prediction accuracy than the Masket formula, Barrett True-K formula, and the mean value of all formulas. Improvement in accuracy is needed, and new technology that can measure total corneal power accurately combined with advanced formulas will likely provide more accurate IOL power prediction in these specific patients.. WHAT WAS KNOWN - Intraocular lens (IOL) power calculation is more difficult in eyes with previous refractive laser surgery. - Published data on IOL power calculation after previous hyperopic laser surgery is scarce.. WHAT THIS PAPER ADDS - Most formulas of the American Society of Cataract and Refractive Surgery postrefractive calculator showed comparable refractive accuracy in predicting IOL power in eyes after previous hyperopic laser surgery. - The modified Masket formula had lower accuracy than the Masket formula, Barrett True-K formula, and the mean value of all formulas in IOL power prediction in these eyes.. 84.

(11) IOL calculation formulas of the ASCRS calculator for eyes after hyperopic laser. REFERENCES 1. . Solomon KD, Fernández de Castro LE, Sandoval HP, Biber JM, Groat B, Neff KD, Ying MS, French JW, Donnenfeld ED, Lindstrom RL. for the Joint LASIK Study Task Force. LASIK world literature review; quality of life and patient satisfaction. Ophthalmology 2009; 116:691–701 2. Koch DD, Wang L. Calculating IOL power in eyes that have had refractive surgery [editorial]. J Cataract Refract Surg 2003; 29:2039–2042 3. Hoffer KJ. Intraocular lens power calculation after previous laser refractive surgery. J Cata ract Refract Surg 2009; 35:759–765 4. Aramberri J. Intraocular lens power calculation after corneal refractive surgery: double-K method. J Cataract Refract Surg 2003; 29:2063–2068 5. Chokshi AR, Latkany RA, Speaker MG, Yu G. Intraocular lens calculations after hyperopic refractive surgery. Ophthalmology 2007; 114:2044–2049 6. Awwad ST, Kelley PS, Bowman RW, Cavanagh HD, McCulley JP. Corneal refractive power estimation and intraocular lens calculation after hyperopic LASIK. Ophthalmology 2009; 116:393–400 7. Shammas HJ, Shammas MC, Hill WE. Intraocular lens power calculation in eyes with previ ous hyperopic laser in situ keratomileusis. J Cataract Refract Surg 2013; 39:739–744 8. Hamill EB, Wang L, Chopra HK, Hill W, Koch DD. Intraocular lens power calculations in eyes with previous hyperopic laser in situ keratomileusis or photorefractive keratectomy. J Cata ract Refract Surg 2017; 43:189–194 9. Hill WE, Abulafia A, Wang L, Koch DD. Pursuing perfection in IOL calculations. II. Measure ment foibles: measurement errors, validation criteria, IOL constants, and lane length [guest editorial]. J Cataract Refract Surg 2017; 43:869–870 10. Masket S, Masket SE. Simple regression formula for intraocular lens power adjustment in eyes requiring cataract surgery after excimer laser photoablation. J Cataract Refract Surg 2006; 32:430–434 11. Barrett GD. An improved universal theoretical formula for intraocular lens power predic tion. J Cataract Refract Surg 1993; 19:713–720 12. Shammas HJ, Shammas MC, Garabet A, Kim JH, Shammas A, LaBree L. Correcting the corneal power measurements for intraocular lens power calculations after myopic laser in situ keratomileusis. Am J Ophthalmol 2003;136:426–432 13. Haigis W. Intraocular lens calculation after refractive surgery for myopia: Haigis-L formula. J Cataract Refract Surg 2008; 34:1658–1663 14. Hoffer KJ, Aramberri J, Haigis W, Olsen T, Savini G, Shammas HJ, Bentow S. Protocols for studies of intraocular lens formula accuracy [editorial]. Am J Ophthalmol 2015; 160:403–405 15. Abulafia A, Hill WE, Koch DD, Wang L, Barrett GD. Accuracy of the Barrett True-K formula for intraocular lens power prediction after laser in situ keratomileusis or photorefractive keratectomy for myopia. J Cataract Refract Surg 2016; 42:363–369 16. Wang L, Hill WE, Koch DD. Evaluation of intraocular lens power prediction methods using the American Society of Cataract and Refractive Surgeons post-keratorefractive intraocular lens power calculator. J Cataract Refract Surg 2010; 36:1466–1473. 85. 6.

(12) Chapter 6 17. . 18. . 19. . 20. . 21. . 22. 23. 24. . 25. 26. 27. 28. . 29. . 86. Wang L, Tang M, Huang D, Weikert MP, Koch DD. Comparison of newer intraocular lens power calculation methods for eyes after corneal refractive surgery. Ophthalmology 2015; 122:2443–2449 Vrijman V, van der Linden JW, van der Meulen IJE, Mourits MP, Lapid-Gortzak R. Multifocal intraocular lens implantation after previous corneal refractive laser surgery for myopia. J Cataract Refract Surg 2017;43:909–914 Alfonso JF, Fernández-Vega L, Baamonde B, Madrid-Costa D, Montés-Micó R. Refractive lens exchange with spherical diffractive intraocular lens implantation after hyperopic laser in situ keratomileusis. J Cataract Refract Surg 2009; 35:1744–1750 Vrijman V, van der Linden JW, van der Meulen IJE, Mourits MP, Lapid-Gortzak R. Multifocal intraocular lens implantation after previous hyperopic corneal refractive laser surgery. J Cataract Refract Surg 2018; 44:466–470 Lundström M, Barry P, Henry Y, Rosen P, Stenevi U. Evidence-based guidelines for cataract surgery: guidelines based on data in the European Registry of Quality Outcomes for Cata ract and Refractive Surgery database. J Cataract Refract Surg 2012; 38:1086–1093 Gale RP, Saldana M, Johnston RL, Zuberbuhler B, McKibbin M. Benchmark standards for refractive outcomes after NHS cataract surgery. Eye 2009; 23:149–152 Melles RB, Holladay JT, Chang WJ. Accuracy of intraocular lens calculation formulas. Ophthalmology 2018; 125:169–178 Reitblat O, Assia EI, Kleinmann G, Levy A, Barrett GD, Abulafia A. Accuracy of predicted refraction with multifocal intraocular lenses using two biometry measurement devices and multiple intraocular lens power calculation formulas. Clin Exp Ophthalmol 2015; 43:328–334 Wang L, Koch DD, Hill W, Abulafia A. Pursuing perfection in intraocular lens calculations: III. Criteria for analyzing outcomes [guest editorial]. J Cataract Refract Surg 2017; 43:999–1002 Armstrong RA. Statistical guidelines for the analysis of data obtained from one or both eyes. Ophthalmic Physiol Opt 2013; 33:7–14 Fan Q, Teo Y-Y, Saw S-M. Application of advanced statistics in ophthalmology. Invest Ophthalmol Vis Sci 2011; 52:6059–6065 Karakosta A, Vassilaki M, Plainis S, Elfadl NH, Tsilimbaris M, Moschandreas J. Choice of analytic approach for eye-specific outcomes: one eye or two? Am J Ophthalmol 2012; 153:571–579 Bunce C, Patel KV, Xing W, Freemantle N, Doré CJ, on behalf of the Ophthalmic Statistics Group. Ophthalmic statistics note 1: unit of analysis. Br J Ophthalmol 2014; 98:408-412.

(13) IOL calculation formulas of the ASCRS calculator for eyes after hyperopic laser. OTHER CITED MATERIAL A. American Society of Cataract and Refractive Surgery. Online tools. Available at: http:// ascrs.org/online-tools. Accessed January 17, 2019 B. Hill W, Wang L, Koch DD. IOL power calculation in eyes that have undergone LASIK/PRK/ RK, version 4.9. Available at: http://iolcalc.ascrs.org/. Accessed January 17, 2019 C. Hill WE, “IOL Power Calculations Following Keratorefractive Surgery,’’ presented at the ASCRS Symposium on Cataract, IOL and Refractive Surgery, San Francisco, California, USA, March 2006 D. Barrett GD. Barrett True K formula for prior myopic or hyperopic LASIK/PRK. Available at: http://www.apacrs.org/barrett_true_K_universal_2/. Accessed January 17, 2019. AUTHOR CONTRIBUTIONS Violette Vrijman contributed to the study concept and design, data acquisition, data analysis and interpretation, writing the manuscript and producing the final manuscript. Adi Abulafia contributed to the study concept and design, data analysis and interpretation and critical revision of the manuscript. Jan Willem van der Linden contributed to the data acquisition, data interpretation and critical revision of the manuscript. Ivanka J.E. van der Meulen contributed to the data acquisition, data interpretation and critical revision of the manuscript. Maarten P. Mourits contributed to the data interpretation and critical revision of the manuscript. Ruth Lapid-Gortzak contributed to the study concept and design, data acquisition, data interpretation, writing the manuscript, critical revision of the manuscript and submission of the final manuscript.. 87. 6.

(14)

No results found