Anterior Segment Cataract
within ±0.5 D. The respective percentages for eyes after surgery for hyperopia were 96.4 %, 82.1 % and 58.9 %.
These results compare favourably with normal eyes, although the error margins for the predicted refraction are slightly higher in eyes after refractive surgery. This can be seen from a comparison of the Haigis-L outcomes with the proposed benchmarks for normal eyes as recommended by Gale et al.38
Gail et al. demand correct
refraction predictions within ±0.5 D in 55 % and within ±1.0 D in 85 % of all cases. The results for our refractive surgery eyes are better for the 0.5 D percentages and close to the 1.0 D percentages for normal eyes.
Comparisons with Other Formulas
Comparisons of different algorithms is often not easy due to the small numbers of cases and/or the different set-ups necessary to apply the different formulas. Recently, two comparative studies were published overcoming these limitations: McCarthy et al.39
report on
173 eyes after LASIK/PRK for myopia and subsequent cataract surgery. They compared the performances of 25 combinations of corneal power adjustment formulas and IOL power formulas (which were used with the double-K correction28 five best formula combinations: Masket33
) and obtained the following /HofferQ, clinical history
method17,18/HofferQ, Latkany Flat-K31/SRK/T and the Shammas no-history29 and Haigis-L9 formulas. The mean arithmetic refractive
1. Kalyani SD, Kim A, Lada JG, Intraocular lens power calculation after corneal refractive surgery, Curr Opin Ophthalmol, 2008;19:357–62.
2. Hoffer KJ, Intraocular lens power calculation after previous laser refractive surgery, J Cataract Refract Surg, 2009;35:759–65.
3. Naseri A, McLeod SD, Cataract surgery after refractive surgery, Curr Opin Ophthalmol, 2010;21:35–8.
4. 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;36:1466–73.
5. Hoffer/Savini tool. Available at:
www.eyelab.com (accessed 4 September 2011).
6. ASCRS Post-refractive surgery IOL calculator. Available at:
www.ascrs.org (accessed 4 September 2011).
7. Biometry calculation post refractive surgery. Available at:
www.apacrs.org (accessed 4 September 2011).
8. Barrett, True-K formula, In: ASCRS EyeWorld Meeting Reporter, under ’Advanced phaco techniques’, 1 July 2008.
9. Haigis W, IOL calculation after refractive surgery for myopia: the Haigis-L formula, J Cataract Refract Surg, 2008;34:1658–63.
10. Fyodorov SN, Kolonko AI, Estimation of optical power of the intraocular lens, Vestnik Oftalmologic (Moscow), 1967;4:27.
11. Marktübersicht Ophthalmometer, Der Augenspiegel, 1995;6/95:44–51.
12. Personal communication, Carl Zeiss Meditec AG, August 2002. 13. Seitz B, Langenbucher A, Intraocular lens calculations status after corneal refractive surgery, Curr Opin Ophthalmol, 2000;11:35–46.
14. Savini G, Carbonelli M, Barboni P, Hoffer KJ, Clinical relevance of radius of curvature error in corneal power measurements after excimer laser surgery, J Cataract Refract Surg, 2010;36:82–6.
15. Haigis W, Corneal power after refractive surgery with myopia: the contact lens method, J Cataract Refract Surg, 2003;29:1397–411.
16. Haigis W, {Intraocular lens calculatin following refractive surgery: problems, pitfalls, special aspects],
evaluated the results for 72 eyes using the ASCRS post-keratorefractive IOL power calculator. They concluded that methods using the achieved refractive change and methods using no previous data gave better results than methods using historic K values and achieved refractive change. Their results in diopters for the arithmetic IOL prediction errors were -0.24 ± 0.81 for the Shammas formula29
prediction errors in diopters for these combinations were: -0.18 ± 0.87, -0.27 ± 1.04, -0.37 ± 0.91, -0.10 ± 1.02, -0.26 ± 1.13. Wang et al.4
and 0.18 ± 0.81 for the Haigis-L formula.9 Summary
The calculation of IOL power after refractive surgery is still a challenge. The error sources leading to incorrect IOL powers (radius measurement, keratometer index and IOL formula error) have been described in detail and the individual contributions to the overall error were assessed using model calculations. Furthermore, the literature was analysed to assess how individual published algorithms address individual error contributions.
Clinical results for different formulas from current studies were presented and compared with updated results for the Haigis-L formula, which is a typical no-history method. With these methods requiring no previous data to calculate IOL power after refractive surgery, it is possible to obtain clinical outcomes of a similar quality to that for normal eyes. n
Ophthalmo-Chirurgie, 2003;15:193–200.
17. Holladay JT, IOL calculations following RK, Refract Corneal Surg, 1989;5:203.
18. Hoffer KJ, Intraocular lens power calculation for eyes after refractive keratotomy, J Refract Surg, 1995;11:490–3.
19. Haigis W, [Corneal refractive power and contact lens method], 2003;220(Suppl. 1):16.
20. Haigis W, Corneal power after refractive surgery with myopia: the contact lens method, J Cataract Refract Surg, 2003;29:1397–411.
21. Rosa N, Capasso L, Lanza M, et al., Reliability of a new correcting factor in calculating intraocular lens power after refractive corneal surgery, J Cataract Refract Surg, 2005;31:1020–4.
22. Wang L, Booth M, Koch D, Comparison of intraocular lens power calculation methods in eyes that have undergone LASIK, Ophthalmology, 2004;111:1825–31.
23. Personal communication, Douglas D Koch, Cullen Eye Institute, Baylor College of Medicine, Houston Texas, April 2004, cited by: Hill W, Determining corneal power following LASIK and PRK. Available at:
www.doctor-
hill.com/physicians/docs/Post-LASIK-old.doc (accessed 25 October 2011).
24. Koch D, Wang I, Calculating IOL power in eyes that have had refractive surgery, J Cataract Refract Surg, 2003;29:2039–42.
25. Jin H, Holzer MP, Rabsilber T, et al., Intraocular lens power calculation after laser refractive surgery, J Cataract Refract Surg, 2010;36:87–96.
26. Savini G, Barboni P, Zanini M, Intraocular lens power calculation after myopic refractive surgery. Theoretical comparison of different methods, Ophthalmology, 2006;113:1271–82.
27. Geggel H, Pachymetric ratio no-history method for intraocular lens power adjustment after excimer laser refractive surgery, Ophthalmology, 2009;116:1057–66.
28. Aramberri J, Intraocular lens power calculation after corneal refractive surgery: double K method, J Cataract Refract Surg, 2003;29:2063–8.
29. Shammas HJ, Shammas M, No-history method of intraocular lens power calculation for cataract surgery after myopic laser in situ keratomileusis, Cataract Refract Surg, 2007;33:31–6.
30. Feiz V, Mannis M, Garcia-Ferrer F, et al., Intraocular lens power calculation after laser in situ keratomileusis for myopia and hyperopia: a standardized approach, Cornea, 2001;20:792–7.
31. Latkany R, Chokshi A, Speaker M, et al., Intraocular lens calculations after refractive surgery, J Cataract Refract Surg, 2005;31:562–70.
32. Walter KA, Gagnon MR, Hoopes PC, Dickinson PJ, Accurate intraocular lens power calculation after myopic laser in situ keratomileusis bypassing corneal power, J Cataract Refract Surg, 2006;32:425–29.
33. 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;32:430–4.
34. Mackool RJ, Ko W, Mackool R, Intraocular lens power calculation after laser in situ keratomileusis: aphakic refraction technique, J Cataract Refract Surg, 2006;32:435–7.
35. Borasio E, Stevens J, Smith GT, Estimation of true corneal power after keratorefractive surgery in eyes requiring cataract surgery: BESSt formula, J Cataract Refract Surg, 2006;32:2004–14.
36. Diehl JW, Yu F, Olson MD, et al., Intraocular lens power adjustment nomogram after laser in situ keratomileusis, J Cataract Refract Surg, 2009;35:1587–90.
37. Awwad ST, Kelley PS, Bowman RW, et al., Corneal refractive power estimation and intraocular lens calculation after hyperopic LASIK, Ophthalmology, 2009;116:393–400.
38. Gale RP, Saldana M, Johnston RL, et al., Benchmark standards for refractive outcomes after NHS cataract surgery, Eye, 2009;23:149–52.
39. McCarthy M, Gavanski GM, Paton KE, Holland SP, Intraocular lens power calculations after myopic laser refractive surgery: a comparison of methods in 173 eyes, Ophthalmology, 2011;118:940–4.
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