International Journal of Keratoconus and Ectatic Corneal Diseases

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VOLUME 8 , ISSUE 1 ( January-June, 2019 ) > List of Articles

Original Article

Clinical Evaluation of a New Approach for IOL Power Calculation in Keratoconus

Vicente J Camps, Ramy R Fikry, Veronica J Mateo, Fady E Labib, Esteban Caravaca-Arens, María T Caballero, David P Piñero

Keywords : Cataract, Intraocular lens calculation, Keratoconus

Citation Information : Camps VJ, Fikry RR, Mateo VJ, Labib FE, Caravaca-Arens E, Caballero MT, Piñero DP. Clinical Evaluation of a New Approach for IOL Power Calculation in Keratoconus. Int J Kerat Ect Cor Dis 2019; 8 (1):1-6.

DOI: 10.5005/jp-journals-10025-1177

License: CC BY-NC 4.0

Published Online: 23-07-2020

Copyright Statement:  Copyright © 2019; The Author(s).


Purpose: To obtain an expression of the adjusted IOL power (PIOLadj) in keratoconus eyes associated with minimal errors in IOL power calculation. Materials and methods: This retrospective study included a total of 25 eyes of 25 patients with ages ranging from 20 years to 76 years. The following IOLs were implanted: Acrysof IQ Toric, Acrysof SA60AT in 9 eyes, Sensar in 3 eyes, Tecnis 1 in 4 eyes, and Tecnis Toric in 2 eyes. The PIOLadj is based on Gauss equations, using adjusted keratometric index (nkadj) specific to keratoconus eyes. From this nkadj, an adjusted keratometric corneal power is calculated (Pkadj). The PIOLadj calculation was performed after estimating the effective lens position (ELP) using a mathematical expression obtained by multiple regression analysis (named ELPadj). Comparison between the PIOLadj and the real intraocular power implanted in each patient (PIOLreal) was carried out. Results: No significant differences between PIOLreal and PIOLadj were found. However, differences could be clinically relevant up to of 2.54 D as PIOLreal increases. But, in the range of PIOLreal between 0 and 20 D, differences were lower than 1.5 D, being most of them below 1 D. Conclusion: A new formula of IOL power calculation (PIOLadj) based on the use of an adjusted keratometric power (Pkadj) that considers a variable keratometric index due to the influence of the posterior corneal surface (nkadj) and adjusted effective lens position (ELPadj) is useful for estimating IOL power in low-to-moderate keratoconus, with more limitation in the most advanced keratoconus.

  1. Olsen T. Calculation of intraocular lens power: a review. Acta Ophthalmol Scand 2007;85(5)472–485. DOI: 10.1111/j.1755-3768.2007.00879.x.
  2. Narvaez J, Zimmerman G, Stulting RD, et al. Accuracy of intraocular lens power prediction using the Hoffer Q, Holladay 1, Holladay 2, and SRK/T formulas. J Cataract Refract Surg 2006;32(12):2050–2053. DOI: 10.1016/j.jcrs.2006.09.009.
  3. Terzi E, Wang L, Kohnen T. Accuracy of modern intraocular lens power calculation formulas in refractive lens exchange for high myopia and high hyperopia. J Cataract Refract Surg 2009;35(7):1181–1189. DOI: 10.1016/j.jcrs.2009.02.026.
  4. Zaldivar R, Shultz MC, Davidorf JM, et al. Intraocular lens power calculations in patients with extreme myopia. J Cataract Refract Surg 2000;26(5):668–674. DOI: 10.1016/S0886-3350(00)00367-9.
  5. Camps VJ, Piñero DP, De Fez D, et al. Minimizing the IOL power error induced by keratometric power. Optom Vis Sci 2013;90(7):639–649. DOI: 10.1097/OPX.0b013e3182972f50.
  6. Kamiya K, Iijima K, Nobuyuki S, et al. Predictability of intraocular lens power calculation for cataract with keratoconus: a multicenter study. Sci Rep 2018;8(1):1312. DOI: 10.1038/s41598-018-20040-w.
  7. Leccisotti A. Refractive lens exchange in keratoconus. J Cataract Refract Surg 2006;32(5):742–746. DOI: 10.1016/j.jcrs.2006.01.063.
  8. Thebpatiphat N, Hammersmith KM, Rapuano CJ, et al. Cataract surgery in keratoconus. Eye Contact Lens 2007;33(5):244–246. DOI: 10.1097/ICL.0b013e318030c96d.
  9. Watson MP, Anand S, Bhogal M, et al. Cataract surgery outcome in eyes with keratoconus. Br J Ophthalmol 2014;98(3):361–364. DOI: 10.1136/bjophthalmol-2013-303829.
  10. Park DY, Lim DH, Chung TY, et al. Intraocular lens power calculations in a patient with posterior keratoconus. Cornea 2013;32(5):708–711. DOI: 10.1097/ICO.0b013e3182797900.
  11. Shammas HJ, Hoffer KJ, Shammas MC. Scheimpflug photography keratometry readings for routine intraocular lens power calculation. J Cataract Refract Surg 2009;35(2):330–334. DOI: 10.1016/j.jcrs.2008.10.041.
  12. Ho JD, Tsai CY, Tsai RJ, et al. Validity of the keratometric index: evaluation by the pentacam rotating Scheimpflug camera. J Cataract Refract Surg 2008;34(1):137–145. DOI: 10.1016/j.jcrs.2007.09.033.
  13. 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(12):2004–2014. DOI: 10.1016/j.jcrs.2006.08.037.
  14. Tang M, Li Y, Avila M, et al. Measuring total corneal power before and after laser in situ keratomileusis with high-speed optical coherence tomography. J Cataract Refract Surg 2006;32(11):1843–1850. DOI: 10.1016/j.jcrs.2006.04.046.
  15. Gobbi PG, Carones F, Brancato R. Keratometric index, videokeratography, and refractive surgery. J Cataract Refract Surg 1998;24(2):202–211. DOI: 10.1016/S0886-3350(98)80201-0.
  16. Dunne MC, Royston JM, Barnes DA. Normal variations of the posterior corneal surface. Acta Ophthalmol 1992;70(2):255–261. DOI: 10.1111/j.1755-3768.1992.tb04133.x.
  17. Fam HB, Lim KL. Validity of the keratometric index: large population-based study. J Cataract Refract Surg 2007;33(4):686–691. DOI: 10.1016/j.jcrs.2006.11.023.
  18. Olsen T. On the calculation of power from curvature of the cornea. Br J Ophthalmol 1986;70(2):152–154. DOI: 10.1136/bjo.70.2.152.
  19. Camps VJ, Pinero Llorens DP, de Fez D, et al. Algorithm for correcting the keratometric estimation error in normal eyes. Optom Vis Sci 2012;89(2):221–228. DOI: 10.1097/OPX.0b013e31823ac694.
  20. Piñero DP, Camps VJ, Mateo V, et al. Clinical validation of an algorithm to correct the error in the keratometric estimation of corneal power in normal eyes. J Cataract Refract Surg 2012;38(8):1333–1338. DOI: 10.1016/j.jcrs.2012.03.026.
  21. Jin H, Holzer MP, Rabsilber T, et al. Intraocular lens power calculation after laser refractive surgery. Corrective algorithm for corneal power estimation. J Cataract Refract Surg 2010;36(1):87–96. DOI: 10.1016/j.jcrs.2009.07.011.
  22. Liu Y, Wang Y, Wang Z, et al. Effects of error in radius of curvature on the corneal power measurement before and after laser refractive surgery for myopia. Ophthalmic Physiol Opt 2012;32(4):355–361. DOI: 10.1111/j.1475-1313.2012.00921.x.
  23. Camps VJ, Piñero DP, Mateo V, et al. Algorithm for correcting the keratometric error in the estimation of the corneal power in eyes with previous myopic laser refractive surgery. Cornea 2013;32(11):1454–1459. DOI: 10.1097/ICO.0b013e31829e1eb5.
  24. Camps VJ, Piñero DP, Caravaca-Arens E, et al. New approach for correction of error associated with keratometric estimation of corneal power in keratoconus. Cornea 2014;33(9):960–967. DOI: 10.1097/ICO.0000000000000190.
  25. Piñero DP, Camps VJ, Caravaca-Arens E, et al. Estimation of the central corneal power in keratoconus: theoretical and clinical assessment of the error of the keratometric approach. Cornea 2014;33(3):274–279. DOI: 10.1097/ICO.0000000000000048.
  26. Camps VJ, Piñero DP, Mateo V, et al. Clinical Validation of adjusted corneal power in patients with previous myopic lasik surgery. J Ophthalmol 2015;2015:824293.
  27. Piñero DP, Camps VJ, Caravaca-Arens E, et al. Algorithm for correcting the keratometric error in the estimation of the corneal power in keratoconus eyes after accelerated corneal collagen crosslinking. J Ophthalmol 2017;2017:8529489.
  28. Piñero D, Camps V, Ramón M, et al. Positional accommodative intraocular lens power error induced by the estimation of the corneal power and the effective lens position. Indian J Ophthalmol 2015;63(5):438–444. DOI: 10.4103/0301-4738.159882.
  29. Piñero DP, Camps VJ, Ramón ML, et al. Error induced by the estimation of the corneal power and the effective lens position with a rotationally asymmetric refractive multifocal intraocular lens. Int J Ophthalmol 2015;8(3):501–507.
  30. Piñero DP, Camps VJ, Ramón ML, et al. Preliminary evaluation of an algorithm to minimize the power error selection of an aspheric intraocular lens by optimizing the estimation of the corneal power and the effective lens position. Int Eye Sci 2016;16(6):1001–1008.
  31. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986;1(8476):307–310. DOI: 10.1016/S0140-6736(86)90837-8.
  32. Camps VJ, Piñero DP, Caravaca E, et al. Preliminary validation of an optimized algorithm for intraocular lens power calculation in keratoconus. Indian J Ophthalmol 2017;65(8):690–699. DOI: 10.4103/ijo.IJO_274_16.
  33. Savini G, Abbate R, Hoffer KJ, et al. Intraocular lens power calculation in eyes with keratoconus. J Cataract Refract Surg 2019;45(5):576–581. DOI: 10.1016/j.jcrs.2018.11.029pii: S0886-3350(18)30968-4.
  34. Schröder S, Langenbucher A. Relationship between effective lens position and axial position of a thick intraocular lens. PLoS ONE 2018;13(6):e0198824. DOI: 10.1371/journal.pone.0198824.
  35. Kamiya K, Kono Y, Takahashi M, et al. Comparison of simulated keratometry and total refractive power for keratoconus according to the stage of Msler-Krumeich classification. Sci Rep 2018;8(1):12436. DOI: 10.1038/s41598-018-31008-1.
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