Intraocular lens power calculation by ray-tracing after myopic excimer laser surgery

Am J Ophthalmol. 2014 Jan;157(1):150-153.e1. doi: 10.1016/j.ajo.2013.08.006. Epub 2013 Oct 5.


Purpose: To investigate the refractive outcomes of intraocular lens (IOL) power calculation by ray-tracing after myopic excimer laser surgery.

Design: Prospective, interventional case series.

Methods: setting: Multicenter study. participants: Twenty-one eyes of 21 patients undergoing phacoemulsification and IOL implantation after myopic laser in situ keratomileusis or photorefractive keratectomy were enrolled. intervention: IOL power calculation was performed using internal software of a Scheimpflug camera combined with a Placido disc corneal topographer (Sirius; CSO). Exact ray-tracing was carried out after the axial length (measured either by immersion ultrasound biometry or partial coherence interferometry), target refraction, and pupil size had been entered. main outcome measures: Median absolute error, mean absolute error, and mean arithmetic error in refraction prediction, that is, the difference between the expected refraction (as calculated by the software) and the actual refraction 1 month after surgery.

Results: The mean postoperative refraction was -0.43 ± 1.08 diopters (D), with a range between -1.28 and 0.85 D. The mean arithmetic error was -0.13 ± 0.49 D. The median and mean absolute errors were +0.25 D and 0.36 D, respectively. Also, 71.4% of the eyes were within ± 0.50 D of the predicted refraction, 85.7% were within ± 1.00 D, and 100% within ± 1.50 D.

Conclusions: Ray-tracing can calculate IOL power accurately in eyes with prior myopic laser in situ keratomileusis and photorefractive keratectomy, with no need for preoperative data.

Publication types

  • Multicenter Study

MeSH terms

  • Biometry
  • Female
  • Humans
  • Interferometry
  • Keratomileusis, Laser In Situ*
  • Lasers, Excimer / therapeutic use*
  • Lens Implantation, Intraocular
  • Lenses, Intraocular*
  • Male
  • Middle Aged
  • Myopia / surgery*
  • Optics and Photonics*
  • Phacoemulsification*
  • Postoperative Care
  • Prospective Studies
  • Refraction, Ocular / physiology
  • Visual Acuity / physiology