title: Accuracy of Corneal Power Measurements for Intraocular Lens Power Calculation after Myopic Laser In situ Keratomileusis.
abstract: OBJECTIVE
  To evaluate the accuracy of corneal power measurements for intraocular lens (IOL) power calculation after myopic laser in situ keratomileusis (LASIK).
  
  
  METHODS
  The study evaluated 45 eyes with a history of myopic LASIK. Corneal power was measured using manual keratometry, automated keratometry, optical biometry, and Scheimflug tomography. Different hypothetical IOL power calculation formulas were performed for each case.
  
  
  RESULTS
  The steepest mean K value was measured with manual keratometry (37.48 ± 2.86 D) followed by automated keratometry (37.31 ± 2.83 D) then optical biometry (37.06 ± 2.98 D) followed by Scheimflug tomography (36.55 ± 3.08). None of the K values generated by Scheimflug tomography were steeper than the measurements from the other 3 instruments. Using equivalent K reading (EKR) 4 mm with the Double-K SRK/T formula, the refractive outcome generated 97.8% of cases within ± 2 D, 80.0% of cases within ± 1 D, and 42.2% of cases within ± 0.5 D. The best combination of formulas was "Shammas-PL + Double-K SRK/T formula using EKR 4 mm."
  
  
  CONCLUSIONS
  Scheimflug tomography imaging using the Holladay EKR 4 mm improved the accuracy of IOL power calculation in post-LASIK eyes. The best option is a combination of formulas. We recommended the use the combined "Shammas-PL ± Double-K SRK/T formula using EKR 4 mm"h for optical outcomes.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors.forename: Hany A
authors.initials: HA
authors.lastname: Helaly
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors.forename: Mohammad A M
authors.initials: MA
authors.lastname: El-Hifnawy
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors.forename: Mohamed Shafik
authors.initials: MS
authors.lastname: Shaheen
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors.forename: Amr F
authors.initials: AF
authors.lastname: Abou El-Kheir
mesh_terms: D000328:Adult; D000368:Aged; D001699:Biometry / Q000379:methods; D002386:Cataract / Q000150:complications; D003315:Cornea / Q000503:physiopathology*; D019781:Corneal Topography; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D055095:Optics and Photonics; D018918:Phacoemulsification; D011446:Prospective Studies; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
keywords: Biometry; Intraocular Lens Calculation; Laser In situ Keratomileusis; Pentacam