title: Comparison of Newer IOL Power Calculation Methods for Eyes With Previous Radial Keratotomy.
abstract: To evaluate the accuracy of the optical coherence tomography-based (OCT formula) and Barrett True K (True K) intraocular lens (IOL) calculation formulas in eyes with previous radial keratotomy (RK).
  
  
  
  In 95 eyes of 65 patients, using the actual refraction following cataract surgery as target refraction, the predicted IOL power for each method was calculated. The IOL prediction error (PE) was obtained by subtracting the predicted IOL power from the implanted IOL power. The arithmetic IOL PE and median refractive PE were calculated and compared.
  
  
  
  All formulas except the True K produced hyperopic IOL PEs at 1 month, which decreased at ≥4 months (all P < 0.05). For the double-K Holladay 1, OCT formula, True K, and average of these three formulas (Average), the median absolute refractive PEs were, respectively, 0.78 diopters (D), 0.74 D, 0.60 D, and 0.59 D at 1 month; 0.69 D, 0.77 D, 0.77 D, and 0.61 D at 2 to 3 months; and 0.34 D, 0.65 D, 0.69 D, and 0.46 D at ≥4 months. The Average produced significantly smaller refractive PE than did the double-K Holladay 1 at 1 month (P < 0.05). There were no significant differences in refractive PEs among formulas at 4 months.
  
  
  
  The OCT formula and True K were comparable to the double-K Holladay 1 method on the ASCRS (American Society of Cataract and Refractive Surgery) calculator. The Average IOL power on the ASCRS calculator may be considered when selecting the IOL power. Further improvements in the accuracy of IOL power calculation in RK eyes are desirable.
authors.affiliation: McGovern Medical School University of Texas Health Science Center at Houston, Houston, Texas, United States.
authors.forename: Jack X
authors.initials: JX
authors.lastname: Ma
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, United States.
authors.forename: Maolong
authors.initials: M
authors.lastname: Tang
authors.affiliation: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States.
authors.forename: Mitchell P
authors.initials: MP
authors.lastname: Weikert
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon, United States.
authors.forename: David
authors.initials: D
authors.lastname: Huang
authors.affiliation: Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, United States.
authors.forename: Douglas D
authors.initials: DD
authors.lastname: Koch
mesh_terms: D000368:Aged; D001699:Biometry / Q000379:methods; D002386:Cataract / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007646:Keratotomy, Radial; D007910:Lenses, Intraocular; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D055095:Optics and Photonics; D018918:Phacoemulsification; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013997:Time Factors; D041623:Tomography, Optical Coherence / Q000379:methods