title: Comparison of aphakic refraction formulas for secondary in-the-bag intraocular lens power estimation in children.
abstract: OBJECTIVE
  Intraocular lens (IOL) formulas based on aphakic refraction alone have been proposed as an alternative to biometry-based formulas. The purpose of this study was to determine the relative accuracy of these simplified formulas.
  
  
  METHODS
  Records of patients who received secondary in-the-bag (IOL) implants and for whom aphakic refraction was obtainable were retrospectively studied. The formulas for IOL power calculation by Hug (J Pediatr Ophthalmol Strabismus 2004;41;209-11) and Khan and by AlGaeed (Br J Ophthalmol 2006;90:1458-60; modified to account for greater K values in our population) were compared with the biometry-based Holladay 1 formula by calculating the absolute prediction error for each.
  
  
  RESULTS
  Twenty eyes met the inclusion criteria. The average age at IOL implantation was 4.8 ± 3.4 years. The mean of the absolute value of the prediction error when we used the Hug's formula was 2.4 ± 2.1 D; with Khan's formula, 2.4 ± 2.0 D; and with biometry, 1.6 ± 1.4 D. None of these differences was statistically significant (paired t test: Hug vs Khan, P = 0.9; biometry vs Hug, P = 0.3; biometry vs Khan, P = 0.2). The absolute prediction error was more than 2 D in 8 of 20 eyes (40%) when we used Hug's formula, 11 of 20 eyes (55%) with Khan's formula, and 5 of 20 eyes (25%) with biometry.
  
  
  CONCLUSIONS
  Although the 0.8 D reduction in accuracy of the refraction-based formulas was not statistically significant, we recommend continued use of biometry-based formulas for IOL power calculation. Aphakic refraction may be used to confirm IOL power prediction when biometry is difficult.
authors: Department of Ophthalmology, Medical University of South Carolina, Charleston, SC, USA.
authors: Ghada
authors: G
authors: Abdel-Hafez
authors: Rupal H
authors: RH
authors: Trivedi
authors: M Edward
authors: ME
authors: Wilson
authors: Dipankar
authors: D
authors: Bandyopadhyay
mesh_terms: D000465:Algorithms; D001035:Aphakia / Q000503:physiopathology*; D001699:Biometry / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D019654:Lens Implantation, Intraocular; D007910:Lenses, Intraocular; D008297:Male; D012029:Refraction, Ocular / Q000502:physiology*; D015203:Reproducibility of Results; D012189:Retrospective Studies