title: An evaluation of keratometry in 6-year-old children.
abstract: OBJECTIVE
  To evaluate the repeatability and comparability of keratometry measured by both the IOLMaster and RK-F1 AutoRef-Keratometer in children.
  
  
  METHODS
  Keratometry results from a sample (n = 447) of 6-year-old children who were examined in the Sydney Myopia Study were analyzed. Corneal power was analyzed along the flattest and steepest meridians to determine if there were any systematic differences between repeat measurements or between the two instruments. The 95% limits of repeatability (LR) and 95% limits of agreement (LA) (mean difference +/- 1.96 x standard deviation of differences) were calculated.
  
  
  RESULTS
  There were no systematic differences in repeat measurements for each instrument. For the IOLMaster, mean difference of the flattest corneal meridian was -0.01 (D) (P = 0.3, 95% LR, -0.22, 0.21 D) and of the steepest corneal meridian, 0.01 D (P = 0.3, 95% LR, -0.35, 0.38 D). For the RK-F1, mean difference of the flattest corneal meridian was -0.02 D (P = 0.3, 95% LR, -0.25, 0.21 D); and of the steepest corneal meridian, 0.00 D (P = 0.9, 95% LR, -0.39, 0.39 D). Systematic differences, however, were found between the two instruments. The IOLMaster gave significantly (P < 0.0001) steeper readings than the RK-F1 for both the flattest corneal meridian, 0.29 D (95% LA, -0.08, 0.66 D), and the steepest corneal meridian, 0.18 D (95% LA, -0.29, 0.65 D).
  
  
  CONCLUSIONS
  Keratometry was highly repeatable for both the IOLMaster and RK-F1 instruments when used in young children. These instruments would be suitable for use in monitoring changes of corneal curvature over time. Small significant systematic differences in keratometry between the two instruments were also found.
authors: Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia.
authors: Son C
authors: SC
authors: Huynh
authors: Tung Q
authors: TQ
authors: Mai
authors: Annette
authors: A
authors: Kifley
authors: Jie Jin
authors: JJ
authors: Wang
authors: Kathryn A
authors: KA
authors: Rose
authors: Paul
authors: P
authors: Mitchell