BACKGROUND: In this investigation the clinical usefulness of an automatic handkeratometer was compared to well-known methods of corneal power measurement. Moreover, we examined the influence of the patient's position on the results.PATIENTS AND METHODS: One investigator measured 31 eyes of children in the age of 4-11 years (mean 6.3 y.) and 60 eyes of adults in the age of 22-71 years (mean: 48.3 y.) without corneal disorders consecutively by handkeratometer standing and lying, by autokeratometer and computerized videokeratography. Steepest (r1) and flattest (r2) radius, cylinder power and corresponding axis were subjected to statistical analysis.RESULTS: The mean values of the corneal radii (r1/r2) of the children were 7.63/7.82 mm for handkeratometer standing, 7.63/7.84 mm for handkeratometer lying, 7.62/7.84 mm for autokeratometer and 7.70/7.87 mm for videokeratoscope. The cylinder power was 1.11 dpt for handkeratometer standing, 1.09 dpt for handkeratometer lying, 1.23 dpt for autokeratometer and 0.95 dpt for videokeratoscope. Analysis of intraindividual variability produced by the instruments concerning astigmatism (dpt) showed in substraction for comparison of handkeratometer standing with handkeratometer lying 0.02 +/- 0.29 SD, of handkeratometer standing with autokeratometer -0.12 +/- 0.37 and of handkeratometer standing with videokeratoscope 0.16 +/- 0.35. A further comparison concerning cylinder (dpt) of handkeratometer lying with autokeratometer was -0.13 +/- 0.42 and handkeratometer lying with videokeratoscope 0.14 +/- 0.43. Difference comparison of astigmatism measurements in the 95% confidence interval (aspired difference of zero) demonstrated a high statistically significant relationship of handkeratometer standing (p < or = 0.0001) and handkeratometer lying (p < or = 0.0002) with the videokeratoscope. Mean values of the adult eyes (r1/r2) valued 7.56/7.76 mm in handkeratometer standing, 7.56/7.76 mm in handkeratometer lying, 7.57/7.78 mm in autokeratometer and 7.6/7.76 mm in videokeratoscope. The mean cylinder power with the corresponding axis was 1.15 dpt/80.5 degrees in handkeratometer standing, 1.15 dpt/77.8 degrees in handkeratometer lying, 1.15 dpt/78.3 degrees in autokeratometer and 0.95 dpt/75.2 degrees in videokeratoscope.CONCLUSIONS: The results and standard deviations of corneal power measurements of the handkeratometer were independent on patient's position and very similar to those of a common autokeratometer and videokeratoscope. Because of its quick and simple operation the handkeratometer was well accepted for corneal examination of children and can therefore be a useful alternative.
Adult Aged