Repeatability of manual and portable handheld automated keratometric measurements in pediatric population

Background: The cornea is not only responsible for the majority of the refraction of the eye, but is also readily accessible for measurement and modification. The refractive power of the anterior corneal curvature can be measured by an instrument known as keratometer and various manual and automated keteratometers are available for this purpose. Objective: To study the comparison between keratometric measurements by Bausch and Lomb manual keratometer (MK) and Nidek KM-500 portable handheld automated keratometer (PAK) in pediatric age group. Methods: 404 eyes of 202 children of age between 5-16 years were examined. Three sets of readings of vertical, horizontal meridia and axis measurements were taken for each eye using both instruments. Results: The mean of average vertical, horizontal keratometry and axis readings using MK were 43.24 ± 1.52 D, 42.86 ± 1.47 D and 10.33 ± 36.47 degrees respectively. The mean of average vertical, horizontal keratometry and axis readings using PAK were 43.29 ± 1.41 D, 42.99 ± 1.34 D and 20.78 ± 12.39 degrees respectively. The mean of average keratometric astigmatism (KA) for MK and PAK were 0.661 ± 0.796 D and 0.663 ± 0.590 D respectively. The reliability coefficients of MK and PAK were 0.888 and 0.994 respectively for vertical meridia, 0.993 and 0.989 respectively for horizontal meridia, 0.973 and 0.963 respectively for axis measurements. Conclusion: Both the instruments had good comparability and repeatability. Keratometric measurements using MK and PAK were significantly similar. However, there was statistically significant difference in the axis measurements using both the instruments