VALIDATION OF A HAND-HELD AUTOMATED KERATOMETER IN ADULTS

Purpose: To evaluate the Nidek handheld automated keratometer and comp are it with the manual Zeiss keratometer. Setting: St. Paul's Eye Unit , Royal Liverpool University Hospital, Liverpool, United Kingdom. Meth ods: Forty-five normal adult volunteers were included in the study. Th ree sets of randomized keratometry measurements were taken from both e yes of each adult, with both instruments by two independent observers. Readings included powers of the steep and flat meridians and axis of the flat meridian. The mean difference between the two instruments was calculated. The variance of each instrument was calculated for the ax is, the steep and flat meridians, and the mean of the two meridians. R esults: There was no significant difference between the mean Nidek and Zeiss keratometry readings for the steep (0.015 mm; P = .167) or flat (0.054 mm; P = .069) meridian or axis measurements (P = .172). On rep eated measurements, the within-subject and within-group variabilities, calculated separately for each instrument, were significantly less fo r the Nidek automated keratometer than the Zeiss keratometer (P < .01) when measuring the steep and flat meridians. There was, however, a si gnificant increase in axis variability using the Nidek keratometer (ra nge 20 degrees; P < .01). Conclusion: The Nidek automated keratometer was accurate, reliable, and easy to use and compared favorably with th e manual Zeiss keratometer when measuring corneal curvature. In the ha ndheld mode, the Nidek is not suitable for axis measurements. It has t he additional advantage of portability.