A new, hand-held keratometer: comparison of theNidek KM-500 auto keratometer with the B&L keratometer and the topcon RK-3000A keratometer

The Nidek KM-500 is a recently introduced hand-held automatic keratometer. If the accuracy and reliability of thisinstrument are good then it offers a number of benefits to contact lens practitioners and other clinicians. This study investigated the repeatability and reproducibility of readings taken using the hand-held Nidek KM-500, the Topcon RK-3000A and the Bausch & Lomb keratometer. The Nidek KM-500 was found to be reliable when used according to the manufacturer's instructions and the readings equated well with those obtained with the table-mounted Topcon KR-3000A. The repeatability of the Bausch & Lomb keratometer can be improved by taking the mean of three readings. Clinicians should consider conducting a simple repeatability study of the keratometer used in their own practice. The results may help to pinpoint a weakness in technique when using a non-automated instrument, and will establish the criterion for a true change in corneal radius.