Inter-device measurement variability of vital data parameters for keratorefractive and cataract refractive surgery

INTRODUCTION: The measurements of corneal white-to-white (WTW) diameter and pupil size are critical for decision making in refractive surgery. Currently, automatic measurement of keratometry, corneal WTW, and pupil size are implemented in several ocular devices. The purpose of this study was to examine the agreement between two commonly used devices, an autorefractor and an optical biometer, for these parameters. METHODS: Measurements were performed with both a Lenstar LS-900 and Nidek ARK-1 by an experienced examiner in random order. The devices were placed in close proximity within the same dimly lit room. RESULTS: The measurements of 65 right eyes were analyzed. The results of the flat, steep, and mean keratometric reading were not significantly different (p = 0.96, p = 0.90, p = 0.93, respectively). Corneal WTW distances showed only moderate agreement between devices and were found to be significantly different (r = 0.8071; p < 0.01). Pupil diameters showed poor agreement between devices and were significantly different (r = 0.4890; p < 0.01). Agreement between implantable contact lens sizing, based on the measurements obtained by the two devices, was achieved for 19 of the 51 eyes (37.3%). CONCLUSION: We found a significant difference in WTW and pupil size measurements between ARK-1 and Lenstar. Results for both of the devices cannot be considered interchangeable for these data parameters.