Manual keratometry and videokeratography after photorefractive keratectomy

Purpose.. To examine the relative accuracy of manual keratometry and videok eratography in eyes treated by photorefractive keratectomy (PRK). Setting: Eye Clinic, Cantonal Hospital, Lucerne, Switzerland. Methods: Results of manual keratometry and videokeratography were compared with those of subjective refraction in 128 eyes before and 6 months after P RK. Results: Six months after PRK, the mean subjective refraction of all eyes d ecreased more than the mean corneal dioptric power measured with videokerat ography (P <.0001). The change in the mean subjective refraction compared w ith the corresponding difference in the mean manual keratometry of all eyes was also significant (P <.0001). Conclusions: This study confirmed an earlier observation that there is a di sparity between the change in refraction and the reduction in corneal power measured by videokeratography and with the manual keratometer. Topographic al changes from PRK and the subsequent wound-heating processes are likely t o falsify objective measurements. The keratometric value in the center of t he cornea, since it is not measured by manual keratometry and videokeratogr aphy, may actually be lower. J Cataract Refract Surg 2000; 26:1748-1752 (C) 2000 ASCRS and ESCRS.