EyeWorld Weekly News
Volume 10, Number 44 November 28, 2005

http://www.eyeworld.org/ewweek.php?id=395#2

The optical zone/pupil ratio (fractional clearance, FC) has a significant impact on HOA induction after wavefront-guided LASIK, according to a study to be published in the December issue of the Journal of Cataract & Refractive Surgery. The study, “Influence of pupil and optical zone diameter on higher order aberrations after wavefront-guided myopic LASIK,” examined 27 myopic eyes of 19 patients. It was authored by Jens Bühren, M.D.; Christoph Kühne, M.D.; and Thomas Kohnen, M.D. Goethe University, Frankfurt am Main, Germany. They wrote that the ratio of optical zone to pupil was higher correlated with HOA induction after wavefront-guided LASIK than pupil diameter alone. The change in HOA root mean square and primary spherical aberration (Z 4, 0) was significantly correlated with FC, according to the study. If the optical zone [OZ] was 16.5% larger than the pupil (FC=1.17), only half of the amount of HOA is expected to be induced as if the OZ equaled the pupil, Dr. Bühren wrote. In contrast, an OZ that was 9% smaller than the pupil (FC=0.91) resulted in an HOA induction of 50% higher as at FC=1, according to the study. All patients underwent uneventful wavefront-guided LASIK using a Zyopix laser (Bausch & Lomb, Rochester, N.Y.).