Abstract
Abstract: :
Purpose: When applying precise wavefront measurements of optical aberrations to the practice of laser refractive surgery, it is important to understand subtle differences in corneal geometry among potential patients. The purpose of this study was to investigate the differences in corneal geometry between Asian and Caucasian eyes. Methods: Patients scheduled to undergo wavefront–driven refractive surgery were measured on the VISX WaveScan Wavefront® aberrometer. In addition to Shack–Hartman images, the instrument captures an image of the measured eye. Image–processing algorithms allow significant landmarks to be identified, including the limbus and its center, the pupil and its center, and the corneal vertex (typically located at the first Purkinje reflection created by the measurement beam of the instrument). The distances between these landmarks in more than 300 Asian and Caucasian patients from multiple surgical centers around the world were analyzed and statistically compared. Results: The distance from the limbus center to the corneal vertex is significantly different in Caucasians and Asians. In all the Caucasian patients, the corneal vertex was located significantly more nasally than the limbus center (0.40 ± 0.12 mm). In a significant percentage of the Asian patients the center of the limbus and the corneal vertex were virtually coincidental (within 0.10 mm nasally or temporally). No significant differences in relative pupil–center position were found between the two groups. Conclusions:Corneas of many Asian subjects are more symmetrical in relationship to the limbus, which is defined by the outer boundary of the iris. In Caucasian subjects, the corneal vertex is always located more nasally than the limbus center.
Keywords: cornea: clinical science • anatomy • refractive surgery: corneal topography