Influence of Spatial Relationship of Pupil Center and Corneal Vertex on Laser Ablation Centration Landmarks in Refractive Surgery
Evaluating the location and shift of the pupil center with respect to the corneal light reflex and the influence of other ocular variables may lead to improved guidelines for laser ablation centration. This study investigates the spatial relationship between pupil center and cornea vertex in myopic and hyperopic Caucasian eyes.
Dynamic pupillometry with the Topolyzer Vario (Alcon Laboratories, Inc.) was performed in 248 eyes of 124 patients scheduled for corneal laser refractive surgery. High-resolution images were obtained using the infrared-sensitive camera (incorporated in the videokeratoscope) under mesopic and photopic conditions. Measurements of pupil diameters, distance between the pupil center and keratoscopic axis, spatial shift of the pupil center and angle lambda were obtained and analyzed.
The mean distance between the pupil center and corneal vertex in mesopic and photopic conditions of illumination in myopic eyes was 0.27±0.14 (range 0.02 to 0.70mm) and 0.24±0.12mm(range 0.06 to 0.65mm) respectively, whereas it was 0.36±0.15 (range 0.03 to 0.70mm) and 0.31±0.16mm (range 0.03 to 0.77mm) in hyperopic eyes, respectively. The mean spatial pupil center shift was significant: 0.11± 0.07mm (range 0.02 to 0.57mm) in myopic eyes and 0.12±0.09 mm (range 0.02 to 0.47mm) in hyperopic eyes. The pupil center shifted consistently temporally as the pupil dilated. Pupil center shift was not significantly related to sex, age, laterality, or refractive error.
Mean distance between pupil center and corneal vertex is greater in hyperopic than in myopic eyes. Pupil center shifts temporally with pupil dilation and the shift is consistently small in all groups. This may influence the planning of refractive surgery centration in relation to the corneal light reflex.