Background/purpose: Accuracy of ocular alignments is emphasized in laser refractive surgery. We evaluate pupil centroid shift and cyclotorsion and the correlation between both eyes in bilateral wavefront-guided laser refractive surgery.
Methods: A retrospective study was performed to analyze pupil centroid shift and cyclotorsion using an iris registration system of Zyoptix 100 platform in 186 eyes of consecutive 93 patients at National Taiwan University Hospital. Pearson's correlation analysis was used.
Results: The mean pupil centroid shift was 0.179±0.096mm, and 42.2% of eyes had more than 0.2mm shift between wavefront measurement with dilated pupil and laser ablation with undilated pupil. When the pupil was pharmacologically dilated, pupil centers predominantly shifted to inferonasal direction (59% of eyes). The vertical shift was larger than the horizontal shift. The correlations between both eyes in horizontal and vertical shifts were statistically significant, indicating a symmetric mirror pattern. A good opposite correlation of pupil centroid shifts was observed between in wavefront measurement and in laser treatment. The mean amount of cyclotorsion between the seated and supine positions was 3.22±2.53° with a maximum of 13.51°. A total of 112 eyes (60.2%) had cyclotorsion > 2°, while 39 eyes (21.0%) had cyclotorsion > 5°. Moderate correlation was observed between cyclotorsion of both eyes and was statistically significant.
Conclusion: Inferonasal pupil centroid shift as the pupil pharmacologically dilated and a significant amount of cyclotorsion with good correlation between both eyes was observed in refractive surgery and could be compensated by iris registration.
Copyright © 2012. Published by Elsevier B.V.