Evaluation of Cyclotorsion in Relation to Operated Eye, Corneal Curvature, and Refractive Error
Narrative Responses:
Purpose
To determine the degree of cyclorotation that occurs intraoperatively during LASIK and its relation to the operated eye, corneal curvature and refractive errors.
Methods
Intraoperative cyclorotation was measured in 200 eyes from 136 patients with a mean age of 30 years (range: 20 to 60 years) undergoing LASIK. 106 eyes (53.0%) were right and 94 eyes (47.0 %) were left. Preoperatively, an iris image of each eye was obtained with the ALLEGRO Topolyzer VARIO System (Alcon Surgical) with iris registration. An EX500 Excimer laser (Alcon Surgical) was later used to measure the cyclotorsion after flap creation.
Results
The mean cyclotorsion was 2.74 ± 2.44 with 41.5% incylcotorsion and 49% excylcotorsion. 89.0% were myope and 11.0% hyperope. The mean cycltorsion in hyperopes(3.58 ± 1.78)was larger than myopes (2.97 ± 2.44)but this was not statistically significant p=0.067. There was positive correlation between the cylindrical refractive error and the amount of cyclotorsion r=0.159 p= 0.025. There was positive correlation between both the flattest K and the steepest K and amount of cyclotorsion which was statistically significant. In relation to the operated eye, there was no statistically significant difference between the right and left eye in the amount and direction of cyclotorsion.
Conclusion
Significant changes in cyclotorsion is noted prior to surgery as well as intraoperatively. It may be advantageous to engage iris registration immediately prior to ablation.