Measurement of Cyclotorsional Displacement using Iris Registration among Refractive Surgery Candidates with Moderate and High Astigmatism

To determine cyclotorsional eye movement between the upright position and the supine position, in Iranian patients with high preoperative astigmatism This prospective cross sectional study contains 102 eyes of 59 patients who were candidates for refractive surgery with Technolas 217z100 excimer laser system for correction of high astigmatism. Wavefront measurements using Zywave II, Hartmann Shack aberrometer were performed in seated position. For all patients the amount of cyclotorsion before surgical procedure in supine position was measured by iris registration and the comparison between preoperative examinations in seated position with the supine position resulting in the amount of cyclotorsion was conducted by iris registration. The mean cyclotorsion was found 3.18±2.37 (SD) degrees significantly greater than zero degrees 3.28±2.28 (SD) degrees in excyclotorsion and 3.01±2.54 (SD) degrees in incyclotorsion. Excyclotorsion was predominant trend of rotation in comparison with incyclotorsion in both right and left eyes. The amount of rotation greater than 2, 5 and 7 degrees occurred in 59.8%, 21.6% and 5.9% of the eyes, respectively. This study confirms significant rotational movement between the upright position and the supine position. Proper registration for appropriate correction of astigmatism and higher order aberrations (HAOs) for achieving optimal visual outcomes is recommended.