Influence of Ocular Cyclorotation on the Outcome of Refractive Laser Surgery

Abstract

Abstract: : Purpose: To assess the amount of ocular cyclotorsion induced by change of body position from erect to supine and by changing from monocular to binocular viewing condition. Cyclopositional changes could influence the outcome of aberration-free refractive correction by creating a wrong astigmatic axis. Methods: Eye movement recordings were performed using the video-oculography technique ("3D-VOG"). Objective cycloposition of ten healthy individuals (mean age 33.5 years, range 21-49) was measured in erect and supine position both monocularly and binocularly. The target was created by a He-Ne laser pointer mounted to the VOG-mask, thus assuring constant eye position in the different body positions. The distance between subject and laser target was the same whether erect or supine. Results: A change in body position from erect to supine or vice versa induced a considerable amount of cycloduction. Mean cycloduction of all subjects was about 2.5°. Two subjects showed a cyloduction of 3°, one of 4.5°, and one individual exhibited a cycloductional change of almost 10°. Cycloduction induced by changing from monocular to binocular viewing condition was minor, ranging below 1° in 7 subjects, around 1.5° in 2 individuals, and 3.2° in 1 subject. Conclusions: Our results demonstrate that a considerable amount of cyclotorsion can be induced by change of body position and thus torsional errors between wave front sensing while erect and refractive correction while supine can occur. Depending on the amount of astigmatism and aberrations of higher degrees, it seems plausible that the visual outcome could be affected by uncorrected torsional changes.

Keywords: refractive surgery: complications • eye movements: recording techniques • refractive surgery: LASIK