It has been well known by laser eye surgeons that the eyes of some patients will undergo clyclotorsion, also known as cyclorotation, when laying flat for laser vision correction.
This means that in some patients the measurements taken with the patient sitting up may be misaligned with respect to rotational axis when laying flat for LASIK or PRK. This is of particular importance for patients with higher astigmatism who need an accurate treatment on the correct axis and for those undergoing custom wavefront ablation in which the patient’s individual abberations are measured and then corrected with the laser.
A recent article in the Journal of Cataract and Refractive Surgery (Kim H, Joo CK. 1: J Cataract Refract Surg. 2008 Apr;34(4):557-61) studied cyclorotation with the iris registration features on the Visx WaveScan Wavefront system with the patient seated and the Visx Star S4 Laser with the patient laying flat as they would for laser eye surgery. They found that 13% of eyes tested had cyclorotation of greater than 5 degrees. This amount of cyclorotation could affect outcomes of astigmatism and custom wavefront laser eye treatments.
In the past some surgeons have used an eye marking technique to compensate for cyclorotation for patients with high astigmatism. With this technique a small ink mark is made on the cornea and then the surgeon will rotate the patient’s head to compensate. Other factors such as head tilting or patient position on the bed can cause the eye to be rotated with respect to the laser treatment even if there is no actual cyclorotation of the eye.
Western Laser Eye Associates is pleased to offer the iris recognition feature with cyclorotation control to our LASIK and PRK patients who are candidates for custom WaveScan treatments.