Intraoperative cyclorotation and pupil centroid shift during LASIK and PRK

Area of Science:

• Ophthalmology
• Refractive Surgery
• Ophthalmic Imaging

Background:

• Laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are common refractive surgical procedures.
• Accurate eye alignment is crucial for achieving optimal visual outcomes in refractive surgery.
• Intraoperative eye movements can potentially affect surgical precision and patient results.

Purpose of the Study:

• To quantify intraoperative cyclorotation and centroid shift during LASIK and PRK.
• To assess the degree of ocular positional changes during excimer laser refractive surgery.

Main Methods:

• A prospective study involving 63 eyes from 34 patients undergoing LASIK or PRK.
• Iris registration using the VISX WaveScan Wavefront System for pre-operative imaging.
• Measurement of cyclotorsion and pupil centroid shift using the VISX Star S4 laser at baseline and post-keratomileusis or epithelial removal.

Main Results:

• Mean intraoperative cyclorotation was 1.48° for LASIK and 2.02° for PRK.
• Significant centroid shifts occurred: 71% of LASIK eyes and 55% of PRK eyes shifted >100 μm in the x or y axis.
• Cyclorotation exceeded 2° in 21% of LASIK eyes and 32% of PRK eyes.

Conclusions:

• Both LASIK and PRK involve significant intraoperative cyclotorsion and centroid shifts.
• Iris registration immediately before laser ablation is recommended to account for eye position changes.
• Real-time eye tracking and registration may enhance refractive surgery accuracy.