Comparison Between Cyclorotation Angle Levels In Lasik And Prk

Published 2025 - 43rd Congress of the ESCRS

Reference: PO767 | Type: Free paper | DOI: 10.82333/rth6-gz31

Authors: Ahmed Samir* ¹ , mohammed kamal ¹

¹ophthalmology,magrabi eye hospital,jeddah,Saudi Arabia

Purpose

Cylorotation angle correction in photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis (LASIK) is crucial for effective astigmatic correction. Addressing cyclorotation through iris registration is increasingly integrated into modern excimer lasers, yet the degree of cyclorotation and its impact on refractive and visual results remains an area of active investigation. Thus many surgeons tilt patients’ heads prior to commencing surgery to achieve smaller angles, which is a time-consuming maneuver that may lead to stromal dehydration and inferior results. Our goal was to assess the differences between small, medium, and large cyclorotation angles in terms of visual and refractive outcomes of RK and LASIK.

Setting

Care Vision Laser Center, Tel Aviv, Israel

Methods

This retrospective comparative study included consecutive patients who underwent PRK or LASIK between 2012 and 2023. The following analysis was done for the 3 independent groups- myopic PRK, myopic LASIK, hyperopic LASIK, and for the combined LASIK group. At each instance, patients were divided into three groups according to their cyclorotation angle magnitude. A comparison of baseline and intraoperative parameters was performed. Refractive and visual outcomes were assessed, including efficacy and safety indexes, and an alpins vector analysis was performed. Multiple linear regression was performed to identify the effect of potential confounders.

Results

Over 15,000 eyes were analyzed, with angles <3.33° being most common and slight male predominance. Myopic LASIK (N=6,920, age=30.7±8.7) showed minor BCVA differences (small: 0.98±0.10, medium: 0.97±0.10, large: 0.97±0.11; p=0.04), with no significant correlations in other outcomes including safety and efficacy indexes. Hyperopic LASIK (N=621, age=44.5±12.6) and combined LASIK (N=7,676, age=31.9±9.8) showed no significant outcome differences. Myopic PRK (N=17,214, age=25.9±7.5) revealed lower BCVA and UCVA in large angles, confounded by preoperative BCVA. Other visual/refractive outcomes, Alpins vectors, and indexes showed no significant differences or strong correlations with angles.

Conclusions

Differences in cyclorotation angle groups were limited to BCVA and UCVA in myopic LASIK and PRK patients only, primarily attributed to baseline variations and clinically negligible. More importantly, safety and efficacy indexes—holistic measures of pre-and-postoperative outcomes—showed no significant differences, reaffirming procedural consistency. Refractive outcomes, including Alpins’ vectors and indexes, were also uniform across groups. These findings validate the reliability of cyclorotation autocorrection within device limits, eliminating the need for patient head tilting, reducing stromal dehydration, and optimizing surgical outcomes.