EFFECT OF OPTICAL ZONE DIAMETER ON THE EFFICACY OF ASTIGMATISM CORRECTION IN KERATOREFRACTIVE LENTICULE EXTRACTION SURGERY WITH AUTOMATIC CENTERING AND CYCLOTORSION COMPENSATION

To evaluate the influence of optical zone (OZ) diameter on the effectiveness of astigmatism correction in patients undergoing KLEx with automatic centering and cyclotorsion correction.

Experimental Eye Research Institute, University Eye Hospital, Ruhr-University Bochum, Germany

Sphere Eye Clinic, Moscow, Russian Federation

A total of 121 eyes from patients with myopic astigmatism (44 men, 77 women; mean age 29 ± 7.3 years) were analyzed one month postoperatively. The eyes were divided into three groups based on the OZ diameter: Group 1 (OZ = 7.3 mm, 53 eyes) had a preoperative sphere of −1.25 to −5.25 D and a cylinder of −0.5 to −2.5 D; Group 2 (OZ = 7.0 mm, 48 eyes) had a sphere of −2.0 to −6.25 D and a cylinder of −0.25 to −1.5 D; and Group 3 (OZ < 7.0 mm, 20 eyes) had a sphere of −4.5 to −7.75 D and a cylinder of −0.25 to −1.5 D. All procedures were performed using KLEx procedure with automatic centering and cyclotorsion correction. Uncorrected (UDVA) and corrected distance visual acuity (CDVA), refractive accuracy, residual astigmatism, predictability, effectiveness and safety were evaluated.

In Group 1, 100% of eyes achieved UDVA ≥ 1.0 and 40% achieved UDVA = 1.2. All eyes maintained or improved CDVA; none lost any lines. Spherical equivalent (SE) was within ± 0.13 D in 98% cases, and postoperative astigmatism ≤ 0.25 D in 100% of eyes. Coefficient of determination (R²) = 1.0. In Group 2, 95% of eyes reached UDVA ≥ 1.0, 95% maintained or improved CDVA (5% lost ≤ 1 line), 100% were within ± 0.13 D of target in SE, postoperative astigmatism ≤ 0.5 D in 97%, ≤ 1.0 D in 100%, R² = 0.9738. In Group 3, 94% achieved UDVA ≥ 1.0, 100% maintained or improved CDVA, 100% within ± 0.13 D of target refraction, postoperative astigmatism ≤ 0.25 D in 100%, R² = 1.0.

KLEx with automatic centering and cyclotorsion correction is a safe and effective procedure for the correction of myopic astigmatism. Increasing the optical zone diameter up to 7.3 mm provides a slight improvement in astigmatic correction efficacy.