Dynamic distribution of angle kappa and its biomechanical relationships in population who are suitable for excimer laser refractive surgery

Background To explore the dynamic distribution of pupil size and center,the eccentricity distribution of angle kappa, and its correlation with other biomechanics about suitable for excimer laser refractive surgery. Methods Randomly selected 225 patients (407 eyes) who underwent femtosecond laser combined with excimer laser in situkeratomileusis,preoperative use of Wavelight Allegro Topolyzer Corneal Topography ( Wavelight Laser Technologies AG, Erlangen, Germany ) to measure the pupil size and center position, the German Wavelight EX500 excimer Laser (500Hz) records the deviation between the pupil center and the coaxially sighted corneal light reflex when the patient is supine. Results The average displacement distribution of P-Dist (the eccentricity between the pupil center and the coaxially sighted corneal light reflex point) is 0.225 ± 0.102 mm, and 80% of the eyes are ≤ 0.30 mm.The coaxially sighted corneal light reflex point is mainly deviated to the superior temporal side of the corneal center (34%).Under the dark light condition, the x-axis of the left eye was: -0.046 ± 0.091 mm, the x-axis of the right eye was: -0.152 ± 0.084 mm, with statistical difference ( P = 0.015) (the right eye shifted to the temporal side), the y-axis direction had no statistical change ( P = 0.062). The WTW was positively correlated with changes of pupil diameter (dark pupil diameter-bright pupil diameter) ( r = 0.270, P <0.001).The SE and measured centroid shift was negative correlated ( r = - 0.214, P = 0.002). Conclusion The pupil of the left eye becomes smaller, the anterior chamber becomes shallower, and the angle kappa increases relative to the right eye.In patients with large WTW, a darker light environment is maintained during the operation to improve the efficiency of pupil matching.The dynamic change of angle kappa in high myopia population is small.