Ray-tracing–Guided or Q-Value–Adjusted FS-LASIK for Correction of Myopia and Myopic Astigmatism: A Comparative Contralateral Eye Study

Purpose To compare the safety and efficacy of individualized ray-tracing–guided femtosecond laser–assisted in situ keratomileusis (FS-LASIK) for correction of myopia and myopic astigmatism. Methods This prospective, randomized, double-blind, contralateral eye study included 68 eyes of 34 patients with myopia or myopic astigmatism requiring FS-LASIK treatment. For each patient, one eye was randomly assigned to receive the ray-tracing–guided treatment, whereas the contralateral eye underwent Q-value–adjusted ablation. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), sphere, cylinder, effective optical zone (EOZ), and 6-mm corneal aberrations were measured and analyzed before operation and after a 3-month postoperative follow-up. Results At 3 months postoperatively, the UDVA of 20/16 or better was measured in 94% of eyes in the ray-tracing group and 85% of eyes in the Custom-Q group ( P = .064). Forty-seven percent in the ray-tracing group and 32% in the Custom-Q group gained one or more Snellen lines of CDVA ( P = .043). The MRSE, refractive astigmatism, surgically induced astigmatism, and difference vector were better in the Custom-Q group ( P < .05). The postoperative corneal HOAs and optical path difference were significantly better in the ray-tracing group ( P = .008). The EOZs of the ray-tracing and Custom-Q groups were 5.77 and 5.43 mm ( P < .001), and the average ablation depths of the ray-tracing and Custom-Q groups were 100.97 and 85.24 µm ( P < .001), respectively. Conclusions Despite the overcorrection and excessive ablation of corneal tissue, ray-tracing–guided FS-LASIK in clinical practice was found to be safe and effective for myopic correction both with and without astigmatism, particularly in achieving UDVA and inducing fewer corneal HOAs and less OPD. [ J Refract Surg . 2024;40(11):e804–e813.]