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As myopia prevalence rises, the pursuit of safer and more satisfying refractive surgery has spurred the development of various treatment techniques and excimer laser ablation profiles.1 To date, most of the ablation profiles used in corneal laser vision correction surgery, whether conventional or customized, were developed from the Gullstrand reduced eye model.2 The calculations were based on average refractive values of the eye. However, the eyeball is a complex multi-lens optical system.3 Although those laser ablation profiles were proven extremely effective in correcting sphere, cylinder, and even higher order aberrations (HOAs), they did not resolve all ocular optical errors and resulted in relatively unsatisfactory postoperative vision and visual quality.
In 2008, Mrochen et al3 proposed a laser ablation profile based on ray-tracing theory, which took into account all optically significant structures of the eye. The new optical ray-tracing algorithm uses data from a beam of light passing through the various refracting media of the eye to focus precisely on the fovea, contributing data to a highly individualized custom ablation profile.4 Previous studies have evaluated the safety and efficacy of the ray-tracing algorithm (Wave-Light Plus; Alcon Laboratories, Inc), using multiple instruments to supply biometry, tomography, and wavefront patient data to the algorithm.4,5 Recently, a single diagnostic device called InnovEyes Sightmap (Alcon Laboratories, Inc) integrated three ocular measuring instruments into one. These measurements are applied to the InnovEyes platform (Alcon Laboratories, Inc) to generate an automated ray-tracing algorithm that could treat sphere, cylinder, and HOAs simultaneously. Additionally, the algorithm also provided an enhanced precompensation calculation that considers laser efficiency, corneal epithelial remodeling, and expected biomechanical changes.6–8
Aspherical ablation profile or Q-value–adjusted or Custom-Q ablation algorithm is currently a widely used method, and both are based on the manifest refraction.9 In this study, we compared two methods of corneal ablation performed using femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK) in myopic eyes with or without astigmatism. We conducted a prospective randomized controlled study between two eyes in the same individual. For each patient, one eye was treated with ray-tracing and the contralateral eye was treated with Custom-Q. Both methods required the use of the WaveLight EX500 (Alcon Laboratories, Inc) excimer laser system.
Patients and Methods
Patients
This prospective, randomized, comparative...