Excimer Laser Correction of Myopia Using Aspheric Technology. Literature Review

The article presents a literature review of scientific sources on the use of aspheric technology for the correction of refractive errors at the present stage of development of excimer laser surgery. The article highlights the pressing challenge of developing algorithms that improve quality indicators, maintaining subtle visual functions (low-contrast visual acuity, visual acuity in various illuminating conditions) after excimer laser correction of ametropy. The literature data on the etiology of visual acuity reduction after refractive operations are given. Special consideration is given to the description of asphericity indicators by the researchers, the importance of influence of the indicators on the qualitative characteristics of vision. The mechanism of influence of the modified aberration balance of the cornea after refractive interventions on the indicators of spatial-contrasting characteristics of vision in refractive patients is clarified; the importance of evaluating these indicators before and after refractive surgeries is emphasized. The types of aspherical ablation algorithms used in modern, both foreign and domestic, excimer laser systems, and their differences are described. Advantages and disadvantages of the aspherical algorithms used have been analyzed, historical evolution of the software that was developed and introduced into the new excimer laser systems for aspherical operations has been traced. Fundamental difference between aspheric ablation optimized with respect to wavefront with average asphericity index, introduced by the manufacturer of the facility, and the algorithm, where aspheric ablation is performed with personalized Q-factor, which can be controlled by the surgeon himself, is presented in detail. The problem of developing optimized technology of aspheric ablation algorithm in correcting myopia due to the existence of restrictions on the use of aspheric techniques on domestic “Microscan-VIZUM” excimer laser unit is emphasized.