## Mathematical model of correction of refractive disorders due to corneal asphericity by «Microscan-VIZUM» excimer laser

**I****.****A****. ****MUSHKOVA**^{1}**, ****A****.****N****. ****KARIMOVA**^{1}**, ****V****.****G****. ****MOVSHEV**^{2}**, ****E****.****G****. ****POGODINA**^{3}

^{1}S. Fyodorov Eye Microsurgery Federal State Institution, 59а Beskudnikovsky Blvd, Moscow, Russian Federation, 127486

^{2}Optosystems Ltd, 1-A Promyshlennaya Str., Troitsk, Russian Federation, 142191

^{3}Orenburg branch of S. Fyodorov Eye Microsurgery Federal State Institution, 17 Salmyshskaya Str., Orenburg, Russian Federation, 460047

** ****Mushkova I.A.** ― D. Sc. (medicine), Head of the Laser Refractive Surgery Department, Scientific Secretary of the Dissertation Council, ophthalmologist, e-mail: [email protected]

**Karimova A.N.** ― D. Sc. (medicine), Researcher of the Laser Refractive Surgery Department, e-mail: [email protected]

**Movshev V.G.** ― Cand. Phys. and Math. Sc., Head of the Department of Medical Lasers at Thematic Design Department №7, e-mail: [email protected]

**Pogodina E.G.** ― ophthalmologist of the Laser Surgery Department, e-mail: [email protected]

*The results are presented of creating a mathematical model of aspherical ablation algorithm for the following tasks: to identify differences between spherical and aspherical ablation profiles on «Microscan-VIZUM» excimer laser; to determine the conditions which reduce the advisability of aspheric operation by «Microscan-VIZUM» excimer laser; to derive a formula showing the influence of each parameter on the efficiency of the aspherical operation; to modify the formula for calculating the aspherical ablation with derivation of Q-factor (conic constant) in target value to determine a target conic constant of postoperative surface on «Microscan-VIZUM» excimer laser. The following features of aspherical ablation algorithm were found: the depths of standard and aspheric ablation differ by 9.8%; aspherical ablation is directly proportional to the Q-factor, with an initial value of spherocylindrical component equal to zero; aspheric ablation depth is not equal to zero and it is 10 microns; the advisability of aspherical correction decreases with diopter increase; value of ablation depth at the aspherical correction depends on the optical zone diameter. The conditions for the effectiveness of aspherical ablation algorithm and the conditions under which the application of this algorithm is impractical were determined: the use of aspherical correction for myopia with spheroequivalent refraction of 8.0 diopters and more is inadvisable; the use of aspherical ablation is also inadvisable if the decrease in the optical zone is less than 6.0 mm. The established theoretical conclusions require further experimental confirmation.*

**Key words****:** *aspherical ablation, conic constant.*

(**For citation:** Mushkova I.A., Karimova A.N., Movshev V.G., Pogodina E.G. Mathematical model of correction of refractive disorders due to corneal asphericity by «Microscan-VIZUM» excimer laser. Practical Medicine. 2018)

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