| 摘要 |
FIELD: medicine.SUBSTANCE: eye cornea is exposed to eximer laser irradiation with a wavelength of 193-222 nm, energy in a pulse 0.8-2.1 mJ, a diameter of the laser spot of 0.5-1.5 mm, the pulse duration of 5-8 ns, the pulse repetition frequency of 30-500 Hz. Optic surfaces and surfaces of the transitional zone are formed under such an impact, which ensures the successive layer-by-layer removal of the cornea sections. The first ellipsoidal convex optic surface is formed within the entire optic zone (OZ) of the cornea. In the process of its formation a zone in the form of an internal central segment (ICS) is created, which is not subjected to ablation. The ICS is formed by two parallel chords and a circumference with a diameter of the impact zone (IZ). The centre of the ICS symmetry is superposed with the centre of the optic zone. The axis of the ICS symmetry, located parallel to the chords, is superposed with the strong axis of astigmatism. After that, the second optic surface in the form of a convex rotation ellipsoid with a negative conic constant from -0.1 to -0.4 is formed. A ratio of a diameter of the second optic surface to the OZ diameter is within the interval from 0.85 to 0.95 of the OZ diameter. After that, transitional zone surfaces (TZS) are formed. The first TZS is formed in the form of a part of the convex external surface of the first circular toroid. The first TZS is formed in such a way that its external edge is conjugated with the section of the cornea which is not subjected to an impact. The second TZS is formed in the form of a part of the convex internal surface of the second circular toroid. The internal edge of the second TZS must be conjugated with the external edge of the first optic surface and the external edge - with the internal edge of the first TZS.EFFECT: method makes it possible to minimise the volume of ablated tissue of the eye, ensures high visual functions at far and close distance without additional correction by means of glasses, and reduction of the light halo.22 dwg, 3 ex |
