METHOD OF SURGICAL CORRECTION OF COMPLICATED INCORRECT MYOPIC CORNEAL ASTIGMATISM Russian patent published in 2015 - IPC A61F9/08 

FIELD: medicine.

SUBSTANCE: keratotopogram is made. Then the eye cornea is influenced by the irradiation of an excimer laser with a wave length of 193-222 nm, energy in an impulse of 0.8-21.1 mJ, diameter of a laser spot of 0.5-1.5 mm, pulse duration of 5-8 nsec, pulse repetition rate of 30-500 Hz. A regular surface in the optical zone and surfaces of the transition zone are formed by the successive layer-by-layer removal of the cornea parts. The regular surface of the optical zone (03) is formed in the form of a concave ellipsoid of rotation with a negative conical constant from minus 0.1 to minus 0.4. The optical axis of the ellipsoid is shifted in such a way, that the centre of the optical zone corresponds to the position of the centre of the section of the maximal irregularity on the keratotopogram. The diameter of the optical zone is selected according to the diameter of the section of the maximal irregularity, determined by a map of heights on the keraotopogram. After that surfaces of the transitional zone are formed. The first surface of the transitional zone (STZ), adjacent to the zone, which is not subjected to influence, is formed in the form of a part of a convex external surface (PCES) of a circular toroid. An external edge of the first STZ is connected to the section of the cornea, which is not subjected to influence. The width of STZ constitutes 0.04-0.2 of the influence zone (IZ) diameter. The second STZ is formed in the form of a part of a concave internal surface (PCIS) of a circular toroid, adjacent to the optical zone. The width of the second STZ is equal to the width of the first STZ. An internal edge of the second STZ is connected to the external edge of the optical surface, an external edge - with the internal edge of the first STZ.

EFFECT: reduction of the time for carrying out the operation and error in recentring due to carrying out the operation in one stage, reduction of irregularity of the cornea surface with the preservation of physiological conical constant of the cornea and improvement of the patients' visual functions, minimisation of the volume of ablated tissues.

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