METHOD FOR SURGICAL CORRECTION OF COMPOUND IRREGULAR HYPERMETROPIC CORNEAL ASTIGMATISM

摘要

FIELD: medicine.;SUBSTANCE: eye cornea is exposed to excimer laser at wave length 193-222 nm. A pulse energy is 0.8-2.1 mJ; a laser spot diameter is 0.5-1.5 mm; a pulse length is 5-8 ns; a pulse repetition rate is 30-500 Hz. A regular surface and a transient surface are formed in an optical area by a sequential removal of the corneal segments in layers. The regular surface of the optical area (OA) is formed as a dome-shaped ellipsoid of rotation with a negative conical constant from minus 0.1 to minus 0.4. An optical axis of the ellipsoid is displaced so that the OA centre is aligned with the position of the centre of a maximum irregularity on an anterior segment analysis. The OA diameter is specified in accordance with a diameter of the maximum irregularity segment determined by a height map on the anterior segment analysis. A transient area surface (TAS) is formed in the form of a portion of the dome-shaped outer surface (DSOS) of a toroidal ring. An outer edge of the TAS is coupled with an unexposed corneal segment. An inner edge of the TAS is coupled with an outer edge of an optical surface. A TAS width makes 0.04-0.2 from an exposure diameter.;EFFECT: reducing the corneal surface irregularity with preserving the physiological conical constant of the cornea and improving the patient's visual functions, minimising the removed tissue volume, eliminating the necessity of the excimer laser re-alignment improves the exposure accuracy and reduces the length of operation.;14 dwg, 3 ex