METHOD FOR SURGICAL CORRECTION OF PRESBYOPY COMBINED WITH SIMPLE HYPERMETROPIC ASTIGMATISM

摘要

FIELD: medicine.;SUBSTANCE: eye cornea is exposed to an eximer laser light at wave length 193-222 nm, pulse energy 0.8-2.1 mJ, laser spot diameter 0.5-1.5 mm, pulse length 5-8 nm, pulse repetition frequency 30 to 500 Hz. This expose aiming at a sequential corneal abrasion is combined with forming optical surfaces and transition surfaces. A first cylindrical convex optical surface is formed within the entire optical cornea (OC). That involves forming a zone in the form of a non-ablated inner central segment (ICS). The ICS is formed by two parallel chords and a circle of an exposure diameter. A centre of ICS symmetry matches with an optical cornea centre. An axis of ICS symmetry lying in parallel with the chords matches with a strong axis of astigmatism. A second optical surface is formed as a convex ellipsoid of rotation with a positive conic constant within +0.75 to +1.5. An optical axis of the second optical surface matches with the OC centre. A diameter of the second optical surface is related to an OC diameter as a value within the range of 0.85 to 0.95 OC diameters. Then, the transitions surfaces (TS) are formed. The first TS is formed as a portion of a convex outer surface of a first O-toroid. A first TS width makes 0.04 to 0.2 diameters of the exposure. The first TS is formed so that its outer border is coupled with the intact cornea. The second TS is formed as a portion of a concave inner surface of a second O-toroid having a width of 0.04 to 0.2 diameters of the exposure. The inner border of the second TS shall be coupled with the outer border of the first optical surface, and its outer border - with the inner border of the first TS.;EFFECT: method enables minimising the amount of the resected eye tissue, provides the high far and near visual functions with no additional spectacle correction with decreased light cap.;22 dwg, 3 ex