METHOD FOR SURGICAL CORRECTION OF PRESBYOPY COMBINED WITH MIXED ASTIGMATISM Russian patent published in 2014 - IPC A61F9/07 A61F9/01 

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 exposure aiming at a sequential corneal abrasion is combined with forming optical surfaces and transition surfaces. First, a concave portion of a hyperbolic paraboloid surface is formed by limiting an ablated centre. The above portion of the paraboloid surface is formed within the entire optical cornea (OC). The centre of central symmetry matches with the OC centre. That is followed by forming a convex portion of the hyperbolic paraboloid surface by limiting a non-exposed centre. A centre of central symmetry matches with the OC centre. An axis of central symmetry matches with a weak 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. 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 non-exposed 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 is 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.

27 dwg, 3 ex