SURGICAL METHOD FOR CORRECTING PRESBIOPIA CASES AGGRAVATED WITH COMPLEX HYPERMETROPIC ASTIGMATISM Russian patent published in 2008 - IPC A61F9/01 

FIELD: medicine.

SUBSTANCE: method involves treating eye cornea with excimer laser radiation in multi-stage mode with optical surfaces and transition zone surface being formed by sequentially layer-by-layer removing cornea segments. Action parameters are wavelength of 193-222 nm pulse power of 0.8-2.1 mJ, laser spot diameter of 0.5-1.5 mm, pulse duration of 5-8 ns, frequency of 30-500 Hz. The first optical surface is ellipsoidal convex one arranged within the whole optical zone. When forming it, central elliptical zone that is not to be withdrawn, is traced. Central elliptical zone symmetry center is made coincide with the optical zone center, major axis of the central elliptical zone is aligned with the strong astigmatism axis and the minor axis of the central elliptical zone with the weak astigmatism axis. The second optical surface is formed as spherical concave surface which optical axis coincides with the optical zone center. The second optical surface diameter is 0.28-0.55 times as large as the optical zone diameter. Then, transition zone surfaces are formed. The first transition zone surface is formed as a part of convex external surface of annular toroid being 0.04-0.2 times as wide as action zone diameter. Its external edge is coupled with cornea portion that is not to be withdrawn. The second transition zone surface is formed as a part of concave internal surface of the second annular toroid being 0.04-0.2 times as wide as action zone diameter. The second internal transition zone surface edge is coupled with external edge of the first optical surface and its external edge is coupled with the first internal transition zone surface edge.

EFFECT: improved visual function in long and short distance; reduced luminous halation; minimized volume of withdrawn eye tissues.

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