SURGICAL CORRECTION METHOD FOR TREATING PRESBIOPIA CASES AGGRAVATED WITH COMPLEX MYOPIC ASTIGMATISM

摘要

FIELD: medicine.;SUBSTANCE: method involves treating eye cornea with excimer laser radiation 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 elliptical concave one arranged within the whole optical zone. Central elliptical zone, which symmetry center coincides with the optical zone center, is marked as one that is not to be withdrawn. The major axis of the central elliptical zone is aligned with weak astigmatism axis and the minor one with strong astigmatism axis. Then, 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, the transition zone surface is formed as a part of convex external surface of annular toroid being 0.04-0.2 times as large as action zone diameter. Internal transition zone surface edge is coupled with external edge of the first optical surface and external transition zone surface edge is coupled with cornea portion that is not to be withdrawn.;EFFECT: improved visual function in long and short distance; reduced luminous halation; minimized volume of withdrawn eye tissues.;17 dwg