SURGICAL METHOD FOR CORRECTING PRESBYOPIA COMBINED WITH SIMPLE HYPERMETROPIC ASTIGMATISM Russian patent published in 2007 - IPC A61F9/01 

FIELD: medicine.

SUBSTANCE: method involves exposing cornea to excimer laser radiation with optical surfaces and transition zone surfaces being formed by means of sequential layer-by-layer removal of cornea areas. Treatment parameters are as follows. Wavelength is 193-222 nm large, impulse power is equal to 0.8-2.1 mJ, laser spot diameter is 0.5-1.5 mm large, pulse duration is equal to 5-8 ns, pulse succession frequency is 30-500 Hz. The first optical surface is shaped as convex ellipsoidal surface belonging to the whole optical zone. Irremovable central elliptic zone is traced when building the surface, elliptic zone symmetry center is superposed with the optical zone center. The greater central elliptic zone axis segment is united with the strong astigmatism axis, the lesser one is united with the weak astigmatism axis. The second optical surface is built as convex spherical surface. Its optical axis coincides with the optical zone center. Ratio between its diameter and optical zone diameter belongs to interval from 0.28 to 0.55. The first surface of the transition zone is built as a portion of convex external surface of the first ring-shaped toroid in a way that it has smooth interface of its external boundary to untreatable cornea portion. The first surface of the transition zone is 0.04-0.2 times as wide as the treatment zone diameter. The second surface of the transition zone of the same width is formed as a portion of the concave external surface of the second ring-shaped toroid. Internal boundary of the second transition zone surface has smooth interface to external boundary of the first optical surface, the external one being conjugated with the internal boundary of the first transition zone surface.

EFFECT: improved vision function in near and far zone; minimized removed eye tissues volume; reduced light halation.

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