Corneal surgery apparatus

A corneal surgery apparatus which ablates corneal tissue with a laser beam, the apparatus comprising:

• a patient positioning unit on which a patient is placed on his back so that his eye faces upward;
• an irradiation unit including a light directing optical system for directing the laser beam to an intended range of a cornea of the patient's upward-facing eye, wherein the laser beam has a wavelength in a far ultra-violet region and an intensity capable of causing ablation to the irradiated corneal tissue;
• a corneal shape measurement unit which measures a three-dimensional shape of the upward-facing cornea, the corneal shape measurement unit including:
• a measurement light projecting optical system, including a first pinhole plate, for projecting a measurement light onto the upward-facing cornea, wherein a convergent point of the projected measurement light is shifted from an anterior surface of the cornea to a posterior surface of the cornea by moving a focusing lens along a central optical axis of the measurement light projecting optical system;
• wherein the central optical axis of the measurement light projecting optical system is made to be coaxial with a central optical axis of the light directing optical system midway on an optical path;
• a measurement light receiving optical system, including a second pinhole plate placed at a position conjugate with the first pinhole plate with respect to the cornea and a photo-detector for receiving reflected measurement light from the upward-facing cornea having passed through the second pinhole plate;
• wherein a central optical axis of the measurement light receiving optical system is divided from the central optical axis of the light directing optical system midway on an optical path;
• a scanning unit which scans a projection spot of the measurement light on the upward-facing cornea in XY directions;
• and
• an arithmetic unit which performs arithmetic to obtain the three-dimensional shapes of the anterior and posterior surfaces of the upward-facing cornea based on a position of the projection spot in the XY directions, a result detected by the photo-detector and a position to which the focusing lens is moved, and to obtain a thickness of the upward-facing cornea based on the obtained three-dimensional shapes of the anterior and posterior surfaces of the cornea;
• and
• arithmetic means for performing arithmetic to obtain an ablation amount at each position of the cornea based on the three-dimensional shape of the anterior surface of the upward-facing cornea and the thickness of the upward-facing cornea obtained by the corneal shape measurement unit.