Method for determining the azimuthal orientation of a patient eye and eye surgical apparatus therefor

A method for determining the azimuthal orientation of a patient eye with respect to a reference fixed with respect to the patient eye, using an eye surgery apparatus which includes:

• imaging optics for generating observation images of a patient eye;
• and,
• a device for determining the azimuthal orientation of the patient eye with respect to a reference fixed with respect to the patient eye;
• said device including:
• a visual display unit configured to simultaneously display:
• a section, composed of pixels, of a captured observation image of the patient eye captured by said imaging optics and said section containing at least one segment of the sclera;
• and, a reference image, composed of pixels, of the patient eye and containing said segment of the sclera;
• an input interface for permitting an observer to effect a movement of the displayed section of the captured observation image of the patient eye relative to the displayed section of the reference image whereby an azimuthal orientation of said captured observation image relative to said reference image changes during said movement;
• a measuring system for determining the change of azimuthal orientation of the captured observation image relative to said reference image because of said movement;
• a computer unit having a computer program for computing the center of a first circular structure of the limbus and/or of the iris of said captured observation image and for computing the center of a second circular structure of the limbus and/or of the iris of said reference image;
• and,
• said visual display unit being further configured to display said pixels of said captured observation image with polar coordinates having a center coincident with the computed center of said first circular structure and to display said pixels of said reference image with polar coordinates in a polar coordinate system having a center coincident with the computed center of said second circular structure;
• the method comprising the steps of:
• comparing at least one section of the captured observation image of the patient eye, which comprises a segment of the limbus and/or of the iris to a section of a reference image of the patient eye containing said segment;
• inferring the azimuthal orientation of the patient eye relative to the azimuthal orientation of the patient eye, on which the reference image is based, from the azimuthal offset (Δφ) of characteristic, mutually corresponding structures of the captured observation image of the patient eye and of the reference image in the region of the limbus;
• displaying said at least one section of the captured observation image of the patient eye and the section of the reference image of the patient eye to an observer in such a manner that they can be moved relative to one another;
• determining the change in an azimuthal orientation (Δφ) of the observation image relative to the reference image when the section of the captured observation image is moved relative to the section of the reference image;
• computing the center of the limbus and/or of the iris of the captured observation image and of the reference image;
• and,
• displaying the section of the image of the patient eye and the section of the reference image in polar coordinates in a polar coordinate system having a center corresponding to the computed center of the limbus and/or of the iris in the captured observation image and in the reference image.