In situ astigmatism axis alignment

A method for enabling in situ determination of an astigmatic axis of an eye of a patient, the eye having an anterior corneal surface with a portion thereof located adjacent an intended plane of ablation of a laser surgery system having laser beam delivery optical elements for directing a laser beam along a beam path to the plane of ablation, the plane of ablation being substantially normal to the laser beam path, said method comprising the steps of:

• (a) presenting a target image viewable by the eye of said patient in an operative position at the plane of ablation of the laser surgery system, said step of providing including the steps of irradiating a target having an image pattern and collimating the target image;
• (b) translating said target image along a path until the image reaches a position corresponding to a desired sphere correction value;
• (c) rotating said image about an axis of rotation having an angular reference position while viewing the image until the patient's perspective of the image achieves a desired endpoint;
• and
• (d) determining the angular axial position of the image with reference to said angular reference position.

A method for enabling in situ determination of an astigmatic axis of a patient's eye, the eye having an anterior corneal surface with a portion thereof located adjacent an intended plane of ablation of a laser surgery system having laser beam delivery optical elements for directing a laser beam along a beam path to the plane of ablation, the plane of ablation being substantially normal to the laser beam path, said method comprising the steps of:

• (a) arranging the patient in a preoperative position with the patient's eye at the plane of ablation of the laser surgery system;
• (b) presenting an image corresponding to a desired sphere correction value for the eye to a position viewable by the patient by irradiating an image element having an image pattern and collimating the resulting image;
• (c) rotating the image element about an axis of rotation having an angular reference position while the patient views the image until the patient's perception of the image achieves a desired end point;
• and
• (d) determining the angular axial position of the image element with reference to said angular reference position.