Method for locating visual axis for laser assisted ophthalmic procedure without corneal marking

A method implemented in an ophthalmic laser system for locating a cornea apex of a patient's eye, comprising:

• (a) by a fixation light source of the ophthalmic laser system, generating a fixation light which exits the ophthalmic laser system along an optical axis of the ophthalmic laser system;
• (b) by one or more docking illumination light sources of the ophthalmic laser system, generating one or more respective docking illumination beams, each of the one or more docking illumination beams exiting the ophthalmic laser system in a direction which has a predefined spatial relationship with the optical axis of the ophthalmic laser system;
• (c) while a patient interface device is coupled to the ophthalmic laser system, the eye is positioned below the patient interface within a predefined distance range, the eye is looking through the patient interface device at the fixation light, and the one or more docking illumination beams are incident on the eye, obtaining a first image of the eye by a camera of the ophthalmic laser system;
• (d) after the patient interface is coupled to the eye, obtaining a second image of the eye by the camera;
• and
• by a controller of the ophthalmic laser system:
• (e) based on the first image, identifying positions of one or more light spots representing reflected light of the one or more docking illumination beams, and calculating a pre-docking cornea apex location based on the positions of the one or more light spots;
• (f) based on the first image, identifying a pupil of the eye and calculating a pre-docking pupil center location;
• (g) based on the second image, identifying a pupil of the eye and calculating a post-docking pupil center location;
• and
• (h) calculating a post-docking cornea apex location based on the pre-docking cornea apex location, the pre-docking pupil center location, and the post-docking pupil center location.

An ophthalmic laser system, comprising:

• a fixation light source configured to generate a fixation light which exits the ophthalmic laser system along an optical axis at a beam exit of the ophthalmic laser system;
• one or more docking illumination light sources configured to generate one or more docking illumination beams, each of the one or more docking illumination beams exiting the ophthalmic laser system in a direction which has a predefined spatial relationship with the optical axis of the ophthalmic laser system;
• a patient interface device coupled to the beam exit, having an optical window through which the fixation light and the one or more docking illumination beams pass;
• a camera configured to capture reflected light from an eye disposed below the patient interface device;
• a controller coupled to the camera, programmed to perform the following steps:
• (a) while the eye is positioned below the patient interface within a predefined distance range, the eye is looking through the patient interface device at the fixation light, and the one or more docking illumination beams are incident on the eye, controlling the camera to obtain a first image of the eye;
• (b) after the patient interface is coupled to the eye, controlling the camera to obtain a second image of the eye by the camera;
• (c) based on the first image, identifying positions of one or more light spots representing reflected light of the one or more docking illumination beams, and calculating a pre-docking cornea apex location based on the positions of the one or more light spots;
• (d) based on the first image, identifying a pupil of the eye and calculate a pre-docking pupil center location;
• (e) based on the second image, identifying a pupil of the eye and calculate a post-docking pupil center location;
• and
• (f) calculating a post-docking cornea apex location based on the pre-docking cornea apex location, the pre-docking pupil center location, and the post-docking pupil center location.