Tilt compensation, measurement, and associated adjustment of refractive prescriptions during surgical and other treatments of the eye
Embodiments of the present invention provide methods and systems for determining an ablation treatment for an eye of a patient. The systems and method may involve determining an ellipsoid shape corresponding to an anterior corneal surface of the patient's eye. The ellipsoid shape may include an anterior portion, a major axis, and an apex, where the major axis intersects the anterior portion at the apex. The systems and method may also involve determining a tilted orientation of the eye, such as when the patient fixates on a target during a laser ablation procedure. The systems and method may further involve determining the ablation treatment based on the ellipsoid shape and/or the tilted orientation.
1. A method for determining an ablation treatment for an eye of a patient, comprising:
determining an ellipsoid model corresponding to an anterior corneal surface of the eye, the ellipsoid model having an anterior portion, a major axis, and an apex, wherein the major axis intersects the anterior portion at the apex;
calculating a nominal ablation pattern for the eye based on the ellipsoid model;
determining a tilted orientation of the eye when the patient fixates on a target during a laser ablation procedure, wherein determining the tilted orientation comprises:
determining a surface slope of the anterior corneal surface in a first direction extending radially from the apex;
determining a surface slope of the anterior corneal surface in a second direction extending radially from the apex, wherein the surface slope in the first direction is steeper than the surface slope in the second direction;
determining the ablation treatment by adjusting the nominal ablation pattern based on the surface slope in the first direction and the surface slope in the second direction; and
outputting the determined ablation treatment so as to be suitable for use by a laser eye surgery system.
2. The method of claim 1 , wherein the nominal ablation pattern is based on a surface slope of a non-tilted ellipsoid model.
3. The method of claim 1 , wherein determining the nominal ablation pattern comprises calculating a cosine adjustment measure based on a non-tilted ellipsoid model; and wherein determining the ablation pattern comprises adjusting the cosine adjustment measure based on an adjusted surface slope corresponding to the tilted orientation.
4. The method of claim 1 , wherein:
calculating the nominal ablation pattern comprises applying a cosine adjustment measure to a wavefront guided treatment plan; and
adjusting the nominal ablation pattern comprises adjusting the cosine adjustment measure based on the tilted orientation.
5. The method of claim 1 , further comprising:
determining a misalignment between an axis of a laser beam and a vertex of the ellipsoid model, the vertex corresponding to a foremost point of the anterior corneal surface; and
adjusting the ablation pattern based on the misalignment.
6. A method for determining a treatment plan for an eye of a patient, comprising:
determining an ellipsoid model corresponding to an anterior corneal surface of the eye, the ellipsoid model having an anterior portion, a major axis, and an apex, wherein the major axis intersects the anterior portion at the apex;
calculating a nominal treatment pattern for the eye based on the ellipsoid model;
determining a tilted orientation of the eye when the patient fixates on a target during a laser treatment procedure, wherein determining the tilted orientation comprises:
determining a surface slope of the anterior corneal surface in a first direction extending radially from the apex;
determining a surface slope of the anterior corneal surface in a second direction extending radially from the apex, wherein the surface slope in the first direction is steeper than the surface slope in the second direction;
determining the treatment plan by adjusting the nominal treatment pattern based on the surface slope in the first direction and the surface slope in the second direction;
outputting the determined treatment plan to a laser eye surgery system; and
generating a laser beam with the laser eye surgery system for altering a refraction of the eye per the determined treatment plan.
7. The method of claim 6 , wherein the nominal treatment pattern is based on a surface slope of a non-tilted ellipsoid model.
8. The method of claim 6 , wherein determining the nominal treatment pattern comprises calculating a cosine adjustment measure based on a non-tilted ellipsoid model; and wherein determining the treatment plan comprises adjusting the cosine adjustment measure based on an adjusted surface slope corresponding to the tilted orientation.
9. The method of claim 6 , wherein:
calculating the nominal treatment pattern comprises applying a cosine adjustment measure to a wavefront guided treatment plan; and
adjusting the nominal treatment pattern comprises adjusting the cosine adjustment measure based on the tilted orientation.
10. The method of claim 6 , further comprising:
determining a misalignment between an axis of a laser beam and a vertex of the ellipsoid model, the vertex corresponding to a foremost point of the anterior corneal surface; and
adjusting the treatment plan based on the misalignment.