Abstract: Apparatus and techniques for performing prolate shaped corneal reshaping. In accordance with the techniques, an ablation scanning laser system includes fitter modules to fit input refractive or topographical measurement data to a three (3) variable ellipsoid model. This provides pre- and post-operative approximations of a cornea. A desired prolate shaped ablation profile is determined based on a desired prolate ellipsoidal shape. In accordance with the principles of the present invention, the spheroequivalent ellipsoid model has only three degrees of freedom (not four as in a conventional biconic technique) to define a desired ablation profile, providing extremely accurate and predictable long term vision correction. To arrive at an ellipsoid model having only three numbers of freedom, a spheroequivalent (SEQ) value of asphericity QSEQ is generated. The spheroequivalent eccentricity QSEQ value replaces two degrees of freedom (i.e.

Abstract: A method and apparatus to detect a center of a visual axis (or any spot on the pupil) that can adapt to a varying pupil size. Due to the dynamic nature of the human pupil that changes location registration with the visual axis with changes in the pupil size, the following method is provided as a means to remove positional errors induced by this cause. The visual axis correction is provided by means of a functional estimation using linear, polynomial, parametric or piece-wise functional estimation. Methods for determining this estimator and the typical uses of the estimator are provided in the invention specification.

Abstract: Methods are provided for material sculpting with a device which functions similar to a laser on human cornea or plastic that reduces surface roughness and computational overhead. These methods are based upon teachings of volumetric ablation based upon layer slices of the volume. The first method demonstrates how to apply the slice based sculpting to a regularly spaced sampling grid using stochastic perturbing from the grid points. The second method demonstrates how to apply a directly volumetric sculpting approach where a discrete estimate of the average beam size and shape is made and applied directly to the volume to ablate until all of the required volume is removed.

Abstract: A method is provided of reconstructing the height data from the radial distance data gathered by a corneal measurement device such as a corneal topographer or videokeratometer. The present invention performs the height reconstruction using an algorithm that is more accurate than the prior art. The prior art uses the circle arc-step or midpoint height reconstruction algorithms, while the present invention teaches the ellipse arc-step height reconstruction. This is important because it is now known that the eye surface is better modeled with an ellipsoid approximation than a spherical approximation.

Abstract: A method is provided to correct visual axis offset errors. Such errors in the visual axis offset are large if they significantly affect the patient's vision. The visual axis offset is the difference between the visual axis and the reference axis, commonly the pupillary axis. Although correcting the visual axis offset error may be most often performed by refractive surgery, the visual axis offset error may also be corrected in spectacles or contacts lenses. A benefit of correcting large visual axis offset errors secondary to patient vision is aesthetic appeal. Significant visual axis correction may require patient training. Although this may not compensate entirely for amblyopic vision, it may alleviate part of the dysfunction. Another benefit of correcting larger visual axis errors is providing the patient with a larger area of better vision within the aperture.

Abstract: The optimal optical zone for a patient is determined based upon the Stiles-Crawford effect and patient-specific scotopic pupil parameters. This invention is especially useful in refractive surgery where the chosen optical zone is crucial and affects both the depth and volume of the ablation. This optimal optical zone may be used in the creation of corrective lenses and other ocular surgery in addition to refractive surgery. Provided with the optimal optical zone, a refractive surgeon may better choose the surgical parameters for the treatment. Current methods consist of choosing a default value for all patients or only choosing the scotopic pupil diameter or contour, either of which may not be optimal and may lead to a deeper or bigger treatment.

Abstract: A method is provided of removing less corneal tissue during refractive surgery, when a visual axis or optical axis of an eye is not aligned with a pupil center. The method determines an initial keratometry surface around the visual axis. A visual system error is determined and the visual system error is applied to the initial keratometry surface to determine a target keratometry surface. The initial and target keratometry surfaces are offset by an amount substantially equal to an offset of the visual axis from the pupil center. The target keratometry surface is subtracted from the initial keratometry surface to establish values along a chosen corneal treatment zone diameter. All the values along the chosen corneal treatment zone diameter and within it are set to be positive, thereby defining a resulting ablation profile. The resulting ablation profile is used as a guide for corneal tissue to remove, with greater positive values defining deeper ablation depths.