BACKGROUND

Before the advent of the wavefront aberrometer, many patients' visual symptoms were collectively referred to as a result of “irregular astigmatism”. Increasingly, more ophthalmologists and optometrists have begun measuring wavefront errors of patients' eye. A wealth of information is now available, that was not heretofore, from autorefractor or cornea topography measurements. Use of a wavefront map as a diagnosis tool is also gaining popularity, and vision care professionals use it to explain diagnoses to patients having visual complaints.

It is useful to understand the source of a problem. However, patients are most interested in solutions; such as getting rid of visual complaints, and improving their quality of vision. Currently, laser refractive surgery, such as LASIK, is one possible solution. However, laser surgery is invasive and the tissue healing process following surgery can induce its own set of aberrations, often rendering an attempt to correct the pre-operation errors fruitless. It has been proposed to correct high order aberrations (HOA) with non-invasive devices such as spectacles or contact lenses.

It was proposed in US application 2004/0160576A1, which is hereby incorporated by reference, to identify high order wavefront errors with a patient feedback control process. However, lacking in that disclosure is the basis for a patient to adjust each of the wavefront components. The '160576 application does disclose use of visual acuity as a measure to find an end point. As it was pointed out in the '160576 application, an acuity chart, or Snellen letter chart, is not an ideal target for wavefront optimization. More importantly, no method is presented regarding how a patient may choose which Zernike function to vary among the dozens of Zernike functions, without which the patient would have to go on a random walk, using by trial and error on all or substantially all of the Zernike functions. Without a clear step by step procedure, a patient may not even be able to find an optimal sphere, cylinder and axis, much less the high order Zemike components, wherein the effect of those aberrations on acuity is much smaller. The patient might get totally lost in the process, and it might take hours to come to any final optimized combination, if it ever got there at all.

RECOGNIZED BY THE INVENTOR

Improving quality of vision is more complicated than measuring the HOA and canceling them. Higher order aberrations are typically much smaller in amplitude compared to the defocus and astigmatism terms, and they vary from eye to eye. The question arises as to whether there would be visual benefits by correcting them in some patients. Also, the brain plays a key part in interpreting and in forming perceived images of what one sees. The optical image formed at the retina is only a starting point.

If one can measure the HOA; then one can cancel them optically. However, as it was pointed out, it is not clear whether if this cancellation results in improvement in one patient, then the same approach will work for a different patient.

In embodiments described herein, tools are provided for performing a subjective method for a patient. In a preferred embodiment, not just the sphere and cylinder and axis are handled, but the HOA errors are refracted as well. That is, using a technique in accordance with a preferred embodiment, a patient can actually see through a combination of wave plates that are adjustable in amplitude, and preferably also in angle. With this technique, a patient can actually see whether a wavefront correction, as presented to the patient, provides any benefits. A subjective technique in accordance with a preferred embodiment stands in contrast with objective techniques in which HOA errors of an eye are measured and a spectacle or contact lens is provided to cancel the HOA, and wherein the patient finds out only later if the device offers any benefits at all when he or she receives the corrective device.

In a preferred embodiment, an instrument is provided that comprises wave plates of Zernike functions, each of which is continuously adjustable in amplitude, and preferably also in angle. In addition, a continuously variable wave plate assembly is alternatively provided for utilizing a series of wave plates in small increment steps. These wave plates can be arranged on a disk, like a series of lenses in a phoropter, and the system can be made affordable for most eye care professionals.

SUMMARY OF THE INVENTION

A wavefront device that produces adjustable amplitudes in optical path differences and adjustable axis orientation angles is provided. Two substantially identical wave plates have a wavefront profile of at least the third order Zernike polynomial functions which are not circularly symmetric, as denoted by Z(i,j) where i≥3 and j≠0. The wave plates are mounted in rotatable mounts with their optical centers substantially aligned with each other.

The device may include a pinion gear engaging with bevel gears including at least one bevel gear attached to each of the rotatable mounts, wherein rotating the pinion gear may cause the wave plates to rotate in opposite direction at a substantially equal angular rate to cause a change in amplitude of the device. Electric motors with drive mechanisms may drive the wave plates at a same angular rate substantially in synchronization, while the wave plates move in equal amount and in opposite direction to change a wavefront amplitude. The wave plates are moved in a same direction to change an optic axis angle direction.

A method of generating a subjective optical prescription with a Zemike wave plate having an ability to substantially continuously adjust its amplitude and optic axis angle is also provided. Two substantially identical wave plates have a wavefront profile of a Zernike polynomial function. Optical centers of the wave plates are aligned. The wave plates are rotated in opposite direction in one or more substantially identical angular amounts until a patient indicates an optimal setting. The entire assembly is rotated including the two wave plates to an optic axis angle indicated as optimal by the patient. An optical prescription is generated based on initial positions and rotation amounts of the two wave plates. The rotating of the two wave plates may include rotating a pinion gear which engages with bevel gears that are mounted with the wave plates.

A method of determining second order and higher order aberrations of a patient's eye is also provided. Zemike functions are provided in a predetermined order in a priority list. At least one point source is provided as a viewing target. A first adjustable wave plate is selected according to the order in the priority list. The first adjustable wave plate is placed in a patient's line of sight. A refractive error of the patient is minimized by adjusting amplitude and angle of the first adjustable wave plate while the patient is looking at the viewing target. These are repeated for one or more further wave plates according to the order in the priority list, until no appreciable further improvement in image quality of the point source is observed by the patient.

The priority list may include Z(2,0), Z(2,+/−2), and Z(3, +/−1), in that order, and may further include Z(3+/−3) after Z(3, +/−1), and may further include Z(4,+/−2), Z(5.+/−1), Z(4,+/−4), Z(5,+/−3), Z(6,+/−2), Z(6,+/−4), Z(5,+/−5), in that order, after Z(3+/−3). The placing of the first adjustable wave plate may include positioning the first wave plate of the Zernike function at a conjugate corneal or pupil plane of the patient.

Refractive errors of third or higher order Zernike function aberrations may also be minimized. An input device is provided to the patient. An optic axis angle of an adjustable wave plate of third or higher order Zernike profile which is disposed at a conjugate corneal or pupil plane of the patient is varied while the patient is looking at the viewing target. An amplitude of the adjustable wave plate of third or higher order is varied also while the patient is looking at the viewing target. An indication is received from a patient that a predetermined end point has been reached by activation of the input device, The method may also include varying the angle of the wave plate of third or higher order, finding an optimal angle position, and then varying the amplitude of the adjustable wave plate. The predetermined end point may include a sharpest image of the point source target as indicated by the patient.

Contact or intraocular lenses may be provided and/or an ablation profile of refractive surgery may be determined such as for LASIK, PRK, LASEK, and/or intra-corneal surgery.

A method of correcting refractive errors of second and higher order aberrations of an eye is also provided. Second order aberrations are determined using adjustable Z(2,0) and Z(2,+/2) Zernike wave plates. Higher orders aberrations are corrected using Z(2,0) and higher Zernike terms, wherein Z(2,0) substantially corrects aberrations of all higher order Zernike terms that are spherically symmetric.

A further device for determining or correcting aberrations of an eye is also provided. The device includes at least one adjustable wave plate having adjustable amplitude and optic axis angle. A priority list of Zernike functions is provided such that adjustable wave plates may be selected in accordance with an order of Zernike functions in the list. A point source is provided as a viewing target. The one or more selected wave plates are placed at a conjugate corneal or spectacle plane of a patient's eye. A patient searches for predetermined image end points while looking at the point source while angle and amplitude of the selected wave plate are varied.

The priority list may include Z(2,0), Z(2,+/−2), and Z(3, +/−1), in that order, and may further include Z(3+/−3) after Z(3, +/−1), and may further include Z(4,+/−2), Z(5,+/−1), Z(4,+/−4), Z(5,+/−3), Z(6,+/−2), Z(6,+/−4), Z(5,+/−5), in that order, after Z(3+/−3). The placing of the first adjustable wave plate may include positioning the first wave plate of the Zernike function at a conjugate corneal or pupil plane of the patient.

The ordering of the priority list may be modified according to an aberration amplitude of the patient's eye in Zernike function as determined by a subjective wavefront aberrometer. The priority list may be modified by a condition of the patient's eye, including a keratoconus and/or a corneal transplant condition. The priority list may be modified by weighting factors with relative values affecting the ordering of the list as determined by the clinical experience of a physician.

The adjustable wave plate may include adjustable wave plates Z(2,0) and Z(2,+/−2), and/or another wavefront device such as liquid crystal wave plates or deformable mirrors. The other wavefront device may produce adjustable amplitudes in optical path differences and adjustable axis orientation angles, and include two substantially identical wave plates with wavefront profile of at least the third order Zernike polynomial function, which are not circularly symmetric, as denoted by Z(i,j) where i≥3 and j≠0. The wave plates may be mounted in rotatable mounts with their optical centers substantially aligned with each other.

The adjustable wave plate may include at least one substantially identical pair of wave plates having a Zernike function optical path difference profile, a deformable mirror and/or a liquid crystal wave plate.

An optical instrument is also provided for generating a prescription for one or more corrective lenses or corrective procedures for a patient by subjective refraction. The instrument includes a stable frame having a defocus corrector assembly (DCA) and an astigmatism corrector assembly coupled thereto. The DCA causing a change of defocus power at the patient's eye, and includes a first motor and at least two DCA lenses disposed along an optical axis between an image source and the patient's eye. At least one of the DCA lenses is movable relative to the frame along the optical axis for adjusting defocus power and/or is replaceable with one or more further lenses with incremental dioptric powers. The defocus power may be thereby measurably adjustable until the patient indicates that an initially blurry view of the image source has become substantially sharp. The ACA causes a change of astigmatism power, and includes a second motor and at least two astigmatism plates disposed along the optical axis that are relatively rotationally adjustable and/or wherein at least one of the ACA astigmatism plates is replaceable with one or more further cylindrical lenses. The astigmatism power is thereby measurably adjustable until the patient indicates that an initially elongate view of the image source has become substantially round.

The instrument may further include electrical and/or electronics hardware and/or computer programs for performing individually or collectively one or more of the following tasks:

(i) drive movement of one or more optical elements in the DCA or ACA, or both, to change defocus or astigmatism power, or both;

(ii) display a location of an optical element;

(iii) convert a location or orientation reading, or both, to a refractive power in units of diopters;

(iv) collect data relating to adjustments to the DCA and ACA;

(v) set limits of movement range for the DCA or ACA or both to avoid over-correction;

(vi) automatically advance DCA or ACA refractive power, or both, when such task is requested; or

(vii) automatic align the ACA optical axis when such task is requested, or combinations thereof.

The ACA may provide a variable astigmatism correction amplitude or variable axis angle, or both. The ACA may include a first wave plate having a second order Zernike polynomial of astigmatism wavefront correction profile in an x-y plane. A second wave plate may have a second order Zernike polynomial of astigmatism wavefront correction profile in the x-y plane. The first and the second wave plates may be mounted with their wavefront profile origins aligned along an axis (Z-axis). One or more of the wave plates may be angularly adjustable with respect to said Z-axis. The wavefront profile of the Zernike polynomial of astigmatism of the first and second wave plates may include Z(2,2) or Z(2,−2). Both of the wave plates may be angularly adjustable with respect to the Z-axis.

First and second ACA astigmatism plates may be mounted on first and second rotary ball bearings, and first and second bevel gears may be coupled to the first and second ball bearings. A first pinion gear may drive the first and second bevel gears for oppositely rotating the first and second ACA plates. A second motor may drive the first pinion gear. A rotary angle sensing device may be coupled to a rotary encoder. A second pinion gear may be mounted between the first and second bevel gears.

The ACA may be further for causing a change in orientation of axis angle. At least two astigmatism plates of said ACA may be rotatable together as a whole. The optical instrument may further include third and fourth ball bearings coupled to the first and second ball bearings, respectively, and to the frame. A third bevel gear may be coupled to at least one of the third and fourth ball bearings. A third motor may be for rotating the astigmatism plates of the ACA assembly together. A second rotary encoder may be coupled to a fourth pinion gear for sensing angular rotation of the ACA assembly.

The instrument may include an optics holder for each of the DCA lenses. A linear slide may be coupled to the optics holder of at least one of the DCA lenses. A motor and lead screw may move the linear slide.

A computer program product may include a processor and a computer program for calculating amplitudes of the ACA plates from relative and/or absolute angular movement and/or for calculating diopter power of the DCA. Readable results may be output. The computer program product may also form an ordered list of decreasing significance of Zemike functions based on RMS amplitude of a patient's measured wavefront errors. The computer program product may also control measurements according to the ordered list. Measurements for Zernike functions having a RMS amplitude less than 0.05 may be omitted. The ordered list may include second order Zernike function, Coma, Trefoil and secondary astigmatism.

The optical instrument may further include an input device for the patient or for an examination administrator or both. The image source may include a plane wave light source including substantially a point light source as a viewing target. A quality vision marker (QVM) may include one or more display items including one or more lines, one or more circles, one or more points disposed along a pattern of one or more lines or circles, or combinations thereof. The marker may provide a display pattern including one or more rings and/or parallel lines. A reference marker may provide a sweep line overlapping at the image source and having an orientation which is adjustable using the at least one input device until the patient indicates that the sweep line is aligned with a sharper linear image of the image source. Axis angle data of astigmatism errors of the patient's eye may be thereby provided.

The image source may include a plane wave point source placed two meters or farther away from the patient and having a diameter of two millimeters or less, or a substantially collimated light beam from a laser source that simulates a point source positioned two meters or farther away from the patient. An additional lens may be disposed to cause the image source to appear to the patient to be two meters or farther away. Spectral contents of the image source may include white light, substantially blue light, substantially yellow light, or substantially red light.

One or more spectacle, contact or intraocular lenses may have a prescription based on measurements by the optical instrument described herein.

A defocus power of the DCA and ACA may be adjusted within predetermined limits, including:

(i) searching for a residual line image of the point light source along the sweep line orientation;

(ii) reducing a diopter power of the DCA to attain a least minus power and at which a sharp line image is formed at the point source; and

(iii) increasing ACA diopter power to reduce the line image to a small and substantially round point image.

The defocus power of the DCA and ACA may be differently adjusted within predetermined limits, including:

(i) searching for a residual line image of the point light source perpendicular to the sweep line orientation;

(ii) reducing diopter power of the DCA to attain the least minus power and at which a sharp line image is formed at the point source; and

(iii) decreasing ACA diopter power to reduce the line image to a small and substantially round point image.

A display may be provided as a second viewing target centered approximately at the location of the point light source. The display may provide one or more viewing items including a sweep line. An orientation of the sweep line may be adjusted until the patient indicates that the sweep line has become substantially aligned with an orientation of the line image of the point source.

The optical assembly may include an astigmatism corrector assembly (ACA) including a pair of astigmatism wave plates, and the adjusting may include rotating an optical axis of the ACA to an orientation substantially perpendicular to the orientation of the sweep line. An amplitude of astigmatism correction may be increased by changing a subtended angle of the astigmatism wave plates until the line image of the point is reduced to a substantially round image.

One or more corrective lenses is/are also provided having a prescription generated by the subjective refraction method set forth above and/or below herein.

A further subjective refraction method is provided for generating a prescription for one or more corrective lenses. A collimated light beam is provided including substantially plane wave wavefronts. The plane wave wavefronts are projected into a patient's eye. An image of the wavefronts is formed at the patient's retina through an optical assembly in the light path including a defocus corrector assembly (DCA) or astigmatism corrector assembly (ACA), or both. The image initially includes refractive errors or optical aberrations, or both, of the patient's eye. While subjectively observing a shape of the image, the patient is instructed to search for and indicate at least one end point by adjusting the DCA or the ACA, or both. A prescription is determined for a corrective lens for the patient's eye based on known parameters of the optical assembly and on the adjusting of the DCA or the ACA, or both.

The at least one end point may include a line image which is observed by the patient to be at its sharpest or at its longest, or both.

A subjective refraction method for revising a prescription for one or more corrective lenses to correct higher order aberrations (HOA) of the eye of a patient is also provided. A point light source including substantially collimated plane wave wavefronts is provided at the patient's eye as a first viewing target. A low order prescription is input to a defocus corrector assembly (DCA) and an astigmatism corrector assembly (ACA) that are disposed along an optical path between the point light source and the eye of the patient, including setting an optical axis of the ACA to a cylindrical axis of the low order prescription. A brightness of the light source is adjusted to avoid eye saturation. The patient is instructed to observe one or more higher order aberration features around a point image of the plane wave. An angle of the optical axis or the power of the ACA or the power of the DCA, or combinations thereof, are adjusted to reduce the one or more higher order aberration features around the point source image.

The prescription is revised based on known parameters of the ACA or DCA or both and on the adjusting.

The size or the dimensions of the point source may be controlled or adjusted to provide high acuity vision of better than 20/15. A display may be provided as a second viewing target. The display may provide one or more rings centered approximately at the location of the point light source, or multiple circles, one line or multiple lines, a single point source, or multiple point sources arranged along one or more lines or circles, or combinations thereof. The diameter of at least one ring may be adjusted to provide a reference marker for the extent of the HOA. The brightness of one or more point sources or a size of one or more point sources, or both, may also be adjusted.

A subjective refraction apparatus is also provided for generating a prescription for one or more corrective lenses of a patient. A plane wave light source includes substantially a point light source as a viewing target. At least one input device is provided for the patient or for an examination administrator or both. An optical system is disposed along an optical axis between the point light source and the patient's eye which initially forms a blurry image of the point light source at the patient's eye. The optical system includes a defocus corrector assembly (DCA) including a fixed lens and a lens that is movable along the optical axis using the at least one input device for adjusting defocus power until the patient indicates that the blurry image has become a relatively sharp line image. An astigmatism corrector assembly (ACA) includes a pair of astigmatism wave plates that are relatively adjustable along its z-axis (perpendicular to the wave plate surface). One may use the at least one input device for adjusting the DCA or the ACA, or both, for astigmatism power or axis angle, or both, until the patient indicates that the line image has become a substantially round image.

A reference marker provides a sweep line overlapping at the point source and having an orientation which is adjustable using the at least one input device until the patient indicates that the sweep line is aligned with the sharp line image of the point source, thereby providing axis angle data of astigmatism errors of the patient's eye.

The plane wave light source may include a point source placed two meters or farther away from the patient and may have a diameter of two millimeters or less. The plane wave light source may include a substantially collimated light beam from a laser source that simulates a point source positioned two meters or farther away from the patient. A lens may cause an image of the point source to appear to the patient to be two meters or farther away.

Spectral contents of the light source may include white light, substantially blue light, substantially yellow light, or substantially red light.

The marker may provide a display pattern including one or more rings or parallel lines, a circle or multiple circles, one line or multiple lines, a single point source or multiple point sources arranged along one or more lines or circles, or combinations thereof.

Electrical or electronics hardware or computer programs, or combinations thereof, may be provided that perform individually or collectively one or more of the following tasks:

(i) drive movement of one or more optical elements in the DCA or ACA, or both, to change defocus or astigmatism power, or both;

(ii) display a location of an optical element;

(iii) convert a location or orientation reading, or both, to a refractive power in units of diopters;

(iv) collect data relating to adjustments to the DCA and ACA;

(v) set limits of movement range for the DCA or ACA or both to avoid over-correction;

(vi) automatically advance DCA or ACA refractive power, or both, when such task is requested; or

(vii) automatic align the ACA optical axis when such task is requested, or combinations thereof.

