WO2006085889A1

WO2006085889A1 - Method for using a wavefront aberrometer

Info

Publication number: WO2006085889A1
Application number: PCT/US2005/010672
Authority: WO
Inventors: Kevin L. Waltz, M.D.
Original assignee: Kevin L Waltz M D
Priority date: 2005-02-10
Filing date: 2005-03-30
Publication date: 2006-08-17
Also published as: EP1845836A4; EP1845836A1

Abstract

A method of using a wavefront aberrometer to orient an artificial lens having a major axis of symmetry for implantation into an eye, including activating a wavefront aberrometer and generating a map of the aberration patterns of an eye. Next, a major axis of symmetry of the aberration pattern of the eye is identified. The major axis of symmetry of the artificial lens is likewise identified and the two major axes of symmetry are aligned. The artificial lens is then implanted into the eye with the axes of symmetry still aligned.

Description

METHOD FOR USING A WAVEFRONT ABERROMETER

TECHNICAL FIELD OF THE INVENTION

This invention relates to optics, and, more particularly, to a method for using a wavefront aberrometer to assist in determining the proper orientation of a surgically implantable artificial lens or other surgical treatment for presbyopia.

BACKGROUND OF THE INVENTION

The human eye is one of the marvels of evolution. As illustrated in FIG. 1 , light 1 enters the eye 2 through the cornea 3 and pupil 4. The pupil 4 is an aperture of variable size formed through the iris 5. Light travels through the pupil 4 through the lens 6 (sometimes referred to as the crystalline lens 6), where it is redirected and is focused on the back wall or retina 7. The pattern of light falling on the retina 7 forms an image that is detected by detectors distributed over the retina 7. The detectors transducer the light energy impinging upon them to nerve impulses that are transmitted to the brain via the optic nerve 8, where the impulses are interpreted as sight.

The eye 2 is generally spherical in shape and has an average diameter of generally about 24 milimeters. The eye ball 2 is defined by the cornea 3 and sclera 9 (an outer cover membrane), the choroid 10 (an interior region containing the network of blood vessels servicing the eye 2) and the retina 7. The cornea 3 is tough transparent tissue that covers the front portion of the eye 2. The sclera 9 is an opaque membrane that connects to the cornea 3 and encloses the remainder of the eye 2. The choroid 10 includes a ciliary body 1 1 and the an iris diaphragm 5. The pupil 4 of the iris diaphragm 5 contracts and expands to control the size of the pupil 4 and thus the amount of light 1 that may enter the eye 2.

The lens 6 is made up of concentric layers of transparent fibrous cells and is suspended by fibers or zonules 12 that attach to the ciliary body 1 1. As illustrated in FIGs. 2A and 2B, the lens 6 operates to focus light 1 travelling therethrough by changing its shape. More specifically, when the ciliary muscle 1 1 connected to the fibers 12 relaxes, the changes in the ciliary processes 1 1 cause changes in the curvature of the lens 6 (such as flattening or becoming less convex and thus enabling the lens 6 to focus light 1 from objects at a remote distance [see FIG. 2A] or contracting or becoming more convex to enable the eye 2 to refocus on an object at a closer distance [see FIG. 2B]). This adjustment in the shape of the lens 6 to focus at various distances is referred to as "accommodation" or the "accommodative process" and is associated with a concurrent change in dimension of the pupil 4. Accommodation is also associated with changes in corneal curvature, constriction of the pupil, an increase in higher order aberrations, and convergence or medial rotations of the two eyes 2.

The innermost membrane of the eye is the retina 7, which lies on the inside of the entire back wall portion of the eye 2. When the eye 2 is properly focused, light 1 from an object outside the eye 2 that is incident on the cornea 3 is imaged onto the retina 7. Vision is enabled by the distribution of receptors over the retina 7. The main receptors are rod cells (or rods) that take part in black and white imaging and cone cells (or cones) that take part in color vision. The cones tend to be centralized in the middle portion of the retina 7, called the fovea 13 (or macula). The cones are highly sensitive to color and thus allow the brain to experience color vision. The rods are more evenly distributed over a much larger area and provide the brain with a more general image of the field of view. In an optical context, an aberration is any perceived or real imperfection in the formation of a visual image. Aberrations may be regular and measurable, such as spherical aberration, chromatic aberration, and coma. Alternately, aberrations may be irregular, as might be noticed when looking through a pane of handblown glass. Instruments that measure aberrations of the visual system are called 'wavefront analyzers' or aberrometers.

Coma is a lens aberration that results from different magnifications happening in different portions of the lens. Light rays 1 traveling through the center of a lens 6 can be focused to a point. If light rays 1 go through the lens 6 off-axis (at an angle), the light rays 1 will not focus to a point and the image thus appears as a fuzzy circle. The farther off-axis the path of the light rays 1, the larger the fuzzy circle, yielding imaged objects having comet-like appearances (hence the term "coma"). Coma is typically observed in the outer portions of an image field that is some distance from the principal axis of the eye 2.

Astigmatism is a vision defect arising from the radius of curvature of the optics of the eye 2, especially the cornea 3, being unequal at different orientations around the visual axis. Lines or bars at different orientations are not all simultaneously in focus, and thus there may be distortions for some orientations.

Myopia, or near-sightedness, is a defocus aberration wherein vision is better close-up than at a distance, and is corrected by concave lenses. Hyperopia, or far-sightedness, is the opposite condition wherein objects at a distance more easily resolved than closer objects. Hyperopia is corrected by convex lenses. Presbyopia is a condition characterized by a loss of flexibility in the natural lens 6. When young, the natural lens 6 is quite flexible and easily accommodates for close focus. As it ages, the lens 6 accumulates layers of protein acumulate on its outer surface (akin to the growth rings in a tree trunk). The lens 6 thus becomes thicker, denser, and less flexible and, as a result, close focusing becomes difficult. Optical aberrations such as myopia, hyperopia and astigmatism, as well has many other higher order aberrations, blur images formed on the retina and thus impair vision. Higher order aberrations include subtle, regular and measureable imperfections in the lens that are not corrected with simple sphero-cylindrical lenses. An astronomer and mathematician in the early 20th Century named Fritz Zernike developed a series of polynomial equations to describe low-order and higher-order aberrations in lathe-cut lenses. These equations, dubbed Zernike polynomials, form the basis for analysis and decription of aberration patterns in many current systems designed for wavefront analysis of the human eye 2.

Cataracts occur when the eye's lens 6 becomes cloudy or opaque. Eventually, the lens 6 will become so opacified that vision becomes significantly impaired. When this occurs, the natural lens 6 may be removed via cataract surgery. Typically, the natural lens 6 is replaced via intraocular lens implantation (IOL) surgery, wherein an artificial lens 20 is implanted in the eye 2. (See FIG. 3). Generally, artificial lenses 20 have been assumed to be stationary and hard, and thus unable to adjust to focus or accommodate.

However, as illustrated in FIG. 4, new accommodating artificial lenses 30 have been developed that allow the eye 2 to focus, and thus enable a patient having an implanted lens 30 to enjoy both near and far focus. These lens systems 30 are elongated in design, with a pair of connectors or haptics 32 oriented linearly (i.e., with one-hundred and eighty degree separation) about an artificial optical lens member 34. The artificial lens system 30 further includes at least one hinge or flexure point 36 formed in a haptic 32 to accommodate such changes in focus. As shown in FIGs. 5A-5B, 6A-6B, and 7A-7C, when the lens system 30 is implanted in the eye 2 the hinge(es) 36 are connected between the some of the zonules 12 and the lens member 34, and thus enable the lens member 34 to move within the eye 2 in response to changes in tension of the zonules 12 to thus change the focus of the eye 2. One drawback of the artificial accommodating lens 30 arises from its partial asymmetry. The lens system 30 is characterized by 180-degree rotational symmetry about an axis of rotation passing through the lens member 34 and oriented perpendicular to an axis or line 38 passing through the lens member 34 and the haptics 32. This line 38 may be thought of as a major axis of symmetry of the lens system 30. Thus, how well the lens 30 functions to allow accommodation is at least partially a function of its orientation relative in the eye 2. More particularly, the ability of the lens system 30 to allow focus is at least partially a function of the strength, resilience and integrity of the zonules 12 to which it is attached and the ciliary muscles to which the zonules 12 are attached. If those zonules 12 and muscles are weak and loose, they may not be able to actuate flexure/movement of the artificial lens system 30 to change the focus of the eye 2. Further, the lens system 30 may experience some degree of lateral movement and/or change in surface curvature of the IOL in the eye 2. The degree of controlled (or uncontrolled) effective changes in the curvature of the lens system 30 and/or lateral movement of the lens system 30 may be a function of the strength and/or resilience of the muscles 1 1 and zonules 12 to which the lens system 30 connects. Currently, there is no set protocol regarding the orientation at which the lens systems 30 are implanted.

Thus, there is a great need in the art for an improved method of orienting the lens system 30 for implantation into the eye. The present invention addresses this need.

SUMMARY OF THE INVENTION

The present invention relates to method and apparatus for determining the proper orientation for implantation of an accommodating lens system in the eye. One object of the present invention is to provide an improved method of orienting a lens system for surgical implantation in an eye. Related objects and advantages of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view of the human eye.

FIG. 2A is an enlarged sectional view of the human eye with the lens capsule stretched.

FIG. 2B is an enlarged sectional view of the human eye with the lens capsule relaxed.

FIG. 3 is an enlarged plan view of an artificial implantable lens known in the prior art.

FIG. 4 is an enlarged plan view of an artificial implantable accommodating lens known in the prior art and having hinged haptics.

FIG. 5A is a schematic diagram of the prior art lens system of FIG. 4 with the haptics oriented at a first angle relative the lens to provide a relatively long haptic arm length.

FIG. 5B is a schematic diagram of the prior art lens system of FIG. 4 with the haptics oriented at a second angle relative the lens to provide a relatively short haptic arm length.

FIG. 6A is an enlarged sectional perspective view of the prior art lens of FIG. 4 as implanted in an eye and occupying a first, relaxed position.

FIG. 6B is an enlarged sectional perspective view of the prior art lens of FIG. 4 as implanted in an eye and occupying a second, vaulted position.

FIG. 7A is a sectional side elevation view of the prior art lens of FIG. 4 as implanted in an eye and occupying an unflexed orientation to accommodate intermediate vision.

FIG. 7B is a sectional side elevation view of the prior art lens of FIG. 4 as implanted in an eye and occupying an anteriorially flexed orientation to accommodate intermediate near vision.

FIG. 7C is a sectional side elevation view of the prior art lens of FIG. 4 as implanted in an eye and occupying a posteriorally flexed orientation to accommodate distance vision. FIG. 8 A is a graphical representation of the wavefront comparison display showing the orientation of lens aberrations for a first eye of a relatively young patient not requiring corrective lenses.

FIG. 8B is a graphical representation of the wavefront comparison display showing the orientation of lens aberrations for a second eye of the relatively young patient not requiring corrective lenses.

FIG. 9A is a graphical representation of the wavefront comparison display showing the orientation of lens aberrations for a first eye of a relatively old patient requiring corrective lenses of moderate strength.

FIG. 9B is a graphical representation of the wavefront comparison display showing the orientation of lens aberrations for a second eye of the relatively old patient requiring corrective lenses of moderate strength.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the principles of the invention and presenting its currently understood best mode of operation, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, with such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

FIGs. 8A-9B relate to a first embodiment of the present invention, a method for determining the orientation of an artificial accommodating lens 30 necessary to substantially optimize the ability of the patient to focus on both near and far objects after surgery. The recipient of an artificial accommodating lens 30 is expected to have more ability to change the focus of the post-surgery eye 2 because the lens 30 has the ability to move within the eye, thus enabling a change of focus. The lens 30 may move by vaulting toward the front or the back of the eye 2 (anterior and posterior vaulting), by laterally moving from side to side along its axis 38 as it is pulled to and fro by the cilial muscles 1 1 and zonules 12 to which it is connected, by modifying the anterior or posterior curvature of the crystalline lens or artificial lens or by any combination of the mechanisms. Vaulting movement moves the entire lens forward or backward to change focal length, while lateral movement changes the lens thickness through which the light 1 travels. Anterior or posterior lens curvature changes may be symmetrical or asymmetrical about the visual axis. Either mechanism (or all) operate to change the focus of the eye 2, and all mechanisms are initiated by contractions and expansions of the cilial muscles 1 1 and zonules 12.

A wave front aberrometer may be used to map the pattern of aberrations 38 in the eye 2 while the eye 2 is focused on a target or targets positioned at different distances. By obtaining and comparing aberration patterns 38 for the eye 2 at two substantially different focuses, the contribution of surface aberrations may be subtracted to isolate the aberration contributions from the lens 6, which are graphed as a calculated differential aberration pattern 40. These differential aberattion patterns 40 may be plotted to reveal the orientations, if any, of the aberration of the lens 6. Referring to FIGs. 8A and 8B, differential aberration plots 40 were generated for the eyes of a relatively young, optically healthy patient not in need of any corrective lenses. The differential plots reveal only minor lens aberrations uncharacterized by any major axes of orientation or directional components.

In contrast, FIGs. 9A and 9B, differential aberration plots 40 taken of the eyes of an older patient requiring corrective lenses of moderate strength for myopia, reveal lens aberrations with significant directionality as illustrated by axes of symmetry 42. Aberration axes 42 may be generated from the differential aberration plots 40, and such axes 42 may be used to determine the best orientation for the placement of an artificial accommodating lens 30. In other words, the aberration axes 42 are indicative of the direction across the lens 6 wherein the eye 2 is able to generate the greatest force to achieve the largest amount of accommodation. This directionality is a result of nonuniform lens thickening and/or stiffening, local weakening of the zonules 12 and/or the cilial muscles 1 1 at certain positions around the iris, or a combination of the two. It should be noted that, although the examples of FIGs. 9A and 9B include two relatively orthogonal axes 42, the axes 42 do not necessarily have to be orthogonal to one another and may lie at other angular relationships. Likewise, there may be other numbers of axes 42 besides two, such as a single axis of symmetry 42 or three or more distinct axes 42. However, it is usually easy for one of ordinary skill in the art to distinguish the most major axis of symmetry 42 from the aberration plot 40, as the major axis 42 is generally significantly more pronounced that the other axes 42, if there are other axes 42 at all. In operation, a wavefront aberrometer is used to determining the optimum orientation for the implantation of an artificial accommodating lens 30 by first generating a first aberration map 38 of an eye 2 as focused on an object located substantially at infinity and generating a second aberration map 38 for the same eye 2 as focused on an object located relatively nearby. The first and second maps 38 are compared to mathematically subtract the aberration contributions from the surface of the eye to yield an aberration map 40 of the lens 6. The aberration map 40 of the lens 6 is analyzed to determine if any axes of symmetry of aberrations of the lens 6 exist and, if so, to identify the major axis of symmetry 42 of the aberrations of the lens 6; such an axis 42 is indicative of the orientation of the major aberrations of the lens 6 and is typically the most pronounced axis 42 visible. The axis of symmetry of the artificial lens 30 is then identified and the axis of the lens 30 is aligning relative the aberration axis of symmetry 42 to provide optimal lens 30 function. The lens 30 is then implanted into the eye 2 at this orientation.

The artificial accommodating lens 30, as discussed above, generally includes a circular lens disc and at least one generally linear elongated haptic member extending therefrom; more typically, the artificial accommodating lens 30 includes a generally circular lens disc and a pair of oppositely disposed generally linear elongated haptic members extending therefrom to define its axis.

In other words, an optimized orientation for an implantable artificial lens 30 is determined by conducting wavefront aberration analysis of an eye 2 to generate a refraction map 38 of the aberrations of the eye 2, isolating the aberration contributions from the lens 6 of the eye 2, and determining if a major axis of symmetry 42 of the aberration of the lens 6 of the eye 2 is present. If a major axis of symmetry 42 of the aberration of the lens 6 of the eye 2 is present, the haptics of the artificial accommodating lens 30 are oriented relative the major axis of symmetry 42. If a major axis of symmetry 42 of the aberration of the lens 6 of the eye 2 is not present, the haptics of the artificial accommodating lens 30 are oriented at will. The so oriented artificial accommodating lens 30 is then implanted into the eye 2.

It should be noted that although the above example relates to measurement of the aberrations of the natural lens 6, the same techniques may be used for patients already having an implanted artificial lens system 30. For example, the near vision of a patient having an implanted artificial lens system 30 may be measured and evaluated to determine if the lens system 30 is not functioning correctly (i.e., if the lens system 30 is not focusing as it should) and a modified surgical plan may then be developed to address and correct the situation.

It should also be noted that although the above discussion includes specific examples of lenticular treatments for accommodation problems, the above-related technique of identifying the unique aberrations of an individual eye by measuring the near and/or distance wavefront and using them to create a unique surgical plan for that eye are equally applicable for use with other presbyopia treatments, such as corneal surgery , scleral surgery, and the like.

Likewise, the above techniques may be used to estimate the lost accommodation patterns for an adult based on those of a genetic relative, such as a child, who still retains some or all of his original accommodation. This technique for estimating the original and now lost or partially lost (or extinguished) accommodation pattern for the older patient is based on the assumption that close genetic relatives have a high likelihood of having similar accommodation patterns; thus, measurement of the accommodation patterns of one or more close genetic relatives may yield pattern information that will allow the generation of an estimated accommodation pattern for the older patient that approximates the original accommodation pattern enjoyed in youth and thus allow the physician to select the best lens type (accommodative, pseudoaccommodative [monofocal or multifocal]) to best restore some or all of the patient's original accommodative pattern. This process could also be used to determine the orientation of the specific IOL used to restore the accommodation.

Further, it is theorized that the brain response plays an important role in interpreting the accommodative pattern of the eye. The above technique may be used in conjunction with brain analysis techniques, such as PET scans, MRI scans, ECG's and the like, to indicate first if the patient is capable of making an accommodative lens function properly and, if so, which type of accommodative lens is likely to work best for that patient.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. It is understood that the embodiments have been shown and described in the foregoing specification in satisfaction of the best mode and enablement requirements. It is understood that one of ordinary skill in the art could readily make a nigh-infinite number of insubstantial changes and modifications to the above-described embodiments and that it would be impractical to attempt to describe all such embodiment variations in the present specification. Accordingly, it is understood that all changes and modifications that come within the spirit of the invention are desired to be protected

Claims

What is claimed is:

1. A method for using a wavefront aberrometer for determining the optimum orientation for the orientation of an artificial accommodating lens, comprising: a) generating a first aberration map of an eye focused on an object located substantially at infinity; b) generating a second aberration map of an eye focused on an object located relatively nearby; c) comparing the first and second maps to determine a first major axis of symmetry of the aberrations of the lens; d) determining a second axis of symmetry of an artificial lens; and e) aligning the axes of symmetry in preparation for the implanting of an artificial accommodating lens into the eye with the aligned axes of symmetry.

2. The method of claim 1 wherein the artificial accommodating lens includes a generally circular lens disc and at least one generally linear elongated haptic member extending therefrom.

3. The method of claim 1 wherein the artificial accommodating lens includes a generally circular lens disc and a pair of oppositely disposed generally linear elongated haptic members extending therefrom.

4. The method of claim 1 further comprising: after b and before c, comparing the first and second maps to determine multiple axes of symmetry of the aberrations of the lens; and defining a first major axis of symmetry as the most pronounced previously defined axis.

5. A method of determining an optimized orientation for an implantable artificial lens, comprising in combination: conducting wavefront aberration analysis of an eye to generate a refraction map of the aberrations of the eye; isolating the aberration contributions from the lens of the eye; determining if a major axis of symmetry of the aberration of the lens of the eye is present; if a major axis of symmetry of the aberration of the lens of the eye is present, orienting the haptics of an artificial accommodating lens relative the major axis of symmetry; if a major axis of symmetry of the aberration of the lens of the eye is not present, orienting the haptics of an artificial accommodating lens at will; and implanting the oriented artificial accommodating lens into the eye.

6. The method of claim 5 wherein the artificial accommodating lens includes a generally circular lens disc and at least one generally linear elongated haptic member extending therefrom.

7. The method of claim 1 wherein the artificial accommodating lens includes a generally circular lens disc and a pair of oppositely disposed generally linear elongated haptic members extending therefrom.

8. The method of claim 5 wherein orienting the haptics of an artificial accommodating lens relative the major axis of symmetry includes orienting the artificial accommodating lens along the major axis of symmetry.

9. The method of claim 5 wherein orienting the haptics of an artificial accommodating lens relative the major axis of symmetry includes orienting the artificial accommodating lens perpendicular to the major axis of symmetry.

10. The method of claim 5 wherein there are two major axes and wherein orienting the haptics of an artificial accommodating lens relative the major axis of symmetry includes orienting the artificial accommodating lens transverse to the two major axes of symmetry.

1 1. A method of using a wavefront aberrometer to orient an artificial lens having a major axis of symmetry for implantation into an eye, comprising: a) activating a wavefront aberrometer; b) generating a map of the aberration pattern of an eye; c) identifying a major axis of symmetry of the aberration pattern of the eye; d) identifying the major axis of symmetry of the artificial lens; and e) aligning the major axes of symmetry.

12. The method of claim 1 1 further comprising: f) isolating the aberration contributions from the lens; and g) implanting the aligned artificial lens in the eye; wherein f) occurs after b) and before c).

13. The method of claim 1 1 wherein the artificial accommodating lens includes a generally circular lens disc and at least one generally linear elongated haptic member extending therefrom.

14. The method of claim 1 1 wherein the artificial accommodating lens includes a generally circular lens disc and a pair of oppositely disposed generally linear elongated haptic members extending therefrom.