This application claims priority from us patent application 16/380,622 entitled "high definition and extended depth of field intraocular lens" filed on 4/10/2019. The contents of the above referenced application are incorporated herein by reference in their entirety.
Disclosure of Invention
A virtual aperture integrated into an intraocular lens (IOL) is disclosed. This structure and arrangement allows light rays that intersect the virtual aperture and are widely scattered on the retina, thereby effectively preventing light from reaching detectable levels on the retina. The virtual aperture helps to eliminate monochrome and chromatic aberrations, resulting in a high-definition retinal image. For a given definition of acceptable vision, the depth of field increases over a larger diameter optical zone IOL. Eyes with cataracts may develop secondary problems due to ocular disease that is not well corrected by injury, previous ophthalmic surgery, or normal IOL design. Examples of eyes with complications include: asymmetric astigmatism, keratoconus, post-operative corneal transplantation, asymmetric pupil, very high astigmatism, etc. Our virtual-iris IOL design will be very effective in providing enhanced vision compared to normal large-optic IOLs, since it can remove unwanted aberrations.
It is an object of the present invention to teach a method of making thinner IOLs because the optical zone can have a smaller diameter, which allows for smaller corneal incisions and easier implantation surgery. Eyes with cataracts may develop secondary problems due to ocular disease that is not well corrected by injury, previous ophthalmic surgery, or normal IOL design. Examples of eyes with complications include: asymmetric astigmatism, keratoconus, post-operative corneal transplantation, asymmetric pupil, very high astigmatism, etc. The disclosed virtual-iris IOL design is effective in providing enhanced vision compared to normal large-optic IOLs due to its ability to remove unwanted aberrations.
It is another object of the present invention to teach a virtual aperture IOL that exhibits reduced monochromatic and chromatic aberrations, as well as an extended depth of field, while providing sufficient contrast for the resolution of the image over a selected range of distances.
It is a further object of the present invention to teach a virtual aperture IOL that provides a smaller central thickness than other isopowered IOLs.
It is another object of the invention to teach a virtual aperture that can be implemented as an alternating high power positive and negative lens profile.
It is a further object of the invention to teach a virtual aperture that can be implemented as a high power negative lens surface.
It is another object of the invention to teach a virtual aperture that can be implemented as a high power negative lens surface in combination with an alternating high power positive and negative lens profile.
It is yet another object of the invention to teach a virtual aperture that can be implemented as a prismatic profile in combination with alternating high power positive and negative lens profiles.
It is another object of the present invention to overcome these limitations by providing a phakic or aphakic intraocular lens which, while: provides defocus and astigmatism correction, reduces high order and chromatic aberrations, and provides an extended depth of field to improve vision quality.
It is another object of the present invention to teach a virtual aperture that can be used for phakic or aphakic IOLs, corneal implants, contact lenses, or for corneal laser surgery (LASIK, PRK, etc.) procedures to provide an extended depth of field and/or to provide a high definition field of view.
It is yet another object of the present invention to provide an IOL for an eye having complications such as asymmetric astigmatism, keratoconus, post-operative corneal transplants, asymmetric pupil, very high astigmatism, and the like.
It is a further object of the present invention to provide an IOL capable of removing unwanted aberrations to provide enhanced vision as compared to normal large optic IOLs.
It is another object of the invention to teach replacing the virtual aperture with an actual opaque aperture and achieve the same optical benefits as the virtual aperture.
Other objects and further advantages and benefits associated with the present invention will become apparent to those skilled in the art from the ensuing description, embodiments and claims.
Detailed Description
Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific functional and structural details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.
Fig. 1 illustrates a single converging lens 1 centered on an optical axis 2. The incident ray 3 is parallel to the optical axis and will intersect the focal point 4 of the lens. If the viewing plane 5 is located at a greater distance from the focal point, the incident ray will continue until it intersects the viewing plane. If we were tracing all incident rays with the same ray height as the incident ray 3, we would locate a blur circle 6 on the viewing plane. Other incident rays having a ray height less than the incident ray 3 will fall within the blur circle 6. One of the rays is incident ray 7, which is closer to the optical axis than incident ray 3. The incident ray 7 also intersects the focal point 4 and then intersects the viewing plane 5. Tracing all incident rays with a ray height equal to the incident ray 7 traces a circle of confusion 8 smaller than the circle of confusion 6.
The optical principle presented here is that as the height of a parallel incident ray decreases, the corresponding blur circle decreases. This simple relationship is suitable for the human eye. In other words, for a given amount of defocus (power error) in the eye, vision improves as the height of the incident light decreases. This principle is used when someone squints their eyes in an attempt to see out-of-focus objects more clearly.
The traces in fig. 1 are for a single wavelength of incident light. For polychromatic light, in this case three wavelengths, we have the situation in fig. 2. It is well known that the components of the eye, like typical optical materials, decrease in refractive index with increasing wavelength. In fig. 2A, the converging lens 21 has an optical axis 22. The incident light ray 23 consists of three wavelengths of blue (450nm), green (550nm) and red (650nm) light. Due to the different refractive indices of the three wavelengths, blue light 24 is refracted more than green light 25, and green light is refracted more than red light 26. If the green light is focused, it will then pass through the viewing plane 27 at the optical axis. The dispersion of these three rays results in a chromatic blur circle 28 in the viewing plane. In fig. 2B, the light incident on the color line 29 is lower in height than the color line 23 in fig. 2A. This results in a smaller circle of chromatic blur 33 at the viewing plane. Thus, as with the monochrome of FIG. 1, as the color light level decreases, the color blur decreases.
Fig. 1 and 2 illustrate that reducing the height of rays (reducing the pupil diameter) reduces the monochromatic and chromatic aberrations at the retina, thereby improving visual quality. Described another way, the depth of field increases as the light height decreases.
Fig. 3A shows a converging lens 34 having an optical axis 2 and an aperture 35. The incident ray 36 passes through the aperture and hence the lens focal point 37 and intersects the viewing plane 38 where it traces a small circle of confusion 39. The incident ray 40 is blocked by the aperture and therefore cannot continue to the viewing plane to form a larger blur circle 41. An aperture that limits the height of the incident light reduces the blur on the viewing plane. In FIG. 3B, we illustrate the "virtual aperture" we describe. That is, it is not an aperture that really blocks light, but the optical effect is almost the same. The light rays 43 propagating through the virtual aperture 42 are widely spread out and therefore contribute little to stray light (blur light) at any one point on the observation plane. This is the primary mechanism of operation of the IOL invention. Occasionally, within months to years after cataract surgery and intraocular lens implantation, a disease known as Posterior Capsule Opacification (PCO) can develop in the clear posterior capsule and can affect vision quality. It has been reported that the incidence of PCO is 5% to 50% in eyes receiving cataract surgery and intraocular lens implantation. Treatment to remove PCO typically involves post-capsulotomy with a Nd: YAG laser. In this case, the laser is focused through the IOL to perform the capsulotomy. If the virtual aperture is opaque, e.g. a real aperture, the process will be disabled. The disclosed virtual aperture is intentionally designed to provide the benefits of a small aperture while allowing YAG capsulotomy to treat PCO.
FIG. 4 illustrates the basic layout of an IOL employing a virtual aperture. In this figure, the central optical zone 46 provides correction for defocus, astigmatism, and any other correction required by the lens. Generally, for an intraocular lens using a virtual aperture, the central optical zone is smaller in diameter than a conventional intraocular lens. This results in a smaller central thickness, which makes the intraocular lens easier to implant and allows for a smaller corneal incision during surgery. The virtual aperture 48 is located at the more distal periphery and the IOL haptics 50 are located at the more distal periphery. The virtual aperture is connected to the optical zone by a transition zone 47 and the haptic elements are connected to the virtual aperture by a transition zone 49. The transition regions 47 and 49 are designed to ensure one side of the zero and first order continuity transition regions of the surface. A common method of achieving this is a polynomial function, such as a cubic bessel function. Methods of conversion such as these are known to those skilled in the art.
In a preferred embodiment, the virtual aperture area 48 is a series of high power positive and negative lens profiles. Thus, the rays that intersect this region are widely dispersed downstream of the IOL. These distributions may be implemented as continuous conic sections, polynomials (e.g., Bezier functions), rational splines, diffraction distributions, or other similar distributions, as long as the entire region properly redirects and/or disperses the refracted rays. It is preferred to use a high power distribution that is smooth rather than a diffractive distribution because this simplifies the manufacture of IOLs on high precision lathes or using molds. As is known to those skilled in the art, the posterior side of the haptic elements should include a squared-off edge to inhibit cell growth that causes posterior capsule opacification.
Fig. 5 shows another distribution of the virtual aperture area 51, i.e. a divergent lens distribution. Note that this requires a thicker edge profile than the method in fig. 4. In fig. 6A, we show a preferred high power alternating positive and negative lens distribution and a close-up of the incident and transmitted light rays. Fig. 6B illustrates the effect of combining the distribution in 6A with the underlying prism or negative lens. In this case, the emergent rays are not only widely scattered, but they are also directed away from the macula or central vision portion of the retina of the eye, again at the expense of wider lens edges.
Figure 7A shows a high power IOL60, typically having a relatively small optical diameter and a large central thickness. When the pupil of the eye is larger than the optic zone, the incident light ray 64 may miss the optic entirely and intersect the haptic elements 61 only on the way to the retina 63. This situation can cause noticeable artifacts in the peripheral vision of the eye. Incident light rays 62 that intersect the optic zone as expected are properly refracted into the central vision of the retina. In fig. 7B, we illustrate the same optics, but now with a virtual aperture 65 between the optics and the haptic elements. In this case, the incident light rays 64 that intersect the lens outside the optical zone are dispersed on the retina without causing significant artifacts.
Taken together, these characteristics of an IOL incorporating a virtual aperture can be accurately characterized as High Definition (HD) and extended depth of field (EDOF).
The basic layout of the virtual iris IOL is shown in fig. 4. In a preferred embodiment, the central optical zone 46 has a diameter of 3.0mm and the virtual aperture 48 has a width of 1.5 mm. Thus, the combination of the central optical zone and the virtual aperture is a 6.0 mm diameter optic, similar to a common commercially available IOL.
Spherical, toric and zero aberration vision zones. A significant proportion of cataract patients have astigmatic corneas. After removal of the lens, the residual optical system of the astigmatic corneal eye is preferably corrected with a toric or astigmatic lens. For these patients, the central optic portion of our lens is toric to provide better vision correction. Furthermore, even if the optical part is small, some spherical aberration can be corrected. Thus, the best correcting optic zone will provide spherical aberration correction for all lenses and toric correction for those suffering from corneal astigmatism.
Toric correction is readily performed by those skilled in the art by providing two principal powers in two principal directions aligned with the corneal astigmatism of the eye.
Spherical aberration of a spherical lens or toric lens is corrected by employing a conical profile on one or more surfaces of the lens. Such a lens is said to have zero aberration because the monochromatic aberration in the lens is zero for a coaxial distant object. The apex radius Ra of the cone distribution calculates the required paraxial power of the lens as usual. The conic constant K is then selected based on the refractive index of the lens material, the lens center thickness, and the shape of the front and back surfaces of the lens.
In case the correction is astigmatism, at least one of the lens surface shapes is biconical with a conical profile in two orthogonal main directions. In a preferred embodiment, the toric lens has an equal bi-convex design in which each surface is a biconic surface. The non-toric optical element has an equal biconvex design, where each surface is a conical surface. In the case of a biconical or conical surface, the optimal conic constant K for the surface is determined using ray tracing as known to those skilled in the art.
A plurality of focal points. Some patients may prefer multifocal optics to provide vision correction for a particular distance. One example is bifocal optics, which typically provide focusing capabilities for near and distance vision. Another example is trifocal optics that provide focusing power for near, intermediate, and far vision. In either case, to implement a multifocal IOL, the optical regions are modified to create these focal regions using refractive or diffractive optical regions, and the virtual aperture remains outside the last focal region.
In some applications, the virtual aperture may appear as an annular area with an optical zone on each side of the annular area. The shape of the annular virtual aperture can also be free-form, for example to accommodate an astigmatic optic zone or an asymmetric haptic element region. This is illustrated in fig. 8. In the figure, lens a represents an elliptical optical area, so the internal distribution of the virtual aperture must be adapted to this shape. The inner haptic area distribution is circular, and thus the outer virtual aperture distribution is circular. In this figure, lens B depicts the optical area as a circle, so the distribution within the virtual aperture is circular. The inner haptic element distribution is elliptical, and thus the outer virtual aperture distribution is elliptical. In each case, there is a transition region between each region to smoothly connect the regions so that visual artifacts are not introduced into the eye. Alternatively, the transition region may have an iris width such that the inner and outer virtual aperture distributions may be of any desired shape.
The IOL designs contemplated herein may be made from any biocompatible optical material commonly used for IOLs, including hard and soft materials. They may also be manufactured using CNC machines or molds or other methods for manufacturing IOLs. The virtual apertures may be implemented as a one-dimensional distribution symmetrical in the azimuthal direction or as a two-dimensional distribution of tiny lens areas.
In fig. 9, an azimuthally symmetric radial profile is shown. The distributions may all be the same or adjusted in the azimuthal direction. These distributions may be refractive or diffractive in nature. Although eight different radial distributions are illustrated, the radial distributions are continuous in the azimuthal direction. The radial profile may have alternating positive and negative powers, all positive powers or all negative power portions. The connections between all power supply regions are smooth to prevent visual artifacts.
In fig. 10, other symmetrical radial profiles are shown, including a combination of planar, negative power, and sloped bottom shapes, in addition to or instead of the high power curve shown in fig. 8. Referring to fig. 10, element a depicts a simple planar base shape. In fig. 10, element B depicts the negative power base shape. Such a generally negative power profile may be represented by a sphere, a cone, or a portion of a higher order curve (e.g., a polynomial). FIG. 10, element C depicts the segmented negative power profile of element B, where the curve has been segmented to resemble a Fresnel lens to keep the overall lens thickness small. Fig. 10, element D depicts a ramp base shape profile, while fig. 10, element E depicts a segmented version of the ramp base shape, where the ramp has been segmented like a fresnel lens to keep the overall lens thickness small. Although the piecewise distributions of elements C and E are illustrated with distinct discontinuities, in practice, the boundaries of the segments are implemented using a smoothing function (e.g., rounded corners or bezier curves) to prevent observable artifacts caused by sharp discontinuities. Further, as described elsewhere herein, the smooth transition region is located between the optic zone and the virtual aperture. These basic shapes can be used in combination with or instead of the high power features to increase the effectiveness of the virtual aperture.
FIG. 11 illustrates a two-dimensional lens region oriented with polar coordinate sampling. The high power lenses alternate in both radial and azimuthal directions with positive and negative powers. Two positive power lenses and two negative power lenses are shown. The actual geometry of these two-dimensional aurora lenses is of the order of the radial distribution.
Alternatively, the two-dimensional high power lenses may be all positive lenses or all negative lenses. In this case, the high power lenses are separated by small smooth transition regions (e.g., continuous polynomial interpolators such as bezier curves) to prevent visual artifacts. This is the preferred two-dimensional high power lens configuration when there are multiple lens sampling rates in the azimuth direction. In this case, the single lens looks like a small pillow, which is above the base for positive power lenses and below the base for negative power lenses.
Fig. 12 illustrates the geometry of one of the two-dimensional high power lenses. In the upper right part of the figure we show a front view of a high power lens. There is a central high power optical zone and a surrounding transition zone. The radial extent of this region is given by r, the width of the transition region by t, and the azimuth angle by θ. At the bottom left of the figure we show a side view of one of the shot distributions. The middle part represents a high power light area, and the curves at the two sides represent transition areas. The interface between the optical zone and the transition zone has zero and first order continuity. At the edge of the lens boundary, the transition coincides with the virtual iris base shape (usually a perpendicular line on the IOL). There is also zero order and first order continuity between the lens edge, the transition curve (typically a polynomial curve) and the edge. This small high power lens region is shaped such that the radial extent r is approximately equal to the arc length of the central portion of the region.
The central optical zone can be designed using standard IOL design concepts to provide spherical, cylindrical and axial correction, as well as higher order corrections such as spherical aberration control. These design concepts are known to those skilled in the art.
The preferred virtual aperture profile shown in FIG. 4 has alternating positive and negative lens profiles with focal lengths on the order of +/-1.5 mm. The lens surface distributions may be generated using conic sections, polynomials (e.g., cubic bezier splines), rational splines, and combinations of these and other curves. The geometry of the lens distribution is selected to adequately disperse the transmitted light through the retina while being relatively easy to manufacture on a high precision lathe or die process. It is also possible to place a smooth surface on one distribution (e.g. the front surface) and a small high power lens distribution on the other distribution (e.g. the back surface).
Using the preferred virtual aperture distribution shown in FIG. 4, the edge thickness of the IOL and the center thickness of the central optical zone can be very small, even for high power IOLs. The material of the optic is the same as that used for other soft or hard intraocular lens designs.
Intraocular lens designs provide very good, high-definition distance vision, and the extent of "clear vision" can be controlled by specifications on the meaning of "clear vision" (e.g., 20/40 acuity), as well as the relative magnitude of "clear vision". A central viewing zone and a virtual aperture width. A simple equation [ Smith G, relationship between spherical defocus and vision, Optomery Vis. Sci.68,591-8,1991] gives the method of estimating vision given pupil diameter and spherical defocus in equations (1a and 1 b).
A=k D E (1a)
A-the acuity in arc minutes (a-Sd/20), i.e. the minimum resolution angle
k is a constant determined by clinical studies with an average of 0.65
D is the diameter of the pupil (mm)
E ═ spherical optical power
Sd ═ Snellen denominator
The second equation is assumed to be more accurate for low levels of optical focus misalignment and gives reasonable results.
For E-0, a-1 arc or 20/20.
Solving for (1b) of E yields equation (2).
Equation (1b) tells us the vision a at a given focal power and pupil diameter D for the depth of field range (Ex 2).
Equation (2) gives the depth of field range (in power) for a given acuity a and pupil diameter D. For example, for:
20/40, acuteness of A40/20 2 minutes arc
D is 3.0mm
k=0.65
The depth of field is 2E 1.8D. With the use of (1b),
the concept of virtual aperture may be used for phakic or aphakic IOLs, corneal implants, contact lenses, or for corneal laser surgery (LASIK, PRK, etc.) procedures to provide an extended depth of field and/or to provide high definition vision. Furthermore, the virtual aperture can be replaced by an actual opaque aperture and the same optical advantages as the virtual aperture are achieved.
It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein.
Those skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended as examples and are not intended as limitations on the scope. Variations thereof and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. While the invention has been described in connection with certain preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.