Patent Application
20080269882
This application is related to the following co-pending applications concurrently filed herewith, each of which is herein incorporated by reference: “Intraocular Lens With Peripheral Region Designed to Reduce Negative Dysphotopsia,” (Attorney Docket No. 2817), “IOL Peripheral Surface Designs to Reduce Negative Dysphotopsia,” (Attorney Docket No. 3345), “Intraocular Lens with Asymmetric Haptics,” (Attorney Docket No. 3227), “Intraocular Lens With Edge Modification,” (Attorney Docket No. 3225), “A New Ocular Implant to Correct Dysphotopsia, Glare, Halo, and Dark Shadow,” (Attorney Docket No. 3226), “Haptic Junction Designs to Reduce Negative Dysphotopsia,” (Attorney Docket No. 3344), and “Graduated Blue Filtering Intraocular Lens,” (Attorney Docket No. 2962).
The present invention relates generally to intraocular lenses (IOLs), and particularly to IOLs that provide a patient with an image of a field of view without the perception of visual artifacts in the peripheral visual field.
The optical power of the eye is determined by the optical power of the cornea and that of the natural crystalline lens, with the lens providing about a third of the eye's total optical power. The process of aging as well as certain diseases, such as diabetes, can cause clouding of the natural lens, a condition commonly known as cataract, which can adversely affect a patient's vision.
Intraocular lenses are routinely employed to replace such a clouded natural lens. Although such IOLs can substantially restore the quality of a patient's vision, some patients with implanted IOLs report aberrant optical phenomena, such as halos, glare or dark regions in their vision. These aberrations are often referred to as “dysphotopsia.” In particular, some patients report the perception of dark shadows, particularly in their temporal peripheral visual fields. This phenomenon is generally referred to as “negative dysphotopsia.”
Accordingly, there is a need for enhanced IOLs, especially IOLs that can reduce dysphotopsia, in general, and the perception of dark shadows or negative dysphotopsia, in particular.
The present invention generally provides asymmetric intraocular lenses (IOLs) with asymmetric optics that alleviate, and preferably eliminate, the perception of dark shadows that some IOL patients report.
The present invention is based, in part, on the discovery that the shadows perceived by IOL patients can be caused by a double imaging effect when light enters the eye at very large visual angles. More specifically, it has been discovered that in many conventional IOLs, most of the light entering the eye is focused by both the cornea and the IOL onto the retina, but some of the peripheral light misses the IOL and it is hence focused only by the cornea. This leads to the formation of a second peripheral image. Although this image can be valuable since it extends the peripheral visual field, in some IOL users it can result in the perception of a shadow-like phenomenon that can be distracting.
To reduce the potential complications of cataract surgery, designers of modern IOLs have sought to make the optical component (the “optic”) smaller (and preferably foldable) so that it can be inserted into the capsular bag with greater ease following the removal of the patient's natural crystalline lens. The reduced lens diameter, and foldable lens materials, are important factors in the success of modern IOL surgery, since they reduce the size of the corneal incision that is required. This in turn results in a reduction in corneal aberrations from the surgical incision, since often no suturing is required. The use of self-sealing incisions results in rapid rehabilitation and further reductions in induced aberrations. However, a consequence of the optic diameter choice is that the IOL optic may not always be large enough (or may be too far displaced from the iris) to receive all of the light entering the eye.
Moreover, the use of enhanced polymeric materials and other advances in IOL technology have led to a substantial reduction in capsular opacification, which has historically occurred after the implantation of an IOL in the eye, e.g., due to cell growth. Surgical techniques have also improved along with the lens designs, and biological material that used to affect light near the edge of an IOL, and in the region surrounding the IOL, no longer does so. These improvements have resulted in a better peripheral vision, as well as a better foveal vision, for the IOL users. Though a peripheral image is not seen as sharply as a central (axial) image, peripheral vision can be very valuable. For example, peripheral vision can alert IOL users to the presence of an object in their field of view, in response to which they can turn to obtain a sharper image of the object. It is interesting to note in this regard that the retina is a highly curved optical sensor, and hence can potentially provide better off-axis detection capabilities than comparable flat photosensors. In fact, though not widely appreciated, peripheral retinal sensors for visual angles greater than about 60 degrees are located in the anterior portion of the eye, and are generally oriented toward the rear of the eye. In some IOL users, however, the enhanced peripheral vision can lead to, or exacerbate, the perception of peripheral visual artifacts, e.g., in the form of shadows.
Dysphotopsia (or negative dysphotopsia) is often observed by patients in only a portion of their field of vision because the nose, cheek and brow block most high angle peripheral light rays—except those entering the eye from the temporal direction. Moreover, because the IOL is typically designed to be affixed by haptics to the interior of the capsular bag, errors in fixation or any asymmetry in the bag itself can exacerbate the problem—especially if the misalignment causes more peripheral temporal light to bypass the IOL optic.
In many embodiments of the invention, the IOL's optic is extended asymmetrically in the nasal direction to receive peripheral light rays entering the eye from the temple side (herein referred to as temporal peripheral rays) at large visual angles and to capture and/or redirect those rays so as to eliminate the perception of dark shadows by the IOL user. In some cases, this is achieved by ensuring that those rays would not form a second peripheral image. More preferably, rather than inhibiting the formation of the second peripheral image, some of the light rays are directed, e.g., via scattering, to a shadow region between a primary image, formed by the IOL, and a secondary peripheral image formed by light rays that miss the IOL, so as to inhibit dyphotopsia while preserving the second peripheral image—albeit in an attenuated form. Such redirecting of the peripheral light rays allows the IOL user to enjoy the expanded peripheral vision provided by the second peripheral image without the perception of visual artifacts due to dysphotopsia.
In one aspect, an intraocular lens (IOL) is disclosed that includes an optic having a central portion and a peripheral extension that partially surrounds the central portion. Once the IOL is implanted in the eye, the optic forms an image of a field of view with the peripheral extension inhibiting (i.e., ameliorating and preferably preventing) the perception of visual artifacts in the patient's peripheral vision. For example, the peripheral extension can inhibit the formation of a secondary image by peripheral light rays entering the eye at large visual angles or can redirect some light rays to a shadow region between such a secondary image and an image formed by the central portion. In other words, the peripheral extension can inhibit dysphotopsia.
In a related aspect, the peripheral extension is formed as a contiguous optical structure that is asymmetrically disposed relative to the optic's central portion.
In related aspects, the peripheral extension can provide focusing of light incident thereon onto the retina such that, together with the light focused by the central portion, a single image of a field of view can be formed. Alternatively, the peripheral extension can include at least one textured surface that inhibits the peripheral rays incident thereon from forming a secondary image on the retina or to cause some of the peripheral light rays to be directed to a shadow region between an image formed by the IOL and a second peripheral image formed by rays that miss the IOL and are refracted only by the cornea onto the retina. In other embodiments, the peripheral extension can be opaque or translucent so as to inhibit dysphotopsia. In other cases, the peripheral extension can include a diffractive structure or a Fresnel lens.
The IOL's optic can include an anterior surface and a posterior surface, each of which is characterized by a central surface portion and a peripheral surface extension that partially surrounds the central portion. While in some embodiments, the central portion and the peripheral extension of each surface form a contiguous optical surface, in other embodiments, they can be formed as separate surfaces that are coupled to one another. In many embodiments, the peripheral extension of the anterior surface is adapted to receive at least some of the peripheral light rays entering the eye at visual angles in a range of about 50 degrees to about 80 degrees. By way of example, in many embodiments the central portion of each surface is characterized by a radial distance from an optical axis of the optic (e.g., an axis about which the central portion is rotationally symmetric) in a range of about 2 mm to about 3.5 mm while the respective peripheral extension is characterized by a maximum radial extension from that axis in a range of about 2.5 mm to about 4.5 mm.
In many embodiments, the optic is foldable to facilitate its insertion into the eye, and the peripheral extension is rotationally asymmetric about the optical axis so as to ensure that the IOL can be inserted in a folded state into the eye through a small incision. In many embodiments, the peripheral extension can be in the form of a crescent-shaped section that partially surrounds the central portion. In some such embodiments, each of the anterior and posterior surfaces can be characterized by two orthogonal meridians one of which exhibits a radial extension relative to the optical axis greater than about 3.5 mm and other exhibits a smaller radial extension (e.g., less than about 3.1 mm).
In some embodiments in which the peripheral extension of the IOL has a focusing function, at least one of the anterior or posterior surfaces exhibits an asphericity to ameliorate, and preferably prevent, spherical aberration effects that might arise as a result of focusing of the rays entering at large visual angles into the eye. By way of example, such an asphericity can be characterized by a conic constant in a range of about −10 to about −100, and preferably in a range of about −15 to about −25. In other embodiments, the IOL can include one or more toric surfaces.
In another aspect, in the above IOL, a diffractive structure can be disposed on at least one of the surfaces of the optic such that the IOL would provide a far-focus as well as a near-focus power. In some cases, the diffractive structure includes a plurality of diffractive zones that are separated from one another by steps that exhibit decreasing heights as a function of increasing radial distance from the optical axis so as to change the balance of energy diverted to the near and far foci based on the pupil size.
In another aspect, an IOL is disclosed that includes an optic disposed about an optical axis, where the optic provides an optical power for generating an image of a field of view on the retina of a patient's eye in which the IOL is implanted. The IOL further includes an optical flange that at least partially surrounds the optic, where the flange is adapted to inhibit dysphotopsia, e.g., by inhibiting the formation of a secondary image by peripheral light rays entering the eye at large visual angles or by directing some light rays into a shadow region between the image formed by the IOL and such a secondary image.
In a related aspect, in the above IOL, the optic has a maximum radial extension in a range of about 2 mm to about 3.5 mm relative to the optical axis and the optical flange has a maximum radial extension in a range of about 2.5 mm to about 4.5 mm from that axis.
In other aspects, the optical flange can include at least one surface that is textured (e.g., it is characterized by physical surface undulations with amplitudes in a range of about 0.2 microns to about 2 microns) so as to scatter peripheral light rays incident thereon in order to inhibit those rays from forming a secondary image, or to redirect at least some of the light rays into the shadow region. Alternatively or in addition, the optical flange can be opaque or translucent to visible light. In some cases, the optical flange can include a diffractive structure or a Fresnel lens.
Further understanding of various aspects of the invention can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below.
The present invention generally provides intraocular lenses (IOLs) that ameliorate, and preferably prevent, the perception of dark shadows that some IOL patients report. As noted above, such an effect is known generally in the art as dysphotopsia. As discussed in more detail below, in many embodiments, the IOLs of the invention include larger optics with asymmetric profiles that can be characterized as having a central portion that extends to a peripheral extension. In many cases, the peripheral extension can receive peripheral light rays entering the eye at large visual angles and can capture or redirect those rays to inhibit the perception of peripheral visual artifacts (e.g., shadows) by the IOL user. In some cases, the surfaces of the IOL's optic are extended in certain directions (typically in the nasal direction) to provide the peripheral extension. In other cases, the peripheral extension is in the form of a separate flange that partially surrounds a central optic. The term “intraocular lens” and its abbreviation “IOL” are used herein interchangeably to describe lenses that are implanted into the interior of the eye to either replace the eye's natural lens or to otherwise augment vision regardless of whether or not the natural lens is removed.
More specifically, with reference to
The optic 3 is preferably formed of a biocompatible material, such as soft acrylic, silicone, hydrogel, or other biocompatible polymeric materials having a requisite index of refraction for a particular application. For example, in some embodiments, the optic can be formed of a cross-linked copolymer of 2-phenylethyl acrylate and 2-phenylethyl methacrylate, which is commonly known as Acrysof®. The IOL 1 also includes a plurality of fixation members (haptics) 13 that facilitate its placement in the eye. Similar to the optic 3, the haptics 13 can also be formed of a suitable biocompatible material, such as polymethylmethacrylate (PMMA). While in some embodiments, the haptics can be formed integrally with the optic, in other embodiments (commonly referred to as multipiece IOLs), the haptics are formed separately and attached to the optic in a manner known in the art. In the latter case, the material from which the haptics are formed can be the same as, or different from, the material forming the optic. It should be appreciated that various haptic designs for maintaining lens stability and centration are known in the art, including, for example, C-loops, J-loops, and plate-shaped haptic designs. The present invention is readily employed with any of these haptic designs.
Referring again to
Further in some implementations, the peripheral extension of the IOL's optic can be slanted anteriorly or posteriorly relative to its central portion. By way of example,
With reference to
More particularly, during cataract surgery, a clouded natural lens can be removed and replaced with the IOL 1. By way of example, an incision can be made in the cornea, e.g., via a diamond blade, to allow other instruments to enter the eye. Subsequently, the anterior lens capsule can be accessed via that incision to be cut in a circular fashion and removed from the eye. A probe can then be inserted through the corneal incision to break up the natural lens via ultrasound, and the lens fragments can be aspirated. An injector can be employed to place the IOL in a folded state in the original lens capsule. Upon insertion, the IOL can unfold and its haptics can anchor it within the capsular bag.
In some cases, the IOL is implanted into the eye by utilizing an injector system rather than employing forceps insertion. For example, an injection handpiece having a nozzle adapted for insertion through a small incision into the eye can be used. The IOL can be pushed through the nozzle bore to be delivered to the capsular bag in a folded, twisted, or otherwise compressed state. The use of such an injector system can be advantageous as it allows implanting the IOL through a small incision into the eye, and further minimizes the handling of the IOL by the medical professional. By way of example, U.S. Pat. No. 7,156,854 entitled “Lens Delivery System,” which is herein incorporated by reference, discloses an IOL injector system. The IOLs according to the embodiments of the invention, such as the IOL 1, are preferably designed to inhibit dysphotopsia while ensuring that their shapes and sizes allow them to be inserted into the eye via injector systems through small incisions.
Once implanted in a patient's eye, the IOL can form an image of a field of view with its peripheral extension receiving peripheral light rays entering the eye at large visual angles and directing those rays towards the image, thereby inhibiting formation of a secondary image that could lead to perception of dark shadows (that is, the peripheral extension inhibits dysphotopsia). In this embodiment, the peripheral extension 7 is adapted to be positioned, upon implantation of the IOL in the eye, on the nasal side of the eye such that the temporal peripheral light rays would be incident thereon—the nose, eyebrows and cheeks typically block the entry of peripheral light rays from other directions into the eye.
To further illustrate the role of the peripheral extension in inhibiting dysphotosia,
In contrast, as shown schematically in
In some embodiments, at least one of the anterior or posterior surfaces of the IOL 1 exhibits an asphericity designed to ameliorate, and preferably prevent, spherical aberration effects that may arise from focusing of the peripheral light rays by the peripheral extension 7. By way of example, at least one of the surfaces can exhibit an asphericity characterized by a conic constant in a range of about −10 to about −100, or in a range of about −15 to about −25. Further, in some cases one or more surfaces of the IOL can have a toric profile (i.e. a profile characterized by two different optical powers along two orthogonal surface directions). Additional teachings regarding the use of aspheric and/or toric surfaces in IOLs, such as various embodiments discussed herein, can be found in U.S. patent application Ser. No. 11/000,728 entitled “Contrast-Enhancing Aspheric Intraocular Lens,” filed on Dec. 1, 2004 and published as Publication No. 2006/0116763, which is herein incorporated by reference in its entirety.
In other embodiments, the IOL of the invention can include a peripheral extension characterized by at least one textured, opaque, and/or translucent surface. Such peripheral extensions can inhibit the formation of a second peripheral image or redirect light rays into the shadow region to inhibit perception of a dark shadow by the IOL user.
By way of example,
More particularly, in this embodiment, the central portion exhibits a substantially circular cross section, with the optical axis connecting the centers of the central portions of the anterior and posterior surfaces, as shown schematically in
Similar to the previous embodiment, the optic 12 is preferably formed of a biocompatible material, such as those discussed above. The IOL 10 also includes a plurality of fixation members (haptics) 22 that facilitate its placement in the eye. Similar to the optic 12, the haptics 22 can also be formed of a suitable biocompatible material, such as PMMA. While in some embodiments, the haptics can be formed integrally with the optic, in other embodiments, the haptics are formed separately and attached to the optic in a manner known in the art. Further, similar to the previous embodiment, the IOL 10 is foldable so as to facilitate its insertion in the eye.
In this embodiment, the peripheral extension of the optic is textured in order to cause scattering of the peripheral light rays entering the eye at large visual angles so as to ensure that those rays would not form a discernible second peripheral image on the retina whose separation from a primary image formed by the optic's central portion would lead to the perception of dark shadows. More specifically, as shown schematically in
In many embodiments, the surface undulations have amplitudes that create an optical path distance effect of the order of visible light wavelengths. For example, in some embodiments, the physical surface amplitudes can range from about 0.2 microns to about 2 microns. As discussed in more detail below, upon implantation of the IOL in a patient's eye to replace a clouded natural lens, the surface undulations can cause scattering of peripheral light rays incident thereon, and hence inhibit formation of an image by those rays.
In this embodiment, once the IOL is implanted in the eye, its peripheral extension 20 is positioned on the nasal side of the eye in order to receive peripheral rays entering the eye from the temporal side, as discussed below. More specifically, with reference to
In other words, the IOL's peripheral extension effectively increases the IOL's size on the nasal side, which moves the IOL's edge further into the far temple visual field. This allows the IOL to capture the temporal peripheral rays 42 and substantially inhibit, and preferably prevent, them, via scattering, from forming a secondary image.
In some embodiments, the IOL's textured extension, rather than inhibiting formation of a second peripheral image, scatters some of the light rays incident thereon into a shadow region between a primary image formed by the IOL and a second peripheral image generated by rays that miss the IOL and are focused only by the cornea onto the retina. By way of example,
Although in some of the above embodiments, the peripheral extension of the IOL 10 inhibits formation of a secondary peripheral image by scattering the peripheral rays incident thereon, in some other embodiments, the peripheral extension can be opaque to visible radiation so as to significantly reduce, and in some cases eliminate, the intensity of peripheral rays that pass through it to reach the retina. While in some cases the opaque peripheral extension prevents such peripheral rays, e.g., via absorption, from reaching the retina, in other cases it can redirect such rays to the retina but at a reduced intensity (it can absorb some of the rays, but allow the passage of others). By way of example,
The peripheral extension is, however, substantially opaque to visible radiation so as to inhibit the light rays entering the eye at large visual angles from reaching the retina, thus preventing the formation of a secondary image. The term “opaque to visible radiation,” as used herein, refers to an opacity that would result in a reduction in the intensity of the visible radiation, e.g., radiation with wavelengths in a range about 380 nm to about 780 nm, by more than about 25%, or by more than about 40%, or by more than about 90%, or by more than about 95%, or by 100%. By way of example, in many embodiments, the intensity of the incident light passing through the opaque peripheral extension is reduced by a factor greater than about 25%, and more preferably greater than about 50%.
The opaque portion of the optic can be formed by a variety of techniques, e.g., by impregnating the polymeric material with one or more suitable dye(s). Some examples of dyes that can be in used are provided in U.S. Pat. No. 5,528,322 (entitled “Polymerizable Yellow Dyes And Their Use In Ophthalmic Lenses”), U.S. Pat. No. 5,470,932 (entitled “Polymerizable Yellow Dyes And Their Use In Ophthalmic Lenses”), U.S. Pat. No. 5,543,504 (entitled “Polymerizable Yellow Dyes And Their Use In Ophthalmic Lenses), and U.S. Pat. No. 5,662,707 (entitled “Polymerizable Yellow Dyes And Their Use In Ophthalmic Lenses), all of which are herein incorporated by reference. Further, while in this embodiment the entire peripheral extension is opaque, in other embodiments such opacity can be imparted to only portions of the peripheral extension, e.g., portions in proximity of the extension's anterior and/or posterior surfaces.
In other embodiments, the peripheral extension of the optic can be translucent so as to inhibit the peripheral light rays that enter the eye at large visual angles from generating a secondary image, or to redirect some light into a shadow region between such a secondary image and an image formed by the IOL. By way of example,
In some cases, a diffractive structure or a Fresnel lens can be disposed on a surface of the peripheral extension to direct light incident thereon onto a reduced intensity retinal region between an image formed by the central portion of the optic and a second peripheral image formed by light rays entering the eye that miss the optic. For example,
wherein,
With reference to
In many embodiments, such as those discussed above, the peripheral extension spans partially around the central portion of the optic. The extent by which the peripheral extension spans around the central portion can vary from one embodiment to another. In many cases the angular span of the peripheral extension is selected based on the following considerations: (1) ensuring that the peripheral extension would receive sufficient number of peripheral rays to inhibit perception of dark shadows and (2) ensuring that the increase in the size of the IOL would not hinder its insertion in the eye. By way of example, in many embodiments an angle θ corresponding to an arc spanned by the peripheral extension can be in a range of about 30 degrees to about 80 degrees.
In the above embodiments, the peripheral extension of each surface of the optic is integrally formed with its central portion. In some other embodiments, the IOL can include a central optic and an asymmetric separate flange that is coupled to the optic's periphery (e.g., it can abutt against the optic) by employing known techniques in the art.
By way of example,
In many embodiments, the peripheral flange is adapted to receive, once the IOL is implanted in the eye, at least some of the light rays entering the eye at large visual angles in a range of about 50 to about 80 degrees. In some embodiments, the central optic has a radius R relative to the optical axis in a range of about 2 mm to about 3.5 mm, and the peripheral flange has a maximum radial distance (R′) from the optical axis in a range of about 2.5 mm to about 4.5 mm.
In this embodiment, once the IOL is implanted in the eye, the central optic 64 focuses the light rays incident thereon onto the retina so as to form an image of a field of view, while the optical flange 66 is adapted to be on the nasal side of the eye so as to receive at least a portion of the temporal peripheral rays. As discussed in more detail below, the flange 66 can inhibit such peripheral rays from forming a secondary image on the retina displaced from the image formed by the central optic that would lead to negative dysphotopsia, or redirect light into a shadow region between the peripheral edge of an image formed by central optic and secondary peripheral image formed by rays that miss the IOL. For example, the optical flange can function as a focusing element to redirect the peripheral light rays incident thereon to the retina so as to form, together with the central optic, a single image of a field of view. Alternatively, the optical flange can include one or more textured, opaque and/or translucent surface(s) that would inhibit the peripheral light rays from forming a secondary image, or redirect those rays into the shadow region.
By way of example, in some embodiments, at least one surface of the optical flange is textured to cause sufficient scattering of the peripheral rays so as to inhibit those rays from forming a secondary image on the retina. For example,
In this exemplary embodiment, upon implantation of the IOL in a patient's eye, the peripheral optical flange 72 is positioned on the nasal side of the IOL such that the peripheral light rays entering the eye at large visual angles from the temporal side would be incident thereon. The textured anterior surface of the flange causes scattering of such peripheral rays, thereby inhibiting the formation of a secondary image by those rays. Alternatively, in some embodiments, the textured flange surface can scatter some light rays incident thereon into a shadow region between a secondary peripheral image, formed by peripheral rays that might miss the IOL, and a primary image formed by the IOL.
In other embodiments, the optical flange is opaque to visible radiation so as to substantially inhibit (via reduction in intensity), and or in some cases prevent, the peripheral rays from reaching the retina. By way of example,
With continued reference to
In yet other embodiments, the peripheral flange can include one or more curved surfaces adapted to direct the peripheral rays entering the eye at large visual angles towards the periphery of an image formed by the central optic on the patient's retina to enhance the IOL user's peripheral vision while inhibiting dysphotopsia. By way of example,
With continued reference to
In some other embodiments, the optical power provided by the flange is slightly less than that of the central optic. For example, the optical power of the flange can differ from that of the central optic by a factor in a range of about 25% to about 75%. By way of example, in some embodiments, the optical power of the flange is less than by about 50% than that of the optic.
In some embodiments, a diffractive structure or a Fresnel lens can be disposed on at least a surface of the peripheral flange to direct light incident thereon to the reduced intensity retinal region. By way of example,
Further in some implementations, the IOL's peripheral flange can be slanted anteriorly or posteriorly relative to its central optic. By way of example, with reference to
Although in the above embodiments, the IOL provides a single optical power, in other embodiments, it can include a diffractive structure so as to provide both a far-focus optical power as well as a near-focus power. By way of example, with reference to
With continued reference to
wherein
wherein
In this exemplary embodiment, the diffractive zones are in the form of annular regions, where the radial location of a zone boundary (ri) is defined in accordance with the following relation:
r
i
2=(2i+1)λƒ Equation (3)
wherein
A variety of IOL fabrication techniques known in the art, such as injection molding, can be employed to form IOLs according to the teachings of the invention.
Those having ordinary skill in the art will appreciate that various changes can be made to the above embodiments without departing from the scope of the invention.
