MULTIFOCAL LENS DESIGN AND METHOD FOR PREVENTING AND/OR SLOWING MYOPIA PROGRESSION

Abstract

Contact lenses incorporate multifocal power profiles that at least one of slow, retard or preventing myopia progression. The lens includes a first zone at a center of the ophthalmic lens and at least one peripheral zone surrounding the first zone. The at least one peripheral zone has a different width and dioptric power than the first zone. The first zone and at least one peripheral zone are stepped or discontinuous. The multifocal power profile has substantially equivalent foveal vision correction to a single vision lens and has a depth of focus and reduced retinal image quality sensitivity that slows, retards, or prevents myopia progression.

Claims

1. An ophthalmic lens for at least one of slowing, retarding or preventing myopia progression, the ophthalmic lens comprising: a central zone at a center of the ophthalmic lens; and at least two peripheral zones surrounding the central zone, said at least two peripheral zones having different widths and dioptric powers than said central zone, wherein the central zone and at least two peripheral zones are stepped or discontinuous, thereby providing a multifocal lens power profile having equivalent foveal vision correction to a single vision lens, and having a depth of focus and reduced retinal image quality sensitivity that slows, retards, or prevents myopia progression, wherein the power is equal to 0.26 D for a radial range of between 0 mm to less than 1.15 mm, equal to 0.32 D for a radial range of greater than or equal to 1.15 mm to less than 2.19 mm, and equal to 0.95 D for a radial range of greater than or equal to 2.19 mm to less than 3.43 mm.

2. The ophthalmic lens according to claim 1, wherein the at least one peripheral zone comprises two zones.

3. The ophthalmic lens according to claim 1, wherein the multifocal power profiles are adjustable based upon pupil size to achieve a balance between foveal vision correction and an effective depth of focus and reduced retinal image quality sensitivity for treating myopia progression.

4. The ophthalmic lens according to claim 1, wherein the central zone comprises a width in the range from about 0.5 mm to about 1.2 mm.

5. The ophthalmic lens according to claim 1, wherein the at least one peripheral zone comprises a width in the range from about 0.5 mm to about 1.6 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The foregoing and other features and advantages of the invention will be apparent from the following, more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

[0023] FIGS. 1A, 1B and 1C, illustrate the change of Defocus Z.sup.0.sub.2, Spherical Aberration Z.sup.0.sub.4 terms, and entrance pupil diameter as a function of vergance for myopic and emmetropic population.

[0024] FIGS. 2A, 2B, and 2C are illustrations of power profiles for a spherical lens, an aspheric lens with +1.50 D positive longitudinal spherical aberration (LSA) at 5.0 mm pupil aperture, and an ACUVUE bifocal lens (a multiconcentric alternating distance and near zone lens) with +1.50 D add power, respectively.

[0025] FIG. 3A is an illustration of a power profile for a first multifocal lens design in accordance with the present invention.

[0026] FIG. 3B is a graph showing the neural sharpness and depth of focus for the multifocal lens design of FIG. 3A.

[0027] FIG. 3C is a graph showing neural sharpness at various accommodative states for the multifocal lens design of FIG. 3A.

[0028] FIG. 4A is an illustration of a power profile for a second multifocal lens design in accordance with the present invention.

[0029] FIG. 4B is a graph showing the neural sharpness and depth of focus for the multifocal lens design of FIG. 4A.

[0030] FIG. 4C is a graph showing the neural sharpness at various accommodative states for the multifocal lens design of FIG. 4A.

[0031] FIG. 5A is an illustration of a power profile for a third multifocal lens design in accordance with the present invention.

[0032] FIG. 5B is a graph showing the neural sharpness and depth of focus for the multifocal lens design of FIG. 5A.

[0033] FIG. 5C is a graph showing the neural sharpness at various accommodative states for the multifocal lens design in FIG. 5A.

[0034] FIG. 6A is an illustration of a power profile for a fourth multifocal lens design in accordance with the present invention.

[0035] FIG. 6B is a graph showing the neural sharpness and depth of focus for the multifocal lens design of FIG. 6A.

[0036] FIG. 6C is a graph showing the neural sharpness at various accommodative states for the multifocal lens design in FIG. 6A.

[0037] FIG. 7A is an illustration of a power profile for a fifth multifocal lens design in accordance with the present invention.

[0038] FIG. 7B is a graph showing the neural sharpness and depth of focus for the multifocal lens design of FIG. 7A.

[0039] FIG. 7C is a graph showing the neural sharpness at various accommodative states for the multifocal lens design of FIG. 7A.

[0040] FIG. 8 is a diagrammatic representation of an exemplary contact lens in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0041] FIGS. 2A, 2B, and 2C are illustrations of power profiles for a spherical lens, an aspheric lens with +1.50 D of positive longitudinal spherical aberration (LSA) at 5.0 mm pupil aperture, and an ACUVUE bifocal (a multiconcentric lens having alternating distance and near zones) lens with +1.50 D add power, respectively. There have been observations that the aspheric lens and ACUVUE bifocal +1.50 lens both may have an effect on treating myopia. Thus, a mechanism beyond changing spherical aberration, as disclosed in U.S. Pat. No. 6,045,578, is needed for describing lenses for preventing, treating, or slowing myopia progression.

[0042] According to the present invention, multifocal power profiles are developed for ophthalmic lenses that provide foveal vision correction, and have an increased depth of focus and reduced IQ sensitivity that treats or slows myopia progression.

[0043] In accordance with one exemplary embodiment, a multifocal power profile may be described by:

[00001]$\begin{array}{cc}P\left(r\right)=P_{\mathrm{Seg}}\left(r\right)+24.Math.\sqrt{5}\mathrm{SA}\frac{r^2}{{3.25}^4}-12.Math.\sqrt{5}\frac{\mathrm{SA}}{{3.25}^2},& \left(1\right)\end{array}$

[0044] wherein P represents the dioptric power (D);

r represents a radial distance from a geometric lens center;
SA represents an amount of spherical aberration; and
P.sub.Seg(r) represents a step function that has a number of zones with different magnitudes.

[0045] To measure vision correction, neural sharpness at 4.5 mm EP (entrance pupil) and 6.5 mm EP is utilized as a determinant of retinal image quality. It is important to note that any other suitable means and/or methods (for example, area under the MTF curve, Strehl ratio, and the like) that measure the goodness of retinal image quality may be utilized.

[0046] Neural sharpness is given by the following equation:

[00002]$\begin{array}{cc}\mathrm{NS}=\frac{{}_{-}^{}.Math.{}_{-}^{}.Math.{\mathrm{psf}}_{\left(x,y\right).Math.\mathrm{gn}\left(x,y\right).Math.\mathrm{dxdy}}}{{}_{-}^{}.Math.{}_{-}^{}.Math..Math.{\mathrm{psf}}_{{\mathrm{DL}}_{\left(x,y\right).Math.\mathrm{gn}\left(x,y\right).Math.\mathrm{dxdy}}}},& \left(2\right)\end{array}$

[0047] wherein psf or point-spread function is the image of a point object and is calculated as the squared magnitude of the inverse Fourier transform of the pupil function P(X,Y) where P(X,Y) is given by

P(X,Y)=A(X,Y)exp(ikW(X,Y)),(3)

[0048] wherein k is the wave number (2/wavelength) and A(X, Y) is an optical apodization function of pupil coordinates X,Y, psf.sub.DL is the diffraction-limited psf for the same pupil diameter, and g.sub.N (X,Y) is a bivariate-Gaussian, neural weighting function. For a more complete definition and calculation of neural sharpness see Thibos et al., Accuracy and precision of objective refraction from wave front aberrations, Journal of Vision (2004) 4, 329-351, which discusses the problem of determining the best correction of an eye utilizing wavefront aberrations. The wavefront W(X, Y) of the contact lens and the eye is the sum of each as given by:

W.sub.CL+eye(X,Y)=W.sub.CL(X,Y)+W.sub.eye(X,Y).(4)

[0049] To determine image quality sensitivity or slope of a lens+eye system for an object at a specific target vergence, three major steps are required: identification of coupling effect of ocular accommodation system, estimation of the corresponding accommodating state for the object, and calculation of the image quality sensitivity.

[0050] Step 1: Identification of Coupling Effect of Ocular Accommodation System:

[0051] As the human eye accommodates from distance to near, two ocular structures change simultaneously: the iris aperture becomes smaller; the crystal lens becomes bulkier. These anatomical changes leads to three optical related parameters change in a coupled manner in the lens+eye system: entrance pupil diameter, defocus (e.g. Zernike defocus Z.sub.2.sup.0), and spherical aberration (e.g. Zernike spherical aberration Z.sub.4.sup.0). Note in particular, since the pupil size decreases as the target moves closer and conventional Zernike defocus and spherical aberration highly depends on the pupil sizes, it is challenging to specify the these Zernike aberration terms in a conventional manner. As an alternative, to gauge the Zernike defocus and aberration across different pupil sizes, these terms were sometimes presented in a diopter manner. To convert to the classic Zernike coefficients via equations as follows:

Z.sub.20.sup.microns=Z.sub.20.sup.Diopter*(EPD/2).sup.2/(4*3)

Z.sub.40.sup.microns=Z.sub.40.sup.Diopter*(EPD/2).sup.4/(24*5)

[0052] wherein EPD is the diameter the entrance pupil, Z.sub.20.sup.Diopter (unit: D) and Z.sub.40.sup.Diopter (unit: D/mm.sup.2), note sometimes in the figures, as well as in some literatures, the unit of this term is also specified as D in short) are the Zernike defocus and spherical aberration terms specified in diopter manner, and Z.sub.20.sup.microns and Z.sub.40.sup.microns are corresponding conventional Zernike terms.

[0053] Ghosh et al 2012 (Axial Length Changes with Shifts of Gaze Direction in Myopes and Emmetropes, IOVS, September 2012, VOL. 53, No. 10) measured the change of these three parameters in relation to target vergence for emmetropes and myopes. FIG. 1A is a graphical representation of defocus vs. target vergence, FIG. 1B, is graphical representation of Spherical Aberration vs. Target Vergence and FIG. 1C, is a graphical representation of enterance pupil diameter vs. target vergence. As the target vergence changes, these three parameters change simultaneously. Since these data were measured on the human subject eyes without contact lens, the relation between these optical parameters and target vergence with lens+eye system differs. Nevertheless, the coupling relation among the optical parameters (entrance pupil size, defocus, and spherical aberration) remains the same because their changes originates from the same anatomical source. Different interpolation techniques could then be used to model such coupling relations among the three parameters from the experimental data.

[0054] Step 2: Estimation of the Corresponding Accommodating State for the Object at Near:

[0055] Once the coupling relation among the entrance pupil, defocus and spherical aberration during the accommodation is modeled at step 1, it could then be used to estimate the resting accommodating state of lens+eye system for a target at any given distance. The scientific essence of this step is to find how the eye accommodates to the near target in the presence of contact lens. For example, a target at specific distance at near (e.g. 2 D) results blurs for a distance corrected lens+eye system (e.g. the system that combines the lens in FIG. 3A and an eye model 0.06 D/mm.sup.2 SA). To determine the resting accommodating state of this system, the entrance pupil, defocus, and spherical aberration of the eye were systematically adjusted per the coupling model in step 1 so that the corresponding image quality improves to a threshold. For example, in FIG. 3C, the entrance pupil, defocus, and spherical aberration are found to be 5.3 mm, 1.5 D, 0.03 D/mm.sup.2 to boost the image quality (NS) to be 1.6 (roughly 20/25 VA).

[0056] Calculation of the image quality sensitivity for the specific target vergence: Once the accommodating state, and the corresponding entrance pupil, defocus, and spherical aberration are determined, the retina image quality sensitivity or slope could be readily calculated as follows:

IQ sensitivity=d.NS/d.Rx(5)

[0057] wherein d.NS/d.Rx is the derivative of Neural Sharpness to defocus value. For example, for design 3A with the standard eye model and target 2 D away, the corresponding IQ sensitivity is calculated to be 0.7.

[0058] By setting ranges for the number of zones, width of the zones, magnitudes of the zones, and spherical aberration in Equation (1), different multifocal power profiles can be obtained. Exemplary, non-limiting ranges of these variables are listed below in Table 1.

TABLE-US-00001 TABLE 1 Zone1 Zone2 Zone3 Zone4 Zone1 Zone2 Zone3 Zone4 width width width Width mag mag mag mag SA (mm) (mm) (mm) (mm) (D) (D) (D) (D) (D/mm.sup.2) max 1.2 1.6 1.5 1.0 0.5 0.8 0.6 0.2 0 min 0.5 0.5 0.6 0 0.8 0.5 1 0.2 0.5

[0059] Resulting multifocal power profiles are illustrated in FIGS. 3A, 4A, 5A, 6A, and 7A. The parameters for the first three multifocal lens designs or embodiments 1-3, and as illustrated in FIGS. 3A, 4A, and 5A, respectively, are listed below in Table 2.

TABLE-US-00002 TABLE 2 Zone1 Zone2 Zone3 Zone4 Zone1 Zone2 Zone3 Zone4 width width width width mag mag mag mag SA Design (mm) (mm) (mm) (mm) (D) (D) (D) (D) (D/mm.sup.2) #1 1.15 1.04 1.24 NA 0.26 0.32 0.95 NA 0.31 FIG. 3A #2 0.98 1.65 0.80 NA 0.04 0.39 0.56 NA 0.48 FIG. 4A #3 0.53 0.60 1.37 0.79 0.63 0.56 0.17 0.06 0.16 FIG. 5A

[0060] FIG. 3A shows a power profile for a three-zone lens design, which is stepped or discontinuous. The Rx or prescription for the ophthalmic lens is 3.00 D. In FIG. 3B, image quality (as measured by neural sharpness) for the ophthalmic lens would be sharpest at 0.00 diopter defocus, indicating that the optic system carries the sharpest image when it is well focused. As refractive error (both positive and negative) is introduced into the optical system, the image quality starts to drop. A threshold neural sharpness value of 2.2 is chosen to quantify DOF. When the neural sharpness value is larger than 2.2, patients still have reasonably good near vision for reading. In FIG. 3B, a horizontal threshold line at 2.2 is drawn. The line intersects the through-focus curve. The width between the two intersections corresponds to DOF. In this embodiment, the DOF is 1.18 D.

[0061] FIG. 3C is a graph of neural sharpness at 2 D, 3 D, 4 D and 5 D accommodative states (target vergence) and a calculated defocus error of 0.40 D to 1.10 D, which is typically associated with accommodation lag, for the lens design of FIG. 3A. Each curve is characterized by a shoulder at a neural sharpness threshold value of 1.6, having a specific defocus (Z20), spherical aberration (Z40) and Entrance Pupil size (EP). The slope of the shoulder is indicative of reduced retinal IQ sensitivity. In this embodiment, the IQ sensitivity is 0.67, 0.38, 0.70 and 0.95, respectively.

[0062] FIG. 4A shows a power profile for an alternate three zone lens design, which is stepped or discontinuous. The Rx or prescription for the ophthalmic lens is 3.00 D. In FIG. 4B, a threshold neural sharpness value of 2.2 is chosen to quantify DOF. The line intersects the through-focus curve. The width between the two intersections corresponds to DOF. In this embodiment, the DOF is 1.26 D.

[0063] FIG. 4C is a graph of neural sharpness at 2 D, 3 D, 4 D and 5 D target vergence and a calculated defocus error 0.50 D to 0.90 D, which is typically associated with accommodation lag, for the lens design of FIG. 4A. The curves are characterized by a shoulder at a neural sharpness threshold value of 1.6, having a specific defocus (Z20), spherical aberration (Z40) and Entrance Pupil size (EP). The slope of the shoulder is indicative of reduced retinal IQ sensitivity. In this embodiment, the IQ sensitivity is 1.01, 0.66, 0.40 and 0.30, respectively.

[0064] FIG. 5A shows a power profile for a four zone lens design, which is stepped or discontinuous. The Rx or prescription for the ophthalmic lens is 3.00 D. In FIG. 5B, a threshold neural sharpness value of 2.2 is chosen to quantify DOF. The line intersects with through-focus curve. The width between the two intersections corresponds to DOF. In this embodiment, the DOF is 1.04 D.

[0065] FIG. 5C is a graph of neural sharpness at 2 D, 3 D, 4 D and 5 D target vergence at a defocus error of 0.40 D to 1.00 D, which is typically associated with accommodation lag, for the lens design of FIG. 5A. The curves are characterized by a shoulder at a neural sharpness threshold value of 1.6, having a specific defocus (Z20), spherical aberration (Z40) and Entrance Pupil size (EP). The slope of the shoulder is indicative of reduced retinal IQ sensitivity. In this embodiment, the IQ sensitivity is 0.84, 0.33, 0.64 and 0.87, respectively.

[0066] FIG. 6A shows a power profile for a four zone lens design, which is stepped or discontinuous. The Rx or prescription for the ophthalmic lens is 3.00 D. In FIG. 6B, a threshold neural sharpness value of 2.2 is chosen to quantify DOF. The line intersects the through-focus curve. The width between the two intersections corresponds to DOF. In this embodiment, the DOF is 1.16 D.

[0067] FIG. 6C is a graph of neural sharpness at 2 D, 3 D, 4 D and 5 D target vergence and a calculated defocus error 0.50 D to 1.00 D, which is typically associated with accommodation lag, for the lens design of FIG. 6A. The curves are characterized by a shoulder at a neural sharpness threshold value of 1.6, having a specific defocus (Z20), spherical aberration (Z40) and Entrance Pupil size (EP). The slope of the shoulder is indicative of reduced retinal IQ sensitivity. In this embodiment, the IQ sensitivity is 1.10, 0.47, 0.43 and 0.36, respectively.

[0068] FIG. 7A shows a power profile for a five zone lens design, which is stepped or discontinuous. The Rx or prescription for the ophthalmic lens is 3.00 D. In FIG. 7B, a threshold neural sharpness value of 2.2 is chosen to quantify DOF. The line intersects the through-focus curve. The width between the two intersections corresponds to DOF. In this embodiment, the DOF is 1.03 D.

[0069] FIG. 7C is a graph of neural sharpness at 2 D, 3 D, 4 D and 5 D target vergence and a calculated defocus error of 0.50 D to 0.90 D, which is typically associated with accommodation lag, for the lens design of FIG. 7A. The curves are characterized by a shoulder at a neural sharpness threshold value of 1.6, having a specific defocus (Z20), spherical aberration (Z40) and Entrance Pupil size (EP). The slope of the shoulder is indicative of reduced retinal IQ sensitivity. In this embodiment, the IQ sensitivity is 1.14, 0.15, 0.66 and 0.83, respectively.

[0070] As shown below in Table 3, the neural sharpness at an entrance pupil (EP) of 4.5 mm and 6.5 mm is calculated for the multifocal lens designs. The depth of focus (DOF) and IQ sensitivity are calculated at threshold neural sharpness values of 2.2 and 1.6, respectively.

TABLE-US-00003 TABLE 3 IQ IQ IQ IQ Neural Neural Sensitivity Sensitivity Sensitivity Sensitivity Sharpness Sharpness Depth at 2D at 3D at 4D at 5D 4.5 mm EP 6.5 mm EP of Field vergence vergence vergence vergence Sphere 0.40 0.54 0.76 8.15 5.95 4.43 3.75 Aspheric 0.88 1.62 1.16 1.10 1.31 3.91 5.62 ACUVUE 1.34 2.01 0.89 2.79 2.41 0.76 0.25 bifocal Design #1 0.64 1.46 1.18 0.67 0.38 0.70 0.95 FIG. 3A Design #2 0.68 0.93 1.26 1.01 0.66 0.40 0.30 FIG. 4A Design #3 0.47 0.38 1.04 0.84 0.33 0.64 0.87 FIG. 5A Design #4 0.40 0.77 1.16 1.10 0.47 0.43 0.36 FIG. 6A Design #5 0.41 0.27 1.03 1.14 0.15 0.66 0.83 FIG. 7A

[0071] As shown in Table 3, the multifocal lens designs as illustrated in FIGS. 3A, 4A, 5A, 6A, and 7A have better neural sharpness than the aspheric and ACUVUE bifocal +1.50 D lenses and comparable or better myopia treatment efficacy as measured by the depth of focus as illustrated in FIGS. 3B, 4B, 5B, 6B, and 7B and by low IQ sensitivity as illustrated in FIGS. 3C, 4C, 5C, 6C, and 7C.

[0072] Referring to FIG. 8, there is illustrated a diagrammatic view of a contact lens 700 in accordance with an embodiment of the present invention. The contact lens 700 comprises an optic zone 702 and an outer zone 704. The optic zone 702 comprises a first, central zone 706 and at least one peripheral zone 708. In specific embodiments, the diameter of the optic zone 702 may be selected to be 8.0 mm, the diameter of the substantially circular first zone 706 may be selected to be 4.0 mm, and the boundary diameters of an annular outer peripheral zone 708 may be 5.0 mm and 6.5 mm as measured from the geometric center of the lens 700. It is important to note that FIG. 8 only illustrates an exemplary embodiment of the present invention. For example, in this exemplary embodiment, the outer boundary of the at least one peripheral zone 708 does not necessarily coincide with the outer margin of the optic zone 702, whereas in other exemplary embodiments, they may coincide. The outer zone 704 surrounds the optic zone 702 and provides standard contact lens features, including lens positioning and centration. In accordance with one exemplary embodiment, the outer zone 704 may include one or more stabilization mechanisms to reduce lens rotation when on eye.

[0073] It is important to note that the various zones in FIG. 8 are illustrated as concentric circles, the zones may comprise any suitable round or non-round shapes such as an elliptical shape.

[0074] It is important to note that as the entrance pupil size of the eye and target vergence/accommodation varies among subpopulations. In certain exemplary embodiments, the lens design may be customized to achieve both good foveal vision correction and myopic treatment efficacy based on the patient's average pupil size and preferred target vergence. Moreover, as pupil size correlates with refraction and age for pediatric patients, in certain exemplary embodiments, the lens may be further optimized towards subgroups of the pediatric subpopulation with specific age and/or refraction based upon their pupil sizes. Essentially, the power profiles may be adjusted or tailored to pupil size to achieve an optimal balance between foveal vision correction, increased depth of focus, and reduced IQ sensitivity.

[0075] Currently available contact lenses remain a cost effective means for vision correction. The thin plastic lenses fit over the cornea of the eye to correct vision defects, including myopia or nearsightedness, hyperopia or farsightedness, astigmatism, i.e. asphericity in the cornea, and presbyopia, i.e., the loss of the ability of the crystalline lens to accommodate. Contact lenses are available in a variety of forms and are made of a variety of materials to provide different functionality.

[0076] Daily wear soft contact lenses are typically made from soft polymer materials combined with water for oxygen permeability. Daily wear soft contact lenses may be daily disposable or extended wear disposable. Daily disposable contact lenses are usually worn for a single day and then thrown away, while extended wear disposable contact lenses are usually worn for a period of up to thirty days. Colored soft contact lenses use different materials to provide different functionality. For example, a visibility tint contact lens uses a light tint to aid the wearer in locating a dropped contact lens, enhancement tint contact lenses have a translucent tint that is meant to enhance one's natural eye color, the color tint contact lens comprises a darker, opaque tint meant to change one's eye color, and the light filtering tint contact lens functions to enhance certain colors while muting others. Rigid gas permeable hard contact lenses are made from siloxane-containing polymers but are more rigid than soft contact lenses and thus hold their shape and are more durable. Bifocal contact lenses are designed specifically for patients with presbyopia and are available in both soft and rigid varieties. Toric contact lenses are designed specifically for patients with astigmatism and are also available in both soft and rigid varieties. Combination lenses combining different aspects of the above are also available, for example, hybrid contact lenses.

[0077] It is important to note that the multifocal lens design of the present invention may be incorporated into any number of different contact lenses formed from any number of materials. Specifically, the multifocal lens design of the present invention may be utilized in any of the contact lenses described herein, including, daily wear soft contact lenses, rigid gas permeable contact lenses, bifocal contact lenses, toric contact lenses and hybrid contact lenses. In addition, although the invention is described with respect to contact lenses, it is important to note that the concept of the present invention may be utilized in spectacle lenses, intraocular lenses, corneal inlays and onlays.

[0078] Although shown and described is what is believed to be the most practical and preferred embodiments, it is apparent that departures from specific designs and methods described and shown will suggest themselves to those skilled in the art and may be used without departing from the spirit and scope of the invention. The present invention is not restricted to the particular constructions described and illustrated, but should be constructed to cohere with all modifications that may fall within the scope of the appended claims.