Patent Grant
10921614
This invention relates generally to improved spectacle lenses, in more detail to spectacle lenses that reduce eye-strain and relax convergence, and alter proprioceptive feedback.
With normal vision, an individual is able to focus at objects located at different distances. Ideally, an individual is able to focus on distant objects, referred to as distance-vision, and on near objects, referred to as near-vision. The optical system of the eye uses numerous muscles to focus for both distance-vision and for near-vision. These muscles adjust various aspects of the eye when transitioning between distance-vision and near-vision. The muscle adjustments include making subtle changes to the shape of the crystalline lens to ad just the focus of the lens, rotating the eyeballs to rotate their optical axes, and changing the size of the pupils.
Presbyopia is a natural deterioration of near vision caused by loss of flexibility in the eye's crystalline lenses as one ages. Presbyopia can be partially compensated by wearing “reading” glasses that correct near-vision refraction errors so that the eye does not have to focus as strongly when gazing at near objects. Presbyopic persons need different optical corrections for near-vision and for distance-vision. However, using two glasses and changing them with great frequency is distracting. To avoid continually exchanging eyeglasses, bifocals may be used that offer different optical collections for near-vision and for distance-vision. The transition between these two vision regions can be abrupt or gradual. The latter eyeglasses are called Progressive Addition Lenses (PALs). Abrupt change bifocals have a visible line separating the two vision regions, while PALs have no lines or edges visible between the regions with different dioptric powers.
In spite of all this progress, some types of vision-related discomforts still persist. One of these discomforts is related to a shift of habits in the modem, digital lifestyle. A large and increasing fraction of professions require workers to spend a large and increasing fraction of their working time focusing at close-distance digital interfaces, including computer screens and mobile devices. The same is true for the private lives of many, spending hours playing video games, texting and checking updates on cell phones, among others. All these professional and behavioral shifts rapidly increased the time people spend looking at digital screens, devices, displays, and monitors at a much closer distance than before. The increased time of the eye being trained at near-vision targets places excessive demands on the muscles involved in near-vision, often straining them beyond the comfort zone. This can lead to fatigue, discomfort, pain, or even digitally induced migraines. Up to now, there is no widely accepted consensus on the precise causation mechanism of these digital-device related visual discomforts, pains and migraines. Therefore, there is a need for glasses, or other optometric solutions than can provide relief for digital eye discomforts.
Embodiments include a convergence-reducing lens of a low-convergence spectacle, wherein; a central normal of the convergence-reducing lens defines a z-axis, and a center of the convergence-reducing lens defines a tangential, centered x-y plane, together defining an x-y-z coordinate system of the convergence-reducing lens, the convergence-reducing lens comprising a distance-vision region, having a negative distance-vision optical power, configured to refract a light ray, directed parallel to the z-axis at a distance-vision region point at an x-distance from a y-z plane of the coordinate system, so that its extension intersects the y-z plane at a distance-vision intersection z-distance; and a near-vision region, having a near-vision optical power that matches the distance-vision optical power within 0.5 D, configured to refract a light ray, directed parallel to the z-axis at a near-vision region point at the x-distance of the distance-vision region point, at a corresponding y height, so that its extension intersects the y-z plane at a near-vision intersection z-distance that is smaller than the distance-vision intersection z-distance.
Embodiments further include a convergence-reducing lens, wherein a central normal of the convergence-reducing lens defines a z-axis, and a center of the convergence-reducing lens defines a tangential, centered x-y plane, together defining an x-y-z coordinate system of the convergence-reducing lens, the convergence-reducing lens comprising a distance-vision region, having a negative distance-vision optical power, configured to refract a light ray, directed by a source at a distance-vision region point at an x-distance from a y-z plane of the coordinate system, to form a distance-vision light-convergence angle with the y-z plane, wherein the source is located on the z-axis at an intersection z-distance from a center of the coordinate system; and a near-vision region, having a near-vision optical power that matches the distance-vision optical power within 0.5 D, configured to refract a light ray, directed by the source at a near-vision region point at the x-distance from the y-z plane of the coordinate system, at a corresponding y height, to form a near-vision light-convergence angle with the y-z plane, wherein the source is located on the z-axis at the intersection z-distance from the center of the coordinate system; and an x-component of the near-vision light-convergence angle is greater than an x-component of the distance-vision light-convergence angle.
Embodiments of the invention are placed into context by first describing the effect of regular, monovision lenses of existing spectacles on the gaze-convergence angles for near-vision. This will be followed by the description of the embodiments of the invention.
A negative optical power monovision lens refracts the light rays away from the optical axis, so that the source-side extensions of die rays intersect at a (virtual) focus point F. It is customary to characterize this by saying that the negative power lenses have a negative focal length.
There are different, related ways to characterize the amount of refraction by a lens region at a radial distance r from the axis. One characterization is by the refraction angle α itself. Another is by the tangent of this same refraction angle, expressed as a ratio of r, the radial distance of the region of the lens from a lens optical axis 3, to f, the focal distance of the lens:
tan α=r/f. (1)
This relation shows that a lens of optical power of D diopters, defined as D=1/f[1/m], induces a refraction angle α for rays that are incident at the lens at a radial distance r from the axis 3 of the lens 1, where α is given by
tan α=r*D. (2)
The lower graph of
αx=x*D. (3)
The lower graph in
Analogous definitions of αx include tan αx=sin ϕ*tan α, which accounts more precisely for the geometry of projections of the refracted light rays 2. However, for the present small angles these two definitions yield very similar numerical values. Finally, the formula can be extended for light rays 2 that are not parallel with the optical axis 3, but, rather, form an angle β with the optical axis 3. In general, such extensions would yield an object-angle dependent expression, through a dependence on the angle β. Notably though, such a β-dependent formula can be expanded in α. Such an expansion would reproduce Eq. (2) in leading order in α.
αx characterizes the x-component of the refraction angle α that in turn determines how much a wearer of the spectacle need to turn her/his gaze to concentrate on these light rays. The greater the αx in a region of the lens 10, the more the light 2 passing through this region is refracted by the lens 10 and the more a wearer has to turn her/his gaze relative to the lens 10 to align with this refracted light 2.
As mentioned before, the eyeballs are rotated by muscles attached externally to the eye. In particular, the lateral, x-directional, rotations are controlled by the medial recto and the lateral recurs muscles, and the vertical rotations are controlled by the superior rectus and the inferior rectus, and superior oblique and inferior oblique muscles. When the medial rectus muscles of the left-eye and the right-eye contract, the gazes of these eyes converge towards each other. A person, training his/her eye on a near object, such as an electronic screen, a digital screen, a screen of a mobile electronic device, work-related papers, or even a book, for extended periods requires the continuous contraction of the medial recurs muscles and the superior oblique muscles, and thus exerts substantial strain on them. This “digital eyestrain” can lead to fatigue, leading to headache, eventually culminating in migraines, caused by the demands of the modern, digital lifestyle.
The digital lifestyle can induce other forms of asthenopia, or eye-strain, and other types of convergence-disorders, including proprioceptive disparity and fixation disparity. Proprioceptive disparity is an imbalance between where the eyes are consciously focused and the perception of where the object is located in space. This disparity depends on different factors. The brain of a patient with a proprioceptive disparity can compensate for this disparity. However, doing so may overstimulate the trigeminal nerve, resulting in patients experiencing headaches, eye fatigue, pain around the eyes, blurred vision, neck pain, dry eyes, and other general symptoms of asthenopia.
A class of symptoms especially worthy of mentioning is Computer Vision Syndrome (CVS), which is estimated to affect More than 100 million Americans. Computer Vision Syndrome is the physical eye discomfort felt after spending a prolonged time viewing near-distance computer devices. CVS can include, or induce, a variety of asthenopia symptoms, and thus can have negative effects on health, well-being, mood and productivity.
Another large class of symptoms is known by the name of Chronic Daily Headaches (CDR). CDH symptoms are estimated to affect more than 30 million Americans. These patients suffer from an over-stimulation of the trigeminal nerve that manifests itself in chronic daily headaches. Various factors and triggers are believed to contribute to debilitating chronic daily headaches. In the absence of a consensus on its causation, patients suffering from CDH are limited to treatment options that merely seek to dull the symptoms. Applicants noted, however, that a substantial fraction of chronic daily headache patients exhibit objective signs of a misalignment between how the central visual system, the peripheral visual system, and the neurological system interact. Therefore, Applicants propose to alleviate the root causes of asthenopia, CVS, and CDH by developing spectacle lenses that modify the gaze convergence and address the observed misalignment.
With this x-y-z coordinate system, and with reference to
The x-z locations of the eye-center representative locations 8 in
Since the optical power of the near-vision region 120 can be very close, and in some embodiments, equal to the optical power of the distance-vision region 110, embodiments of the convergence-reducing lens 100 can be called a monovision lens, or a single-vision lens. This aspect can distinguish these lenses from other, traditional bi-focal lenses where the near-vision and distance-vision optical powers are different.
For clarity, in this document the term “optical power” refers to the optical power specifically related to the focal length f of the lens, and is measured in diopters D that are inversely related to the focal length: D=1/f. Also,
In the embodiments of
Related eye-strain reducing lenses with non-negative optical power in the distance-vision region have been described in the co-pending and commonly owned patent applications U.S. Ser. No. 15/289,157: “Eye-strain reducing lens”; U.S. Ser. No. 15/289,163: “Low convergence spectacles”; and U.S. Ser. No. 15/289,194: “Lens with off-axis curvature center”, all three to J. P. Krall, A. Plumley and G. T. Zimanyi. A point of difference between the presently described embodiments and those described in these three applications is that non-negative power lenses exacerbate eye-strain in the near vision region, while the here described negative power lenses may reduce eye-strain to a limited degree. In spite of this reduction, however, Applicants found, while working with patients, that further relief is often needed. This further relief of eye-strain is delivered by the here described eye-strain reducing spectacles 100′.
Bifocal glasses have a near-vision region separate from the usual distance-vision region. Such glasses can be bestowed with the additional medical benefit of eye-strain reduction by making the convergence, or refractive, properties of these two vision regions also different.
A distinguishing feature of the here-described single-vision, or monovision convergence-reducing lenses 100 is that they have a near-vision region 120 with a refractive power different from the refractive power of the distance-vision region 110, in spite of the two regions having matching optical powers. This is to be contrasted with the just-mentioned bifocal lenses, where both the refractive and the optical powers of the two vision regions are different. This is a qualitative, crucial distinction for at least the following reasons.
(1) Bifocal spectacles already have two vision regions with a differing optical property, the optical power. Therefore, it may occur to a lens designer to make a further optical property also different, such as the refractive power, to reduce convergence. However, in monovision lenses it is far from obvious for a designer to think of, and to create a near-vision region for the sole purpose of delivering a different refractive power in a lens where the optical power of the near-vision region is the same as that of the distance-vision region of the lens.
(2) The global market for spectacle lenses exceeded 1 billion units sold worldwide in 2015, and more than 320 million in the US alone. It is also estimated that 75% of the US population, or about 240 million people wear some sort of vision correcting spectacles. By far the broadest market segment of spectacles sold in the US today, about 90% of the total market, have monovision lenses, and only about 10%, or 20-25 million people wear bifocals. The mostly younger and early-middle age wearers of monovision lenses simply do not need bifocal lenses. Some industry surveys estimate the number of people who suffer, or report, Computer Vision. Syndrome to exceed 100 million people, Earlier we have cited other sources that estimated the potential patients at 30 million, based different symptoms and definitions; Therefore, introducing convergence-reducing near-vision regions into monovision spectacles will extend the reach of the convergence-reduction technology from the narrow, 10-20 million unit/year market segment of bifocals to the 100 million-plus unit/year market segment of monovision glasses. Therefore, the here-described monovision glasses will dramatically broaden the group of people to whom the medical benefit of convergence-reduction can be delivered.
(3) Convergence-reducing monovision glasses with zero or near zero optical powers will qualitatively broaden the market penetration to yet another wide class. These glasses will deliver the medical benefit of convergence reduction to people who do not need optical power correction at all, and therefore did not think of wearing glasses up to now. For this reason, zero, or near-zero, optical power monovision spectacles will dramatically extend the segment of the population to whom the medical benefit of convergence-reduction is delivered even further.
Finally, it is mentioned that in present-day optometric practice, most doctors have a different theory of the cause of eye-strain, and therefore offer very different treatments and procedures to alleviate eye-strain, or asthenopia. Optometrists often prescribe switching to glasses with blue light filters, or, suggest using humidifiers. Therefore, prescribing glasses with the here-described convergence-reduction technology rests on a very different medical insight regarding what causes eye-strain, and an inventive treatment to alleviate it that is genuinely different from what is prescribed by the majority of today's optometric practitioners.
In this patent document, the term monovision lens, or single-vision lens, is used in a broader sense. Naturally, its scope includes lenses whose front and rear surfaces each have a single radius of curvature. Beyond that, the term can also include lenses whose shape has components beyond the single radius of curvature. An example is an aspheric component, where components can be defined in different manners, including Zernike decompositions. Typically, aspheric components are introduced to compensate for an optical distortion of the lens. Several factors can cause the optical distortion: the finite thickness of the lens, aspects of the index of refraction, and the far-from axis behavior of the light rays, among others. An aspheric component can also be introduced not for compensating a distortion, but to achieve an optical benefit. The term monovision can also include lens shapes that combine a single optical power with a power-neutral benefit. Typical examples include a cylinder, astigmatism, or coma, introduced into an otherwise single-vision lens, to compensate a corresponding vision distortion. The scope of single-vision lenses does not include bifocal lenses. To summarize, in the described convergence-reducing lenses 100 at least one of the distance-vision region 110, or the near-vision region 120, can include an aspheric component, a power-neutral component, a cylinder, a coma, or an astigmatic component.
Here and later in the text, the light propagation is described as originated by the source 11, or interchangeably from an object 11. The source 11 can be a laser pointer or another, directed light source that actively generates a light ray 2. In some other embodiments, the object 11 may not be an active light source, rather, an object or mirror that reflects an incident light as the described light 2 toward the convergence-reducing lens 100, wherein the incident light originated somewhere else. From the viewpoint of the light propagation, these two cases can be interchangeable. The object 11, or source 11, can be at a z-distance zo/s from the x-y plane of the convergence-reducing lens 100.
In embodiments of the convergence-reducing lens 100, the distance-vision region 110 can be configured to refract the light ray 2, directed by the source 11, or object, 11 at the distance-vision region point Pd at the distance-vision x-distance xPd, to intersect a y-z plane of the coordinate system with a distance-vision gaze-convergence angle βd; whereas the near-vision region 120 can be configured to refract the light ray 2, directed by the source 11 at the near-vision region point Pn at the near-vision x-distance xPn, to intersect the y-z plane with a near-vision gaze-convergence angle βn. In these embodiments of the convergence-reducing lens 100 the near-vision gaze-convergence angle βn, can be smaller than the distance-vision gaze-convergence angle βd. Typically, the intersection of the refracted light 2 with the y-z plane with the gaze convergence angle βn/d occurs at the eye-center representative location 8.
Here, the gaze-convergence angles βd and βn characterize the convergence of the eye's gaze, and thus they can correspond to the x-component of the overall, 3d dimensional rotation angle of the eyes, in analogy to αx, the x-component of the overall refraction angle α.
The reduction of the gaze-convergence angle βn in the near-vision region 120 relative to the gaze-convergence angle βd in the distance-vision region 110 is a second expression that when the wearer looks at an object 11 through the near-vision region 120 of the convergence-reducing lens 100, she/he does not need to rotate her/his eyes away from the z-axis 3 as much as in the case of looking at the same object through the distance-vision region 110 of the lens 100. Therefore, embodiments of the convergence-reducing lens 100 indeed reduce the convergence angle β of the gaze of its wearer, when looking at objects through the near-vision region 120, compared to looking at the same object through the distance-vision region 110 at the corresponding y height, or even through an analogous regular negative power lens 10.
In some embodiments of the convergence-reducing lens 100, the distance-vision region 110 can be configured to refract the light ray 2, directed by or from the source 11 at the distance-vision region point Pd at the distance-vision x-distance xPd, by a distance-vision refraction angle αd, whereas the near-vision region 120 can be configured to refract the light ray 2, directed by or from the source 11 at the near-vision region point Pn at the near-vision x-distance xPn, by a near-vision refraction angle αn. In such embodiments of the convergence-reducing lens 100, an x-component αnx of the near-vision refraction angle αn can be greater than an x-component αdx of the distance-vision refraction angle αd. This is a third expression that the lens 100 is reducing the gaze-convergence β, when its wearer is looking at the object 11 through the near-vision region 120, relative to looking at the same object 11 through the distance-vision region 110 at the appropriate y height.
The above three related expressions of the gaze-convergence reducing aspects of the convergence-reducing lens 100 are stated as boxed inequalities in FIG. SB. These inequalities are repeated here:
xPn<xPd, (4)
βn<βd, and (5)
αdx<αnx, (6)
all for the same fixed object, or source, distance zo/s. Embodiments of the convergence-reducing lens 100 satisfy at least one of these three inequalities (4)-(6).
The above descriptions of embodiments of the convergence-reducing lens 100 also articulate auditing protocols to determine, whether a lens is a convergence-reducing lens.
(1) It is possible to measure the described distance xPd and angles αdx and βd directly, when a wearer of the lens is looking at an object through a distance-vision region of a lens, followed by measuring the corresponding distance xPn and angles αnx and βn as the wearer looks through a corresponding near-vision region of the lens, and then to compare the measured angles and distances to verify whether they satisfy at least one of the described three inequalities (4)-(6). For lenses, where the changes of the angles are small, an eye-tracking, or eye-imaging, system can be used to determine the changes in the wearer's gaze-angle to detect the small changes and differences.
(2) Instead of measuring angles and directions of a wearer's gaze, an eye model with realistic parameters can be used as well. The eye model can include a disk of a diameter of about 20-25 mm, such as 24 mm, rotatable around a y-axis, positioned at an eye-center representative location 8. The from of the eye model can be positioned 10-15 mm behind the lens 100, the eye-center representative location 8 about 20-30 mm behind the lens 100. The eye model can include an appropriate model lens, with a total optical power approximately equal to that of the cornea, about 40-45 D, plus that of the eye lens 7, about 15-25 D. A directed light source, such as a laser pointer, or equivalents, can be deployed in place of the source 11. Its light can be pointed at the distance-vision region, and then separately at the near-vision region of an audited lens. The eye model can be appropriately rotated, so that after refraction by the model lens, the light goes through the eye-center representative location 8 of the eye model in both cases. The above-described angles and distances of inequalities (4)-(6) can then be measured to determine whether at least one of the three above inequalities applies to the audited lens.
(3) Finally, measurements without involving a wearer's eye, or even an eye-model, can also be sufficient to determine whether an audited lens is an embodiment of the convergence-reducing lens 100. A lens can be audited on a fixed optical table by pointing a laser pointer from a position of the source 11 at the lens such that its light after refraction by the lens propagates through a candidate point for an eye-center representative location 8, about 20-30 mm behind the center of the lens 100 along the z-axis 3. The light's propagation can be tracked, e.g., by implementing a screen in the y-z plane of the lens 100 on the side opposite to the source 11. The light of the laser pointer 11 can be directed at a distance-vision region of the audited lens, then subsequently through a near-vision region of the audited lens, ensuring that the refracted light in both cases intersects the y-z plane at the same z-distance from a center of the coordinate system that is representative of an eye center 8. As described above, such representative locations can be 20-30 mm behind the center of the lens, on the z-axis 3. Once the angles and distances, discussed before, are measured for the light directed at the distance-vision and then the near-vision regions, a lens is an embodiment of the convergence-reducing lens 100 if at least one of the three inequalities in
Adjusting the “corresponding y height” of the eye-center representative location 8 in
For each of these cases, however, analogous alternative “lens-adjusting protocols” can be defined and performed, where the y height of the convergence-reducing lens 100 is adjusted instead of that of the images, or the sources by lifting or lowering the lens itself, while keeping the y heights of the source and the image fixed. For these protocols, the “corresponding y height” of the eye-center representative location 8 of the near-vision region 120 is the same as for the distance-vision region 110. These lens-adjusting protocols can also be used to audit whether any one of the inequalities (4)-(6) is satisfied by the audited lens, and thus capture the embodiments of the convergence-reducing lens 100 in an equivalent manner.
A third class of alternative, “source-adjusting protocols” keep the y heights of both the images and the convergence-reducing lens 100 fixed, and adjust the y heights of the sources instead. As before, these source-adjusting protocols can be used to audit whether any one of the inequalities (4)-(6) is satisfied by the audited lens, and thus capture the embodiments of the convergence-reducing lens 100 in an equivalent manner.
In sum, in embodiments of the convergence-reducing lens 100, or eye-strain-reducing lens 100 the near-vision x-distance xPn can be smaller than the distance-vision x-distance xPd as determined by at least one of an image-adjusting protocol, a lens-adjusting protocol, or a source-adjusting protocol. Yet other auditing protocols will be described later, in relation to
The convergence-reducing lens 100 can include a progression region 140 where at least one of xPp, the x-distance of a progression region point Pp; or a progression region gaze-convergence angle βP, or an x-component of the progression-region refraction angle, αpx, transitions between its near-vision region value and its distance-vision region value. Formally, at least one of the following inequalities hold in the progression region 140: xPn<xPp<xPd; or βn<βp<βd; or αpx<αnx. An example of such a progression region 140 will be described in some detail in
With these introductory considerations, some embodiments of a convergence-reducing lens 100 can have a distance-vision region 110, having a negative distance-vision optical power, that is configured to refract a light ray 2 directed by a source 8r at a distance-vision region point Pd, at a distance-vision x-distance xPd from the center of the coordinate system, to propagate to an image point 11r. The image point 11r, in some sense the reverse-pair of the object/source 11 of the embodiments in
This embodiment of the convergence-reducing lens 100 can further include a near-vision region 120, having a near-vision optical power that matches the distance-vision optical power within 0.5 D, configured to refract a light ray 2 directed by the source 8r, located at the same source-z-distance zs from a center of the coordinate system, at a near-vision region point Pn at a near-vision x-distance xPn from the center of the coordinate system to propagate to an x-z location of the image point 11r, at a corresponding y height. In these embodiments, the near-vision x-distance xPn can be smaller than the distance-vision x-distance xPd, in analogy to inequality (4) of the embodiments of
The x-z locations of the image points 11r in
As discussed earlier, in some embodiments, analogous protocols can be defined where a y height of the convergence-reducing lens 100 is adjusted instead the y height of the image point 11r, so that the y directional angle of the light ray 2 does not need to be adjusted when switching from the distance-vision region 110 to the near-vision region 120. Finally, in yet other alternative embodiments, a y height of the source 8r can be adjusted when redirecting the light rays 2 from the distance-vision region 110 to the near-vision region 120, while preserving the y heights of the convergence-reducing lens 100 and the image point 11r. As before, image-adjusting, lens-adjusting, and source-adjusting protocols can define closely related embodiments of the convergence-reducing lens 100.
In some embodiments, the distance-vision region 110 can be configured so that the source 8r can direct the light ray 2 to propagate to the image point 11r via a refraction at the distance-vision region point Pd by directing the light ray 2 with a distance-vision gaze-convergence angle βd relative to a y-z plane of the coordinate system; and the near-vision region 120 can be configured so that the source 8r can direct the light ray 2 to propagate to the x-z location of the image point 11r via a refraction at the near-vision region point Pn by directing the light ray 2 with a near-vision gaze-convergence angle βn relative to the y-z plane of the coordinate system. In these embodiments, the near-vision gaze-convergence angle βn can be smaller than the distance-vision gaze-convergence angle βd, in analogy to inequality (5) above.
In some embodiments, the distance-vision region 110 can be configured to refract the light ray 2, directed by the source 8r at the distance-vision region point Pd to propagate to the image point 11r, by a distance-vision refraction angle αd. The near-vision region 120 can be configured to refract the light ray 2, directed by the source 8r at the near-vision region point Pn to propagate to the x-z location of die image point 11r, by a near-vision refraction angle αn. In embodiments, αnx, the x-component of the near-vision refraction angle αn can be greater than αdx, the x-component of the distance-vision refraction angle, αd, in analogy to inequality (6) above.
As before, the convergence-reducing lens 100 can include a progression region 140 where at least one of the xPp, the x-distance of a progression region point Pp, a progression region gaze-convergence angle βP, and an x-component of the progression-region refraction angle, αpx, transitions between its near-vision region value and its distance-vision region value.
The convergence-reducing lens 100 can also include a progression region 140, where the x component of the refraction angle αpx varies from αdx values related to the distance-vision region 110 to αnx values related to the near-vision region 120. The progression region 140 is shaped such that αpx, the x component of the refraction angle α in the progression region 140 smoothly interpolates between αdx and αnx: αdx<αpx<αnx. Further, this progression region 140, at least partially between the distance-vision region 110 and the near-vision region 120, can be configured to refract the light ray 2, directed by the source 11 at a progression region point Pp at a progression x-distance xPp to propagate to the eye-center representative location 8; wherein the progression x-distance xPp can be between the near-vision x-distance xPn and the distance-vision x-distance xPd: xPn<xPp<xPd. Finally and correspondingly, the gaze convergence angle βp of the progression region 140 can also smoothly interpolate between its values in the distance-vision region 110 and the near-vision region 120: αn<αp<αd.
In some embodiments, an area of the near-vision region 120 can be greater than 5 mm2. In some embodiments, the area of the near-vision region 120 can be greater than 10 mm2.
γdvr<γnvr. (7)
This inequality is one way to design a convergence-reducing lens 100 that achieves at least one of the three inequalities (4)-(6). Several other designs can be consistent with this inequality also. In some cases, the inequality of the angles in inequality (7) can be solely driven by only one of the tangentials being different, such as the near-vision front-tangential 145fn being inward-rotated relative to the distance-vision front-tangential 145fd, while the rear tangentials 145rn and 145rd being the same.
In some cases, the convergence-reducing lens 100 can be a meniscus lens 100, as shown. It is also noted that these angles γnvr and γdvr depend on the x-distance where the tangentials were fitted to the surfaces 140r and 140f: γnvr=γdvr(x), and γdvr(x). The angles γnvr (x) and γdvr (x) are to be determined and compared at the same nasal x-distances from the center of the coordinate system.
γnvr=γdvr. (8)
Instead of modifying the surface tangentials, in these embodiments the distance-vision region 110 has a distance-vision z-axis 3; the near-vision region 120 has a near-vision z-axis 3, and the near-vision z-axis 3 is angled, rotated, or twisted, in a nasal direction relative to the distance-vision z-axis 3. The twist is illustrated from looking down on the lens from the +y axis direction. The distance-vision z-axis 3 at the highest y heights of the lens 100 where the distance-vision region 110 is naturally located, can be essentially parallel to the overall lens z-axis 3. Progressing towards lower y heights, where the near-vision region 120 is naturally located, the x-y plane of the lens is getting rotated so that the z-axis 3 is rotated in the nasal direction. Two of the rotated, or twisted cross sections are shown in
It is noted that a manufacturing process of the embodiment of
Next, the embodiments of
zln<zld. (9)
In some embodiments of the convergence-reducing lens 100, the distance-vision region 110 can be configured to refract the light ray 2, directed parallel to the z-axis 3 at the distance-vision region point Pd at the x-distance xPd, by a distance-vision refraction angle αd. The near-vision region 120 can lie configured to refract the light ray 2, directed parallel to the z-axis 3 at the near-vision region point Pn at the x-distance xPn, (xPn=xPd), at the corresponding y height, by a near-vision refraction angle αn. In embodiments, αnx, an x-component of the near-vision refraction angle αn can be greater than αdx, an x-component of the distance-vision refraction angle αd:
αdx<αnx. (10)
Here and subsequently, the refraction angles α and gaze-convergence angles β refer to the magnitude of the angles. In some embodiments of the convergence-reducing lens 100, the distance-vision region 110 can be configured to refract the light ray 2, directed parallel to the z-axis 3 at the distance-vision region point Pd at the x-distance xPd so that its extension intersects the y-z plane with a distance-vision gaze-convergence angle αd. The near-vision region 120 can be configured to refract the light ray 2 directed parallel to the z-axis 3 at the near-vision region point Pn at the same x-distance xPn=xPd, at the corresponding y height, so that its extension intersects the y-z plane with a near-vision gaze-convergence angle βn. In embodiments, the near-vision gaze-convergence angle βn can be greater than the distance-vision gaze-convergence angle βd:
βd<βn. (11)
The inequalities (9)-(11) characterize the embodiments of
As before, embodiments of the convergence-reducing lens 100 can further include a progression region 140, at least partially between the distance-vision region 110 and the near-vision region 120, that is configured to refract a light ray 2, directed parallel to the z-axis 3 at a progression region point Pp at the x-distance xPp that is the same as of the distance-vision region point xPp=xPn=xPd so that its extension intersects the y-z plane at a progression intersection z-distance zip that is between the near-vision intersection z-distance zIn and the distance-vision intersection z-distance zldzln<zlp<zld.
δdx<δnx. (12)
Correspondingly, in some embodiments of the convergence-reducing lens 100, the distance-vision region 110 can be configured to refract the light ray 2, directed by the source 15r at the distance-vision region point Pd at xPd, the x-distance from the y-z plane of the coordinate system, by a distance-vision refraction angle αd. Further, the near-vision region 120 can be configured to refract a light ray 2, directed by the source 15r at the near-vision region point Pn at xPn, the x-distance from the y-z plane of the coordinate system, at the corresponding y height, by a near-vision refraction angle αn. In embodiments αnx, an x-component of the near-vision refraction angle αn can be greater than αdx, an x-component of the distance-vision refraction angle αd:
αdx−αnx. (13)
Inequalities (12)-(13) characterize the embodiments of
The convergence-reducing lens 100 can include the above-mentioned distance-vision region 110 with a negative distance-vision optical power, having a distance-vision front surface 140df with a radius of curvature Rdf and a center of distance-vision front curvature CCdf, and a distance-vision rear surface 140dr with a radius of curvature Rdr and a center of distance-vision rear curvature CCdr. The convergence-reducing lens 100 can further include a near-vision region 120 with an optical power within 0.5 D of the distance-vision optical power, having a near-vision front surface 140nf with a radius of curvature Rnf and a center of near-vision front curvature CCnf, and a near-vision rear surface 140nr with a radius of curvature Rnr and a center of near-vision rear curvature CCnr; wherein an x-coordinate of the center of near-vision front curvature x(CCnf) can be nasal relative to an x-coordinate of the center of distance-vision front curvature x(CCdf), or an x-coordinate of the center of near-vision rear curvature x(CCnr) can be temporal relative to an x-coordinate of the center of distance-vision rear curvature x(CCdr). Expressing the above attributes in inequalities, and using the directionality of the x-axis, such that points lying to the right, temporal direction have greater x coordinates than points lying to the left, nasal direction, these conditions can be written as:
x(CCnf)<x(CCdf), or (14)
x(CCnf)>x(CCdr). (15)
x(CCnf)<0, or (16)
x(CCnr), the x-coordinate of the center of near-vision rear curvature is temporal relative to the z-axis 3 of the coordinate system, i.e.
x(CCnr)>0. (17)
In this sense, embodiments of the convergence-reducing lens 100 are off-axis center of curvature lenses. As before, a y height corresponding to the near-vision region 120 and its surfaces 140nf and 140nr can be lower than a y height of the distance vision region 110 and its surfaces 140df and 140dr.
The above-described coordinates and x-distances of the centers of curvature x(CCnf), x(CCnr), x(CCdf), and x(CCdr) can be determined with specialized tools and devices, such as spherometers and lens profilometers.
Designs of the convergence-reducing lens 100 can achieve the optical power of the near-vision region 120 to match the optical power of the distance-vision region 110 within 0.5 D, in spite of the centers of curvature being off axis. This is so because the optical power in first approximation is given only by the radii of curvature of the lens front and rear surfaces, not the location of the centers of curvature: Optical power (distance−vision)=f(Rdf, Rdr), and Optical power (near−vision)=f(Rnf, Rnr). In the thin lens approximation, the optical power is proportional to f(R1, R2)=(n−1) (1/R1-1/R2). As long as f(Rnf, Rnr)=f(Rdf, Rdr), the optical powers in the two regions are matching in a leading order approximation.
Designs of the convergence-reducing lens 100 can be viewed as built on the recognition that it is possible to leave the optical power of the near-vision region 120 essentially equal to that of the optical power of the distance-vision region 110 by not manipulating the radii of the corresponding curvatures, yet, to adjust and manipulate the near-vision refraction angles relative to the distance-vision refraction angles by moving the centers of curvature off the z-axis 3 of the convergence-reducing lens 100, More concisely, in designs of the convergence-reducing lens 100 it is possible to form the refraction angles αax of the near-vision region 120 different from the refraction angles αdx of the distance-vision region 110, while preserving that the optical power of the near-vision region 120 remains matching of the optical power of the distance-vision region 110. The refraction angles and the optical powers of these two regions are adjustable relatively independently from each other, in leading order of the off-center displacements.
Some embodiments of these convergence-reducing lenses 100 can be further characterized as follows, With reference to
γdvr<γnvr (18)
The off-axis curvature center, convergence-reducing lenses 100 of
It is noted that the near-vision region 120 of the convergence-reducing lenses 100 of
The near-vision region 120 can be formed by a variety of methods. Some techniques may use a free-form generator, or five-axis generator. Other techniques may use a 3 dimensional (3D) printer. Finally, in some cases, the shape of the near-vision region 120 may not differ from the distance-vision region 110. Rather, the different optical performance of these regions can be achieved by modulating the index of refraction n of the lens material differently in these regions. For example, nn, the index of refraction in the near-vision region 120 can be larger than nd, the index of refraction in the distance-vision region: nn>nd. Such embodiments of the convergence-reducing lens 100 can deliver many of the optical performances described in relation to
While this document contains many specifics, these should not be construed as limitations on the scope of an invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or a variation of a subcombination.
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