Ophthalmic equipment and lens elements

Abstract

An ophthalmic device comprising at least two corrective lenses (5, 5'), at least one of which is a variable-focus lens consisting of a superimposed anterior lens element (131) and a posterior lens element (141) arranged to have a variable focal length depending on their relative lateral distance (d), where d=0 is the overall horizontal meridian power Φ corresponding to the prescription of the user for whom the variable-focus lens is intended. p The front lens element (131) has a fixed power Φ f and the rear lens element (141) has a fixed power Φ r where Φ A 0 is the power provided by the variable focus lens at d=0, and Φ r is Φ p and Φ p is approximately 5% to 80% of the JPEG2025512047000014.jpg11167

Description

[Technical field]

[0001] The present invention relates to optical lenses with adjustable focal length. More specifically, the present disclosure relates to an improved Alvarez-type variable focus lens and ophthalmic devices incorporating same. [Background technology]

[0002] WO 2021 / 069930 A1, the contents of which are incorporated herein by reference, discloses a pair of spectacles 11 of the kind shown in Figures 1 and 2. The spectacles 11 are composed of two variable focus lenses 21, 22 mounted in a frame 12. The variable focus lenses 21, 22 are a type of lens composed of two optically transparent solid lens elements arranged one behind the other in a direction of looking through the lenses (indicated in Figure 2 by axis Z for each of the lenses 21, 22) and slidable relative to each other in a direction transverse to the direction of looking (indicated in Figure 2 by axis X) to vary the focal length of the lenses. The lenses 21, 22 are mounted in the frame 12 such that, in normal use, the transverse axis X of the sliding of the lens elements 31, 41 is approximately horizontal to the user, as shown in Figure 2.

[0003] This type of variable focus lens is well known in the art and is often commonly referred to as an Alvarez lens or a Roman lens. The Alvarez lens is disclosed in U.S. Pat. No. 3,305,294 A, the contents of which are incorporated herein by reference. Other adjustable lenses with cubic and higher order surfaces are disclosed in U.S. Pat. Nos. 3,583,790 A, 7,338,159 B2, 7,717,552 B2, 5,644,374 A, and WO 2013 / 030603 A1, the contents of all of which are also incorporated herein by reference. In general, this type of adjustable lens is composed of two overlapping lens elements, each lens element having opposing front and rear optical surfaces, which are configured to control the thickness between the surfaces of each lens element. This allows the lens to converge or diverge a light ray in a manner equivalent to a spherical lens when the light ray passes through both lens elements in succession. The thickness of each lens element varies complementarily with respect to the other lens elements according to a cubic function in the x,y plane perpendicular to the line of sight through the lens, so that the nearest equivalent spherical power (NES) of the lens varies with the relative lateral distance of the lens elements.

[0004] A suitable equation defining the thickness t between the opposing front and back surfaces of each lens element is: JPEG2025512047000002.jpg11151 where D is a constant representing the coefficient of the prism to be removed to minimize the thickness of the lens, which may be zero; E is a constant representing the thickness of the lens element at the optical axis z of the lens; x and y represent coordinates on a Cartesian coordinate system centered on the optical axis and lying in a plane perpendicular to the optical axis; A is a constant representing the rate of change of the refractive power of the lens with relative movement of the lens elements in the x direction, which is positive for one lens element and negative for the other lens element. However, as noted above, numerous variations and extensions to this formula are known in the art, and the invention is not limited in this respect.

[0005] As one skilled in the art will appreciate, a single lens element of an Alvarez lens does not have an optical axis, but a pair of lens elements functions like a normal spherical lens. Therefore, for any relative position of the lens elements, the optical axis can be defined as the position relative to the center of the effective spherical lens, i.e., the position at which there is no angular deflection of light rays passing through the lens. In equation (1) above, the "optical axis" is the origin of a formula conveniently used to define the Z-axis when aligning lenses in optical programs, etc., but does not necessarily correspond to the effective optical axis of the entire lens, depending on other surfaces. In reality, if one element is stationary and the other element is moving, the optical axis will also move closer to a central position between the origins of the two three-dimensional surfaces.

[0006] Conveniently, one surface of each lens element is flat or formed by a regular surface of revolution such as a sphere, while the opposite surface has a cubic surface as described above to control the thickness of the lens element. The cubic surface of each lens element may in some embodiments be suitably formed on an (as)pheric base curve in a manner known in the art. Thus, the lens elements may be arranged to slide relative to each other along a straight line or along a defined path (e.g., an arc with a component on the Z axis). For example, in some cases, the lens elements may be arranged to slide relative to each other on an arc in the horizontal (X, Z) plane relative to the user. In the following example, the cubic surfaces are configured on adjacent inner surfaces of the front and rear lens elements, rather than on the corresponding outer surfaces. This preferred configuration reduces aberrations due to off-axis fields.

[0007] In the glasses of WO 2021 / 069930A1, the two lenses 21, 22 are similar in structure, so for convenience, only the left lens 21 as seen by the user is described below for reference, but the right lens 22 is similar and mirrors the movement of the left lens 21 with respect to a central plane extending in the Z direction midway between the two lenses 21, 22. Therefore, the following description of the left lens 21 applies equally to the right lens 22. However, it is quite common for eyeglass wearers to have different corrective powers in both eyes when correcting refractive errors.

[0008] Thus, variable focus lens 21 comprises a front lens element 31 and a rear lens element 4. Front lens element 31 has a front surface 32 that is convex spherical, spherocylindrical, multifocal or freeform, and a cubic curved rear surface 33 as described above. Rear lens element 41 has a cubic curved front surface 42 as described above and a concave spherical, spherocylindrical, multifocal or freeform rear surface 43 that complements the rear surface 33 of front lens element 31 to form an Alvarez lens.

[0009] Typically, the front surface 32 of the front lens element 31 and the rear surface 43 of the rear lens element 42 have the same spherical curvature, thus providing the lens 21 with no net refractive power. However, in some cases, the front surface 32 of the front lens element 31 and the rear surface 43 of the rear lens element 41 may be configured relative to one another to cause light rays passing through both elements to converge or diverge, such as in spherical lenses with positive or negative refractive power. Thus, the lens 21 may be provided with a fixed prescription depending on the user's requirements.

[0010] It has been observed that in spectacles provided with such a fixed prescription, the amount of prism Δ exhibited by a variable focus lens as the optical centre of the lens moves towards the bridge 14 can cause discomfort to the wearer of said spectacles due to irritation due to excessive convergence or divergence of the eyes, as will be explained below with reference to Figures 3A and 3B.

[0011] 3A is a partial view of a pair of spectacles 111 having a variable focus lens 121 including a front lens element 131 fixed to a frame 113, with a fixed prescription provided solely by a movable rear lens element 141. In FIG. 3A, the front lens element 131 and the rear lens element are shown with a relative lateral distance d of nominally zero. In this configuration, the lens 121 is configured for farsightedness, with a total prescription power Φ p As shown, in the absence of a prism in place, light ray 150 is able to pass undeviated near the optical center of lens 121 and enter eye 160 of the wearer of eyeglasses 111.

[0012] FIG. 3B shows the same eyeglasses 111 as in FIG. 3A, but with rear lens element 141 offset by a lateral distance d relative to front lens element 131, and with a power Φ for focusing suitable for near vision. p +Φ n where Φ n is the add power resulting from the relative arrangement of lens elements 131, 141. In this case, a light ray 150 emanating from a point at which the wearer of the spectacles 111 wishes to focus is deflected by an angle α as it passes through lens 121, so that the wearer sees an angle (Φ p +Φ n As a result, the eye 160 must look along a useful line of sight 170 that does not match what the brain predicts through its accustomed useful accommodation. This problem is known as excess prism, and is well known to be a source of discomfort to eyeglass wearers. Summary of the Invention [Problem to be solved by the invention]

[0013] It is an object of the present invention to provide an ophthalmic device with a variable focus lens that ameliorates one or more of the above-mentioned problems.

[0014] Thus, according to a first aspect of the present invention, there is provided an ophthalmic device comprising at least two corrective lenses mounted on a support for supporting the lenses in front of a user's eye, thereby defining a line of sight through each lens, at least one of the lenses being a variable focus lens comprising front and rear superimposed lens elements shaped such that the focal length of the variable focus lens is variable depending on the relative lateral distance d of the front and rear lens elements, and having a power Φ A where d=0 is the overall horizontal meridian power Φ corresponding to the prescription of the user for whom the variable focus lens is intended. p is defined as the relative positions of the anterior and posterior lens elements that provide a fixed power Φ f and the rear lens element has a fixed power Φ r and the following equation holds: JPEG2025512047000003.jpg7143 Here, Φ A 0 is the power provided by the variable focus lens at d=0, and Φ r is Φ p has the same sign as Φ p between about 5% and about 80% of

[0015] Thus, the ophthalmic device of the present invention divides the fixed power of the lens (i.e., the power contribution not attributable to relative lateral displacement of the lens elements) between the front and rear lens elements. As described in more detail below, the inventors have discovered that such an arrangement advantageously reduces the amount of prism that occurs when stacked lens elements are laterally displaced relative to one another.

[0016] The ophthalmic device may, for example, comprise a pair of spectacles. However, in principle, the ophthalmic device may comprise any binocular vision device. The other corrective lens may also be a variable focus lens. The other variable focus lens may be a substantially identical mirror image of another lens. Such an arrangement may, for example, be appropriate in an ophthalmic device used by a wearer who requires the same corrective prescription for both eyes. However, as is often the case, the corrective prescriptions of the two variable focus lenses may be different, for example if the wearer's eyes require different corrective prescriptions.

[0017] It is also within the scope of the present invention to provide a variable focus lens with a required fixed prescription power, although in some embodiments the variable focus lens has a prescription power Φ of at least about 2 diopters in magnitude. p In other embodiments, the variable focus lens may be configured to provide a prescription power Φ having a magnitude of at least about 3 diopters. p may be configured to provide.

[0018] A variable focus lens has a fixed power Φ of the second lens element. r may be constructed to meet the following criteria: JPEG2025512047000004.jpg16150

[0019] where d max is the maximum relative lateral distance of the anterior and posterior lens elements, k is the power addition provided by the anterior and posterior lens elements as they are displaced laterally relative to one another, and P d is the interpupillary distance of the user of the device, and v is the distance between the center of rotation of the eyeball and the rear surface of the variable-focus lens. For adults, P d is typically between about 50 and about 75 millimeters. v may be between about 10 and about 30 millimeters. Δ is measured in diopters / meter, d=d max The variable-focus lens can be configured with a prism amount Δ in the range of approximately -0.66 to +0.58.

[0020] The variable focus lens may be configured such that 50 < k < 500 (diopters / mm). In some embodiments, the variable focus lens may be configured such that 150 < k < 300 (diopters / mm).

[0021] The variable focus lens may be configured to operate with a relative lateral distance between the front and rear lens elements in the range of about 2 mm to about 8 mm. However, in other embodiments of the present invention, the variable focus lens may be configured to operate over a smaller or larger range of the lateral distance.

[0022] The variable focal length lens is Φ r has the same sign as Φ p and may be configured to be equal between about 10% and about 60% of Φ p . In some embodiments, the variable focus lens is such that Φ r has the same sign as Φ p and is configured to be equal to at least about 20% of Φ p , preferably at least about 40% of Φ p .

[0023] In some embodiments, the variable focus lens may include a variable focus region. The variable focus region may be configured to provide a diopter change of about 0.5 D or more over at least a portion of the region. The variable focus region may be a bifocal, trifocal, or other type of multifocal region. The variable focus region may be a progressive addition region. When a variable focus region is provided in the variable focus lens, the lens has, at least in the region outside the variable focus region, Φ r has the same sign as Φ p and may be configured to be equal between about 5% and about 80% of Φ p .

[0024] When the variable focus lens includes a variable focus region, the contribution of the Alvarez lens to the add power and the contribution of the progressive add to the rate of change of inset with add power in the variable focus region are each within about 1 prism diopter. Also, the contribution of the Alvarez lens to the add power and the contribution of the progressive add to the rate of change of inset with add power in the variable focus region may be equal to within 0.5 prism diopters, and in some embodiments may be within 0.25 prism diopters, respectively.

[0025] The front lens element is fixedly mounted to the support and the rear lens element is movable relative to the front lens element to change the relative lateral distance of the lens elements. In other embodiments, the rear lens element may be fixedly mounted to the support and the front lens element may be movable relative to the rear lens element. In some embodiments, both lens elements are configured to move to some degree when changing the relative lateral distance of the lens elements.

[0026] The ophthalmic device may be an object worn on the eye, such as a pair of glasses, that has an adjustable focal length. The ophthalmic device may be part of an AR, VR or XR headset.

[0027] The device may form part of a visor or other corrective head wear. The device may include multiple lenses, one for each eye.

[0028] The other corrective lens may be a variable focus lens including any of the features disclosed above with respect to the at least one variable focus lens. For example, the other corrective lens may be a variable focus lens having similar characteristics as the at least one variable focus lens, such that both corrective lenses provide equivalent correction to the left and right eyes of the wearer of the device. Alternatively, the other corrective lens may be a variable focus lens having different characteristics than the at least one variable focus lens, such that the corrective lenses provide different correction to the left and right eyes of the wearer of the device, as desired.

[0029] According to a second aspect of the invention there is provided a pair of lens elements suitable for forming front and rear superimposed lens elements of at least one variable focus lens according to the first aspect of the invention. The pair of lens elements according to the second aspect of the invention may comprise any of the features of the respective front and rear lens elements according to the first aspect of the invention.

[0030] In the following, embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0031] [Figure 1-2] Fig. 1 is a top perspective view of the left front side of a pair of eyeglasses with two variable focus lenses mounted in a frame, and Fig. 2 is a top perspective view of the left front side of the eyeglasses of Fig. 1, showing the rear lens element of the variable focus lens detached from the cooperating front lens element. [Figure 3A-3B] Figure 3A is a schematic diagram showing an eye gazing through a variable focus Alvarez lens in which the relative lateral distance between the anterior and posterior lens elements is zero. Figure 3B corresponds to Figure 3A, but with the posterior lens element offset by a lateral distance d relative to the anterior lens element. [Figure 4A-4B] Figure 4A is a schematic top view of a person wearing the glasses looking at a nearby object, and Figure 4B is a close-up of the left eye and lens shown in Figure 4A. [Figure 5-6] Figure 5 is a graph showing the values ​​of posterior lens prescription power Φr that produce acceptable prism for a given value of target prescription power Φp for a fixed prescription Alvarez lens. Figure 6 plots the results shown in Figure 5 in terms of Φr / Φp. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The inventors have discovered that in ophthalmic devices including Alvarez-type lenses that provide a fixed prescription in addition to the variable focus power provided by the relative lateral displacement of the lens elements, the lenses can be made optically comfortable, lighter and thinner by distributing the fixed prescription among the lens elements to reduce the amount of prism exhibited by the lens as the lens elements are laterally displaced relative to one another.

[0033] Fig. 4A is a schematic diagram showing a pair of eyes 1, 1' separated by an interpupillary distance Pd looking at an object 3 at a distance D through a pair of lenses 5, 5'. The lenses 5, 5' provide a fixed prescription for distance vision along the horizontal meridian of the lenses 5, 5'. For illustrative purposes, the horizontal meridian H of the left variable focus lens 21 of the spectacles 11 is shown in Fig. 1. As can be seen, the horizontal meridian is the line defined by the front lens element 31 and the rear lens element 41, which intersects the line of sight through the lenses 21 when the wearer's eyes are directed from left to right or vice versa without causing an angular change in the vertical direction.

[0034] As shown in Figure 4B, when viewing an object 3, the eye must rotate by a line of sight angle θ relative to the orientation when viewing an object 5 from a distance to focus on the object 3, and the line of sight through the lenses 5, 5 is set a distance δ inward along the horizontal meridian from the center 51 of the lens 5. This center 51 is the optical center position when viewing a distant object through the lens.

[0035] The user selects a positive add power Φ to correct vision at near distance D. nIf we want a lens with JPEG2025512047000005.jpg9146where v is the distance between the center of rotation of the eyeball and the lens, and D is approximately approximated as 1 / δ. This assumes that D>>δ. For example, if a user has a positive add power Φ n If a user requires spectacles with a cornea, the add power can be provided by a suitable inset distance δ obtained from equation (2) to ensure a suitable convergence accommodation ratio and therefore optical comfort for the user. This correction is known in the field of single-element progressive and bifocal lenses.

[0036] It is also known in the art that the equation for δ can be modified to accommodate convergent or divergent correcting lenses, and the following analysis can be extended accordingly, although the following analysis is described for eye convergence when vision is corrected without interference, such as when contact lenses are worn.

[0037] [Alvarez Lens Prisms with Fixed Distance Prescription] In an Alvarez lens of the type shown in FIGS. 3A and 3B, the lens elements are offset from one another by a distance d, so that the optical surfaces of the lens elements provide a positive add power Φ n In this case, for a given relative lateral distance d, the positive add power Φ n is expressed as follows: JPEG2025512047000006.jpg10146Here, Φ A d is the total add power in the Alvarez lens at the relative lateral distance d, and Φ A 0is the total add power of the Alvarez lens at d=0, and k is the power addition rate (in diopters per meter) due to the relative movement of the two Alvarez elements (which is closely related to the A coefficient in equation (1) above). Combining equation (3) with equation (2) shows that for the Alvarez lens, the inset varies with the relative lateral distance of the lens elements. JPEG2025512047000007.jpg8146

[0038] As previously mentioned, the relative lateral distance d of the lens elements is the add power Φ n An Alvarez lens pair providing a prescription power Φ f and a fixed front lens element providing a prescription power Φ r and a movable rear lens providing a lateral distance d of 0.5 mm, then the total prism Δ experienced along the wearer's line of sight is equal to the sum of the components of prism provided by the front prescription, the rear prescription, and the relative lateral distance d of the lens elements. The total prism Δ can be approximated using Prentiss's law as follows: JPEG2025512047000008.jpg8146

[0039] The horizontal meridian power Φ of a distance prescription intended to be observed with the relative lateral distance of the lens elements at zero p Note that is given by: JPEG2025512047000009.jpg9152

[0040] Substituting equations (4) and (6) into equation (5), the prescription power of the rear lens element, Φ r is the horizontal meridian power of the long-distance prescription Φ p It can be expressed as follows: JPEG2025512047000010.jpg11144

[0041] [Alvarez Lens Optimization to Provide Fixed Prescription with Minimal Prism] Ideally, to optimize the user's viewing comfort, the amount of prism Δ provided by the lens should be zero. Thus, for a given distance prescription, the horizontal meridian power Φ p For the appropriate prescription power of the rear lens element, Φ f can be calculated from equation (7) by setting Δ=0. JPEG2025512047000011.jpg11144

[0042] The results are plotted in Figure 5 for values ​​of k of about 85, about 200, and about 500 diopters per meter, and d of about 6 mm, which represent the maximum lateral distance for which a pair of spectacles including such lenses can be designed. These values ​​of k and d allow the lenses to achieve the maximum add power Φ n For the plot, we provide values ​​for 0.5D, 1.25D, and 3D. The plots show typical v and P values ​​for typical eyeglass wearers. d Values ​​of k are also used. For many types of eyeglasses using common materials such as polycarbonate, k is usually assumed to be between 85 and 500 diopters per meter. For values ​​of k below 85, there is little add power in the Alvarez lens, and it may be little worthwhile to manufacture such lenses. A value of k of 500 diopters per meter is already in the region where common materials require highly curved Alvarez surfaces. Such lenses may not be aesthetically acceptable to the typical wearer, and the achievable relative lateral movement where the curves meet may be limited by the interference of the curves with each other.

[0043] Furthermore, it has been found that lens wearers can usually tolerate some prism and still see comfortably. It is known that the exact limits of prism tolerance vary widely from lens wearer to lens wearer. However, some general limits are known in the prior art. For example, the Percival criterion is -1.33 ≤ P ≤ +1.33, where P is the prism expressed as a percentage of the maximum sustainable binocular divergence or convergence. For long distance vision, various standards exist, such as ISO 21987 and ANSI Z80.1. Using such limits as inputs for Δ in equation (7), the Φ plotted against k ≈ 200 in Figure 5 can be calculated as r min and Φ r max As shown by the line, for a given Φ p for Φ r A range of acceptable values ​​for can be determined.

[0044] Figure 5 shows Φ r For most values ​​of , the ideal prism balance requires the power of the movable rear lens element Φ r should not be zero. Instead, the prescription power of the posterior lens element Φ r is the power of the long-distance prescription Φ p and other parameters in equation (7). As a concrete example, if k ≈ 200, then Φ p <-4, movable lens element Φ r = 0 is Φ r min and Φ r max It can be seen that the range is outside the comfortable range shown by the line. Therefore, in this case, the fixed prescription is Φ r min and Φ r max The thickness should be appropriately distributed between the front and rear elements within the range defined by the line.

[0045] Figure 6 shows the results of Figure 5 for k = 85 and k = 500. r / Φ p, and the Φ obtained by Percival's criterion for these values ​​of k. r min / Φ p and Φ r max / Φ p For values ​​of k between 85 and 500, Φ r / Φ p The tolerance for Φ at k=85 is r min / Φ p and Φ at k=500 r max / Φ p The embodiment of the present invention can be implemented to accommodate any Φ required by the user's prescription. p However, as can be seen from Fig. 6, the varifocal lens can have a value of approximately -3<Φ p Within the range <3, the prism constraint is not very restrictive and suitable lenses are Φ r = 0. However, this Φ p Outside the range of Φ 0.01, it may be particularly advantageous to split the fixed prescription of the variable focus lens into a front lens element and a rear lens element. Thus, embodiments of the present invention provide for Φ 0.01 for values ​​greater than about 3 diopters. p It is assumed that the variable focus lens has a value of

[0046] Furthermore, the inventors have discovered that in the case of Alvarez-type variable focus lenses that also provide a fixed progressive add power, such as by bifocal lenses, trifocal lenses, varifocal lenses, or progressive lenses, the Alvarez contribution to the add power and the progressive add contribution to the add power in the rate of change of inset with add power should be within the tolerance range of each other, in order to avoid exciting convergence accommodation conflicts in the arrangement that provides myopic add power.

[0047] When a fixed focus lens (i.e., a lens whose focal length cannot be adjusted by the user) has a progressive add power like a variable focus lens, the progressive add is typically adjusted by an inset δ (e.g., determined by equation (2)) to enforce a proper convergence accommodation ratio with increasing add power, thereby ensuring comfort in near vision for users of ophthalmic devices equipped with such a pair of lenses.

[0048] In some embodiments of the present invention, it may be desirable to provide an Alvarez-type variable focus lens with a progressive add power. However, the Alvarez lens element also has an inherent inset rate with the add power determined by equation (8). Thus, an Alvarez-type lens with a progressive add power necessarily produces an add power and an inset with the relative distance of the Alvarez lens elements, which overlap with the range of add powers provided by the progressive add power. If the contribution of the Alvarez lens and the contribution of the progressive add to the rate of change of the inset with the add power are not consistent for a particular pair of such variable focus lenses, a user of an ophthalmic device including such a variable focus lens may see an array of inconsistent convergence accommodation ratios when viewing an object through the lenses at a particular focal distance with different relative lens placements.

[0049] To maintain user comfort with an Alvarez-type variable focus lens with progressive add, the inventors have discovered that the contribution of the Alvarez lens and the contribution of the progressive add in the rate of change of inset with add should ideally be configured to be within about 1 prism diopter of each other. In embodiments of the invention, the inset rate of the add of the Alvarez contribution and the progressive add contribution are set to within about 0.5 prism diopters of each other, and in some embodiments, within about 0.25 prism diopters of each other.

[0050] Additionally, some embodiments of the present invention may be subject to constraints to ensure that the aesthetic qualities of a variable focus lens are similar to those of a fixed focus lens. For example, to reduce reflections and have a similar appearance to a fixed focal length lens, the curvature of the front surface of the front lens element should preferably be greater than about +1D, and the curvature of the rear surface of the rear lens element should preferably be less than about -0.5D.

Claims

1. It is an ophthalmic device, It comprises at least two corrective lenses attached to a support that holds the lenses in front of the user's eyes, thereby defining the direction of line of sight through each lens, At least one of the lenses is a variable focus lens including lens elements superimposed on the front and rear sides, The aforementioned lens elements have optical outer surfaces that cooperate with each other, The optical outer surface is shaped such that the focal length of the variable focus lens is variable according to the relative lateral distance d between the front and rear lens elements, thereby changing the power Φ A Provided, Here, d = 0 is the overall horizontal meridian degree Φ for which the variable focus lens corresponds to the prescription of the target user. ｐ Defined as the relative positions of the front and rear lens elements that provide, The aforementioned front lens element has a fixed power Φ ｆ The rear lens element has a fixed power Φ ｒ It has the following relationship, Here, Φ A 0 d=0 is the power provided by the variable focus lens, Φ ｒ has the same symbol as Φ ｐ and is equal to between about 5% and about 80% of Φ ｐ ​ Ophthalmology equipment.

2. An ophthalmic device according to claim 1, The aforementioned variable focus lens is configured to provide prescription powers of less than approximately -3 diopters or greater than approximately +3 diopters, and is an ophthalmic device.

3. An ophthalmic device according to claim 1 or 2, The variable focus lens has a fixed power Φ of the rear lens element. ｒ It is configured to meet the following criteria: Here d ｍａｘ This is the maximum relative lateral distance between the front lens element and the rear lens element. k is the rate of increase in power provided by the lateral displacement of the front lens element and the rear lens element in the lens element relative to each other. P ｄ This is the interpupillary distance of the user on whom the ophthalmic device is configured. v is the distance between the center of eye rotation and the rear surface of the variable focus lens. Δ is d = d ｍａｘ The total prism of the variable focus lens in the above-mentioned region, measured in units of diopters per meter, The aforementioned variable focus lens is an ophthalmic device composed of a prism Δ in the range of approximately -0.66 to approximately +0.

58.

4. An ophthalmic device according to claim 3, The aforementioned variable focus lens is configured such that 50 < k < 500 diopters / millimeter, and is an ophthalmic device.

5. An ophthalmic device according to claim 1 or 2, The variable focus lens is configured such that the relative lateral distance between the front and rear lens elements is between approximately 2 and 8 mm, in an ophthalmic device.

6. An ophthalmic device according to claim 1 or 2, Φ ｒ is, Φ ｐ It has the same sign, and Φ ｐ Ophthalmic equipment, which accounts for approximately 10% to 60% of the total.

7. An ophthalmic device according to claim 1 or 2, Φ ｒ is, Φ ｐ It has the same sign, and at least Φ ｐ Approximately 20% of, preferably at least Φ ｐ Ophthalmic equipment accounts for approximately 40% of the total.

8. An ophthalmic device according to claim 1 or 2, An ophthalmic device comprising a variable focus lens having a variable focus region configured to provide a power change equal to about 0.5D over at least a portion of its region.

9. An ophthalmic device according to claim 8, The aforementioned variable focal region is a progressive addition region, Φ ｒ is, Φ ｐ It has the same sign, and at least in the lens region above the progressive addition region, Φ ｐ Ophthalmic equipment, which accounts for approximately 5% to 80% of the total.

10. An ophthalmic device according to claim 8, An ophthalmic device in which, within the aforementioned variable focal range, the contribution to the add power due to being an Alvarez lens and the contribution to the add power due to being a progressive lens are each within approximately 1 prism diopter.

11. An ophthalmic device according to claim 1 or 2, The aforementioned front lens element is fixedly attached to the support. An ophthalmic device in which the rear lens element is movable relative to the front lens element so as to adjust the relative lateral distance between the lens elements.

12. An ophthalmic device according to claim 1 or 2, Eyeglasses with adjustable focal length; an ophthalmic device.

13. An ophthalmic device according to claim 1 or 2, An ophthalmic device that constitutes part of an AR, VR, or XR headset.

14. An ophthalmic device according to claim 1 or 2, An ophthalmic device that constitutes part of a visor or other corrective head device.

15. A pair of lens elements suitable for forming a lens element superimposed on the front and rear sides of at least one of the variable focus lenses according to claim 1 or 2.

Images