Dynamic diffractive tear- and blink-driven multifocal contact lens

Abstract

This disclosure describes systems and methods for treatment of presbyopia using contact lenses that include a plurality of diffractive elements on the front surface of the lenses. The diffractive elements are step wise features that create cavities between each of the plurality of diffractive elements. When the lens is placed on an eye, the tear film will fill the cavities with tear fluid, which will shift the impact of the diffractive elements and the majority of the light passing through the pupil will be focused at a distance. For example, immediately following a blink, the tear film will increase and the cavities will fill with tear fluid, which will have a diffractive effect that improves distance viewing. When the tear film starts to thin, and the cavities between the diffractive elements are exposed to air, the light distribution will shift towards the near focus and improve the near image.

Description

DYNAMIC DIFFRACTIVE TEAR- AND BLINK-DRIVEN MULTIFOCALCONTACT LENSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 575,894, filed April 8, 2024, the disclosure of which is hereby incorporated by reference in its entirety.INTRODUCTION

[0002] Presbyopia is an age-related disorder that diminishes the ability of the crystalline lens in the eye to focus on near positioned objects. Presbyopia is prevalent in many individuals around forty-five years of age and beyond. Presbyopia is caused by the inevitable hardening of the crystalline lens in the eye, making it less flexible and reducing its focusing capacity. Accordingly, the onset of presbyopia causes a need for increasing additional optical power to offset the gradual failure of the lens of the eye for near vision. The so-called “reading addition” needed by most adults is typically around +1.00 Diopters (“D”) at age forty-five, +2.00D at age fifty-five, and it reaches a maximum of +2.50D to +3.00D after age sixty. There is currently no cure for presbyopia and it is usually treated with corrective optics that provide additional optical power to appropriately correct near vision. Sufferers of presbyopia will usually use “readers” or reading spectacles to comfortably read day to day, and a second set of spectacles may be required for those that need optical correction to focus on distant objects, as the two circumstances (i.e., near vision correction and distance vision correction) call for differing focal powers. Bifocal or varifocal spectacles are also common solutions where different parts of the lens have different focal powers, selected by shifting the line of sight through the appropriate region of the lens. For those who are unhappy with wearing spectacles for cosmetic or functional reasons (such as during sports) a contact lens solution is highly desirable.

[0003] Currently available contact lenses available to treat presbyopia include monovision lenses, wherein each eye is corrected differently with single vision lenses: one lens for near vision and one lens for distant vision. Alternatively, multifocal contact lenses are designed with separate zones for near and distant vision correction within a single lens using aspheric surfaces and refractive optical design. Refractive multifocalcontact lenses are static and thus the portion of the lens meant for near vision is always in the patient’s vision, even when looking at other distances (e.g., distance vision while driving), and thus can create unwanted halos, glare, and reduced contrast sensitivity. These current static refractive and diffractive multifocal lenses rely upon the individual’s brain to adapt and distinguish between the unwanted near portion of the optic the retinal images that are perceived when viewing objects at far distances and the unwanted distance portion of the optic when viewing objects at near distances. Thus, static modem day refractive or diffractive multifocal contact lenses cause, at most distances, images to be of less than optimal quality since only the light tailored to the object distance under observation will be in focus, with other sections of the optic zone providing light of varying degrees of defocus. This results in retinal images which are, at best, lower in contrast, but more often also defocused, causing the appearance of secondary or “ghost” images or soft focus. For some individuals, static refractive multifocal contact lenses meet their daily needs for vision correction because they can ignore or adapt to the unwanted images, but for a significant proportion of the presbyopic population they are unacceptable. It is with respect to these and other general considerations that embodiments have been described herein.DYNAMIC DIFFRACTIVE TEAR- AND BLINK-DRIVEN MULTIFOCAL CONTACT LENS

[0004] This disclosure describes systems and methods for treatment of presbyopia using contact lenses that include diffractive elements on the front surface of the lenses. The diffractive elements may be diffraction gratings that are designed to provide a split in the incoming light from distant objects and near objects simultaneously. In some examples, the diffractive elements may be sawtooth elements having sawtooth type reliefs formed on the front surface of the lenses. The diffractive elements may be formed by forming rings on the anterior surface of the lenses surrounding a center curved portion of the lens, wherein the center curved portion of the lens is substantially smooth. This bifocal design, by using a plurality of diffractive elements, provides a single near viewing addition, the power of which is controlled by the spacing between the diffractive elements, i.e., the width of each diffractive element. The diffractive elements, or sawtooth diffractive elements is some embodiments, may cover a large proportion of the front optic zone of the lens to ensure coverage of the pupil with the diffractive elements.The diffractive elements are arranged to form a cavity between each diffractive element. When the lens is placed on an eye, tear fluid from the tear film will cover the lens and fill the cavities between the diffractive elements, which will shift the impact of the diffractive elements and cause the majority of the light passing through the pupil to be focused at a distance. Accordingly, for example, immediately following a blink, the tear film will increase and the cavities will fill with tear fluid, which will have a diffractive reducing effect that improves distance viewing. When the tear film starts to thin due to evaporation and the cavities of the diffractive elements are exposed to air, the light distribution will start to shift towards the near focus, degrading the quality of the distance image but improving the near image. Thus, the tear film thickness drives the dynamic nature of the multifocal lens described herein, wherein a thicker tear film improves distance viewing and a thinner tear film improves near viewing.

[0005] The typical blink rate of individuals observing distant objects, such as while driving, is around five seconds between blinks, whereas the blink rate while focusing on near objects, such as while reading a book or looking at a computer screen, increases to approximately twenty seconds between blinks. The diffractive tear lens described herein leverages the natural difference in blink rate between focusing on distant and far objects to provide a user-controlled dynamic multifocal lens. For example, when an individual is looking at a near object (e.g., while reading a book), their blink rate interval will be longer, and the tear film will evaporate and thin to a greater degree, causing the light distribution to shift to a predominately near focus, thereby improving the retinal image quality of the near image. Conversely, when an individual is looking at a far object (e.g., while driving), their blink rate is generally shorter and they will blink more frequently, causing the cavities to remain more full with tear fluid, which shifts the impact of the diffractive elements to cause a majority of the light passing through the pupil to be focused at a distance so that distance viewing is improved. This dynamic element of the tear film changing thickness and gradually exposing the cavities of the diffractive elements to air between blinks allows the fixed design of the diffractive elements on the front surface of the lens to change its distribution of light from predominantly distance focus to predominantly near focus, with blink interval being the controlling factor. Accordingly, while the diffractive tear lens described herein does utilize the general notion that more frequent blinking occurs while focusing on a distant object and less blinking occurs while focusing on a near object, an individual can further control whetherdistance viewing or near viewing is in focus with the diffractive tear lens by controlling their blink rate (e.g., blinking more or less frequently).

[0006] These and various other features as well as advantages which characterize the systems and methods described herein will be apparent from a reading of the following detailed description and a review of the associated drawings. Additional features are set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the technology. The benefits and features of the technology will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

[0007] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The following drawing figures, which form a part of this application, are illustrative of described technology and are not meant to limit the scope of the invention as claimed in any manner, which scope shall be based on the claims appended hereto.

[0009] FIG. la a side view of an example diffractive tear lens.

[0010] FIG. lb is a close-up side view of a diffractive portion of an example diffractive tear lens.

[0011] FIG. 2 is schematic sectional view of an example diffractive tear lens having sawtooth diffractive elements.

[0012] FIG. 3 a is a schematic sectional view of an example diffractive tear lens having sawtooth diffractive elements and full thickness tear film.

[0013] FIG. 3b is a schematic sectional view of an example diffractive tear lens having sawtooth diffractive elements and receding tear film.

[0014] FIG. 3 c is a schematic sectional view of an example diffractive tear lens having sawtooth diffractive elements and no tear film.

[0015] FIG. 4 is graph showing the light distribution from a sawtooth diffractive element submersed in tear fluid compared to a sawtooth diffractive element exposed to air.

[0016] FIG. 5 is graph showing tear film receding to uncover a sawtooth diffractive element.

[0017] FIG. 6 is a graph showing diffraction efficiency relative to height of a diffractive element at various orders of diffraction.

[0018] FIG. 7 is a graph showing diffraction efficiency at a near optimum diffractive element height.

[0019] FIG. 8 is a schematic depiction of an example test diffractive tear lens.

[0020] FIG. 9a is a schematic depiction of an experimental setup to test an example diffractive tear lens.

[0021] FIG. 9b is a close-up schematic depiction of a portion of the experimental setup to test an example diffractive tear lens.

[0022] FIG. 10a is a digital image of a vertexometer display screen showing a calibration measurement in air.

[0023] FIG. 10b is a graph created using Image J analyzing the image of FIG. 10a

[0024] FIG. I la is a digital image of a vertexometer display screen showing a calibration measurement in saine.

[0025] FIG. 1 lb is a graph created using Image J analyzing the image of FIG. I la.

[0026] FIG. 12a is a digital image of a vertexometer display screen showing a measurement of an example test diffractive tear lens in saline focused at distance viewing.

[0027] FIG. 12b is a graph created using Image J analyzing the image of FIG. 12a.

[0028] FIG. 13a is a digital image of a vertexometer display screen showing a measurement of an example test diffractive tear lens in saline focused at near viewing.

[0029] FIG. 13b is a graph created using Image J analyzing the image of FIG. 13a.

[0030] FIG. 14a is a digital image of a vertexometer display screen showing a measurement of an example test diffractive tear lens in air focused at distance viewing.

[0031] FIG. 14b is a graph created using Image J analyzing the image of FIG. 14a.

[0032] FIG. 15a is a digital image of a vertexometer display screen showing a measurement of an example test diffractive tear lens in air focused at near viewing.

[0033] FIG. 15b is a graph created using Image J analyzing the image of FIG. 15a.

[0034] FIG. 16 is a graph of visual acuity of a test subject testing three different test diffractive tear lenses.

[0035] FIG. 17 is a graph of visual acuity of a test subject testing three different test diffractive tear lenses.

[0036] FIG. 18a is a graph of average visual acuity of a group of test subjects testing six different test diffractive tear lenses.

[0037] FIG. 18b is a graph of average visual quality of a group of test subjects testing six different test diffractive tear lenses.

[0038] FIG. 19 is a series of digital images of an example test diffractive tear lens worn by a test subject during different stages of a blink cycle.

[0039] FIG. 20 is a digital image of an example test diffractive tear lens worn by a test subject.

[0040] FIG. 21 is a digital image of an example test diffractive tear lens worn by a test subject.

[0041] FIG. 22 is a digital image of an example test diffractive tear lens worn by a test subject.

[0042] FIG. 23 is a close-up view of an anterior surface of an example diffractive tear lens having sawtooth diffractive elements.

[0043] FIG. 24 is a top view of an example diffractive tear lens having a plurality of sawtooth diffractive elements.

[0044] FIG. 25 is a side view of an example diffractive tear lens having a plurality of sawtooth diffractive elements.

[0045] FIG. 26 is a top-side view of a molding used to manufacture diffractive tear lenses.DETAILED DESCRIPTION

[0046] Although the techniques introduced above and discussed in detail below may be implemented for a variety of contact lenses, the present disclosure will discuss the implementation of these techniques in a tear lens system. The reader will understand that the technology described in the context of a tear lens system could be adapted for use with other systems.

[0047] This disclosure describes systems and methods for treatment of presbyopia using contact lenses that include diffractive elements on the front surface of the lenses to create a dynamic multifocal lens. The diffractive elements are formed by forming rings on the anterior surface of the lens. In some embodiments, the rings are continuous around the lens. In some embodiments, the rings are concentric around a central axis of the lens. The rings may be indented into the anterior surface of the lens such that the diffractiveelements are indented into the anterior surface to create a cavity. In other embodiments, the rings may be raised from the anterior surface of the lens such that the diffractive elements are anterior to the anterior surface of the lens. The design of the diffractive elements includes step wise features that create height differences across the anterior surface of the lens. The step wise features are configured to create a cavity or feature that retain tear fluid when the lens is worn on an eye. In some embodiments, the diffractive elements have a sawtooth profile. In other embodiments, the diffractive elements may have a sawtooth profile wherein the sawtooth elements are flattened or curved, rather than pointed. In other embodiments, the diffractive elements may have a curved profile, a square profile, a rectangular profile. In some embodiments, the diffractive elements on a lens have the same general profile. In other embodiments, the diffractive elements may have a combination of profiles, such that each diffractive element on the lens may not have the same profile. The diffractive elements are included on a diffractive zone of the contact lens, which may be up to the entire diameter of the lens. Throughout the present disclosure where a sawtooth diffractive element and / or a sawtooth profile is discussed, one or ordinary skill in the art would recognize that other diffractive element shapes and cavity profiles are possible to obtain a diffractive effect on a diffractive tear lens.

[0048] FIG. la a side view of an example diffractive tear lens 100a. The example diffractive tear lens 100a has a curved lens body having a peripheral edge 104a, an anterior surface 106a, and a posterior surface 108a having an anterior surface curve. The example diffractive tear lens 100a also has a diffractive portion 102a including a plurality of diffractive elements on the anterior surface 106a. From afar, the plurality of diffractive elements may not be readily visible on the example diffractive tear lens 100a. The diffractive elements are described in more detail below with respect to at least FIGS. 2, 3a, 3b, and 3c.

[0049] FIG. lb is a close-up side view of the diffractive portion 100b of the example diffractive tear lens of FIG. la. When the diffractive portion of the example diffractive tear lens is scaled in the direction of the optical axis, the diffractive elements 104b may be visible on the anterior surface of the diffractive tear lens. When the diffractive portion of the example diffractive tear lens is scaled in the direction of the optical axis, the curvature of the lens may be less apparent. The diffractive zone is described in more detail below with respect to at least FIGS. 2, 3a, 3b, and 3c.

[0050] FIG. 2 is a schematic sectional view of an example diffractive tear lens 200 having sawtooth diffractive elements. While FIG. 2 shows sawtooth diffractive elements, other embodiments including alternatively shaped diffractive elements are possible. The diffractive tear lens 200 is curved to be worn on an eye, but the schematic sectional view of the diffractive tear lens 200 as shown in FIG. 2 shows the diffractive zone of the diffractive tear lens 200 flattened along the x-axis to highlight the diffractive elements 204. A true sectional view of diffractive tear lens 200 would be curved to fit the shape of an eye.

[0051] The diffractive tear lens 200 of FIG. 2 is shown on a graph depicting waves or wavelengths on the y-axis 208 and the lens anterior radius on the x-axis 210. The diffractive tear lens 200 includes a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having a posterior base curve. The anterior radius of curvature of the base lens controls a distance viewing power of the lens. The diffractive tear lens 200 further includes a center curved portion 202 that includes no diffractive elements. The size of the center curved portion 202 varies depending on the diameter of the diffractive element closest to the center of the lens. For example, the diffractive element ring closest to the center of the lens may surround, either entirely or partially, a center portion of the lens to define the center curved portion 202. A plurality of sawtooth diffractive elements 204 are present on the anterior surface of the diffractive tear lens 200. When looking at a schematic sectional view of diffractive tear lens, the sawtooth diffractive elements 204 radiate from the center curved portion 202 of the diffractive tear lens 200. The sawtooth diffractive elements 204 may be formed by forming a plurality of rings around the diffractive tear lens 200, wherein the rings are indented into the anterior surface of the lens to create sawtooth profiles 206. In examples, the sawtooth diffractive elements 204 are indented from the anterior surface of the diffractive tear lens 200. In other examples, the sawtooth diffractive elements 204 may be level with or anterior to the anterior surface of the diffractive tear lens 200.

[0052] The portion of the lens including the sawtooth diffractive elements 204 may be referred to as the diffractive zone 216. The diffractive zone 216 may be from 2mm in diameter up to the entire diameter of the diffractive tear lens 200 to ensure sufficient coverage of the pupil with the sawtooth diffractive elements 204 when the diffractive tear lens 200 is placed on an eye. In some embodiments, the diffractive zone 216 may be from 4mm in diameter to 12mm in diameter. In even further embodiments, the diffractivezone may be from 8mm in diameter to 9mm in diameter. In the example shown in FIG. 2, there are three diffractive elements 204 radiating from the center curved portion 202 of the diffractive tear lens 200, representing three rings formed on the anterior surface of the diffractive tear lens 200. In other examples, there may be fewer diffractive elements or a greater number of diffractive elements.

[0053] Each diffractive element 204 has a height 214 which controls the proportion of distance viewing relative to near viewing when air is within the sawtooth profiles 206 between each of the plurality of sawtooth diffractive elements 204. When generating the diffractive elements 204, the height 214 may be controlled by controlling, for example, the depth of the rings formed on the anterior surface of the diffractive tear lens 200. For example, to generate a diffractive element 204 with a greater height 214, a ring may be indented deeper into the anterior surface of the diffractive tear lens 200. The distribution of light energy between distance viewing and near viewing can be adjusted by changing the height 214 of the diffractive element 204. The height 214 controls the proportion of the wavelength of light passing through the pupil that the lens is designed to focus at a distant object relative to a near object. For example, for one hundred percent of the light to be focused at a distant object, the height 214 would be zero wavelengths, and for one hundred percent of the light to be focused at a near object, the height 214 would be one full wavelength. Accordingly, for a distribution of light somewhere between distance and near focus, the height 214 may be between zero and one full wavelength of light. The actual height 214 of the diffractive element 204 is calculated based on the refractive index of the diffractive lens material and the surrounding medium, e.g., saline or air. In some examples, each of the plurality of diffractive elements 204 have the same height 214. In other examples, the height 214 of each of the plurality of sawtooth diffractive elements 204 is not uniform, and some sawtooth diffractive elements 204 may have a height greater than or less than others. In some embodiments, the height 214 may be from 0.8pm to 1.3pm. In other embodiments, the height 214 may be from 0.9pm to 1.2pm. In even other embodiments, the height 214 may be from 1.0pm to 1.1 m.

[0054] Each diffractive element 204 has a width 212 configured to control the near viewing power of the diffractive tear lens 200. The base anterior radius of curvature of the diffractive tear lens 200 and the width 212 of the diffractive elements 204 will determine the powers of the diffractive tear lens 200. For example, if the diffractive tear lens 200 has a base power of 0.00D and an add power of +2.00D, the measured powersof the diffractive tear lens 200 will be 0.00D and +2.00D. If the diffractive tear lens 200 is designed with a base anterior radius of curative to create a +3.00D power for distance viewing, and the width 212 of the diffractive element 204 is designed to generate an add power of +1.00D for near viewing, the diffractive tear lens 200 will have powers of +3.00D for distance viewing and +4.00D for near viewing. The width 212 of each diffractive element 204 may different, as shown in the example diffractive tear lens 200 in FIG. 2. In some embodiments, the diffractive elements 204 closer to the center curved portion of the lens 202 will have a larger width 212 than the width 212 of the diffractive elements 204 closer to the peripheral edge of the diffractive tear lens 200. In some examples, the width 212 gets progressively smaller for each diffractive element 204 from the center curved portion of the lens 202 to the peripheral edge. In other examples, the width 212 of each diffractive element 204 may be the same. The width 212 is controlled based on the spacing between subsequent diffractive elements 204. For example, if the rings forming the diffractive elements 204 are spaced closer together, the width 212 will be less than if the rings forming the diffractive elements 204 are spaced further apart. In some embodiments, the width 212 of the diffractive elements is from 0.2mm to 1.5mm.

[0055] Between each diffractive element 204 is a profile 106 configured to retain tear fluid. The profile 206 shown in FIG. 2 is a sawtooth profile 206 based on the sawtooth design of the diffractive elements 204. When the diffractive tear lens 200 is placed on an eye, immediately following a blink a full thickness tear film may be present on the eye and causes the sawtooth profiles 206 to fill with tear fluid such that the entire sawtooth diffractive elements 204 are covered by tear fluid. As the tear film dries between blinks, the amount of tear fluid within the sawtooth profiles 206 will recede and the sawtooth diffractive elements 204 will be exposed to air. At some point, there may be no tear film remaining and the sawtooth diffractive elements 204 will be completely exposed to air. A subsequent blink by an individual wearing the diffractive tear lens 200 will cause a new tear film to cover the eye and fill the sawtooth profiles 206. This cycle of a full thickness tear film that recedes until the tear film dries out repeats throughout a blink cycle.

[0056] FIGS. 3a-3c described in detail below show an example diffractive tear lens 300a, 300b, 300c in series throughout the course of a blink cycle. Similar to FIG. 3, FIGS. 3a-3c 1 shows the diffractive zone of the diffractive tear lens 300a, 300b, 300c flattenedalong the x-axis to highlight the diffractive elements 304a, 304b, 304c. A true sectional view of diffractive tear lens 300a, 300b, 300c would be curved to fit the shape of an eye.

[0057] The more frequently an individual blinks (e.g., less time between blinks), the more tear film will remain covering the eye and the more tear fluid will remain contained within the sawtooth profiles 106. Conversely, the less frequently an individual blinks (e.g., more time between blinks), the more the tear film will dry out and recede and expose the sawtooth elements 104 to air.

[0058] FIG. 3 a is a schematic sectional view of an example diffractive tear lens 300a having sawtooth diffractive elements 304a and full thickness tear film 302a. In the example show in FIG. 3 a, the full thickness tear film 302a fills the sawtooth profiles 306a with tear fluid. The full thickness tear film 302a may be present when the diffractive tear lens 300a is placed on an eye and immediately after a blink because blinking causes additional tear film to appear on the eye and cover the pupil. When the full thickness tear film 302a is present and the sawtooth profiles 306a are full of tear fluid, which typically occurs while focusing at a distance and blinking more frequently, the impact of the diffractive sawtooth elements 304a submerged in tear fluid causes a majority of the light passing through the pupil to be focused at a distance so that distance viewing is improved.

[0059] FIGS. 3b is a schematic sectional view of an example diffractive tear lens 300b having sawtooth diffractive elements 304b and receding tear film 302b. In the example show in in FIG. 3b, the full thickness tear film 302a from FIG. 3a has begun to dry out between blinks, causing the tear film 302b to recede and lowering the amount of tear fluid retained within the sawtooth profiles 306b. As the tear fluid 302b recedes due to the tear film drying out, the sawtooth elements 304b are exposed to air, causing the light distribution to shift towards the near focus and degrading the quality of the distance image but improving the near image.

[0060] FIG. 3c is a side view of an example diffractive tear lens 300c having sawtooth elements 304c and no tear film. In the example show in in FIG. 3 c, the full thickness tear film 302a from FIG. 3a and the receding tear film 302b from FIG. 3b have completely dried out such that there is no longer any tear film. Accordingly, the sawtooth profiles 306c contain no tear fluid and the diffractive elements 304c are completely exposed to air. The exposure of the sawtooth elements 304c to air causes all of the light to focus on near viewing, and any distance image will be of low quality. The lack of tear fluid and resulting poor quality distance image may trigger an individual wearing the diffractivetear lens 300c to blink again in order to cause the lens to be re-covered with a full thickness tear film so that distance viewing is restored.

[0061] FIG. 4 is graph 400 showing the light distribution from a sawtooth diffractive element submersed in tear fluid compared to a sawtooth element exposed to air. The sawtooth diffractive element, such as sawtooth diffractive elements 204, 304a, 304b, 304c described herein above, is a diffractive grating used to separate and manipulate different wavelengths of light. An arrangement of diffractive elements on a diffractive zone of a diffractive tear lens provides closely spaced sawtooth profiles or grooves on the diffractive gratings that cause incident light to diffract. Different orders of diffraction can occur, each corresponding to a different angle and spectral component. A zero order of diffraction refers to the non-deviated, non-deflected, or unaltered component of light that occurs when light interacts with a diffraction grating or other diffractive element. Thus, the zero order of diffraction corresponds to the central, diffracted beam of light, and is often denoted as m = 0. Higher orders of diffraction correspond to beams that are diffracted at various angles. The angle of deviation for the first order, for example, depends on the wavelength of light and the spacing (e.g., width) of the diffractive gratings. The mathematical relationship that describes the angles of diffraction for different orders is given by the grating equation: mX = dsin(0) (eq. 1) wherein “m” is the order of diffraction, “X” is the wavelength of light, “d” is the spacing of the diffractive gratings (e.g., relative width of sawtooth diffractive elements), and 0 is the angle of diffraction.

[0062] The graph 400 includes information for zero order of diffraction, first order of diffraction, and second order of diffraction, as indicated based on the key 412.

[0063] The x-axis of the graph 410 shows the normalized depth parameter and the y- axis of the graph 408 shows the diffraction efficiency. As the diffraction efficiency of the zero order plot goes from 1.0 down towards 0.0 as the tear film evaporates and thins, and the diffraction efficiency of the first order plot goes from 0.0 towards 1.0, the distribution between distance light energy and near power energy shifts from predominantly distance power, as shown by arrow 404, to predominantly near power, as shown by the arrow 402. This occurs as the proportion of light shifts from being distributed on the zero order to being distributed on the first order as the sawtooth diffractive element is exposed to air as the tear film thins. As indicated by the secondorder plot, there is only a small amount of light being directed to the second order as the diffraction efficiency of the zero order plot goes from 1.0 down towards 0.0 and the diffraction efficiency of the first order plot goes from 0.0 towards 1.0. This is done by design so that the image quality at zero order and first order is high. If, for example, too much light were directed to the second order, then the image quality at the zero order and first order would worsen as light would be redirected to a higher order.

[0064] Adjustments to the amount of shift from distance power to near power during a typical interblink period can be made by raising or indenting the entire diffractive element within the anterior surface of the diffractive lens based on the experience of an individual patient because actual tear film evaporation rate, breakup time, and interblink interval may vary from person to person. For example, if an individual requires more distance viewing, the entire diffractive element may be lowered within the anterior surface of the diffractive lens, and if the individual requires more near view, the entire diffractive element may be raised within the anterior surface of the diffractive lens.

[0065] The diffractive tear lens described above with reference to FIGS. 1, 2, 3a, 3b, and 3c describe only two foci: a distance foci and a near foci. However, for older presbyopic patients, such as those with a reading addition of +2.00D or greater, may find that their retinal image quality at intermediate distances (e.g., 1.5m through 60cm) is not acceptable. To account for intermediate distances, the diffractive tear lens described above may be combined with an aspheric surface across the optic zone of the base contact lens design such that that base lens power changes from the center of the optic zone to the outer edge of the optic zone, e.g., from 0.50D, to 0.75D, to 1.00D. In another example, a trifocal diffractive design may provide a third foci to provide improved visual acuity at intermediate distances. One example method for generating a diffractive trifocal design is to design two bifocal refractive lens designs, for example, a first lens with the distance power focused at a far distance (e.g., 6.0m) and the other focused at an intermediate distance such as 40cm (e.g., +2.50D of optical power), and a second lens with the distance order focused at far distance (e.g., 6.0m) and the other focused at a different intermediate distance such as 80cm (e.g., +1.25D of optical power). The two diffractive design sawtooth patterns can then be overlaid on one another to provide the final single sawtooth pattern for the trifocal design.Theoretical Experimental Simulation

[0066] A theoretical simulation was performed to model the diffraction efficiency of water films on an optic having a diffractive sawtooth element.

[0067] FIG. 5 is graph 500 showing tear film receding to uncover a sawtooth diffractive element. To produce the graph 500, calculations were performed to plot the shape of receding tear film as a series of curves defined by a numerical value “a” or alpha. The differing curvilinear shape of the tear film is defined in graph 500 by alpha. A higher a value represents a more rapid curvilinear tear film recession. As the alpha value increases from a = 1, to a = 4, to a = 8, the curvilinear shape of the tear film over the surface of the cavity formed by the diffractive elements is increased to simulate the gradual evaporation and thinning of tear film as tear fluid dries out after a blink. To calculate a, the following equation may be used: y = (l-x)Aa (eq- 2)

[0068] The x-axis 510 represents the normalized distance of one zone of a diffractive element. The y-axis 512 represents the normalized height of one zone of a diffractive element. When the entire sawtooth profile area is filled with tear fluid, the curve 504 is defined by a = 1. As the tear film begins to recede, the shape of the receding tear film first forms curve 506 defined by a = 4. As the tear film continues to recede, the shape of the receding tear film is reflected in curve 508 defined by a = 8.

[0069] FIG. 6 is a graph 600 showing diffraction efficiency relative to height of a diffractive element at various orders of diffraction. A simulation was performed using ray tracing techniques for a values ranging from 1 to 200 to confirm that an optimal design height for a diffractive element in air from a first order of diffraction, m = 1, does not create significant light loss to higher orders. The x-axis 610 represents a scale factor applied to an optimal design height, i.e., an h scale factor or height factor. The y-axis 612 represents efficiency. To create graph 600, data for a = 30.0 was used. The efficiencies were calculated at various orders of diffraction, e.g., m = -3, m = -2, m = -1, m = 0, m = 1, m = 2, m = 3, as indicated in key 602, and replotted as a function of a height factor applied to an optimal design height. By scaling the height value by the height factor on the x-axis 610, efficiency can be plotted at all orders for heights lower than and higher than the optimal design height for a diffractive element. The resulting graph 600 shows the distribution of light energy diffraction between the various orders of diffraction throughout the phase of a diffractive element profile going from full of fluid (e.g., wateror tear fluid) to receding until the diffractive element is completely exposed to air, and then entering the next phase. The resulting graph 600 confirms that a majority of light is being distributed at m = 0 and m = 1, and substantial light is not being lost to higher orders, such as m = 3 and higher. The resulting graph 600 further illustrates the efficiency of other orders if the height factor is increased or decreased. Based on the simulation, the optimal design height for a diffractive element in air was determined using the peak of the m = 1 curve 604. Accordingly, the height factor was determined to be h = 0.00055mm / (1.49-1) = 0.0011mm.

[0070] FIG. 7 is a graph 700 showing diffraction efficiency at a near optimum diffractive element height. The three curves 702, 704, 706 in FIG. 7 were created using data extracted from graph 600 in FIG. 6, and specifically, using the data for m = 0, m = -1, and m = 1. The x-axis 710 represents a and the y-axis 712 represents the diffraction efficiency. The diffraction efficiency on the y-axis 712 will go up as a diffractive element profile fills with water or tear fluid. The a value on the x-axis 710 increases as the water or tear fluid in the diffractive element profile recedes.

[0071] The three curves 702, 704, 706 reflect diffraction efficiency at different orders of diffraction. Curve 702 is a plot at m = 0, curve 704 is a plot at m = 1, and curve 706 is a plot at m = -1. As reflected in FIG. 7, when a = 1 (e.g., representing a diffracting grating element profile being filled with tear fluid), about 75% of the light energy is directed to distance viewing as indicated by the approximate diffraction efficiency value of 0.75 for the m = 0 curve at a = 1, and about 14% of the light energy is diffracted into the first order for near viewing. When the a value is 10 or higher, the proportion of light energy shifted for distance viewing relative to near viewing is about 15% directed to distance viewing and 60% directed to near viewing. When the a value is around 30, the proportion of light energy shifted for distance viewing relative to near viewing is about 5% directed to distance viewing and 85% directed to near viewing.Experimental Simulation of Test Diffractive Tear Lens

[0072] FIG. 8 is a schematic depiction of an example test diffractive tear lens 800. The diffractive tear lens 800 was manufactured out of rigid PMMA (polymethyl methacrylate) material but having a similar curvature, diameter, and thickness as a soft contact lens. The diffractive tear lens 800 has a peripheral edge 802 and a center curved portion 804. Radiating outward from the center curved portion 804 of the diffractive tear lens 800 is a diffractive zone 806. The diffractive zone 806, or diffractive zone of thelens, includes a plurality of sawtooth diffractive elements on the anterior surface of the diffractive tear lens 800 radiating from the center curved portion 804. The example diffractive tear lens 800 includes a 4mm diffractive zone. As discussed above with reference to FIG. 2, in other example diffractive tear lenses, the diffractive zone may be from 2mm in diameter up to the entire diameter of the diffractive tear lens, from 4mm in diameter to 7mm in diameter, or from 6mmin diameter to 7mm in diameter.

[0073] FIG. 9a is a schematic depiction of an experimental setup 900a to test an example diffractive tear lens. The experimental setup 900a includes a Nikon projection vertexometer 902a designed to measure the power of spectacles and contact lenses. For purposes of the experimental simulations described herein, the vertexometer 902a was fitted with a fixed aperture of 3.0mm for all testing. The vertexometer 902a further includes a mount 904a to hold a lens, and a display screen 906a. The vertexometer 902a further includes a dial 905a configured to adjust the focus on the lens held in the mount 904a. The experimental setup 900a also includes a DSLR digital camera 908a having manual settings for aperture, focus, exposure time, and ISO rating. The camera 908a was used during experimental simulations to take photographs of the display screen 906a at various points throughout the experimental simulation. FIGS. 10a, I la, 12a, 13a, 14a, and 15a described in detail below are photographs taken of the display screen 906a under various experimental conditions.

[0074] Experiments conducted using experimental setup 900a were conducted with all lights in the room turned off. The experimental setup 900a was used to test the diffractive tear lens 800 described above with reference to FIG. 8.

[0075] FIG. 9b is a close-up schematic depiction of a portion 900b of the experimental setup 900a as shown in FIG. 9a. FIG. 9b shows a close-up of the mount 904a discussed above with reference to FIG. 9a. A test diffractive tear lens, such as the diffractive tear lens 800, is placed in an empty wet cell and placed on the mount 904a of the vertexometer.

[0076] FIGS. 10a, 10b, I la, and 11b described in detail below related to calibration measurements performed prior to measuring a test diffractive tear lens with the vertexometer according to the experimental setup 900a.

[0077] FIG. 10a is a digital image 1000a of the vertexometer display screen 906a showing a calibration measurement in air using the experimental setup 900a. The digital image 1000a was taken with camera 908a in experimental setup 900a as described abovewith reference to FIGS. 9a and 9b. No example diffractive tear lens was mounted on the vertexometer when digital image 1000a was captured, rather, a wet cell was measured in air to take a calibration measurement. The dial 905a on the vertexometer is turned until the lines (e.g., three vertical lines and three horizontal lines) on the display screen 906a within the target 1004a are in focus. When the lines are in focus, the power can be measured. The power of the wet cell alone was measured to be 0.00D according to the power indicator 1002a on the vertexometer screen.

[0078] FIG. 10b is a graph 1000b created using Image J, an imaging processing software, to analyze the intensity of the lines on the vertexometer digital image 1000a from FIG. 10a. To further analyze the power of the wet cell measured with the vertexometer, after digital image 1000a was taken, digital image 1000a was input to Image J. A line 1006a, shown on digital image 1000a in FIG. 10a, was drawn on the digital image 1000a to establish the portion of the digital image 1000a to be analyzed by Image J. Line 1006a is drawn horizontally such that the lines within the target 1004a on digital image 1000a will be analyzed for their intensity. The graph 1000b created using Image J scores the image pixel intensity on a gray scale value of 0-255, as shown on the y-axis 1002b, across a predetermined distance, as shown on the x-axis 1004b. In this example, the predetermined distance is the horizontal distance of the line 1006a. The three peaks 1006b, 1008b, 1010b shown on graph 1000b represent the areas on digital image 1000a where the line intensity is the greatest, which in this example, is where the three horizontal lines intersect with the three vertical lines within the target 1004a.

[0079] FIG. I la is a digital image 1100a of the vertexometer display screen 906a showing a calibration measurement in saline using the experimental setup 900a. The digital image 1100a was taken with camera 908a in experimental setup 900a as described above with reference to FIGS. 9a and 9b. No example diffractive tear lens was mounted on the vertexometer when digital image 1100a was captured, rather, a wet cell containing saline was measured to take a calibration measurement. The dial 905a on the vertexometer is turned until the lines (e.g., three vertical lines and three horizontal lines) on the display screen 906a within the target 1104a are in focus. When the lines are in focus, the power can be measured. The power of the wet cell containing saline (and no lens) was measured to be 0.00D according to the power indicator 1102a on the vertexometer screen.

[0080] FIG. 1 lb is a graph 1100b created using Image J to analyze the intensity of the lines on the vertexometer digital image 1100a from FIG. I la. After digital image 1100a was taken, digital image 1100a was input to Image J. A line 1106a, shown on digital image 1100a in FIG. I la, was drawn on the image 1100a to establish the portion of the digital image 1100a to be analyzed by Image J. The graph 1100b created using Image J scores the image pixel intensity on a gray scale value of 0-255, as shown on the y-axis 1102b, across a predetermined distance, as shown on the x-axis 1104b. In this example, the predetermined distance is the horizontal distance of the line 1106a. The three peaks 1106b, 1108b, 1110b shown on graph 1100b represent the areas on digital image 1100a where the line intensity is the greatest, which in this example, is where the three horizontal lines intersect with the three vertical lines within the target 1104a.

[0081] FIGS. 12a, 12b, 13a, and 13b described below relate to measurements performed on a test diffractive tear lens according to the experimental setup 900a while the test diffractive tear lens was in saline in order to mimic the effect of a diffractive tear lens placed on an eye and covered in tear fluid so the cavities between the diffractive elements are filled with tear fluid, thereby improving the distance image.

[0082] FIG. 12a is a digital image 1200a of the vertexometer display screen 906a showing a measurement of an example test diffractive tear lens in saline focused at distance viewing using the experimental setup 900a. The digital image 1200a was taken with camera 908a in experimental setup 900a as described above with reference to FIGS. 9a and 9b. An example test diffractive tear lens, lens 800 as described above with reference to FIG. 8, was placed in a wet cell containing saline in the mount of the vertexometer. Placing the test diffractive tear lens in saline mimics the presence of tear film that surrounds a lens immediately after a blink when the tear film will flood the diffractive element profiles with tear fluid and improve the distance image. Digital image 1200a shows the lens measurement when focused for distance viewing by adjusting the dial 905 on the vertexometer 902a. The distance power of the test diffractive tear lens, according to the power indicator 1202, is about -0.25D. Image 1200a further shows three horizontal lines and three vertical lines intersecting within target 1204a, representing a majority of the light going to the distance focus, with the lines surrounded by a haze representing a dim out of focus near image.

[0083] FIG. 12b is a graph 1200b created using Image J to analyze the intensity of the lines on the vertexometer digital image 1200a from FIG. 12a. After digital image 1200awas taken, digital image 1200a was input to Image J. A line 1206a, shown on digital image 1200a in FIG. 12a, was drawn on the image 1200a to establish the portion of the digital image 1200a to be analyzed by Image J. The graph 1200b created using Image J scores the image pixel intensity on a gray scale value of 0-255, as shown on the y-axis 1202b, across a predetermined distance, as shown on the x-axis 1204b. In this example, the predetermined distance is the horizontal distance of the line 1206a. The three peaks 1206b, 1208b, 1210b shown on graph 1200b represent the areas on digital image 1200a where the line intensity is the greatest, which in this example, is where the three horizontal lines intersect with the three vertical lines within the target 1204a. On either side of the three peaks 1206b, 1208b, 1210b, graph 1200b has a higher intensity of gray value, as compared to graphs 1000b and 1100b, as a result of the out of focus near image caused by the test diffractive tear lens being focused at a distance and the vertexometer picking up the out of focus near image, which causes a haze around the lines and an increased gray value score.

[0084] FIG. 13a is a digital image 1300a of the vertexometer display screen 906a showing a measurement of an example test diffractive tear lens in saline focused at near viewing using the experimental setup 900a. The digital image 1300a was taken with camera 908a in experimental setup 900a as described above with reference to FIG. 9a and 9b. An example test diffractive tear lens, lens 800 as described above with reference to FIG. 8, was placed in a wet cell containing saline in the mount of the vertexometer. Placing the test diffractive tear lens in saline mimics the presence of tear film that surrounds a lens immediately after a blink when the tear film will flood the diffractive element profiles with tear fluid and improve the distance image. Digital image 1300a shows the lens measurement when focused for near viewing by adjusting the dial 905 on the vertexometer 902a. The near power of the test diffractive tear lens, according to the power indicator 1302a, is about +1.75D. Digital image 1300a further shows three horizontal lines and three vertical lines intersecting within target 1304a, representing a majority of the light going to the near focus, with the lines surrounded by a haze representing a dim out of focus distance image.

[0085] FIG. 13b is a graph 1300b created using Image J to analyze the intensity of the lines on the vertexometer digital image 1300a from FIG. 13 a. After digital image 1300a was taken, digital image 1300a was input to Image J. A line 1306a, shown on digital image 1300a in FIG. 13 a, was drawn on the digital image 1300a to establish the portionof the digital image 1300a to be analyzed by Image J. The graph 1300b created using Image J scores the image pixel intensity on a gray scale value of 0-255, as shown on the y-axis 1302b, across a predetermined distance, as shown on the x-axis 1304b. In this example, the predetermined distance is the horizontal distance of the line 1306a. The three peaks 1306b, 1308b, 1310b shown on graph 1300b represent the areas on digital image 1300a where the line intensity is the greatest, which in this example, is where the three horizontal lines intersect with the three vertical lines within the target 1304a.

[0086] In comparing graphs 1200b and 1300b, on either side of the three peaks 1306b, 1308b, 1310b, graph 1300b has a higher intensity of gray value, as compared to graph 1200b, as a result of the out of focus distance image caused by the test diffractive tear lens being focused for near viewing and the vertexometer picking up the out of focus distance image, which causes a haze around the lines and an increased gray value score. The three peaks 1206b, 1208b, 1210b in graph 1200b are more prominent than the three peaks 1306b, 1308b, 1310b in graph 1300b, which is expected because graph 1200b shows measurements of the test diffractive tear lens focused at a distance in saline, and graph 1300b shows measurements of the test diffractive tear lens focused at near in saline. Having the test diffractive tear lens in saline causes a majority of the light to be focused at the distance image, and when the lens is in saline, one would expect the distance image intensity (reflected in FIG. 12b) to be higher than the near image intensity (reflected in FIG. 13b).

[0087] FIGS. 14a, 14b, 15a, and 15b described below relate to measurements performed on a test diffractive tear lens according to the experimental setup 900a while the test diffractive tear lens was in air in order to mimic the effect of a diffractive tear lens placed on an eye just before another blink when the tear fluid is dried up so the cavities between the diffractive elements are exposed to air, thereby improving the near image.

[0088] FIG. 14a is a digital image of the vertexometer display screen 906a showing a measurement of an example test diffractive tear lens in air focused at distance viewing using the experimental setup 900a. The digital image 1400a was taken with camera 908a in experimental setup 900a as described above with reference to FIGS. 9a and 9b. An example test diffractive tear lens, lens 800 as described above with reference to FIG. 8, was placed in a wet cell containing no saline (e.g., only air environment) in the mount of the vertexometer. Placing the test diffractive tear lens in an air only environmentrepresents an alpha value close to 100, and causes the diffractive elements on the diffractive tear lens to be exposed to air so that the near image is improved. The vertexometer was focused for distance viewing by adjusting the dial 905a on the vertexometer. The distance power of the test diffractive tear lens, according to the power indicator 1402a, is about -0.25D. Because the lens was in an air only environment, the majority of the light is focused on near viewing and improving the near image quality, causing the distance image to be out of focus. Thus, the three horizontal lines and three vertical lines intersecting within the target 1404a are defocused, and a defocused near image scattering of light is also present behind the target 1404a.

[0089] FIG. 14b is a graph 1400b created using Image J to analyze the intensity of the lines on the vertexometer digital image 1400a from FIG. 14a. After digital image 1400a was taken, digital image 1400a was input to Image J. A line 1406a, shown on image 1400a in FIG. 14a, was drawn on the digital image 1400a to establish the portion of the digital image 1400a to be analyzed by Image J. The graph 1400b created using Image J scores the image pixel intensity on a gray scale value of 0-255, as shown on the y-axis 1402b, across a predetermined distance, as shown on the x-axis 1404b. In this example, the predetermined distance is the horizontal distance of the line 1406a. Due to the defocused lines on the digital image 1400a, the intensity as shown in graph 1400b does not show three clear peaks, as could be seen in graphs 1000b, 1100b, 1200b, and 1300b.

[0090] FIG. 15a is a digital image of the vertexometer display screen 906a showing a measurement of an example test diffractive tear lens in air focused at near viewing using the experimental setup 900a. The digital image 1500a was taken with camera 908a in experimental setup 900a as described above with reference to FIGS. 9a and 9b. An example test diffractive tear lens, lens 800 as described above with reference to FIG. 8, was placed in a wet cell containing no saline (e.g., only air environment) in the mount of the vertexometer. Placing the test diffractive tear lens in an air only environment represents an alpha value close to 100, and causes the diffractive elements on the diffractive tear lens to be exposed to air so that the near image is improved. Digital image 1500a shows the lens focused for near viewing by adjusting the dial 905a on the vertexometer. Digital image 1500a reveals three horizontal bars and three horizontal bars intersecting within the target 1504a in focus and with high intensity, and with minimal distance image scattering of light from the distance focus as indicated by the lack of haze around the lines. Since the example test diffractive tear lens measured in digital image1500a was in an air environment, the diffractive elements were exposed to air, causing the majority of the light to focus on near viewing and improving the near image quality, which is confirmed by the clear high intensity lines shown within target 1504a.

[0091] FIG. 15b is a graph 1500b created using Image J to analyze the intensity of the lines on the vertexometer digital image 1500a from FIG. 15a. After digital image 1500a was taken, digital image 1500a was input to Image J. A line 1506a, shown on digital image 1500a in FIG. 15a, was drawn on the digital image 1500a to establish the portion of the image 1500a to be analyzed by Image J. The graph 1500b created using Image J scores the image pixel intensity on a gray scale value of 0-255, as shown on the y-axis 1502b, across a predetermined distance, as shown on the x-axis 1504b. In this example, the predetermined distance is the horizontal distance of the line 1506a. The three peaks 1506b, 1508b, 1510b shown on graph 1500b represent the areas on image 1500a where the line intensity is the greatest, which in this example, is where the three horizontal lines intersect with the three vertical lines within the target 1504a.

[0092] In comparing graphs 1400b and 1500b, graph 1400b does not show three clear peaks and shows a higher intensity of gray value along the width of the horizontal distance measured, as compared to graph 1500b, which does three clear peaks 1506b, 1508b, 1510b and a lower intensity of gray value on either side of the peaks. The three peaks 1506b, 1508b, 1510b in graph 1500b are more prominent and of high intensity, as compared to graph 1400b, which is expected because graph 1400b shows measurements of the test diffractive tear lens focused at a distance in air, and graph 1500b shows measurements of the test diffractive tear lens focused at near in air. Having the test diffractive tear lens in air causes a majority of the light to be focused at the near image, and when the lens is in only air, one would expect the near image intensity (reflected in FIG. 15b) to be higher than the distance image intensity (reflected in FIG. 14b).Experimentation of Test Diffractive Tear Lens on Human Eye

[0093] A first experimentation was performed on human test subjects using three different soft diffractive tear lenses having varying parameters. The parameters of the three different soft diffract tear lenses are summarized in Table 1.Table 1:

[0094] The test diffractive tear lenses were tested on human subjects. Subject A and Subject B were tested in a single location using logMAR high contrast test charts. A logMAR test chart includes letters in a multitude of rows, wherein the letters on the top row are the largest, and subsequent rows become progressively smaller. Typically, as the lines go up in size from bottom to top, the size of the letters on each line increase by a factor of 1.25. Letters on a logMAR test chart are typically black on a white background or white on a black background. The logMAR scoring system assigns a numerical value to each row. For example, a row with a logMAR value of 0.00 corresponds to 20 / 20 vision, while a row with a logMAR value of 1.00 represents vision that is significantly impaired. A negative value represents better than 20 / 20 vision.

[0095] For the experimentation of the test diffractive tear lenses, visual acuity was measured by placing a test chart at seven distances: 6.00m, 2.00m, 1.00m, 67cm, 50cm, 40cm, and 33cm. These seven distances represent object vergence at seven different diopters: 0.00D, -0.50D, -1.00D, -1.50D, -2.00D, -2.50D and -3.00D. For a non presbyopic subject, as the distance to the test chart becomes closer, the subject will use the accommodative power of their natural lens to overcome the negative vergence of the light coming from the test chart to focus it clearly on the retina. For a presbyopic subject, however, the lack of accommodation will cause the retinal image to become defocused as the test chart is brought closer to the eye. By measuring the visual acuity atincreasingly closer distances, the impact of this increasing defocus can be measured when the subject is wearing a distance only correction lens.

[0096] FIG. 16 is a graph 1600 of visual acuity of a test subject testing three different test diffractive tear lenses. The test subject is Subject A and the three different test diffractive tear lenses are Designs 1-3 as identified above in Table 1. The x-axis 1610 is the distance the test chart was placed from the subject. The y-axis 1620 is the logMAR score. The data for each of the three test diffractive tear lenses is plotted on a separate line, as indicated by key 1630. Additionally, Subject A had their distance viewing glasses prescription evaluated as well, and the results are plotted on the line denoted “Distance Spec.” Graph 1600 shows a decrease in visual acuity going from a distance of 6.00m to 1.00m, but then a general increase in acuity for the intermediate and near distances as the test chart was brough closer to Subject A. Reading performance was between 20 / 25 and 20 / 32 for Subject A at 50cm, 40cm and 33cm for all three lens designs, which is an improvement over Subject A’s distance viewing spectacle correction.

[0097] FIG. 17 is a graph 1700 of visual acuity of a test subject testing three different test diffractive tear lenses. The test subject is Subject B and the three different test diffractive tear lenses are Designs 1-3 as identified above in Table 1. The x-axis 1710 is the distance the test chart was placed from the subject. The y-axis 1720 is the logMAR score. The data for each of the three test diffractive tear lenses is plotted on a separate line, as indicated by key 1730. Additionally, Subject B had their distance viewing glasses prescription evaluated as well, and the results are plotted on the line denoted “Distance Spec.” Graph 1700 also shows a decrease in visual acuity going from a distance of 6.00m to 1.00m, but then a general increase in acuity for the intermediate and near distances as the test chart was brough closer to Subject A. Reading performance was between 20 / 25 and 20 / 32 for Subject B at 50cm, 40cm and 33cm for all three lens designs, which is an improvement over Subject B’s distance viewing spectacle correction.

[0098] The comfort of the three test diffractive tear lenses, according to Subjects A and B, were not ideal, as the lenses were excessively mobile on the eye with large amount of vertical movement caused by each blink. The increased thickness of the test diffractive tear lenses, as compared to typical soft contact lens, was a contributing factor to the discomfort. Lens fitting was measured, and FIGS. 20-22 show images taken during the lens fitting measurements.

[0099] A third test subject also tested the test diffractive tear lenses in a separate location. The third test subject reported the test lenses to be comfortable. The visual acuity of the third test subject wearing the test diffractive tear lenses while looking at a distance appeared to be equivalent to their distance viewing glasses correction of 20 / 20. The visual acuity of the third test subject wearing the test diffractive tear lenses at 40cm was about 20 / 50, or 0.40 logMAR, as compared to 20 / 160, or 0.90 logMAR while the subject was wearing their distance viewing glasses. The third test subject also reported that the near retinal image improved during the interblink period while wearing the test diffractive tear lenses.

[0100] A second experimentation was performed on five human test subjects using six different test diffractive tear lenses having varying parameters. The results of the second experimentation are described below and with respect to FIG. 18a and FIG. 18b.

[0101] FIG. 18a is a graph 1800a of average visual acuity of a group of test subjects testing six different test diffractive tear lenses. The parameters of the six different test diffractive tear lenses are summarized below in Table 2 below.Table 2:To obtain the data plotted in graph 1800a, five test subjects were evaluated while wearing each of the six test diffractive tear lenses. Additionally, each subject was evaluated while wearing their distance viewing glasses prescription, and the results are plotted on the line denoted “Distance Spec.” Each subject, for each of the six test diffractive lenses and for their distance viewing glasses prescription, was shown a logMAR high contrast test chart at seven different distances: 6.00m, 2.00m, 1.00m, 67cm, 50cm, 40cm, and 33cm. The x-axis 1802a of graph 1800a represents the visual acuity chart distance. A visual acuityscore was assigned based on the number of letters the test subject correctly identified on the logMAR high contrast test chart for each of the seven distances. The visual acuity score was then converted to an absolute logMAR score. The average of the five test subjects’ absolute logMAR score was calculated for each of the six test diffractive lenses and for their distance viewing glasses prescription. The y-axis 1804a of graph 1800a is the average absolute logMAR score. A logMAR value of 0.00 corresponds to 20 / 20 vision. A higher positive logMAR value represents vision that is impaired and becomes more impaired the higher the value gets, and a negative value logMAR represents better than 20 / 20 vision. The data in graph 1800a shows that for all of the test diffractive lenses, the logMAR score got higher (i.e., vision became more impaired) as the visual acuity chart distance got smaller (i.e., near vision was being tested). Lens “E” showed the least amount of visual acuity lost as the visual acuity chart distance got smaller to test near vision.

[0102] FIG. 18b is a graph 1800b of average visual quality of a group of test subjects testing six different test diffractive tear lenses. The data plotted in graph 1800b was collected from the same five test subjects and the same six test diffractive tear lenses discussed above with reference to FIG. 18a. Each subject, for each of the six test diffractive lenses and for their distance viewing glasses prescription, was shown a logMAR high contrast test chart at seven different distances: 6.00m, 2.00m, 1.00m, 67cm, 50cm, 40cm, and 33cm. The x-axis 1802b of graph 1800b represents the visual acuity chart distance. The subject then selected a quality score between zero and one- hundred, wherein zero is very poor quality and one-hundred is very high quality. For example, if a subject could read the letters on the logMAR high contrast test chart and identify each letter accurately, but the letters were blurry, the subject may have assigned a quality score of 80.00. The quality score is a subjective measurement. The average of the five test subjects’ quality score was calculated for each of the six test diffractive lenses and for their distance viewing glasses prescription. The y-axis 1804b of graph 1800b is the average absolute visual quality. The data in graph 1800b shows that for all of the test diffractive lenses, the visual quality score went down as the visual acuity chart distance got smaller. Lens “E” showed the least amount of visual quality lost as the as the visual acuity chart distance got smaller to test near vision.

[0103] FIG. 19 is a series of digital images 1900 of an example test diffractive tear lens worn by a test subject during different stages of a blink cycle. The digital images 1902,1904, 1906 in the series of digital images were captured in white light with no dye added to the tear film. Accordingly, the digital images 1902, 1904, 1906 include reflections off the tear film surface.

[0104] Image 1902 is a digital image of the example test diffractive tear lens immediately after the test subject blinked. In digital image 1902, immediately following a blink, there is tear film covering the diffractive elements, so the diffractive elements on the diffractive zone of the test diffractive tear lens are difficult to see. Image 1904 is a digital image of the example test diffractive tear lens multiple seconds after the test subject blinked and prior to another blink. In digital image 1904, a few seconds following a blink, some tear film has begun to recede and uncover the diffractive elements, so the diffractive elements on the diffractive zone of the test diffractive tear lens are more visible than they were in digital image 1902. Image 1906 is a digital image of the example test diffractive tear lens after the test subject has held their blink longer than they would in a normal blink cycle, and prior to another blink. In digital image 1906, right before another blink when most or all of the tear film has receded and uncovered the diffractive elements, the diffractive elements on the diffractive zone of the test diffractive tear lens are the most visible compared to images 1902 and 1904 in the series of digital images 1900. The series of digital images 1900 taken during the blink cycle, from immediately following a blink to after the test subject has held their blink, shows how the receding tear film surface angle changes throughout the blink cycle.

[0105] FIG. 20, FIG. 21 , and FIG. 22 show another series of digital images 2000, 2100, 2200 of an example test diffractive tear lens worn by a test subject during a blink cycle. Prior to capturing digital images 2000, 2100, and 2200, a high molecular weight fluorescein dye was injected into the tear film of the test subject to provide more contrast of the tear film thickness over the front surface of the test diffractive tear lens. The brightness of the tear film in digital images 2000, 2100, and 2200 is directly related to the thickness of the tear film. Accordingly, as the blink cycle progresses and the tear film recedes into the cavities between the diffractive elements, the tear film thins over the tops of the diffractive elements, causing more variation in tear film thickness across the diffractive zone and therefore more variation in brightness on the diffractive zone when comparing digital image 2000 (captured immediately after a blink) to digital image 2200 (captured towards the end of the blink cycle).

[0106] FIG. 20 is a digital image 2000 of an example test diffractive tear lens worn by a test subject. Digital image 2000 was taken immediately after the test subject blinked. To capture the tear film dynamics shown in digital image 2000, a high-molecular weight fluorescein dye was injected into the eye, and a blue light and sharp cutoff yellow filter was used to reveal the thickness of the tear film over the front surface of the test diffractive tear lens. In digital image 2000, immediately following a blink, there is tear film covering the diffractive elements, so the diffractive elements on the diffractive zone 2002 of the test diffractive tear lens are difficult to see. Additionally, because digital image 2000 was taken immediately after the test subject blinked, the tear film is thicker than the tear film captured in digital images 2100 and 2200, which were taken later in the blink cycle. Thus, the brightness of the tear film in digital image 2000 is more uniform across the diffractive zone 2002 than in digital images 2100 and 2200 because the tear film has not yet begun to recede into the cavities between the diffractive elements and thin on the tops of the diffractive elements.

[0107] FIG. 21 is a digital image 2100 of an example test diffractive tear lens worn by a test subject. Digital image 2100 includes the same test subject eye and the same example test diffractive tear lens as that shown in FIG. 20. Digital image 2100 was taken several seconds after the test subject blinked. In digital image 2100, a few seconds following a blink, some tear film has begun to recede and uncover the diffractive elements, so the diffractive elements on the diffractive zone 2102 of the test diffractive tear lens are more visible than they were in digital image 2000. Additionally, because digital image 2100 was taken later in the blink cycle than digital image 2000, some tear film has begun to recede into the cavities between the diffractive elements and the tear film on the tops of the diffractive elements has thinned. Therefore, the brightness across the diffractive zone 2102 in digital image 2100 is more varied than the brightness across the diffractive zone in digital image 2000.

[0108] FIG. 22 is a digital image 2200 of an example test diffractive tear lens worn by a test subject. Digital image 2200 includes the same test subject eye and the same example test diffractive tear lens as that shown in FIGS. 20 and 21. Digital image 2200 was taken just prior to the subject blinking again. In digital image 2200, right before another blink when most or all of the tear film has receded and uncovered the diffractive elements, the diffractive elements on the diffractive zone 2202 of the test diffractive tear lens are the most visible compared to FIGS. 20 and 21. Additionally, because digitalimage 2200 was taken at the end of the blink cycle, the tear film has receded more completely into the cavities between the diffractive elements, so there is no tear film or very little tear film covering the tops of the diffractive elements. Therefore, there is greater variation in tear film thickness across the diffractive zone 2202, as compared to in digital images 2000 and 2100, so the brightness across the diffractive zone 2202 is more varied as compared to the brightness on the diffractive zones in digital images 2000 and 2100.Diffractive Tear Lens Manufacturing Simulation

[0109] In order to manufacture diffractive tear lenses with the sawtooth diffractive elements on the anterior surface of the lenses, high precision sub-micro lathes may be used to cut the lens surface directly. Alternatively, high precision sub-micro lathes may be used to cut the surface of a mold, such as a metal mold, used to create a polypropylene mold in which a diffractive tear lens is cast. In examples, a diamond tool can be used to cut the sawtooth diffractive elements onto the surface of a lens or to cut a molding insert. A diamond tool uses synthetic diamond crystals as the cutting medium and provide dimensional accuracy, surface finish, and edge sharpness, making a diamond tool useful for precision machining applications. A typical diamond tool may have a radiused cutting edge with a radius value of 0.250mm. However this would not be suitable for cutting sawtooth diffractive elements having a height of from 0.9pm to 2.0pm high. Accordingly, a series of diamond tools may be utilized using reducing diamond radius to achieve the sawtooth diffractive features.

[0110] For the manufacture of the lenses to demonstrate the efficacy of this invention, three diamond tools were used: diamond tool with radius 0.250mm for cutting the base optic surface; diamond tool with radius 0.005mm for cutting the intermediate diffractive step; diamond tool with radius <0.001mm for cutting the final diffractive step. Generally, larger radius diamond tools cut surfaces with low surface roughness, so using multiple diamond tools keeps the surface roughness of the diffractive tear lens to a minimum.

[0111] FIG. 23 is a close-up view of an anterior surface of an example diffractive tear lens having sawtooth diffractive elements. The base optic surface 2302 may be cut with the diamond tool having a radius of 0.250mm. The intermediate diffractive step 2304 may be cut with the diamond tool having a radius of 0.005mm. The final diffractive step 2306 may be cut with the diamond tool having a radius of <0.001mm.

[0112] FIG. 24 is a top view of an example diffractive tear lens 2400 having a plurality of sawtooth diffractive elements. The diffractive tear lens 2400 has a center curved portion 2402 and a peripheral edge 2406. A diffractive zone 2404 of the lens includes a plurality of sawtooth diffractive elements radiating from the curved center portion. The lens may further include transition zones (e.g., 2408) where different surfaces of the lens are blended to form the shape of the lens.

[0113] FIG. 25 is a side view of an example diffractive tear lens 2500 having a plurality of sawtooth diffractive elements. The diffractive tear lens 2500 has a center curved portion 2502, and a diffractive zone 2504 of the lens includes a plurality of sawtooth diffractive elements radiating from the center curved portion 2502.

[0114] FIG. 26 is a top-side view of a molding 2600 used to manufacture diffractive tear lenses. The molding has a spherical top surface with a curved center portion 2604. A plurality of concentric circles 2602 may be cut around the curved center portion of the molding. In examples, the cuts in the molding are created with a diamond tool. In examples, the molding is made of metal. The specification of each molding 2600 may be specific to individual patients in order to manufacture diffractive tear lenses having sawtooth diffractive elements with the requisite height and width necessary to provide appropriate refractive correction individualized for different patients.

[0115] Notwithstanding the appended claims, the disclosure is also defined by the following clauses:1. A diffractive multifocal lens comprising: a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having an anterior surface curve that controls a distance viewing power of the lens; and a plurality of diffractive elements on the anterior surface, the plurality of diffractive elements being rings; wherein the plurality of diffractive elements are arranged to form a cavity between each diffractive element that retains tear fluid from a tear film when the lens is worn on an eye, and the presence of tear fluid in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves distance viewing, and the presence of air in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves near viewing.2. The diffractive multifocal lens of clause 1, wherein the rings are continuous.3. The diffractive multifocal lens of clauses 1-2, wherein the rings are concentric around a central axis of the lens.4. The diffractive multifocal lens of clauses 1-3, wherein each diffractive element of the plurality of diffractive elements has a height that controls the proportion of distance viewing relative to near viewing when air is between each of the plurality of sawtooth elements.5. The diffractive multifocal lens of clauses 1-4, wherein each diffractive element of the plurality of diffractive elements has a width on the anterior surface that controls the near viewing power of the lens.6. The diffractive multifocal lens of clauses 1-5, wherein the plurality of diffractive elements have a sawtooth profile.7. The diffractive multifocal lens of clauses 1-6, wherein the plurality of diffractive elements are indented from the anterior surface of the curved lens body.8. The diffractive multifocal lens of clauses 1-7, wherein the plurality of diffractive elements are anterior to the anterior surface of the curved lens body.9. The diffractive multifocal lens of clauses 1-8, wherein the height of each diffractive element within the plurality of diffractive elements is the same.10. The diffractive multifocal lens of clauses 1-9, wherein the width of each diffractive element within the plurality of diffractive elements is not uniform.11. The diffractive multifocal lens of clauses 1-10, wherein the width of each diffractive element within the plurality of diffractive elements gets smaller as the diffractive elements get closer to the peripheral edge of the lens.12. The diffractive multifocal lens of clauses 1-11, wherein the width of each diffractive element within the plurality of diffractive elements is from 0.2mm and 1.5mm.13. The diffractive multifocal lens of clauses 1-12, wherein the height of each diffractive element within the plurality of diffractive elements is from 0.8pm and 1.3pm.14. The diffractive multifocal lens of clauses 1-13, wherein the plurality of diffractive elements are arranged on a diffractive portion of the lens having a diameter from 2mm to the entire diameter of the lens.15. The diffractive multifocal lens of clauses 1-14, further comprising an aspheric surface on the anterior surface of the lens configured to provide a range of distance viewing power between the center of the lens and the peripheral edge of the lens.16. The diffractive multifocal lens of clauses 1-15, further comprising: a second plurality of diffractive elements on the anterior surface different from the plurality of diffractive elements, wherein the plurality of diffractive elements and the second plurality of diffractive elements are overload to create a trifocal design when the lens is worn on the eye.17. The diffractive multifocal lens of clauses 1-16, wherein: the rings are continuous and concentric around a central axis of the lens, each diffractive element of the plurality of diffractive elements has a height that controls the proportion of distance viewing relative to near viewing when air is between each of the plurality of sawtooth elements and a width on the anterior surface that controls the near viewing power of the lens, the plurality of diffractive elements have a sawtooth profile, the plurality of diffractive elements are indented from the anterior surface of the curved lens body,the width of each diffractive element within the plurality of diffractive elements gets smaller as the diffractive elements get closer to the peripheral edge of the lens and the width of each diffractive element within the plurality of diffractive elements is from 0.2mm and 1.5mm, the height of each diffractive element within the plurality of diffractive elements is from 0.8pm and 1.3pm, and the plurality of diffractive elements are arranged on a diffractive portion of the lens having a diameter from 2mm to the entire diameter of the lens.18. A method of manufacturing a diffractive multifocal lens, comprising: determining a distance viewing refractive correction for the lens; determining a near viewing refractive correction for the lens; forming a diffractive multifocal lens having a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having an anterior surface curve based on the determined distance viewing refractive correction for the lens, and a plurality of diffractive elements on the anterior surface, the plurality of diffractive elements being rings, wherein the plurality of diffractive elements are arranged to form a cavity between each diffractive element that retains tear fluid from a tear film when the lens is worn on an eye, and the presence of tear fluid in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves distance viewing, and the presence of air in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves near viewing, wherein the plurality of diffractive elements are formed to have a width based on the determined near viewing refractive correction for the lens.19. The method of clause 18, wherein the plurality of diffractive elements have a sawtooth profile.20. A method of correcting refractive error of an eye, comprising: placing a diffractive multifocal lens on the eye, the diffractive multifocal lens having a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having an anterior surface curve that controls a distance viewing power of the lens, and a plurality of diffractive elements on the anterior surface, the plurality ofdiffractive elements being rings, wherein the plurality of diffractive elements are arranged to form a cavity between each diffractive element that retains tear fluid from a tear film when the lens is worn on an eye, and the presence of tear fluid in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves distance viewing, and the presence of air in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves near viewing.

Claims

CLAIMSWhat is claimed is:

1. A diffractive multifocal lens comprising: a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having an anterior surface curve that controls a distance viewing power of the lens; and a plurality of diffractive elements on the anterior surface, the plurality of diffractive elements being rings; wherein the plurality of diffractive elements are arranged to form a cavity between each diffractive element that retains tear fluid from a tear film when the lens is worn on an eye, and the presence of tear fluid in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves distance viewing, and the presence of air in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves near viewing.

2. The diffractive multifocal lens of claim 1, wherein the rings are continuous.

3. The diffractive multifocal lens of claim 1, wherein the rings are concentric around a central axis of the lens.

4. The diffractive multifocal lens of claim 1, wherein each diffractive element of the plurality of diffractive elements has a height that controls the proportion of distance viewing relative to near viewing when air is between each of the plurality of sawtooth elements.

5. The diffractive multifocal lens of claim 1, wherein each diffractive element of the plurality of diffractive elements has a width on the anterior surface that controls the near viewing power of the lens.

6. The diffractive multifocal lens of claim 1, wherein the plurality of diffractive elements have a sawtooth profile.

7. The diffractive multifocal lens of claim 1, wherein the plurality of diffractive elements are indented from the anterior surface of the curved lens body.

8. The diffractive multifocal lens of claim 1, wherein the plurality of diffractive elements are anterior to the anterior surface of the curved lens body.

9. The diffractive multifocal lens of claim 4, wherein the height of each diffractive element within the plurality of diffractive elements is the same.

10. The diffractive multifocal lens of claim 5, wherein the width of each diffractive element within the plurality of diffractive elements is not uniform.

11. The diffractive multifocal lens of claim 10, wherein the width of each diffractive element within the plurality of diffractive elements gets smaller as the diffractive elements get closer to the peripheral edge of the lens.

12. The diffractive multifocal lens of claim 5, wherein the width of each diffractive element within the plurality of diffractive elements is from 0.2mm and 1.5mm.

13. The diffractive multifocal lens of claim 4, wherein the height of each diffractive element within the plurality of diffractive elements is from 0.8pm and 1.3pm.

14. The diffractive multifocal lens of claim 1, wherein the plurality of diffractive elements are arranged on a diffractive portion of the lens having a diameter from 2mm to the entire diameter of the lens.

15. The diffractive multifocal lens of claim 1, further comprising an aspheric surface on the anterior surface of the lens configured to provide a range of distance viewing power between the center of the lens and the peripheral edge of the lens.

16. The diffractive multifocal lens of claim 1, further comprising: a second plurality of diffractive elements on the anterior surface different from the plurality of diffractive elements, wherein the plurality of diffractive elements and the second plurality of diffractive elements are overload to create a trifocal design when the lens is worn on the eye.

17. The diffractive multifocal lens of claim 1, wherein: the rings are continuous and concentric around a central axis of the lens, each diffractive element of the plurality of diffractive elements has a height that controls the proportion of distance viewing relative to near viewing when air is between each of the plurality of sawtooth elements and a width on the anterior surface that controls the near viewing power of the lens, the plurality of diffractive elements have a sawtooth profile, the plurality of diffractive elements are indented from the anterior surface of the curved lens body, the width of each diffractive element within the plurality of diffractive elements gets smaller as the diffractive elements get closer to the peripheral edge of the lens and the width of each diffractive element within the plurality of diffractive elements is from 0.2mm and 1.5mm, the height of each diffractive element within the plurality of diffractive elements is from 0.8pm and 1.3pm, and the plurality of diffractive elements are arranged on a diffractive portion of the lens having a diameter from 2mm to the entire diameter of the lens.

18. A method of manufacturing a diffractive multifocal lens, comprising: determining a distance viewing refractive correction for the lens; determining a near viewing refractive correction for the lens; forming a diffractive multifocal lens having a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having an anterior surface curve based on the determined distance viewing refractive correction for the lens, and a plurality of diffractive elements on the anterior surface, the plurality of diffractive elements being rings, wherein the plurality of diffractive elements are arranged to forma cavity between each diffractive element that retains tear fluid from a tear film when the lens is worn on an eye, and the presence of tear fluid in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves distance viewing, and the presence of air in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves near viewing, wherein the plurality of diffractive elements are formed to have a width based on the determined near viewing refractive correction for the lens.

19. The method of claim 18, wherein the plurality of diffractive elements have a sawtooth profile.

20. A method of correcting refractive error of an eye, comprising: placing a diffractive multifocal lens on the eye, the diffractive multifocal lens having a curved lens body having a peripheral edge, an anterior surface, and a posterior surface having an anterior surface curve that controls a distance viewing power of the lens, and a plurality of diffractive elements on the anterior surface, the plurality of diffractive elements being rings, wherein the plurality of diffractive elements are arranged to form a cavity between each diffractive element that retains tear fluid from a tear film when the lens is worn on an eye, and the presence of tear fluid in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves distance viewing, and the presence of air in the cavities between each of the plurality of diffractive elements causes a diffractive effect that improves near viewing.

Images