Geometric volume control corneal refractive therapy contact lens

Abstract

A contact lens for treating myopia in a patient's eye has an anterior surface and a posterior surface having semi-meridians defining a central compressed region in contact with the pre-treatment cornea, a volume control region peripheral to the central compressed region, a secondary compressed region peripheral to the volume control region in contact with the pre-treatment cornea, a peripheral relief region peripheral to the secondary compressed region, a landing region peripheral to the peripheral relief region in contact with the pre-treatment cornea, and a peripheral edge of the landing region.

Description

Technical Field

[0001] The technology of the present disclosure generally relates to contact lenses, and in particular, some embodiments relate to contact lenses and non-surgical methods for reshaping the cornea of the eye to treat vision impairment.

Background Art

[0002] Hard contact lenses were commercialized over 60 years ago. The initial fitting concept rapidly evolved into aspheric and toric designs to facilitate the required lens movement for tear exchange within the non-gas-permeable lens. The movement of the lens due to blinking was essential to allow a new tear layer to move from the lower lid tear meniscus to the lower lens. The simple lathes used in the first 20 years of commercialization enabled the realization of multiple concentric surfaces combined so as not to produce sharp junctions.

[0003] The central radius of the lens was selected in relation to the central corneal curvature. The radius of the base curve could be greater than or less than the central corneal curvature based on the design concept. The radius of the first concentric region (aspheric surface) was always larger than that of the base curve, and the radius of each successive region peripherally with respect to the more inner region was also larger than that of its immediately inner region. Historically, the lens had three or more regions. The radius of all regions outside the central optical region was, in principle, larger than the corneal radius below it. This was a requirement for facilitating lens movement and tear exchange.

[0004] Lenses of such designs had demonstrated a movement of about 1.0 mm to 1.5 mm due to blinking and lateral eye movement. The movement required getting used to. The edge design was also very important for achieving comfort and preventing trauma to the bulbar and palpebral conjunctiva.

[0005] The advent of gas-permeable materials has reduced the need for the high levels of movement and the edge lift in the radial and axial directions required for non-gas-permeable lenses. Nevertheless, conventional design concepts have continued to be used with the new materials. As time has passed, lenses have come to be designed to have less clearance. In the original design, it was common to make the radius of the aspheric surface about 1.4 mm larger than the radius of the base surface, but in gas-permeable designs, there has been a tendency to be 0.8 mm larger than the radius of the base surface. The average difference in the radius of the base surface from the central corneal radius has also tended to become smaller.

[0006] Over the past 10 years, the average overall diameter has also tended to increase. As a result, recent gas-permeable lenses are larger and more closely aligned with the cornea. The initial non-gas-permeable lenses made of polymethyl methacrylate (PMMA) were designed to have an axial edge lift of about 100 μm, but recent lenses can have a small axial edge lift of about 50 μm. Also, compared to the 1.0 - 1.5 mm of movement of the initial PMMA lenses, recent gas-permeable lenses have demonstrated movement of about 0.25 mm or less.

[0007] Nevertheless, current design concepts and teachings continue to use multiple concentric region features and their respective modulations. In lens design programs, the width and local radius of each region are referenced. In educational curriculums, modulations are taught regarding making the radius portion "flatter" or "steeper" and also "narrower" or "wider". Since there is no accurate measurement method generally available for measuring the actual clearance of the lens and the determination of fitting uses the observation of sodium fluorescein, the evaluation of fitting is more of a skilled technique rather than a scientific one based on measurement.

[0008] Also, market trends demand time-efficient management of contact lens fitting. The time spent sitting in a chair must be reduced, and the probability of success in one attempt is an important measure for productivity and optimal distribution. The concept of lens fitting must be simple and require little training to succeed.

[0009] The design of gas-permeable hard contact lenses for overnight corneal reshaping has advanced mainly by using rational fitting systems, in which parameters of a given region are modulated to control the relationship between the vertex lens radius and the vertex corneal radius, the relationship between the midperipheral lens sagittal depth and the midperipheral corneal sagittal depth, and the alignment of the lens periphery with respect to the peripheral cornea. As is known to those skilled in the art, while the cornea is not rotationally symmetric, all commercialized lens designs are rotationally symmetric. The result of placing a rotationally symmetric lens on a non-rotationally symmetric cornea is decentration of the lens. Random treatment accuracy is also an undesirable result.

[0010] Numerous attempts have been continuously made to fit non-rotationally symmetric eyes with significant irregular elevation differences with rotationally symmetric lenses. In some examples, annular peripheral designs or double elevation designs are used to address the elevation differences of the cornea in orthogonal directions. There is also a requirement for non-orthogonal elevation control, which is achieved by designing the lens using individual semi-meridian elevation control points. Each semi-meridian of the lens can be designed to have a predetermined elevation at each control point defined by the distance from the geometric center of the lens. The elevation and sagittal depth of each point from the geometric center at the back of the lens are determined by a design concept algorithm that describes the relationship between the topography of the lower eye at the same location and the desired sagittal depth. Such elevation differences correspond to the irregular elevation of the lower cornea when the lens is applied to the eye.

[0011] Unfortunately, in the standard design paradigm using concentric surfaces, it results in an decentered lens that contacts the cornea near the corneal apex, the amount of tear fluid becomes random under the secondary reverse surface, and the contact of the lens with the cornea fluctuates in the alignment area around the lens. As a result of second-generation overnight corneal reshaping lenses, it can be cited that it is impossible to accurately and consistently induce higher-order aberrations and generate the mid-peripheral refractive power necessary for consistent myopia control. Attempts have been made to address corneal asymmetry in second-generation designs, but the use of coaxial concentric radii of curvature is essentially self-limiting. There are doubts about the accuracy and consistency in fitting.

[0012] The same problem also exists in third-generation designs that incorporate a cubic polynomial in the second region of the lens. In the manufacture of third-generation designs, a design that varies the cubic polynomial by meridian to produce non-rotationally symmetric stiffness has not been commercialized, and regulatory approval does not include the use of individual meridian height control. Furthermore, third-generation designs do not teach about the control of the volume between the pre-treatment cornea and the lens in the mid-periphery of the lens, the control of the inward angle regarding the secondary compression region of the lens, and having a secondary clearance region for compressing the mid-peripheral corneal contact region into the cornea.

[0013] The skill level of the person performing the fitting must be high, and the problem remains that even if the third-generation lens design addresses a specific meridian sagittal depth, a thorough fitting set and reordering of lenses are required to find the optimal fitting. SUMMARY OF THE INVENTION MEANS FOR SOLVING THE PROBLEM

[0014] Embodiments of the device and method may include one or more of the following features. In some embodiments, the back surface of the contact lens is geometrically controlled to have a shape that determines an area (region) on at least one semi - meridian of the space between the contact lens surface and the underlying corneal surface, defined by a first radial position on the back surface, a second radial position on the back surface, and the same radial position on the corneal surface to be treated. In some embodiments, the back surface of the contact lens has a predetermined inward angle from the point of contact of the underlying corneal surface to be treated with the mid - peripheral portion of the lens, forming the peripheral side of the geometrically controlled region of the space between the back surface of the contact lens and the underlying corneal surface.

[0015] Generally, a contact lens for reshaping a pre - treatment cornea of a patient's eye, characterized by one aspect of the present disclosure, comprises a front surface and a back surface having semi - meridians, the semi - meridians defining a central compression region that contacts the treatment membrane cornea, a volume control region peripheral to the central compression region, a secondary compression region peripheral to the volume control region that contacts the pre - treatment cornea, a peripheral relief region peripheral to the secondary compression region, a landing region peripheral to the peripheral relief region that contacts the treatment membrane cornea, and an edge peripheral to the landing region.

[0016] Embodiments of the contact lens may include one or more of the following features. In some embodiments, the radius of the central compression region is spherical. In some embodiments, the radius of the central compression region is aspherical. In some embodiments, the diameter of the central compression region is from 3.0 mm to 7.0 mm. In some embodiments, the volume control region is defined by four or more geometric control points connected by one of a spline, a polynomial, a combination of a conic curve and a non-curved portion, with a second geometric control point around the first geometric control point, a third geometric control point around the second geometric control point, a fourth geometric control point contacting the pre-treatment cornea, and the fourth geometric control point around the third geometric control point. In some embodiments, the first geometric control point of the volume control region is disposed away from the pre-treatment cornea in the z-axis direction within a range of 5 μm to 80 μm. In some embodiments, the second geometric control point of the volume control region is disposed away from the pre-treatment cornea in the z-axis direction so as to define a predetermined area between the back surface within the volume control region and the pre-treatment cornea. In some embodiments, the third geometric control point of the volume control region is disposed to define a predetermined angle between (i) a line connecting the third geometric control point and the fourth geometric control point and (ii) a horizontal line passing through the fourth geometric control point. In some embodiments, the semi-chord radial distance of the fourth geometric control point is within a range of 2.6 mm to 5.2 mm. In some embodiments, the secondary compression region has a width within a range of 0.2 mm to 0.8 mm. In some embodiments, the secondary compression region is defined by a shape having one or more control points within the secondary compression region, and the shape is defined by one of a spline, a polynomial, and a convex conic curve. In some embodiments, the peripheral relief region is defined by one or more control points disposed away from the pre-treatment cornea in the z-axis direction by 6 μm or more per diopter to reduce central refractive aberration. In some embodiments, the peripheral relief region has a width of 0.4 mm to 1.2 mm. In some embodiments, the peripheral landing region is defined by a shape having one or more control points within the peripheral landing region, and the shape is defined by one of a spline, a polynomial, a conic curve, an angled curved portion, and an angled non-curved portion.In one embodiment, the edge of the rear surface begins at the most radially peripheral side of the peripheral landing region, connects to the most peripheral side of the front surface, and the edge of the rear surface is defined by an ellipse, a conic curve, or a spline. In some embodiments, the volume control region and the secondary compression region are defined by a single spline.

[0017] Generally, a method for determining a contact lens manufactured for a patient's eye, characterized by one aspect of the present disclosure, includes determining, according to the corneal topography of the patient's eye, the base surface radius of the central compression region of the contact lens, the semi-meridian radial distance of the periphery of the central compression region of the contact lens, the area of the volume control region adjacent to the central compression region, and the semi-chord radial distance of the secondary compression region adjacent to the periphery of the volume control region and contacting the pre-treatment cornea of the eye; determining the positions of a plurality of control points to define at least the width of the central compression region, the shape of the volume control region that creates a predetermined area between the region surface and the corneal surface to be treated, the semi-meridian radial distance of the secondary compression region, and the inward angle formed by the apex of the secondary compression region; and defining the semi-meridian of the rear surface of the contact lens according to the plurality of control points.

[0018] Embodiments of the present method may include one or more of the following features. Some embodiments include placing a first control point among a plurality of control points at the geometric center of the contact lens and the corresponding geometric center of the pre-treatment cornea. Some embodiments include determining a base surface radius according to the subjective refraction of the eye and corneal curvature measurement or topography measurement, selecting the semi-chord radius direction distance of a second control point among a plurality of control points as the peripheral end of the central compression region, and setting the sagittal depth of the second control point among a plurality of control points at the semi-chord radius direction distance of the selected base surface radius when the first control point among the plurality of control points is in contact with the lower pre-treatment cornea. Some embodiments include selecting the semi-chord radius direction distance of a third control point among a plurality of control points so as to separate a first section of the volume control region and a second section of the volume control region that is peripheral to the first section of the volume control region, and setting the sagittal depth of the third control point among a plurality of control points to a distance equal to the distance of a lens having a predetermined diopter treatment target radius when placed on the average pre-treatment cornea. Some embodiments include selecting the semi-chord radius direction distance of a fourth control point among a plurality of control points to be equal to the semi-chord radius direction distance of the apex of the secondary compression region according to a desired mid-peripheral additional position. Some embodiments include selecting the squeeze angle on the peripheral side of the second section of the volume control region and arranging a fifth control point among a plurality of control points to define the squeeze angle together with the fourth control point among the plurality of control points. Some embodiments include determining the position of a sixth control point among a plurality of control points according to the area of the volume control region selected according to a desired mid-peripheral additional refractive power. Some embodiments include determining the overall diameter of the contact lens according to the corneal diameter of the pre-treatment cornea and determining the position of a seventh control point among a plurality of control points according to the overall diameter of the contact lens. Some embodiments include determining an eighth control point among a plurality of control points that define the inside of the landing region that contacts the pre-treatment cornea according to the corneal topography of the eye and the desired radial distance from the seventh control point among a plurality of control points according to the desired radial width of the landing region.One embodiment includes selecting the diameter of a ninth control point among a plurality of control points, selecting the area of a peripheral relief region between a secondary compression region and a landing region, and determining the sagittal depth of the ninth control point among the plurality of control points according to the selected area of the peripheral relief region or according to a target treatment in diopter units.

[0019] The present disclosure will be described in detail with respect to one or more various embodiments with reference to the accompanying drawings below. The drawings are provided for illustrative purposes only and show only typical and exemplary embodiments.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4A

Figure 4B

Figure 5

Modes for Carrying Out the Invention

[0021] The drawings are not comprehensive and do not limit the present disclosure to the disclosed forms themselves.

[0022] Embodiments of the technology of the present disclosure provide a corneal refractive therapy (CRT) contact lens for nocturnal corneal reshaping and a method for determining the CRT contact lens using a geometric volume control method. This method uses a spline function or other geometric shape to determine the surface profile of the contact lens at predetermined control points or knots on the back surface of the lens, defined by a specified semi-chord radial distance from the center of the lens to the edge of the lens and a sagittal depth from a reference plane. Some embodiments use the corneal topography of each eye to determine the semi-meridian sagittal depth at each control point and apply an algorithm that enables empirical ordering and observational fitting of the eye for nocturnal corneal reshaping. Embodiments of the present disclosure ensure a central corneal radius change to correct pre-existing myopia, produce a desired mid-peripheral additional refractive power and mid-peripheral additional position by an empirical selection of the base curve radius of the lens, and empirically select the surface height of the lens on each semi-meridian at a plurality of predetermined control points on the lens surface from the center of the lens to the edge of the lens.

[0023] FIG. 1 is a plan view of the back surface of a contact lens according to some embodiments of the technology of the present disclosure. Referring to FIG. 1, the back surface of the contact lens includes a plurality of annular regions including a central compression zone (CCZ), a first section (VCZR1) of a volume control zone, a second section (VCZR2) of the volume control zone, a secondary compression zone (SCZ), a peripheral relief zone (PRZ), and a landing zone (LZ). Each region will be described in detail below.

[0024] Figure 2 shows the semi - meridians that define the back surface of an exemplary contact lens according to some embodiments of the technology of the present disclosure. In Figure 2, the semi - meridians of the contact lens are shown as a continuous solid line having a plurality of curves and control points CP. Also, in Figure 2, the pretreatment cornea is shown as a dashed line. The contact lens and the pretreatment cornea are plotted on a grid with millimeter scale markings, but Figure 2 is not to scale. The specific values of the illustrated control points CP are presented merely as examples, and it should be understood that other semi - meridians of the contact lens, or semi - meridians of other contact lenses, may have different values of the control points CP. If the eye were rotationally symmetric, a contact lens could be manufactured using only the control points of one semi - meridian. However, since the eye is not rotationally symmetric, a single contact lens can be manufactured by using the control points of a plurality of semi - meridians having different surface height dimensions.

[0025] Referring to Figure 2, the center of the pretreatment cornea and the center of the contact lens are located at the origin of the grid. In Figure 2, the front surface of the pretreatment cornea and the front surface (not shown) of the contact lens face downward toward the bottom of the grid. As practiced by those skilled in the art of contact lens design and manufacture, the front surface of the contact lens may have a predetermined radius of the central optical region to produce a predetermined lens refractive power together with the radius of the back surface of the central region. The optical region of the front surface may be spherical, aspherical, single - radius, or multi - radius designed to produce a multifocal refractive power. The peripheral portion of the front surface may be designed to produce a constant thickness from the back surface or may be designed to have different thicknesses from each corresponding back - surface control point. This contact lens includes nine control points CP1 - CP2 for each region of the contact lens. However, in other embodiments, a different number of control points may be used.

[0026] The central compression zone (CCZ) contacts the pre-treatment cornea at its center and extends from the control point CP1 at the center of the meridian to the control point CP2. In this example, CP2 is located at a semi-chord radius distance of approximately 2.5 mm.

[0027] There is a volume control zone around the central compression zone, which extends to the control point CP4. In this example, CP4 is located at a semi-chord radius distance of approximately 4 mm. In this example, the volume control zone includes two areas. The first area of the volume control zone (VCZR1) extends to the control point CP3. In this example, CP3 is located at a semi-chord radius distance of approximately 3 mm. There is a second area of the volume control zone (VCZR2) around the first area of the volume control zone, which includes the control points CP6 and CP5 and extends to the control point CP4. In this example, the control points CP6 and CP5 are located at semi-chord radius distances of approximately 3.4 mm and approximately 3.8 mm respectively.

[0028] There is a secondary compression zone (SCZ) around the second area of the volume control zone, where the contact lens also contacts the pre-treatment cornea. There is a peripheral relief zone (PRZ) around the secondary compression zone, which includes the control point CP9 and extends to the control point CP8. In this example, CP8 is located at a semi-chord radius distance of approximately 5 mm. In this example, the control point CP9 is located at a semi-chord radius distance of approximately 4.5 mm.

[0029] There is a landing zone (LZ) around the peripheral relief zone, where the contact lens also contacts the pre-treatment cornea. The landing zone extends to the control point CP7. In this example, CP7 is located at a semi-chord radius distance of approximately 5.4 mm. The peripheral end of the landing zone indicates the edge terminus (ET) of the contact lens.

[0030] Spherical or aspherical base surfaces can be used for the central compression region. The volume control region, the secondary compression region, the peripheral relief region, and the landing region can be configured using a spline function or other geometric shape that varies circumferentially so that a desired sagittal depth difference is obtained at predetermined control points along each radius line. The height difference can be obtained by topographic measurement of the pre-treatment cornea at each control point on each radius line of the cornea to be treated. The height difference between a point on the posterior lens surface and each point on the pre-treatment cornea surface can utilize the axial distance from the lens surface to the cornea surface, or the radial distance from the lens surface to the cornea surface. While the axial distance forms a line parallel to the lens axis, the radial distance is along the direction from the lens surface towards the center of rotation of the cornea surface of each eye. In a preferred embodiment, the axial distance from the lens surface to the pre-treatment cornea surface is used to calculate the height difference between a control point on the posterior lens surface and each point on the cornea surface. The edge of the lens can be adjusted to result in a flat and round, non-flat and round, or non-flat and non-round lens.

[0031] The contact lens of the present disclosure has demonstrated improved centration, optimization of the reduction of refractive myopia of the treated eye, and additional refractive power and position of the mid-peripheral cornea after a given treatment. The volume control region generates a force that produces additional refractive power and position in the mid-periphery, along with the position and angle of the semi-chord radius distance formed by the secondary compression region. The peripheral relief region allows the secondary compression region to contact the corneal epithelium and redistribute the corneal epithelium inwardly toward the volume control region. A uniformly aligned landing region provides central compression and a compressive force that produces compression within the secondary compression region. The high non-rotational symmetry of the landing region being aligned with the height difference of the pre-treatment cornea on two or more meridians provides optimal compressive force, lens stability, and improved lens centration. An edge is added to the landing region. The shape of the back surface of the contact lens is continuous and seamless to prevent trauma induced by the junction. In one embodiment, a cubic spline can be used with knots placed at corresponding control points to produce a smooth, continuous, and seamless surface under each meridian of the volume control region, at a given area, and at a given inward angle from the secondary compression region.

[0032] The contact lens is seamless as each region begins with a local gradient at the end of the region central to that region. The knots of the spline in the volume control region control the relative sagittal depth of the lens at predetermined control points along the back surface of the lens meridian outside the central compression region, and the control of the spline gives the shape of the surface. The most central side of the spline is defined by the height and local gradient at the chord of the optical region junction, and the most peripheral side is defined by the desired height at the next peripheral control point on each meridian. The most peripheral local gradient of the volume control region is defined by a given squeeze angle having a vertex at the deepest point of the secondary compression region. The most peripheral side of the secondary compression region is defined by the most central local gradient of the peripheral relief region, and the most peripheral side of the peripheral relief region is defined by the most central side of the landing region. The edge begins at the most peripheral height of the landing region.

[0033] In one application, the lens can be a dedicated design for each eye. In other applications, a fitting set can be provided from which the lens can be selected. An exemplary fitting set or fitting kit can have one overall diameter (OAD, for example, in the range of 10.5 mm to 11.5 mm), up to five base curve radii increments (BCRI), a single optical zone diameter and one volume control zone width for each BCRI, up to five volume control zone areas for each volume control zone width, three secondary compression zone depths, one peripheral relief zone, and one landing zone. This fitting set can have 75 lenses (1 OAD × 5 BCRI × 5 VCZ areas × 3 SCZ depths). A lookup table or computer application can be generated that proposes the first fitting set lens based on the input of subjective refraction, central corneal curvature measurement, and corneal topography collected by standard clinical tests.

[0034] A preferred empirical method in the case of no corneal topography without using a fitting set is to predict the base curve radius using subjective refraction and standard corneal curvature measurement, predict the first and second zones of the volume control region using the treatment amount in diopters and average biometric data, predict the secondary compression zone depth and standard peripheral relief zone height using the treatment amount and average biometric data, and predict the local gradient and sagittal depth of the central part of the landing zone using average biometric data, thereby empirically designing the first observation lens to be manufactured. This first lens empirically designed from clinical data can function as an observation lens for ordering the second lens. The first observation lens empirically designed is predicted to include non-rotational symmetry based on the average biometric data showing asymmetry.

[0035] Figure 3 is a flowchart showing a schematic process 300 for manufacturing a contact lens for corneal reshaping according to some embodiments of the technology of the present disclosure. Each element of process 300 is shown in a single sequence. However, one or more elements of the process may be executed in a different order or in parallel, or may be completely omitted. Further, process 300 may include other elements in addition to the elements shown.

[0036] Referring to Figure 3, process 300 may include, at 302, conducting a clinical trial of the eye. The clinical trial may include determinations such as uncorrected visual acuity, refraction, binocular vision, peripheral refraction, eye health, corneal curvature measurement, corneal diameter, corneal topography, eyelid position, aperture size, pupil measurement, etc.

[0037] Process 300 may include, at 304, selecting constants and calculating lens parameters. The lens parameters may include base curve radius, optical zone diameter, overall diameter, mid-peripheral additional refractive power, semi-chord radius direction distance from the center of the mid-peripheral additional refractive power, lens refractive power, etc.

[0038] Process 300 may include, at 306, calculating the diameter and sagittal depth for the control points on the back surface of the contact lens. The calculation may be based on average biometric data, measured corneal topography, combinations thereof, etc. The calculation will be detailed below. Following the calculation, control points for the front surface may be calculated, for example, using thickness rules or constants from one or more back surface control points to incorporate the desired center curvature radius (one or more curvature radii) of the front surface and produce the desired lens refractive power (one or more refractive powers) in the case of a multifocal optical system, etc.

[0039] Process 300 may include, at 308, generating a cutting file to manufacture a contact lens. For example, the meridians on the back surface of a contact lens as shown in FIG. 1 can be calculated using control points. The surface of the meridian can be generated using splines, geometric segments, combinations thereof, etc. A contact lens can be manufactured from a standard long - term wear rigid gas - permeable material or the like according to general quality control manufacturing standards. For example, a contact lens can be cut using a non - abrasive computer numerical control lathe. Following the cutting, a contour inspection of the back surface of the contact lens can be performed to determine whether the finished back surface matches the intended shape.

[0040] Process 300 may include, at 310, the application and evaluation of a contact lens. This may include taking an image of the contact lens on a patient's eye. The image can be analyzed to evaluate the relationship between the lens and the eye and to measure the lens centration. The evaluation may include determining the refraction error, measuring the visual acuity, etc. Process 300 may end at 312 by prescribing a contact lens and performing one or more follow - up evaluations.

[0041] FIGS. 4A and 4B are flowcharts of a schematic process 400 for determining a contact lens for corneal reshaping according to some embodiments of the technology of the present disclosure. Each element of process 400 is shown in one sequence. However, one or more elements of the process can be executed in a different order or in parallel, or completely omitted. Further, process 400 may include other elements in addition to the elements shown.

[0042] Referring to FIG. 4A, process 400 may include, at 402, placing control point CP1 at the geometric center of the lens so as to coincide with the geometric center of the pre-treatment cornea. Process 400 may include, at 404, determining a base surface radius according to the subjective refraction and corneal curvature measurement of the eye to be treated, selecting the diameter of control point CP2 as the peripheral end of the central compression zone CCZ, and setting the sagittal depth of control point CP2 at the selected sagittal depth of the selected base surface radius at the selected diameter of control point CP2.

[0043] Process 400 may include, at 406, selecting the diameter of control point CP3 so as to separate the first section of the volume control region from the second section of the volume control region at the periphery of the first section of the volume control region, and setting the sagittal depth of control point CP3 at a predetermined dioptric distance from the vertex radius of the pre-treatment cornea. In one embodiment, the sagittal depth difference of CP3 from the cornea is constant and independent of the target treatment amount. In this embodiment, all treatment lenses have the same sagittal depth difference from the lower cornea at CP3, regardless of the difference in the target treatment or the difference between the central corneal radius and the radius of the base surface of the treatment lens. The second section of the volume control region addresses eyes with different mid-peripheral height differences, equalizes the regions under each meridian, controls the position of the increase in corneal refractive power occurring under that region, and improves the centration of the lens. The equality of the regions under each meridian in the circumferential direction prevents the non-circular annular base surface of the volume control region and the circumferential height difference from having a heavy bearing on the shallow meridians of the pre-treatment cornea, and also eliminates the need for an annular or double height fitting by preventing the z-axis tilt or decentration towards the deep meridians of the cornea.

[0044] Process 400 may include, at 408, selecting the diameter or semi-chord radius distance of control point CP4 for the secondary compression region according to the desired location of the mid-peripheral additional refractive power. The sagittal depth of the secondary compression region SCZ at control point CP4 is a function of the sagittal height of the pre-treatment cornea below control point CP4 (the apex of the region). The process then proceeds to the next control point CP9 that determines the height of the peripheral relief region PRZ. In one embodiment, the height of control point CP9 from the pre-treatment cornea below is determined by the central treatment amount in diopters. For example, the height of control point CP9 from the cornea below may be equal to 6 μm per diopter of treatment. The peripheral relief region then slopes downward towards control point CP8. The altitude of control point CP8 corresponds to the measured altitude of the treatment membrane cornea at the starting semi-chord radius distance of the landing region LZ. The semi-chord radius distance of control point CP8 is determined by the semi-chord radius distance of control point CP7 and the desired minimum width between control point CP8 and control point CP7. In one embodiment, the semi-chord radius distance of control point CP7 is determined by the measured horizontal corneal diameter. For example, the lens diameter may be selected to be 90% of the measured corneal diameter, and the semi-chord radius distance of control point CP7 is determined to be 45% of the corneal diameter. The desired range of the semi-chord width from control point CP8 to control point CP7 is 0.8 mm to 1.6 mm. The edge ET at control point CP7 is integrated into the sagittal depth of the lens at the outermost periphery of the landing region LZ. The sagittal depth of control point CP7 is selected as a function of a predetermined edge elevation from the cornea below at the desired semi-chord radius distance of control point CP7 and the known eye profile.

[0045] The spline for the secondary compression zone SCZ begins with the local gradient of the last control point CP5 of the volume control zone spline and can be calculated to produce an incident angle (referred to herein as the squeeze angle (SA)) of the secondary compression zone SCZ on the pre-treatment cornea below that optimizes the movement of tissue inward into the volume control zone. Process 400 may include, at 410, selecting a squeeze angle on the peripheral side of the second section of the volume control zone and placing control point CP5 to define the squeeze angle together with control point CP4. That angle can be measured from a line perpendicular to the lens axis passing through control point CP4 or from the local gradient of the lower cornea at control point CP4. For example, the local gradient of the pre-treatment cornea at control point CP4 may be measured at 28 degrees, and the desired angle between the pre-treatment cornea and the lens posterior surface may be 5 degrees. Thus, the predetermined angle formed by the inward control point CP5 from the apex of control point CP4 and the horizontal line passing through control point CP4 may be reported as 33 degrees from the horizontal line.

[0046] Next, referring to FIG. 4B, process 400 may include, at 412, selecting the area of the volume control region according to the desired peripheral additional refractive power and determining the position of control point CP6 to produce the desired area of the volume control region. The area of the volume control region may be estimated to approximate the area of the back surface of a second or third generation corneal reshaping lens at a target treatment of 3.00 diopters when the lens is placed on the pre-treatment cornea. Second or third generation CRT lenses are generally fit at a radius approximately 1.00 diopter larger than the target treatment. Thus, the target or desired area of the semi-meridian of the volume control region may be estimated according to the area of a lens with a curvature radius 4.00D larger on an average cornea having an average optical zone diameter, average reverse curve or return zone width, average reverse curve radius or return zone depth. The target or desired total area at a single semi-chord radial distance may include only the entire volume control region from the center of the lens (control point CP1) to control point CP4, from control point CP2 to control point CP4, or only the second section of the second control region from control point CP3 to control point CP4. For example, the area from control point CP2 to control point CP4 for a third or fourth generation CRT lens having an optical zone diameter of 5.0 mm, a reverse curve width of 1.5 mm, and a base curve radius of 4.00 diopters (approximately 0.8 mm longer than the radius of the pre-treatment cornea) is 1.58×10 4 μm 2 , i.e., 0.0158 mm 2It is presumed. The desired area in the meridian line varies according to the semi-chord radius distances of the control points CP2, CP3, and CP4. The control point CP4 determines the semi-chord radius distance of the midpoint of the additional refractive power in the mid-periphery. The more the additional refractive power in the mid-periphery is desired to be closer to the center of the lens, the shorter the semi-chord radius distance of the control point CP4. The shorter the semi-chord radius distance of the control point CP4, the smaller the area of each volume control region when the control points CP2 and CP3 are kept constant. In one embodiment, the semi-chord radius distance of the control point CP2 is kept at 1.5 mm or more, and the control point CP3 is kept at 2.2 mm or more. When the semi-meridian radius distance of the control point CP4 decreases, the semi-meridian radius distance of the midpoint of the additional refractive power in the mid-periphery after treatment decreases. For a given semi-chord radius distance of the control point CP4, the higher the additional refractive power in the mid-periphery, the larger the area of the volume control region. As is clear, the modulation of the semi-meridian radius distance of the control point CP4 controls the radial position of the additional refractive power in the mid-periphery, and the area between the rear surface of the lens and the pre-treatment cornea within the volume control region modulates the additional refractive power in the mid-periphery. The semi-meridian radius distance of the control point CP6 modulates the shape of the additional refractive power in the mid-periphery.

[0047] In process 400, at 414, the overall diameter of the contact lens is determined according to the corneal diameter of the pre-treatment cornea, and the position of the control point CP7 is determined according to the overall diameter of the contact lens.

[0048] Process 400 may include, at 416, determining a control point CP8 that defines a landing region LZ to contact the pre-treatment cornea according to the corneal topography of the eye and the position of the control point CP7. The circumferential height features of the secondary compression region SCZ and the landing region LZ result in a circumferentially uniform edge elevation, promoting improved centration and comfort. The semi-meridian sagittal depth control design may use different splines in one or more semi-meridians of one or more regions of the lens outside the optical region. The amount of the sagittal depth difference may be predetermined near a number of normal ophthalmic nominal values, or may be determined empirically from the height data from the corneal topography.

[0049] Process 400 may include, at 418, selecting the diameter of control point CP9, selecting the area of the peripheral relief region between the secondary compression region and the landing region, and determining the sagittal depth of control point CP9 according to the selected area of the peripheral relief region. In an alternative embodiment, the sagittal depth of control point CP9 is determined as a function of the treatment goal for each eye. As is known to those skilled in the art, the corneal apex retreats approximately 6 μm per diopter obtained in treatment. Control point CP9 may be disposed at a distance of 6 μm per diopter from the lower cornea. For example, if a treatment of 3.00 D is targeted, when control points CP1, CP4, CP8 are disposed in contact with the corneal surface, control point CP9 may be disposed at a distance of 18 μm from the lower corneal surface. While a larger clearance is acceptable, it is understood that a smaller clearance may interfere with treatment or require the entire lens surface from control points CP4 to CP7 to compress the cornea.

[0050] Table 1 below shows an example in which the semi-meridional corneal height at the control point in the semi-meridional radial distance is given and the posterior sagittal depth is determined according to the method of an embodiment of the present invention.

[0051]

Table 1

[0052] Process 400 may include, at 420, determining the semi-chord radial distance and the sagittal depth of the meridians of the posterior surface of the contact lens according to control points CP1 to CP9. Following the determination of one or more meridians, the contact lens may be manufactured as described above, for example. The semi-meridional radial distance and the corresponding depth of the control points serve as inputs to a computer program product that completes the required x, y, and z points across the entire lens surface.

[0053] The technology of the present disclosure is applicable not only to the corneal reshaping portion of a corneal hard lens, but also to the corneal reshaping portion of a lens having a diameter larger than that of the cornea, such as a scleral contact lens, a hybrid contact lens, and a soft contact lens. In the case of an embodiment of a lens having a diameter larger than that of the cornea, the edge does not connect to the front surface at the control point CP7. Rather, the edge of the peripheral landing area connects to the next peripheral area on the rear surface that extends beyond the diameter of the cornea in at least one meridian.

[0054] FIG. 5 shows a block diagram of an exemplary computer system 500 capable of implementing an embodiment of the present disclosure. The computer system 500 includes a bus 502 for information communication or other communication means, and one or more hardware processors 504 connected to the bus 502 for information processing. The hardware processor 504 can be, for example, one or more general-purpose microprocessors.

[0055] The computer system 500 also includes a main memory 506 (such as a random access memory (RAM), a cache, and / or other dynamic storage devices, etc.) connected to the bus 502 for storing instructions and information executed by the processor 504. The main memory 506 can also be used to store temporary variables or other intermediate information during the execution of instructions executed by the processor 504. Instructions stored in a storage medium so as to be accessible by such a processor 504 customize the computer system 500 into a dedicated machine that executes the operations specified by those instructions.

[0056] The computer system 500 further includes a read-only memory (ROM) 508 and other static storage devices connected to the bus 502 for storing static information and instructions for the processor 504. A storage device 510 (such as a magnetic disk, an optical disk, a USB thumb drive (flash drive), etc.) is provided and connected to the bus 502 for storing information and instructions.

[0057] Computer system 500 can be connected via bus 502 to a display 512 (such as a liquid crystal display (LCD) or a touch screen) for displaying information to a computer user. An input device 514 (such as an alphanumeric and other keyboard) is connected to bus 502 to convey information and command selections to processor 504. Another type of user input device is a cursor control 516 (such as a mouse, trackball, cursor indicating keyboard, etc.) for conveying instruction information and command selections to processor 504 and controlling cursor movement on display 512. In some embodiments, the same instruction information and command selections as for the cursor control can be made via reception of touches on a touch screen without a cursor.

[0058] Computer system 500 may include a user interface module that executes a GUI that can be stored in a mass storage device as executable software code executed by a computing device. Such modules and other modules include, for example, components such as software components, object-oriented software components, class components, task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, variables, etc.

[0059] Generally, terms such as "component", "engine", "system", "database", "data store", etc. used in the present application may refer to logic implemented in hardware or firmware, or a set of software instructions (which may have entry points and exit points) written in a programming language (e.g., Java, C, C++ etc.). A software component can be compiled and linked to an executable program, installed in a dynamic link library, or written in an interpreter-based programming language (e.g., BASIC, Perl, Python etc.). A software component can be callable from other components or itself, and / or can be called in response to detected events or interrupts. A software component configured to be executed on a computing device can be provided on a computer-readable medium (CD, DVD, flash drive, magnetic disk, other tangible media), or provided as a digital download (originally stored in a compressed or installable format that requires pre-execution installation, decompression, and decoding). Such software code can be stored partially or completely in the memory device of the execution computing device so as to be executed by the computing device. Software instructions can be implemented in firmware with an EPROM etc. Also, it should be understood that a hardware component can be composed of a plurality of connected logic units such as gates and flip-flops, and / or can be composed of programmable units such as programmable gate arrays and processors.

[0060] Computer system 500 may execute the methods of the present disclosure by using customized wiring logic, one or more ASICs or FPGAs, firmware, and / or program logic, either to make computer system 500 a dedicated machine or in combination with programming the computer system. According to one embodiment, the methods of the present disclosure are performed by computer system 500 in response to a processor 504 executing one or more sequences of one or more instructions included in main memory 506. Such instructions may be read from other storage media, such as storage device 510, into main memory 506. When a sequence of instructions included in main memory 506 is executed, processor 504 executes the process steps of the present disclosure. In an alternative embodiment, wiring circuitry may be used instead of or in combination with software instructions.

[0061] As used herein, terms such as "non-transitory media" refer to media that store data and / or instructions that cause a device to operate in a particular manner. Such non-transitory media may include non-volatile media and / or volatile media. Examples of non-volatile media include optical disks and magnetic disks such as storage device 510. Examples of volatile media include dynamic memories such as main memory 506. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid state drives, magnetic tape, other magnetic data storage media, CD-ROM, other optical data storage media, physical media with patterns of holes, RAM, PROM, EPROM, FLASH-EPROM, NVRAM, other memory chips and cartridges, networked versions of these, and the like.

[0062] A non-transitory medium is distinguished from a transmission medium but can be used in combination with the transmission medium. The transmission medium is involved in transmitting information between non-transitory media. For example, examples of the transmission medium include coaxial cables, copper wires, optical fibers, wires including bus 502, etc. Also, the transmission medium can be in the form of acoustic waves, light waves, such as those generated during data communication of radio waves or infrared rays, etc.

[0063] Also, computer system 500 includes a network (communication) interface 518 connected to bus 502. Network interface 518 provides bi-directional data communication that connects one or more network links to one or more local networks. For example, communication interface 518 can be an ISDN (Integrated Services Digital Network) card, a cable modem, a satellite modem, or a modem that provides a communication connection to a corresponding type of telephone line. In other examples, network interface 518 is a LAN (Local Area Network) card that provides a data communication connection to a compatible LAN (or a WAN component that communicates over a WAN). A wireless link is also feasible. In such embodiments, network interface 518 transmits and receives electrical signals, electromagnetic signals, or optical signals that carry digital data streams representing various types of information.

[0064] A network link typically provides data communication to other data devices via one or more networks. For example, a network link can provide a connection to a host computer or a data device operated by an ISP (Internet Service Provider) via a local network. And in turn, the ISP provides data communication services via the worldwide packet data communication network (now commonly referred to as the "Internet"). Both the local network and the Internet use electrical, electromagnetic, or optical signals that carry digital data streams. Signals via various networks and signals on the network link via the communication interface 518 carry digital data to the computer system 500 and are exemplary forms of transmission media.

[0065] The computer system 500 can send messages and receive data including program code via the network, the network link, and the communication interface 518. In the example of the Internet, a server can send the code for an application program requested via the Internet, the ISP, the local network, and the communication interface 518.

[0066] The received code can be executed by the processor 504 as soon as it is received and / or stored in the storage device 510 or other non-volatile storage for later execution.

[0067] Each of the processes, methods, and algorithms described above can be performed, in whole or in part, automatically, in code components executed by one or more computer systems or computer processors, including computer hardware. Also, one or more computer systems or computer processors can operate to support the execution of related operations in a "cloud computing" environment or as SaaS (Software as a Service). The processes and algorithms can be performed, in part or in whole, by special-purpose circuitry. The various features and processes described above can be used independently of each other or in various combinations. Various combinations and sub-combinations fall within the scope of the present disclosure, and certain methods and process blocks may be omitted in some embodiments. The methods and processes of the present disclosure are not limited to a particular order, and related blocks and conditions can be executed in other orders that are appropriate, in parallel, or in other ways. Blocks and conditions can be added to or removed from the exemplary embodiments of the present disclosure. The execution of certain operations and processes can be distributed across multiple computer systems and computer processors deployed across multiple devices, rather than existing only within the internal components of one device.

[0068] The circuits used in this application can be implemented using any form of hardware or a combination of hardware and software. For example, one or more processors, controllers, ASICs, PLAs, PALs, CPLDs, FPGAs, logic components, software routines, or other mechanisms can be implemented to provide the circuits. In such implementation, the various circuits of the present disclosure can be implemented as individual circuits, or the functions and features of the present disclosure can be shared by part or all of one or more circuits. Although various features and elements related to functions can be individually described and claimed as individual circuits, these features and functions can be shared by one or more common circuits, and it is not essential or implied that individual circuits are required to implement such features and functions. When a circuit is implemented wholly or partially using software, such software can be implemented to operate on a computing system or processing system capable of performing the functions described with respect to a computer system 500 or the like.

[0069] The term "or" as used in this application can be interpreted inclusively or exclusively. Further, a description in the singular form does not exclude the plural form. Conditional descriptions such as "can do", "is possible", "can", "may" etc. generally convey that a particular embodiment includes a particular feature, element and / or step, while other embodiments do not include them, unless otherwise stated or understood within the context in which they are used.

[0070] The terms and expressions used in this application are, unless otherwise specified, not restrictive and are to be construed as open-ended. Expressions such as "conventional", "traditional", "ordinary", "standard", "known", etc. do not limit the described matters to those available during a given period or at a given point in time, but include that conventional, traditional, ordinary, or standard techniques are available or can be known at the present time or in the future. The presence of descriptions that broaden the scope, such as "one or more", "at least", "not limited", etc., does not mean that the scope is intended or required to be narrowed in the absence of such descriptions that broaden the scope.

Claims

1. A contact lens for reshaping a pre-treatment cornea of a patient's eye, having a front surface and a rear surface having semi-meridians, wherein the semi-meridians are a central compression region that contacts the pre-treatment cornea, a volume control region peripheral to the central compression region, the volume control region being defined by four or more geometric control points connected by one of a spline, a polynomial, a combination of a conic curve and a non-curved portion, a second geometric control point being peripheral to a first geometric control point, a third geometric control point being peripheral to the second geometric control point, a fourth geometric control point contacting the pre-treatment cornea, and the fourth geometric control point being peripheral to the third geometric control point; a volume control region, a secondary compression region peripheral to the volume control region and contacting the pre-treatment cornea, a peripheral relief region peripheral to the secondary compression region, a landing region peripheral to the peripheral relief region and contacting the pre-treatment cornea, and an edge peripheral to the landing region, defining the contact lens.

2. The contact lens according to claim 1, wherein the radius of the central compression region is spherical.

3. The contact lens according to claim 1, wherein the radius of the central compression region is aspherical.

4. The contact lens according to claim 1, wherein the diameter of the central compression region is 3.0 mm to 7.0 mm.

5. The contact lens according to claim 1, wherein the first geometric control point of the volume control region is disposed away from the pre-treatment cornea in the z-axis direction within a range of 5 μm to 80 μm.

6. The contact lens according to claim 1, wherein the second geometric control point of the volume control region is disposed away from the pre-treatment cornea in the z-axis direction so as to define a predetermined area between the rear surface and the pre-treatment cornea within the volume control region.

7. The contact lens according to claim 1, wherein the third geometric control point of the volume control region is disposed so as to define a predetermined angle between (i) a line connecting the third geometric control point and the fourth geometric control point and (ii) a horizontal line passing through the fourth geometric control point.

8. The contact lens according to claim 1, wherein the semi-chord radial distance of the fourth geometric control point is within a range of 2.6 mm to 5.2 mm.

9. The contact lens according to claim 1, wherein the secondary compression region has a width within the range of 0.2 mm to 0.8 mm.

10. The contact lens according to claim 1, wherein the secondary compression region is defined by a shape having one or more control points within the secondary compression region, and the shape is defined by one of a spline, a polynomial, and a convex conic curve.

11. The contact lens according to claim 1, wherein the peripheral relief region is defined by one or more control points disposed away from the pre-treatment cornea of the eye in the z-axis direction by 6 μm or more per diopter in order to reduce central refractive aberration.

12. The contact lens according to claim 1, wherein the peripheral relief region has a width of 0.4 mm to 1.2 mm.

13. The contact lens according to claim 1, wherein the landing region is defined by a shape having one or more control points within the landing region, and the shape is defined by one of a spline, a polynomial, a conic curve, an angled curved portion, and an angled non-curved portion.

14. The edge of the rear surface starts at the most radially peripheral side of the landing region and connects to the most peripheral side of the front surface. The contact lens according to claim 1, wherein the edge of the rear surface is defined by an ellipse, a conic curve, or a spline.

15. The contact lens according to claim 1, wherein the volume control region and the secondary compression region are defined by a single spline.

16. A method for determining the contact lens according to any one of claims 1 to 15, manufactured for a patient's eye, comprising: selecting, according to the corneal topography of the patient's eye, the base surface radius of the central compression region of the contact lens, the semi-meridian radial distance of the periphery of the central compression region of the contact lens, the area of the volume control region adjacent to the central compression region, and the semi-chord radial distance of the secondary compression region adjacent to the periphery of the volume control region and contacting the pre-treatment cornea of the eye; determining the positions of a plurality of control points that at least define the width of the central compression region, the area of the volume control region, the semi-meridian radial distance of the secondary compression region, and the inward angle of the apex of the secondary compression region. A method comprising determining a semi-meridian of a rear surface of the contact lens according to the plurality of control points.

17. The method according to claim 16, further comprising disposing a first control point among the plurality of control points at a geometric center of the contact lens corresponding to a geometric center of the pre-treatment cornea.

18. Determining the base surface radius according to the subjective refraction of the eye and the corneal curvature measurement; Selecting a semi-chord radius direction distance of a second control point among the plurality of control points as a peripheral end of the central compression region; Setting a sagittal depth of a second control point among the plurality of control points at a sagittal depth of the base surface radius in the semi-chord radius direction distance of the second control point among the selected plurality of control points when the first control point among the plurality of control points is in contact with the lower pre-treatment cornea. The method according to claim 17, further comprising:

19. Selecting a semi-chord radius direction distance of a third control point among the plurality of control points so as to separate a first section of the volume control region and a second section of the volume control region that is peripheral to the first section of the volume control region; Setting a sagittal depth of a third control point among the plurality of control points at a distance equal to a distance of a lens having a predetermined diopter treatment target radius when disposed on an average pre-treatment cornea. The method according to claim 18, further comprising:

20. The method according to claim 19, further comprising selecting a semi-chord radius direction distance of a fourth control point among the plurality of control points to be equal to a semi-chord radius direction distance of a vertex of the secondary compression region according to a desired mid-peripheral addition position.

21. Selecting a squeeze angle on a peripheral side of a second section of the volume control region; Disposing a fifth control point among the plurality of control points so as to define the squeeze angle together with the fourth control point among the plurality of control points. The method according to claim 20, further comprising:

22. The method according to claim 21, further comprising determining a position of a sixth control point among the plurality of control points according to an area of the volume control region selected according to a desired mid-peripheral additional refractive power.

23. Determining an overall diameter of the contact lens according to a corneal diameter of the pre-treatment cornea; Determining a position of a seventh control point among the plurality of control points according to the overall diameter of the contact lens. The method according to claim 22, further comprising:

24. The method according to claim 23, further comprising determining an eighth control point among the plurality of control points that define the inner side of the landing area that contacts the pre-treatment cornea, according to the corneal topography of the eye and a desired radial distance from a seventh control point among the plurality of control points according to a desired radial width of the landing area. **Claim 25** selecting a diameter of a ninth control point among the plurality of control points; selecting an area of a peripheral relief area between the secondary compression area and the landing area; the method according to claim 24, further comprising determining a sagittal depth of the ninth control point among the plurality of control points according to the selected area of the peripheral relief area or according to a target treatment in diopter units. **Claim 26** The contact lens according to claim 1, wherein a vertex of the secondary compression area has a z-axis direction position that contacts the cornea.

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