SCLERAL CONTACT LENS

Abstract

In general, one aspect disclosed features a scleral contact lens for an eye of a patient, the scleral contact lens comprising: an anterior surface; and a posterior surface, the posterior surface comprising: a central optic zone defined by a base curve according to an apical radius of the cornea of the eye; a peripheral corneal zone peripheral to the central optic zone, a clearance control zone peripheral to the optic zone, and a scleral landing zone peripheral to the clearance control zone, the scleral landing zone having a single surface shape.

Claims

1. A scleral contact lens for an eye of a patient, the scleral contact lens comprising: an anterior surface; and a posterior surface, the posterior surface comprising: a central optic zone defined by a base curve according to an apical radius of the cornea of the eye; a peripheral corneal zone peripheral to the central optic zone, a clearance control zone peripheral to the optic zone, and a scleral landing zone peripheral to the clearance control zone, the scleral landing zone having a single surface shape; wherein the scleral contact lens is configured to not contact the cornea of the eye, the scleral landing zone is configured to contact the eye, and the central optic zone, the peripheral corneal zone, and the clearance control zone are configured to not contact the eye.

2. The scleral contact lens of claim 1, wherein: the base curve of the optic zone is defined by at least one of a spherical radius, an aspherical radius with a conic constant, a torus, a multifocal shape, or a rotationally asymmetric shape.

3. The scleral contact lens of claim 1, wherein: the peripheral corneal zone, the clearance control zone, and the scleral landing zone are defined by a spline having a plurality of knots and/or control points.

4. The scleral contact lens of claim 3, wherein: the peripheral corneal zone is defined by a peripheral most knot and a medial most knot; wherein the peripheral most knot is shallower in sagittal depth than the medial most knot relative to a continuation of the base curve to the semi-chord diameter of the peripheral most knot when the base curve radius is shorter than a predetermined length; and wherein the peripheral most knot is deeper in sagittal depth than the medial most knot relative to the continuation of the base curve to the semi-chord diameter of the peripheral most knot when the base curve radius is longer than the predetermined length.

5. The scleral contact lens of claim 4, wherein: the predetermined length is 8.0 mm.

6. The scleral contact lens of claim 3, wherein: the clearance control zone is defined by at least one knot within the clearance control zone; wherein a location of the at least one knot is selected to control an area between the posterior surface of the clearance control zone and the underlying surface of the eye in at least one semi-meridian.

7. The scleral contact lens of claim 1, wherein: a convex to the eye radius of the scleral landing zone is less than 10 mm.

8. The scleral contact lens of claim 1, wherein: the scleral landing zone is defined by at least one knot of a spline that is equivalent in depth to a convex to the eye radius of less than 10 mm.

9. The scleral contact lens of claim 1, wherein: the scleral landing zone is defined by at least one knot of a spline that is equivalent in depth to a convex to the eye radius of less than 5 mm.

10. A method for defining a shape of a posterior surface of a scleral contact lens for an eye of a patient, the method comprising: defining a base curve for a central optic zone of the scleral contact lens according to an apical radius of the cornea of the eye; defining a peripheral corneal zone peripheral to the central optic zone; defining a clearance control zone peripheral to the optic zone; and defining a scleral landing zone peripheral to the clearance control zone according to a single surface shape; wherein the scleral contact lens is configured to not contact the cornea of the eye, the scleral landing zone is configured to contact the eye, and the central optic zone, the peripheral corneal zone, and the clearance control zone are configured to not contact the eye.

11. The method of claim 10, further comprising: defining the base curve of the optic zone according to at least one of a spherical radius, an aspherical radius with a conic constant, a torus, a multifocal shape, or a rotationally asymmetric shape.

12. The method of claim 10, further comprising: defining the peripheral corneal zone, the clearance control zone, and the scleral landing zone according to a spline having a plurality of knots and/or control points.

13. The method of claim 12, wherein: defining the peripheral corneal zone according to a peripheral most knot and a medial most knot; wherein the peripheral most knot is shallower in sagittal depth than the medial most knot relative to a continuation of the base curve to the semi-chord diameter of the peripheral most knot when the base curve radius is shorter than a predetermined length; and wherein the peripheral most knot is deeper in sagittal depth than the medial most knot relative to the continuation of the base curve to the semi-chord diameter of the peripheral most knot when the base curve radius is longer than the predetermined length.

14. The method of claim 13, wherein: the predetermined length is 8.0 mm.

15. The method of claim 12, further comprising: defining the clearance control zone according to at least one knot within the clearance control zone; and selecting a location of the at least one knot to control an area between the posterior surface of the clearance control zone and the underlying surface of the eye in at least one semi-meridian.

16. The method of claim 10, wherein: a convex to the eye radius of the scleral landing zone is less than 10 mm.

17. The method of claim 10, further comprising: defining the scleral landing zone according to at least one knot of a spline that is equivalent in depth to a convex to the eye radius of less than 10 mm.

18. The method of claim 10, further comprising: defining the scleral landing zone according to at least one knot of a spline that is equivalent in depth to a convex to the eye radius of less than 5 mm.

19. The scleral contact lens of claim 1, wherein: the scleral landing zone having a single surface shape that is convex to the eye.

20. The method of claim 10, wherein: the scleral landing zone having a single surface shape that is convex to the eye.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present disclosure, in accordance with one or more various embodiments, is described in detail with reference to the following figures. The figures are provided for purposes of illustration only and merely depict typical or example embodiments.

[0029] FIG. 1 is a front view of a scleral contact lens of the present invention with knots and zones.

[0030] FIG. 2 illustrates a cross section view of the posterior surface of a scleral contact lens of the present invention showing knots and zones and an underlying ocular surface.

[0031] FIG. 3A illustrates a short radius base curve in an Optic Zone with a shallow Peripheral Corneal Zone.

[0032] FIG. 3B illustrates a long radius base curve in an Optic Zone with a deep Peripheral Corneal Zone.

[0033] FIG. 4A illustrates a shallow Clearance Control Zone with a central knot shifted to increase the area between the meridian of the lens and the underlying eye within the zone.

[0034] FIG. 4B illustrates a deep Clearance Control Zone with a central knot shifted to decrease the area between the meridian of the lens and the underlying eye within the zone.

[0035] FIGS. 5A, 5B and 5C illustrate three lens surfaces to eye relationships; excess apical clearance; proper apical clearance; and inadequate apical clearance with apical touch respectively.

[0036] FIG. 6 is the model for determining the radius of an arc when the width and depth of the arc are known for use in calculating the universal Scleral Landing Zone radius.

[0037] FIG. 7 illustrates the universal Scleral Landing Zone on an underlying sclera post conjunctival compression.

[0038] FIG. 8 illustrates a non-orthogonal sector of a scleral contact lens with asymmetric elevation.

[0039] FIG. 9 is a flowchart illustrating an overview process for producing a scleral contact lens according to some embodiments of the disclosed technologies.

[0040] FIG. 10 is a flowchart illustrating an overview process for defining a shape of a posterior surface of a scleral contact lens for an eye of a patient according to some embodiments of the disclosed technologies.

[0041] FIG. 11 depicts a block diagram of an example computer system in which embodiments described herein may be implemented.

[0042] The figures are not exhaustive and do not limit the present disclosure to the precise form disclosed.

DETAILED DESCRIPTION

[0043] Some embodiments of the disclosed technology provide a lens having four zones: an Optic Zone, a Peripheral Corneal Zone, a Clearance Control Zone and a Scleral Landing Zone. Various embodiments ensure full corneal and limbal clearance by the empirical selection of a base curve radius in the Optic Zone that approximates the radius of the underlying cornea; providing a Peripheral Corneal Zone using corneal topography or biometric mean height data; providing a Clearance Control Zone that is used to regulate the height of the lens above the cornea while normalizing the volume between the zone and the underlying eye; and, providing a novel universal Scleral Landing Zone that spreads lens mass over the underlying sclera without the need to regulate its geometry by modulating radius or angle for the purpose of controlling edge lift or limbal clearance. In this manner, the lens may always have corneal and limbal clearance while having mechanical-trauma-free scleral contact.

[0044] Embodiments of the disclosed technology may provide a scleral contact lenses for wearing on the anterior ocular surface, and methods for defining the scleral contact lenses using single parameter control geometry. These techniques may employ spline mathematics or other geometry to determine the surface contour of a contact lens at predetermined control points or knots on the posterior surface of the lens defined by their specified semi-chord radial distances from the center of the lens to the edge of the lens and their sagittal depth from a reference plane. Some embodiments employ the corneal topography of each eye to apply algorithms for determining the semi-meridian sagittal depth at one or more control points to allow for empirical ordering and observational fitting of an eye for the determination of the single parameter of Clearance Control Zone depth.

[0045] In some implementations, the base curve radius of the Optic Zone is selected using the apical radius of the cornea measured by standard keratometry or using the reference sphere or best fit sphere measured by corneal topography. The base curve geometry may be spherical, toric, aspherical by use of a conic constant, multifocal, or rotationally asymmetric for the purpose of correcting higher order aberrations or irregularity of the anterior corneal surface.

[0046] Furthermore, the Peripheral Corneal Zone may be empirically determined using elevation data from corneal topography or may be empirically determined using the radius of the base curve or effective radius of the base curve. The algorithm may employ an inverse relationship where the shorter the base curve radius, the shallower the knot at the peripheral aspect of the Peripheral Corneal Zone is set; and conversely, the longer the base curve radius the deeper the knot at the peripheral aspect of the Peripheral Corneal Zone is set.

[0047] Clinical observations were gathered for a large population of eyes with irregular corneas for which scleral contact lenses were required. The observations revealed an unexpected trend where eyes with short apical radii did not maintain the short radius in the corneal periphery and eyes with irregular corneas with long apical radii manifested a zone with a short radius outside the central zone having a long radius. These observations support the empirical method for determining the elevation of the peripheral knot in the Peripheral Corneal Zone in the absence of corneal topography elevation data.

[0048] The Clearance Control Zone depth of the disclosed scleral contact lens may be the only parameter that must be selected by observation. The desired pre-compression apical clearance for scleral lenses is commonly reported as 250 to 350 microns. The range of conjunctival compression is understood to be 80 to 120 microns or about 100 microns. A resultant post compression apical clearance of about 150 to 250 microns is considered by those skilled in the art as optimum. Embodiments of the disclosed technology address this understanding and allow for modification if the teaching of optimum post conjunctival compression objectives changes over time.

[0049] Some embodiments of the present invention may provide enhancement for maintaining limbal clearance post compression and address problems of bubble formation in the Clearance Control Zone that straddles the corneal-scleral junction or limbus of the eye. A knot within the Clearance Control Zone may be vertically or laterally positioned as a function of the depth of the zone.

[0050] In some embodiments at least one knot within the Clearance Control Zone may be moved vertically or laterally to control the area within at least one semi-meridian of the posterior surface and the underlying eye within the zone. The knot may be moved inward toward the center of the lens or downward toward the corneal surface when the Clearance Control Zone depth is greater and the knot may be moved outward away from the center of the lens or upward away from the corneal surface when the Clearance Control Zone depth is shallower.

[0051] In some embodiments, the Clearance Control Zone depth may vary in two or more semi-meridians to accommodate the circumferential elevation differences of an eye to be fit with the disclosed scleral contact lens. The difference in depths may be in semi-meridians that are 90 degrees apart, 180 degrees apart or any number of degrees apart. Ocular contour data suggest that the deepest area of the sclera and the shallowest area, as a rule, are not 90 degrees apart. Ocular contour data also suggests that the mean difference in elevation of the sclera at a chord of 14 mm is greater than 200 microns.

[0052] In some embodiments, the Clearance Control Zone is designed with a circumferential depth difference between 100 and 400 microns. In some embodiments the Clearance Control Zone is designed with circumferential depth differences between 150 and 300 microns. In some embodiments the circumferential depth differences are not orthogonal wherein the deepest and shallowest areas are 90 degrees apart; rather, the circumferential depth differences represent a sector where at least one sector of less than 90 degrees varies in depth from the Clearance Control Zone depth of the remainder of the Zone circumferentially and reconciles to the depth of the remainder of the lens in a transverse manner.

[0053] The disclosed universal Scleral Landing Zone design may be designed to solve the needs for one or more of: a) clearance at the medial aspect of the zone; b) edge lift at the peripheral aspect of the zone; c) allowance for compression into the conjunctiva of 80 to 120 microns; or d) a width between 0.8 and 2.5 mm. The optimum radius may be calculated using the formula for determining the radius of an arc when the width and the height of the arc are known: R=h/2+W.sup.2/8h; R denoting the radius for the arc, h denoting the height of the arc and W, denoting the width of the arc. For example, if the width of the universal Scleral Landing Zone equals 1.8 mm and the desired height of the arc allowing for conjunctival compression and edge lift above the conjunctiva equals 0.130 mm (130 microns), solving for R.sub.mm=(0.130/2)+(1.8).sup.2/ (8×0.130)=3.18 mm. Unexpectedly, this value is far shorter than the convex to the eye radius used by any commercial lens manufacturer or reported in published literature.

[0054] In some embodiments the overall diameter of the lens may be selected based on the horizontal visible iris diameter or corneal diameter. The diameter may range from 13.0 mm to 22.0 mm. A fixed diameter between 16.0 and 18.0 mm may be selected. For example, an overall diameter of 16.6 mm may allow for fitting a large number of the distribution of human eyes.

[0055] In some embodiments of the present invention the scleral contact lens may have a base curve radius from 5.0 mm to 12 mm, an Optic Zone diameter in the range of 5.0 to 10.0 mm, a Peripheral Corneal Zone width in the range of 0.2 to 2.0 mm; a Clearance Control Zone width in the range of 0.5 to 2.0 mm, and universal Scleral Landing Zone width in the range of 1.0 to 2.5 mm.

[0056] FIG. 1 illustrates a plan view of a scleral contact lens 100 according to some embodiments of the disclosed technologies. Referring to FIG. 1, the scleral contact lens 100 may have four zones and 6 control points or knots on the posterior surface. The most central zone is the Optic Zone OZ that has a surface shape to achieve optical correction of the eye when coupled with the anterior surface shape. The posterior surface shape of the Optic Zone may be spherical, aspherical with a conic constant, toric, multifocal with two or more radii, or rotationally asymmetrical to correct for corneal irregularity or higher order aberrations. The Optic Zone OZ may have a diameter that may be fixed or that may vary with its radius. The Optic Zone circumference is bounded by a control point CP1 or knot 1 (k1) in each semi-meridian. The zone peripheral to the Optic Zone OZ may be the Peripheral Corneal Zone PCZ.

[0057] The Peripheral Corneal Zone PCZ may be bounded at its peripheral aspect by a control point CP2 or knot 2 (k2). The elevation of k2 is modulated as a function of the base curve radius where the shorter the base curve radius the shallower k2 is placed and the longer the base curve radius the deeper k2 is placed. For example, the sagittal depth of k2 for a base curve radius of 8.00 mm may not deviate from the extension of the same surface to the chord diameter of k2 by way of the same radius of curvature, 8.00 mm, continuing to the chord diameter of k2; while, as base curve radii decrease from 8.00 mm k2 may rise above the extension of the respective radius to the chord diameter of k2; and as base curve radii increase from 8.00 mm, k2 may fall below the extension of the respective radius to the chord diameter of k2.

[0058] The zone peripheral to the Peripheral Corneal Zone PCZ is the Clearance Control Zone CCZ. The Clearance Control Zone 103 is bounded at its peripheral aspect by a control point CP4 or knot 4 (k4) and may have at least one control point CP3 or knot 3 (k3) within the zone. The z-axis position of k4 relative to the z-axis position of k2 determines the Clearance Control Zone depth. The Clearance Control Zone depth may be the single parameter determined by observation of a predicate lens in the absence of ocular contour data for an eye. CP3 (k3) may be modulated in a relatively inward or downward direction or outward or upward direction as a function of the Clearance Control Zone depth; whereby, the greater the depth CP3 (k3) is moved inward toward the center of the lens or downward toward the underlying eye and the shallower the depth CP3 (k3) is moved outward toward the edge of the lens or upward away from the underlying eye.

[0059] The zone peripheral to the Clearance Control Zone CCZ is the Scleral Landing Zone SLZ. The Scleral Landing Zone is bounded at its peripheral aspect by a control point CP6 or knot 6 (k6) where the edge terminus is formed and has at least one control point CP5 or knot 5 (k5) within the zone at its point of maximum depth. The Scleral Landing Zone SLZ may have a convex to the eye spherical geometry or may be formed as part of a cubic spline, basis spline or Bezier function, or the like generated by the positions of the series of knots. The positions of the knots k4, k5 and k6 may first be estimated by the calculation of the radius of an arc of known width and desired height according to the present invention.

[0060] It should be appreciated that the embodiments of FIG. 1 may be used, wholly or partially, in conjunction with other embodiments described herein.

[0061] FIG. 2 illustrates a cross section view of the posterior surface of a scleral lens 200 according to some embodiments of the disclosed technologies. Referring to FIG. 2, knots k1-k6 are shown, as well as zones OZ, PCZ, CCZ, and SLZ.

[0062] FIG. 3A illustrates a short base curve radius 301 in an Optic Zone 300 with a shallow Peripheral Corneal Zone 303. The Peripheral Corneal Zone 303 is bounded by CP1 or knot 1 (k1) at its medial or central aspect and CP 2 or knot 2 (k2) at its peripheral aspect. FIG. 3B illustrates a long base curve radius 302 in an Optic Zone 300 with a deep Peripheral Corneal Zone 304. The Peripheral Corneal Zone 304 is bounded by CP1 or knot 1 (k1) at its medial or central aspect and CP 2 or knot 2 (k2) at its peripheral aspect. The elevation of CP2 (k2) is modulated as a function of the base curve radius 300 where the shorter the base curve radius the shallower k2 is placed and the longer the base curve radius 300 the deeper k2 is placed. It should be appreciated that the embodiments of FIG. 3 may be used, wholly or partially, in conjunction with other embodiments described herein. For example, the sagittal depth of k2 for a base curve radius of 8.00 mm may not deviate from the extension of the same surface to the chord diameter of k2 by way of the same radius of curvature, 8.00 mm continuing to the chord diameter of k2; while, as base curve radii decrease from 8.00 mm k2 may rise above the extension of the respective radius to the chord diameter of k2; and as base curve radii increase from 8.00 mm, k2 306 may fall below the extension of the respective radius to the chord diameter of k2.

[0063] FIG. 4A illustrates a shallow Clearance Control Zone with a CP3 (k3) shifted, outward, upward, or both, to increase the area between the meridian of the lens and the underlying eye 400 within the zone. FIG. 4B illustrates a deep Clearance Control Zone with a CP3 (k3) shifted, inward, downward, or both, to decrease the area between the meridian of the lens 402 and the underlying eye 400 within the zone. CP3 (k3) is modulated in a relatively inward/downward or outward/upward direction as a function of the Clearance Control Zone depth; whereby, the greater the depth CP3 (k3) is moved inward toward the center of the lens or downward toward the underlying eye and the shallower the depth CP3 (k3) is moved outward toward the edge of the lens or upward away from the underlying eye. It should be appreciated that the embodiments of FIG. 3 may be used, wholly or partially, in conjunction with other embodiments described herein.

[0064] FIG. 5A illustrates a deep posterior lens surface 501a to eye 500 relationship where the clearance 502a between the posterior lens surface and the apex of the cornea is too great. For example, this illustration represents a clearance 502a of about 500 microns between the lens surface 501a and the apex of the cornea 500. This observation indicates the Clearance Control Zone depth should be reduced by at least 250 microns. FIG. 5B illustrates a proper lens surface 501b to the apex of the cornea 500 relationship wherein the clearance 502b is in the desired range of 150 to 250 microns. FIG. 5C illustrates a shallow posterior lens surface 501c to eye 500 relationship wherein the clearance 502c between the posterior lens surface 501c and the apex of the cornea 500 is inadequate. This observation indicates the Clearance Control Zone depth should be increased by at least 200 microns.

[0065] FIG. 6 illustrates the model for determining the radius of an arc when the width and depth of the arc are known. This model may be used in calculating the universal Scleral Landing Zone radius. The optimum radius may be calculated using the formula for determining the radius of an arc when the width and the height of the arc are known. The formula is R=h/2+W.sup.2/8h, where R denotes the radius for the arc, h denotes the height of the arc, and W denotes the width of the arc, as shown in FIG. 6.

[0066] FIG. 7 illustrates a cross section of the universal Scleral Landing Zone SLZ with CP4 (k4), CP5 (k5), and CP6 (k6) on an underlying sclera 700 post conjunctival compression. The CP4 knot 4 (k4) medial aspect and the CP6 knot 6 (k6) peripheral aspect of the Scleral Landing Zone SLZ are anterior to the ocular surface 700 while CP5 knot 5 (k5) midpoint of the Scleral Landing Zone SLZ is at the point of greatest compression into the ocular surface under the Scleral Landing Zone SLZ. The pre-compression ocular surface 705 and post compression ocular surface, which coincides with the SLZ in FIG. 7, reflects the amount of the expected conjunctival compression with a scleral contact lens. The illustration represents the manner that the short convex to the eye radius of curvature provides edge lift and provides the desired medial aspect clearance after the scleral contact lens compresses the conjunctiva under the scleral landing zone SLZ.

[0067] FIG. 8 illustrates a plan view of a non-orthogonal sector of a scleral contact lens 800 with asymmetric elevation. The large sector 801 of the lens 800 represents the angular region of the lens having a uniform Clearance Control Zone depth and resultant total depth at the midpoint of the universal Scleral Landing Zone. The smaller sector 802 of the lens 800 represents a region having a shallower depth than sector 801. The lens surface changes in elevation in a transverse manner from the most shallow depth to the greater depth to allow the surface to be seamless and smooth and without step changes in elevation. There may be more than one angular sector of greater or lesser Clearance Control Zone depth to accommodate ocular contour differences. The finished lens with a sector of unequal Clearance Control Zone depth may be planar and not round as illustrated by the path of the perimeter 803 of the lens; or the finished lens with a sector of unequal Clearance Control Zone depth may be round but not planar as illustrated by the path of the perimeter 804. In this manner an edge reconciliation zone is not required to make the lens edge planar and round.

[0068] The posterior surface parameters of the disclosed single parameter control universal landing zone scleral contact lens apparatus may be calculated manually from input data or more efficiently with a computer program product. The steps include: a) use of a the horizontal visible iris diameter or corneal diameter to determine the overall diameter of the scleral contact lens; b) scaling the width of the zones for the overall diameter; c) determining the base curve radius from the measurement of the apical radius of the cornea from keratometry or the reference sphere from corneal topography; d) determining the elevation of k2 from the selected base curve radius; e) determining the Corneal Clearance Zone depth from the single observation of apical clearance from a predicate lens applied to an eye or from a measured scleral sagittal depth at a chord outside the cornea; f) determining the lateral or sagittal movement of k5 from the Corneal Clearance Zone depth value to optimize the volume between the posterior surface of the lens within the Corneal Clearance Zone and the underlying eye.

[0069] The parameters of the anterior surface of the lens may be derived by usual and customary means and may be calculated manually from input data or more efficiently with a computer program product by: a) adding an anterior optic zone radius or radii that creates the desired lens power in concert with the posterior surface of the optic zone and the post lens tear lens; b) selecting an anterior optic zone diameter as a function of lens power to control the center thickness and junction thickness; c) employing thickness rules for the remainder of the annular zone outside the anterior optic zone to create a thickness profile that manages lens flexure, lens breakage and the lid to lens relationship to optimize comfort.

[0070] FIG. 9 is a flowchart illustrating an overview process 900 for producing a scleral contact lens according to some embodiments of the disclosed technologies. The elements of the process 900 are presented in one arrangement. However, it should be understood that one or more elements of the process may be performed in a different order, in parallel, omitted entirely, and the like. Furthermore, the process 900 may include other elements in addition to those presented.

[0071] Referring to FIG. 9, the process 900 may include conducting clinical testing of the eye, at 902. The clinical testing may include determination of unaided visual acuity, refraction, binocular vision, eye health, keratometry, corneal diameter, corneal topography, lid position and aperture size, pupillometry, observation of the apical corneal clearance of a predicate scleral contact lens of known parameters, and the like.

[0072] The process 900 may include selecting constants and calculating lens parameters, at 904. These may include base curve radius, optic zone diameter, overall diameter, Peripheral Corneal Zone width, sagittal depth of k2, Clearance Control Zone width, Corneal Clearance Zone depth, lateral and sagittal position of k3, Scleral Landing Zone width, sagittal depth of k5, lens power, and the like.

[0073] The process 900 may include calculating diameters and sagittal depths for control points and/or knots of the posterior surface of the contact lens, at 906. These calculations may be based on biometric mean data, measured corneal topography, or the like, or combinations thereof. These calculations are described in detail below. Following these calculations, control points and/or knots for the anterior surface may be calculated, for example using thickness rules or constants from one or more of the posterior surface control points to one or more of the anterior surface control points and incorporating the required anterior central radius or radii of curvature to produce the desired lens power or powers in the event of multifocal optics, or the like.

[0074] The process 900 may include creating a cutting file and fabricating a contact lens, at 908. For example, a semi-meridian for the posterior surface of the contact lens may be calculated using the control points or knots, for example as shown in FIG. 2. The semi-meridian surface may be generated using splines, geometric segments, or the like, or combinations thereof. The contact lens may be fabricated with usual and customary good manufacturing practices from standard rigid gas permeable material, or the like. For example, a polish-free computer numerically controlled lathe may be employed to cut the contact lens. Cutting may be followed by a contour inspection of the posterior surface of the contact lens to determine the finished posterior surface matches the intended shape.

[0075] The process 900 may include applying and evaluating the contact lenses, at 910. This may include capturing an image of the contact lens on the eye of the patient. The image may be analyzed to assess the lens-eye relationship and to measure lens centration. The evaluation may include steps to determine the over-refraction, to measure visual acuity, and the like. The process 900 may conclude with dispensing the contact lens, and conducting one or more follow-up evaluations, at 912.

[0076] FIG. 10 is a flowchart illustrating an overview process 1000 for defining a shape of a posterior surface of a scleral contact lens for an eye of a patient according to some embodiments of the disclosed technologies. The elements of the process 1000 are presented in one arrangement. However, it should be understood that one or more elements of the process may be performed in a different order, in parallel, omitted entirely, and the like. Furthermore, the process 1000 may include other elements in addition to those presented.

[0077] Referring to FIG. 10, the process 1000 may include defining a base curve for a central optic zone of the scleral contact lens according to an apical radius of the cornea of the eye, at 1002. The base curve of the optic zone may be defined according to at least one of a spherical radius, an aspherical radius with a conic constant, a torus, a multifocal shape, or a rotationally asymmetric shape.

[0078] The process 1000 may include defining a peripheral corneal zone peripheral to the central optic zone, at 1004. The process 1000 may include defining a clearance control zone peripheral to the optic zone, at 1006. The process 1000 may include defining a scleral landing zone peripheral to the clearance control zone according to a single surface shape, at 1008. The peripheral corneal zone, the clearance control zone, and the scleral landing zone may be defined according to according to a spline having a plurality of knots and/or control points.

[0079] The peripheral corneal zone may be defined according to a peripheral most knot and a medial most knot. The peripheral most knot may be shallower in sagittal depth than the medial most knot relative to a continuation of the base curve to the semi-chord diameter of the peripheral most knot when the base curve radius is shorter than a predetermined length. Alternatively, the peripheral most knot may be deeper in sagittal depth than the medial most knot relative to the continuation of the base curve to the semi-chord diameter of the peripheral most knot when the base curve radius is longer than the predetermined length. In some embodiments, the predetermined length is 8.0 mm.

[0080] The clearance control zone may be defined according to at least one knot within the clearance control zone. A location of the at least one knot may be selected to control an area between the posterior surface of the clearance control zone and the underlying surface of the eye in at least one semi-meridian.

[0081] In some embodiments, a convex to the eye radius of the scleral landing zone may be less than 10 mm. In some embodiments, the scleral landing zone may be defined according to at least one knot of a spline that is equivalent in depth to a convex to the eye radius of less than 10 mm. In some embodiments, the scleral landing zone may be defined according to at least one knot of a spline that is equivalent in depth to a convex to the eye radius of less than 5 mm.

[0082] Table 1 presents the clinical measures that may be used to determine the parameters of the disclosed scleral lens in conjunction with antecedent parameters that may be used to determine additional parameters. The single posterior surface parameter that may be determined by observation of a predicate lens is the Clearance Control Zone depth. All other parameters may be selected or calculated empirically from clinical measurements and predicate parameter selection rules.

TABLE-US-00001 TABLE 1 Example of Empirical System for Calculating Scleral Lens Parameters from Clinical Markers and Predicate Lens Parameters Antecedent Clinical Predicate Lens Nominal Measurement Parameter Lens Parameter Value Algorithm Rule for each of 3 overall diameters Horizontal Visible Iris Overall Diameter (OAD) 16.6 mm less than 11.5 = 15.5; Diameter or Corneal k6 chord location 11.5 to 12.1 = 16.6; Diameter above 12.1 = 17.7 Overall diameter Chord diameter of k2 10.4 mm 15.5 mm OAD = 10.1 mm (OAD) 16.6 mm OAD = 10.4 mm 17.7 mm OAD = 10.7 mm Overall diameter Chord diameter of k4 13.2 mm 15.5 mm OAD = 12.7 mm (OAD) 16.6 mm OAD = 13.2 mm 17.7 mm OAD = 13.7 mm Overall diameter Chord diameter of k5 14.9 mm 15.5 mm OAD = 14.1 mm (OAD) 16.6 mm OAD = 14.9 mm 17.7 mm OAD = 15.7 mm Overall diameter Chord diameter of k6 16.4 mm 0.2 mm less than OAD (OAD) Overall diameter Effective radius of Scleral 3.18 mm 15.5 mm OAD = 1.95 mm (OAD) Landing Zone 16.6 mm OAD = 3.18 mm 17.7 mm OAD = 3.91 mm Overall diameter Sagittal depth of k6 from lens 4.405 mm Sagittal depth of the mean eye at chord of k6 (OAD) geometric center plus 150 microns. Apical Corneal Radius Base curve radius (BCR) 8.0 mm 0.2 mm longer than apical radius; mean apical or best fit sphere or radius = 7.80 mm Reference sphere Base curve radius Optic Zone diameter = Chord 8.0 mm 0.2 longer than apical radius (BCR) diameter of k1 Base curve radius Sagittal depth of k2 of PCZ from 1.920 mm Adjusted by inverse of 25 microns per 0.1 mm (BCR) lens geometric center deviation of BCR from 8.0 mm from sag of BCR at chord diameter of k2 Clearance Control Clearance Control Zone Depth 1.300 mm Increases by microns of observed inadequate Zone Depth (k4 − k2) clearance and decreases by microns of excess observation clearance in 25 micron steps Clearance Control Sagittal depth of k4 from lens 3.220 mm 250 microns deeper than mean eye at k4 chord Zone Depth geometric center Clearance Control Clearance Control Zone volume; 5.90 mm/ Calculated to produce no radial clearance Zone Depth Radial and sagittal position of 2.237 mm from mean eye greater than 150 microns k3 throughout the zone Sagittal Depth of k4; Sagittal depth of k5 3.914 mm Depth of the arc with the effective radius effective radius of calculated using the assumed compression and K5 the width of the Scleral Landing Zone Manifest refraction or BCR Lens power and anterior optic 8.60 mm Usual and customary radius calculation using lens over-refraction zone radius of curvature lens index of refraction and vertex distance adjusted Lens power Anterior optic zone diameter 8.4 mm Decreases as plus and minus lens power increases to maintain constant harmonic thickness of optic zone Overall diameter Center thickness and thickness 0.32 mm Harmonic thickness until taper outside of (OAD) profile cornea; thickness increases and decreases in proportion to OAD

[0083] In one embodiment, the horizontal visible iris diameter or corneal diameter may be the first clinical measure used to determine the overall diameter of the scleral contact lens. The overall diameter may be calculated using a mathematical method or determined by a look up table as presented in Table 1. The overall diameter may be used as a predicate parameter to select the sagittal depth of a predicate lens for observation; to select the chord diameter of knot 2 k2; to select the chord diameter of knot 4 k4; to select the chord diameter of knot 5 k5; to select the knot diameter of k6; and to calculate the effective radius of the universal scleral landing zone; and the knot locations on the anterior surface of the lens to create the thickness profile of the lens.

[0084] The apical radius of the cornea or the best fit sphere or reference sphere from automated corneal topography may be the second clinical measure and used to derive the base curve radius of the posterior optic zone of the scleral lens. In one embodiment, the base curve radius may be calculated to be 0.2 mm longer than the apical radius or best fit or reference sphere. The derived base curve radius may in turn be used to calculate the posterior optic zone diameter and the sagittal depth of knot 2 from the plane of the geometric center of the posterior surface of the scleral contact lens.

[0085] The observation of the apical clearance with at least one predicate contact lens of known parameters may be the third clinical measure used to derive parameters of the scleral lens. The clearance observation may be used to increase or decrease a selected sagittal depth of the Clearance Control Zone depth parameter of a lens to be manufactured for the respective eye. The resultant Clearance Control Zone depth may in turn be used to calculate a horizontal and/or sagittal depth position of knot 3 k3 in the Clearance Control Zone for the purpose of regulating the area between the posterior surface of the lens and the underlying eye in at least one semi-meridian of the Clearance Control Zone or the volume under the Clearance Control Zone of the lens and the underlying eye circumferentially by calculations of the position of k3 in multiple semi-meridians.

[0086] A manifest refraction may be used to empirically calculate lens power by integrating the manifest refraction with the selected base curve radius and measured apical corneal radius. Alternatively, an over-refraction may be conducted by placing a predicate scleral lens of known base curve radius and power on an eye to determine a final lens power by integrating the over-refraction with the base curve radius of the predicate lens, the power of the predicate lens and the new base curve radius derived from the apical radius of the cornea.

[0087] The final lens power parameter may be used to determine the anterior optic zone radius of curvature. The lens power created by the posterior optic zone radius, the anterior optic zone radius and the index of refraction of the material may be used to determine the anterior optic zone diameter for the purpose of controlling the harmonic thickness of the scleral contact lens within the anterior optic zone.

[0088] Table 2 presents the steps for determining the posterior surface parameter values as an example of an embodiment of the disclosed scleral contact lens. Clinical measurements and the single observation of apical clearance with a predicate lens of known parameter values in the diameter determined by the corneal diameter of an eye to be observed with the predicate lens. Table 2 presents sample design rules as an example of one embodiment of the disclosed scleral contact lens along with nominal values for the parameters of the lens.

TABLE-US-00002 TABLE 2 Example Semi- Posterior Clinical meridian Pre- Post- Mean Lens Example Surface Clinical Antecedent Input or radial Compression Compression eye Knot Parameter Design measure Paramete Antecedent Parameter Knot Parameter distance Clearance Clearance Elevation Elevation Selection Step Input Input Parameter Selected Number Label (mm) (microns) (microns) (mm) (mm) Rule 1 Corneal 11.8 mm Overall 6 OAD 8.30 less than 11.5 = 15.5; diameter or Diameter 11.5 to 12.1 = 16.6; horizontal and radial above 12.1 = 17.7 visible iris k2, k3*, diameter k4, k5, k6 radial OAD 16.6 mm Radial 2 PCZ 5.20 15.5 mm OAD = 10.1 mm distance of k2 16.6 mm OAD = 10.4 mm 17.7 mm OAD = 10.7 mm OAD 16.6 mm Radial 3 Volume 5.90* Equals (k4 − k2)/2* may distance of k3 Control shift laterally to control Knot volume in CCZ as a function of sagittal depth difference of k4 − k2; OAD 16.6 mm radial 4 CCZ 6.60 15.5 mm OAD = 12.7 mm distance of k4 16.6 mm OAD = 13.2 mm 17.7 mm OAD = 13.7 mm OAD 16.6 mm radial 5 LZM 7.40 Equals (k6 − k4)/2 distance k5 OAD 16.6 mm radial 6 LZ/OAD 8.20 Equals OAD - edge terminus distance k6 width. 0.1 mm 2 Apical 7.80 mm Base Curve 1 BCR 8.00 Equals keratometry, best radius from Radius fit sphere, or reference keratometry (BCR) in mm sphere value plus a constant. or corneal Example constant = 0.2 mm topography BCR and 8.00 mm k1 radial 1 POZ radial 4.00 Semi-meridian radial k1 radial distance location distance equals BCR in mm value divided by two. BCR and 8.00 mm and k1 sagittal 1 POZ depth 4.00 Varies 150 1.104 1.1072 Sag of 8.00 mm spherical k1 radial 4.0 mm depth with BCR BCR at 4.0 semi chord value BCR and 8.0 mm and k2 sagittal 2 PCZ depth 5.20 250 150 1.925 1.925 Adjusted by inverse of 25 k2 radial 5.20 mm depth microns per 0.1 mm value deviation of BCR from from 8.0 mm from sag of BCR step 1 at chord diameter of k2 3 Pre-compression k2 radial 250 microns k4 sagittal 4 CCZ depth 6.60 100 0 3.070 3.220 Equals the sag of the eye Corneal distance, preferred and depth plus the desired post Clearance k2 depth observed: compression apical observation and k4 k2 − 5.20 mm clearance. Derived by with lens of radial k4 − 6.60 mm observation of a predicate same OAD and distance lens having mean mean knot from parameters for the locations step 1 selected OAD. Depth adjusted in 25 micron steps inverse to observation of pre- compression apical clearance k2 and k4 k3 radial and 3 VCK 5.90 250 150 2.487 2.237 Calculated to produce no radial sagittal position radial post- value location compression clearance and k4 from mean eye greater sagittal than 150 microns depth; throughout the zone biometric mean data k4 and k5 k4 = 6.60 k5 sagittal 5 LZMD 7.45 0 −100 3.664 3.914 Equals the sag of the radial mm/3.320, depth eye plus the pre value k5 − 7.45 mm compression apical and k4 clearance. sagittal depth k6 radial 8.20 mm k6 sagittal 6 LZD 8.20 100 0 4.255 4.405 Equals the sag of the value depth eye plus the desired post compression apical clearance.

[0089] In some embodiments a computer program product may be used to accept the entry fields including the corneal diameter, apical corneal radius, Clearance Control Zone depth observation with a predicate lens of known parameters, parameters of the predicate lens and the manifest refraction or over refraction with a lens of known parameters. The computer program product may calculate the final scleral lens parameters using the clinical measurements, the resultant lens parameters from the clinical measurements, and the Clearance Control Zone depth observation to calculate final scleral lens parameters and cutting files for manufacturing.

[0090] FIG. 11 depicts a block diagram of an example computer system 1100 in which embodiments described herein may be implemented. The computer system 1100 includes a bus 1102 or other communication mechanism for communicating information, one or more hardware processors 1104 coupled with bus 1102 for processing information. Hardware processor(s) 1104 may be, for example, one or more general purpose microprocessors.

[0091] The computer system 1100 also includes a main memory 1106, such as a random access memory (RAM), cache and/or other dynamic storage devices, coupled to bus 1102 for storing information and instructions to be executed by processor 1104. Main memory 1106 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 1104. Such instructions, when stored in storage media accessible to processor 1104, render computer system 1100 into a special-purpose machine that is customized to perform the operations specified in the instructions.

[0092] The computer system 1100 further includes a read only memory (ROM) 1108 or other static storage device coupled to bus 1102 for storing static information and instructions for processor 1104. A storage device 1110, such as a magnetic disk, optical disk, or USB thumb drive (Flash drive), etc., is provided and coupled to bus 1102 for storing information and instructions.

[0093] The computer system 1100 may be coupled via bus 1102 to a display 1112, such as a liquid crystal display (LCD) (or touch screen), for displaying information to a computer user. An input device 1116, including alphanumeric and other keys, is coupled to bus 1102 for communicating information and command selections to processor 1104. Another type of user input device is cursor control 1116, such as a mouse, a trackball, or cursor direction keys for communicating direction information and command selections to processor 1104 and for controlling cursor movement on display 1112. In some embodiments, the same direction information and command selections as cursor control may be implemented via receiving touches on a touch screen without a cursor.

[0094] The computing system 1100 may include a user interface module to implement a GUI that may be stored in a mass storage device as executable software codes that are executed by the computing device(s). This and other modules may include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables.

[0095] In general, the word “component,” “engine,” “system,” “database,” data store,” and the like, as used herein, can refer to logic embodied in hardware or firmware, or to a collection of software instructions, possibly having entry and exit points, written in a programming language, such as, for example, Java, C or C++. A software component may be compiled and linked into an executable program, installed in a dynamic link library, or may be written in an interpreted programming language such as, for example, BASIC, Perl, or Python. It will be appreciated that software components may be callable from other components or from themselves, and/or may be invoked in response to detected events or interrupts. Software components configured for execution on computing devices may be provided on a computer readable medium, such as a compact disc, digital video disc, flash drive, magnetic disc, or any other tangible medium, or as a digital download (and may be originally stored in a compressed or installable format that requires installation, decompression or decryption prior to execution). Such software code may be stored, partially or fully, on a memory device of the executing computing device, for execution by the computing device. Software instructions may be embedded in firmware, such as an EPROM. It will be further appreciated that hardware components may be comprised of connected logic units, such as gates and flip-flops, and/or may be comprised of programmable units, such as programmable gate arrays or processors.

[0096] The computer system 1100 may implement the techniques described herein using customized hard-wired logic, one or more ASICs or FPGAs, firmware and/or program logic which in combination with the computer system causes or programs computer system 1100 to be a special-purpose machine. According to one embodiment, the techniques herein are performed by computer system 1100 in response to processor(s) 1104 executing one or more sequences of one or more instructions contained in main memory 1106. Such instructions may be read into main memory 1106 from another storage medium, such as storage device 1110. Execution of the sequences of instructions contained in main memory 1106 causes processor(s) 1104 to perform the process steps described herein. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions.

[0097] The term “non-transitory media,” and similar terms, as used herein refers to any media that store data and/or instructions that cause a machine to operate in a specific fashion. Such non-transitory media may comprise non-volatile media and/or volatile media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device 1110. Volatile media includes dynamic memory, such as main memory 1106. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, hard disk, solid state drive, magnetic tape, or any other magnetic data storage medium, a CD-ROM, any other optical data storage medium, any physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, NVRAM, any other memory chip or cartridge, and networked versions of the same.

[0098] Non-transitory media is distinct from but may be used in conjunction with transmission media. Transmission media participates in transferring information between non-transitory media. For example, transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise bus 1102. Transmission media can also take the form of acoustic or light waves, such as those generated during radio-wave and infra-red data communications.

[0099] The computer system 1100 also includes a communication interface 1118 coupled to bus 1102. Network interface 1118 provides a two-way data communication coupling to one or more network links that are connected to one or more local networks. For example, communication interface 1118 may be an integrated services digital network (ISDN) card, cable modem, satellite modem, or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, network interface 1118 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN (or a WAN component to communicate with a WAN). Wireless links may also be implemented. In any such implementation, network interface 1118 sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

[0100] A network link typically provides data communication through one or more networks to other data devices. For example, a network link may provide a connection through local network to a host computer or to data equipment operated by an Internet Service Provider (ISP). The ISP in turn provides data communication services through the world wide packet data communication network now commonly referred to as the “Internet.” Local network and Internet both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network link and through communication interface 1118, which carry the digital data to and from computer system 1100, are example forms of transmission media.

[0101] The computer system 1100 can send messages and receive data, including program code, through the network(s), network link and communication interface 1118. In the Internet example, a server might transmit a requested code for an application program through the Internet, the ISP, the local network and the communication interface 1118.

[0102] The received code may be executed by processor 1104 as it is received, and/or stored in storage device 1110, or other non-volatile storage for later execution.

[0103] Each of the processes, methods, and algorithms described in the preceding sections may be embodied in, and fully or partially automated by, code components executed by one or more computer systems or computer processors comprising computer hardware. The one or more computer systems or computer processors may also operate to support performance of the relevant operations in a “cloud computing” environment or as a “software as a service” (SaaS). The processes and algorithms may be implemented partially or wholly in application-specific circuitry. The various features and processes described above may be used independently of one another, or may be combined in various ways. Different combinations and sub-combinations are intended to fall within the scope of this disclosure, and certain method or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate, or may be performed in parallel, or in some other manner. Blocks or states may be added to or removed from the disclosed example embodiments. The performance of certain of the operations or processes may be distributed among computer systems or computers processors, not only residing within a single machine, but deployed across a number of machines.

[0104] As used herein, a circuit might be implemented utilizing any form of hardware, or a combination of hardware and software. For example, one or more processors, controllers, ASICs, PLAs, PALs, CPLDs, FPGAs, logical components, software routines or other mechanisms might be implemented to make up a circuit. In implementation, the various circuits described herein might be implemented as discrete circuits or the functions and features described can be shared in part or in total among one or more circuits. Even though various features or elements of functionality may be individually described or claimed as separate circuits, these features and functionality can be shared among one or more common circuits, and such description shall not require or imply that separate circuits are required to implement such features or functionality. Where a circuit is implemented in whole or in part using software, such software can be implemented to operate with a computing or processing system capable of carrying out the functionality described with respect thereto, such as computer system 1100.

[0105] As used herein, the term “or” may be construed in either an inclusive or exclusive sense. Moreover, the description of resources, operations, or structures in the singular shall not be read to exclude the plural. Conditional language, such as, among others, “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps.

[0106] Terms and phrases used in this document, and variations thereof, unless otherwise expressly stated, should be construed as open ended as opposed to limiting. Adjectives such as “conventional,” “traditional,” “normal,” “standard,” “known,” and terms of similar meaning should not be construed as limiting the item described to a given time period or to an item available as of a given time, but instead should be read to encompass conventional, traditional, normal, or standard technologies that may be available or known now or at any time in the future. The presence of broadening words and phrases such as “one or more,” “at least,” “but not limited to” or other like phrases in some instances shall not be read to mean that the narrower case is intended or required in instances where such broadening phrases may be absent.