Patent Publication Number: US-2020301169-A1

Title: Tear shaping for refractive correction

Description:
RELATED APPLICATION 
     This application is a continuation of application Ser. No. 15/947,136, filed Apr. 6, 2018, entitled “Tear Shaping for Refractive Correction,” which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The invention generally relates to contact lenses and refractive correction by application of contact lenses or other structures to the eye. 
     BACKGROUND 
     Known contact lenses generally cover virtually the entire cornea or cover the cornea centrally while leaving a portion of the peripheral cornea uncovered. Contact lenses known to the Applicant achieve refractive correction because of the optical nature of an optically transparent, rigid, semi-rigid or flexible material that refracts light and thus alters the refraction of light striking the cornea and passing through the other optical parts of the eye to an image formed on the retina. 
     The concept of a tear lens is known to exist in the context of conventional contact lenses. The tear lens is formed by a layer of tears bounded on an anterior surface by the back of a contact lens optical zone and at a posterior surface of the tear lens by the surface of the corneal epithelium. A tear lens, as understood in this conventional sense, contributes to refractive correction primarily in the context of rigid contact lenses. This is because the posterior surface of the rigid contact lens maintains its shape and curvature independent of the shape of the cornea and affects the focusing of light in addition to the refractive power of the contact lens. While a tear lens technically exists in the context of flexible or soft contact lenses, the effect of the tear lens on refraction is negligible because of the general conformity of the soft contact lens shape to the shape of the cornea. 
     Numerous possible complications are known to exist with use of contact lenses on the cornea even though modern contact lenses cause fewer complications than contact lenses of decades ago. The presence of contact lenses can lead to stasis and entrapment of the tear film which can lead to an accumulation of corneal epithelial waste products in the entrapped tear film. Corneal epithelial waste products in high enough concentrations can be toxic to the cells of the corneal epithelium. Mechanical interaction between the posterior surface of the contact lens and the corneal epithelium can lead to abrasion or distortion. Entrapment of solid objects, however tiny between the posterior surface of the contact lens and the anterior corneal epithelium can also lead to corneal epithelial abrasion. Under some circumstances, the reduction of oxygen available to the corneal epithelium by having the barrier of the contact lens between the corneal epithelium and the atmosphere can lead to health complications for the corneal epithelium as well. 
     There is still room for improvement in the arts of refractive correction by application of lenses and other structures to the eye. 
     SUMMARY 
     Embodiments of the invention solve many of the above stated problems by providing a lens having an anterior central cavity which centers on the optical axis of the eye or by other structures which can be applied to the eye to create a desired refractive effect by tear shaping. 
     According to an example embodiment, the central opening is structured such that capillary action forms a meniscus of tears in the opening. According to an example embodiment of the invention, the inventive lens is structured so that a concave meniscus is formed. The concave meniscus is provided for correction of myopia. It is expected that a concave meniscus will form in a relatively larger diameter opening according to embodiments of the invention. According to an example embodiment of the invention, the diameter of the central opening or central cavity falls in a range from 1.0 to 5.0 millimeters. According to another example embodiment the diameter of the central opening falls in a range from 2.0 to 3.0 millimeters and in another example embodiment 2.5 to 2.8 millimeters. A further example embodiment presents a central opening of 2.8 to 3.5 millimeters. 
     According to another example embodiment of the application, a convex meniscus is formed. A convex meniscus is expected to form in a case of a smaller diameter opening in the lens which generally overlies the optical axis of the eye. 
     Formation of the tear meniscus is affected by a number of factors including: tear production, rate of evaporation; temperature, posture of the lens user. These factors can be considered in design of the lens according to the invention. 
     In the case of a central cavity, the anterior surface of the cavity located on the posterior surface of the lens borders and determines the shape of the tear film posterior to the lens and between the posterior lens and the anterior cornea. The tears thus form a lens component that has a refractive effect in addition to the refractive effect of the contact lens. 
     According to another example embodiment of the invention, the opening is non-circular in structure. For example, an oval opening is expected to create a meniscus having a first curvature in a first axis and a second curvature in a second axis and thereby permitting correction of astigmatism by the tear meniscus formed. According to example embodiments of the invention, the central opening may be oval in shape or polygonal having a first axis longer than a second axis to achieve the astigmatic correction. 
     According to example embodiments of the invention, the cross-sectional shape of the edge or periphery of the opening may vary when viewed in cross-section. 
     According to an example embodiment, the cross-sectional shape of the periphery of the opening may demonstrate a thick rim. According to another example embodiment, the cross-sectional shape of the periphery of the opening may demonstrate the thin rim. 
     According to another embodiment, the cross-sectional shape of the periphery of the opening may demonstrate a straight rim. The straight rim may be substantially radial in orientation as compared to the curvature of the lens and opening or may be tilted to create an acute or obtuse angle relative to a tangent to the corneal surface. 
     According to another example embodiment of the invention, the periphery of the opening may demonstrate a concave shape when viewed in cross section. 
     According to another example embodiment of the invention, the periphery of the opening may demonstrate a convex shape when viewed in cross section. 
     According to another example embodiment of the invention, the cross-sectional shape of the periphery of the opening may demonstrate a polygonal cross-section which may be either concave or convex. 
     According to other example embodiments of the invention, the cross-sectional shape of the rim may vary around the circumference of the periphery of the opening. For example, a portion or portions of the periphery of the opening when viewed in cross-section may be concave while other portions may be convex. 
     According to another example embodiment of the invention, the perimeter of the rim may vary in shape when viewed in an anterior-posterior direction. 
     According to another example embodiment of the invention, the perimeter of the rim viewed anterior to posterior may have a smooth continuous curved shape. 
     According to another example embodiment of the invention, the perimeter of the rim when viewed anterior to posterior may include indentations in the rim perimeter. 
     According to another example embodiment of the invention, the rim perimeter may include appendages extending inwardly from the rim. 
     According to another example embodiment of the invention, the periphery of the opening when viewed in an anterior to posterior direction may have a circular shape. According to another example embodiment of the invention, the periphery of the opening when viewed in an anterior to posterior direction may have an oval shape and according to another example embodiment of the invention, the periphery of the opening in viewed in an anterior to posterior direction may have a polygonal shape. The polygonal shape may include a regular polygon or an irregular polygon shape. The polygon may be generally radially symmetrical or may be other than radially symmetrical. 
     According to another example embodiment of the invention, a contact lens includes a centrally located partial depth opening or cavity located centrally on the posterior concave surface of the lens. For example, the cavity may have a diameter of 2 mm to 5 mm at the center of the posterior surface of the lens. According to an example embodiment of the invention, the center or the centroid of the partial depth cavity is collinear with the optical center of the lens and when placed on an eye is substantially aligned with the optical axis of the eye. The partial depth cavity is bounded by an anterior surface which coincides with the posterior surface of the lens within the cavity. In situ, the cavity is also bounded by the anterior surface of the cornea. The anterior to posterior depth of the cavity according to an example embodiment is not less than 25 microns and not more than 100 microns as measured from a center of the tear shaping surface and to an imaginary extension of a base curve of the curved lens body. In this embodiment the base curve of the lens is considered to be the posterior curve immediately surrounding the partial depth cavity. 
     According to example embodiments of the invention, the shaped posterior surface of the lens within the cavity may have a radius of curvature that is more or less than the radius of curvature of the anterior cornea in the region of the cornea where the cavity is located when the lens is on an eye. According to known optics, a shaped posterior surface of the lens having a radius of curvature greater than the radius of curvature of the anterior corneal surface will generally provide a space in which a negative powered tear lens is formed. Conversely, a shaped posterior surface lens bounding the cavity having a radius of curvature less than the radius of curvature of the corneal region that bounds the rear of the cavity will generally lead to a tear lens having positive optical power. 
     According to another example embodiment of the invention, the lens body may define one or more passages having a diameter of no more than about 2 microns and no less than about 0.5 microns. These passages extend from the posterior lens to the anterior lens surface through the body of the contact lens. The openings are expected to promote tear exchange and oxygen exchange between tears under the lens and tears anterior to the lens. 
     According to another example embodiment of the invention, the lens or structure for refractive tear shaping includes a lens body presenting an anterior partial thickness cavity. A contact lens, for example, a soft contact lens, having a partial thickness cavity can be placed on an eye. In situ, the partial thickness cavity will fill with tear fluid. The column of tear fluid, in combination with the surface curvature of the base or posterior surface of the cavity, the layer of contact lens material behind the partial thickness cavity, the tear film and cornea make up a complex optic or optical combination that provides several elements of adjustable dimensions and properties that may be utilized to form an optic or optical combination having desired refractive properties. For example, the shape and contour of the base of the partial thickness cavity may be varied in curvature, toricity, perimeter shape or a combination of the foregoing. In a further example, the thickness of the material way are posterior to the base of the partial thickness cavity may be varied. In another example, the base or posterior curve of the contact lens may be altered in curvature or toricity. The base of the partial thickness cavity, the base curve of the contact lens or both may include a diffractive optical surface. 
     For example, the base surface or posterior base of the partial thickness cavity may have a curvature greater than, less than or equal to the curvature of the posterior surface of the contact lens which generally conforms to the anterior surface of the cornea. 
     According to another example embodiment, the base surface or posterior base of the partial thickness cavity may have a diffractive surface relief. 
     According to an example embodiment of the invention, a soft or rigid contact lens has a partial depth cavity located proximate a center of the lens to form and accommodate a tear fluid reservoir. 
     A diameter of the partial depth cavity, according to an example embodiment of the invention, is in the range of 2.0 mm to 6.0 mm. According to another example embodiment the diameter is between 3.0 mm and 5.0 mm. 
     The contact lens, according to an example embodiment, has a thickness ranging from 50 μm to 500 μm, according to another example embodiment between 80 μm and 350 μm at its optical center. The partial thickness cavity is bounded posteriorly by a layer of contact lens material the thickness of which may vary between 10 μm and 100 μm according to an example embodiment. According to another example embodiment the thickness may vary between 25 μm and 75 μm. 
     The thickness of a contact lens is generally measured as a center thickness. That is, the thickness of the contact lens at the geometrical center of the contact lens. In the case of embodiments of the present invention, the center thickness is affected by the presence of the anterior partial thickness cavity. Accordingly, center thickness in the context of this embodiment of the invention is considered to be the thickness from the posterior concave surface of the contact lens to an imaginary extension of the anterior surface of the contact lens that would exist if the partial thickness cavity were not present. 
     According to example embodiments of the invention, when the contact lens is centered on the cornea the partial thickness cavity is centered so that its center generally aligns with the corneal apex. It is expected that typically the error in centration of the partial depth cavity with respect to the corneal apex is less than approximately 0.5 mm and in another example embodiment less than 0.25 mm. The corneal apex generally coincides with the visual axis of the eye although there is some variation between the location of the visual axis and the corneal apex. 
     According to an example embodiment of the invention, the base surface of the partial depth cavity has a radius of curvature less than the radius of curvature of the posterior surface of the contact lens. According to this example embodiment of the invention, the optic or optical combination created by the partial depth cavity extending over the center of the contact lens optics includes three surfaces. The three surface include the first interface between the tears that fill the anterior partial depth cavity, the second interface between the tears filling the cavity and the material of the lens at the base of the partial depth cavity and the third interface between the posterior concave surface of the lens and the tear film layer behind it. In addition, the anterior corneal surface optically interacts with this example embodiment and thus, a fourth surface is taken into account. The fourth surface is formed by the anterior cornea which has a radius of curvature r 1 . The third surface is formed by the posterior surface of the contact lens for example, a soft contact lens, which has a radius r 2 . The base surface of the partial depth cavity which forms the second surface has a radius of curvature r 3 . The anterior surface of the contact lens to which the interface between the tear film and the atmosphere is expected to conform, has a radius of curvature r 4 . 
     To summarize according to an example embodiment: 
     r 1  represents the radius of curvature of the anterior corneal surface; 
     r 2  represents the radius of curvature of the posterior surface of the soft contact lens; 
     r 3  represents the radius of curvature of the base surface of the partial depth cavity; and 
     r 4  represents the radius of curvature of the anterior surface of the contact lens or anterior interface of the tear film within the partial thickness cavity. 
     If it is determined that the anterior tear film does not substantially conform to the anterior curvature of the contact lens adjustments can be made to the calculation to take this factor into account as is understood by those having skill in the art. 
     In a typical circumstance utilizing a soft contact lens, r 1  is equal to r 2  or approximately equal to r 2  unless a keratoprosthesis (an artificial corneal implant) is present in the cornea. The contact lens may have a total power that is positive or negative or the contact lens may have no net refractive power. Radius of curvature r 4  can be less than, more than or equal to r 2 . The relationship between r 3  and r 2  along with the thickness of the optical segment determine the refractive power of the optical segment that is represented by the central zone of the partial depth cavity when filled with tears. Toric optical surfaces and consequent astigmatic focusing can also be taken into account utilizing known optical principles. An optical train of this sort can be modeled using various optical software programs, for example, Zemax. 
     In this example embodiment, the central optical element created by the partial depth cavity is expected to be used to correct hyperopia, provide add power to fully meet or partially meet accommodative needs of a patient with presbyopia or be used to meet other refractive requirements related to for example, astigmatism. 
     According to another example embodiment, the base surface of the partial depth cavity has a radius of curvature more than the radius of curvature of the posterior surface of the contact lens. Accordingly, it is expected that the central optical element will provide a negative refractive power that may be used to provide an enhancement of the field of view and depth of field, as an example. 
     According to another example embodiment, the base surface of the partial thickness cavity includes a diffractive surface profile. The diffractive surface profile may for example include a phase plate surface for phase modulation or, according to another example embodiment, a phase wrapped surface for amplitude modulation. 
     Typically, the diffractive optic according to example embodiments of the invention is designed according to equation 1. 
         r   n =2 nfλ   Eq (1)
 
     wherein r represents the radius of curvature of the diffractive element, n represents refractive index or the refractive index difference (if the diffractive optic is immersed in a fluid having a refractive index other than that of air), f represents focal length and λ is the wavelength of light. According to example embodiments of the invention, the diffractive optical element is immersed in a fluid, the tear film, having a refractive index different than air which is known. 
     According to example embodiments of the invention, a diffractive optic may be used to provide a plus power for augmentation of natural accommodation for viewing near objects such as reading. Expected advantages are that a diffractive optic may demonstrate a wider field of view and also may be utilized to correct for spherical aberration or astigmatism. 
     The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter hereof. The figures and the detailed description that follow more particularly exemplify various embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures, in which: 
         FIG. 1  is an anterior to posterior view of a lens for refractive tear shaping having a circular central opening therein; 
         FIG. 2  is an anterior to posterior view of a lens for refractive tear shaping having an oval central opening therein; 
         FIG. 3  is a lens for refractive tear shaping having a polygonal opening therein; 
         FIG. 4  is an anterior to posterior view of a lens for refractive tear shaping having a stellate opening with indentations according to an example embodiment of the invention; 
         FIG. 5  is an anterior to posterior view of a lens for refractive tear shaping having a stellate opening with appendages according to an example embodiment of the invention; 
         FIG. 6  is an anterior to posterior view of a lens for refractive tear shaping having a generally rectangular polygonal opening therein according to an example embodiment of the invention; 
         FIG. 7  is a cross-sectional view of a lens for refractive tear shaping in situ on a cornea and with a concave tear meniscus according to any example embodiment of the invention; 
         FIG. 8  is a cross-sectional view of a lens for refractive tear shaping in situ on a cornea with a convex tear meniscus according to an example embodiment of the invention; 
         FIG. 9  is a cross-sectional view of a lens for refractive tear shaping in situ on a cornea with a central opening having inward angled edges and a concave tear meniscus according to an example embodiment of the invention; 
         FIG. 10  is a cross-sectional view of a lens for refractive tear shaping in situ on a cornea with a concave tear meniscus and outwardly angled edges according to an example embodiment of the invention; 
         FIG. 11  is a cross-sectional view of a lens for refractive tear shaping having an opening with concave peripheral edges according to an example embodiment of the invention with the tear meniscus not depicted; 
         FIG. 12  is a cross-sectional view of a lens for refractive tear shaping having an opening with convex peripheral edges in situ on a cornea according to an example embodiment of the invention with the tear meniscus not depicted; 
         FIG. 13  is a lens for refractive tear shaping in situ on a cornea with an opening having polygonal peripheral edges with the tear meniscus not depicted; 
         FIG. 14  is a cross-sectional view of a contact lens having a partial depth cavity with an anterior boundary flatter in curvature than the cornea in situ on a cornea according to an example embodiment of the invention; 
         FIG. 15  is a cross-sectional view of a partial depth cavity contact lens having a curvature steeper than the anterior cornea; 
         FIG. 16  is a cross-sectional view of a contact lens having a partial depth cavity flatter in curvature than the cornea, the lens body being pierced by a series of holes; 
         FIG. 17  is a cross-sectional view of a contact lens with a partial depth cavity having a steeper curvature than the cornea, the lens body pierced by a series of holes; 
         FIG. 18  is a cross-sectional view of a contact lens according to another example embodiment of the invention in situ on an eye; 
         FIG. 19  is a cross-sectional view of a contact lens according to another example embodiment of the invention in situ on the eye; and 
         FIG. 20  is a cross-sectional view of another contact lens according to an embodiment of the invention in situ on an eye; 
         FIG. 21  depicts a contact lens with a partial thickness cavity at the center in an anterior convex surface according to an example embodiment of the invention 
         FIG. 22A  depict a section of a partial thickness cavity with a base surface of the partial thickness cavity having a curvature greater than a posterior surface of the contact lens according to an example embodiment of the invention; 
         FIG. 22B  depicts a section of a partial thickness cavity with a base surface of the partial thickness cavity having a curvature less than a posterior surface of the contact lens according to an example embodiment of the invention; 
         FIG. 22C  depicts a section of a partial thickness cavity with a base surface of the partial thickness cavity having a diffractive surface relief according to an example embodiment of the invention 
         FIG. 23A  depicts an example diffractive optical element as a surface profile at the base of a partial thickness cavity in a soft contact lens according to an example embodiment of the invention; 
         FIG. 23B  depicts an example diffractive optical element is a surface profile at the base of a partial thickness cavity in a soft contact lens according to an example embodiment of the invention; 
         FIG. 24  depicts an optical train according to an example embodiment of the invention that may be modeled using a typical optical software program, for example, Zemax. 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. 
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-13 , embodiments of the invention are directed to lens or structure for refractive tear shaping  20  wherein refractive correction is achieved or enhanced by the shaping of the tear film. 
     Referring particularly to  FIGS. 1-6 , lens for refractive tear shaping  20  according to an example embodiment of the invention generally includes lens body  22  having peripheral edge  24  and defining central opening  26 . Central opening  26  is surrounded by a tear shaping edge  28 . According to the depicted embodiment, tear shaping edge  28  defines circular central opening  30 . Tear shaping edge  28  can have a number of cross sectional structures and shapes as described below. 
     Referring now to  FIG. 2 , another embodiment of lens for refractive tear shaping  20  is depicted. The depicted embodiment includes lens body  22  having peripheral edge  24  and elliptical or oval central opening  32 . Elliptical or oval central opening  32  is bounded by tear shaping edge  28 . 
     Referring to  FIG. 3 , another embodiment of lens for refractive tear shaping  20  is depicted having polygonal central opening  34 . Polygonal central opening  34  is depicted as an irregular hexagon, however polygonal central opening  34  may have more or less than six sides and six vertices. 
     Referring particularly to  FIGS. 2 and 3 , elliptical or oval central opening  32  and polygonal central opening  34  may have long axis  36  and short axis  38 . 
     Referring now to  FIG. 4 , according to another embodiment, lens for refractive tear shaping  20  defines stellate opening  40  having indentations into the material of the lens surrounding stellate opening  40 . While stellate opening  40  is depicted as circularly symmetrical, stellate opening  40  may also have long axis  36  and short axis  38 . 
     Referring now to  FIG. 5 , another embodiment of lens for refractive tear shaping  20  is depicted. According to the depicted embodiment, stellate opening with appendages  44  is depicted. Appendages  46  extend inwardly from outer edge  48 . While depicted as circularly symmetrical, stellate opening with appendages  44  may also have long axis  36  and short axis  38 . 
     Referring now to  FIG. 6 , lens for refractive tear shaping  20  with rectangular opening  50  is depicted. Rectangular opening  50  is depicted having a particular proportional aspect ratio, however this should not be considered limiting as the aspect ratio of rectangular opening  50  may be altered by altering the length of long axis  36  as compared to short axis  38 . 
     Referring now to  FIGS. 7-13 , cross-sectional views of example embodiments of lens for refractive tear shaping  20  are depicted. 
     Referring particularly to  FIG. 7 , an embodiment of the invention including parallel tear shaping edge  52  is depicted. It is noted that lens body  22  in the embodiment depicted in  FIG. 7  that parallel tear shaping edge  52  is generally parallel on opposing sides of central opening  26 . Also depicted in  FIG. 7  is concave tear meniscus  54 . Concave tear meniscus  54  affects a negative refractive power due to its concave shape and is expected to contribute focusing power for correction of myopia. It is expected that the concavity of concave tear meniscus  54  will vary with the size of central opening  26  and with the depth  56  of tear shaping edge  28 . 
     It is expected that to a certain point smaller diameter of central opening  26  will create a more steeply curved concave tear meniscus imparting greater negative refractive power and stronger correction for myopia. It is also expected that increasing depth  56  of tear shaping edge  28  will increase negative refractive power to a certain degree. As discussed above, central opening  26  may have various shapes, some of which include a long axis  36  and short axis  38 . 
     It is expected that by judicious selection of the size of long axis  36  and short axis  38  that astigmatism may be corrected by creating a concave tear meniscus  54  having different shape and therefore differing power on various meridians. 
     Referring now to  FIG. 8 , lens for refractive tear shaping  20  having parallel tear shaping edge  52  is sized and configured to create convex tear meniscus  58 . It is expected that when the size of central opening  26  is reduced to a sufficient degree, convex tear meniscus  58  will be formed in central opening  26 .  FIG. 8  depicts parallel tear shaping edge  52  along with a smaller diameter central opening  26  than does  FIG. 7 . It is expected that when the size of central opening  26  and depth  56  of tear shaping edge are appropriate convex tear meniscus  58  will be formed. 
     Referring now to  FIG. 9 , lens for refractive tear shaping  20  with anterior acute tear shaping edge  60  is depicted. It is noted that anterior acute tear shaping edge  60  is arranged so that tear shaping edge  28  narrows from posteriorly-to-anteriorly. Concave tear meniscus  54  is also depicted. It is expected that anterior acute tear shaping edge  60  will create a more concave tear meniscus  54  thus, creating greater negative refractive power to concave tear meniscus  54 . 
     Referring now to  FIG. 10 , lens for refractive tear shaping  20  having anterior obtuse tear shaping edge  62  is depicted. Anterior obtuse tear shaping edge  62  is structured so that central opening  26  is wider anteriorly and narrower posteriorly. It is expected that anterior obtuse tear shaping edge  62  will create a flatter concave tear meniscus  54  as depicted in  FIG. 10  thus, creating a concave tear meniscus having less negative refractive power than parallel tear shaping edge  52  having a similar posterior diameter. 
     Referring now to  FIG. 11 , lens for refractive tear shaping  20  having concave tear shaping edge  64  is depicted. In  FIG. 11 , no tear meniscus  66  is depicted for clarity. Concave tear shaping edge  64  includes anterior edge  68 , posterior edge  70  and concave portion  72 . 
     Referring now to  FIG. 12 , lens for refractive tear shaping  20  with convex tear shaping edge  74  is depicted. No tear meniscus  66  is depicted for clarity. In the depicted embodiment, convex tear shaping edge  74  has a radius of curvature approximately equal to half of depth  56  of tear shaping edge  20 . This should not be considered limiting however as the radius of curvature of convex tear shaping edge  74  may vary. 
     Referring now to  FIG. 13 , lens for refractive tear shaping  20  with faceted tear shaping edge  76  is depicted. Faceted tear shaping edge  76  presents anterior edge  78 , posterior edge  80  and internal angle portion  82 . 
     Lens for refractive tear shaping  20  according to the various embodiments described herein may be formed from hydrogel polymers of the types used in soft contact lens that are now available or any hydrogel polymer materials to be developed in the future. Hydrogel polymers are generally water absorbent and hydrogel polymers may be used to manufacture lenses for refractive tear shaping  20  according to the invention by methods including but not limited to lathe cutting, cast molding, spin casting and injection molding. Lenses for refractive tear shaping  20  may also be manufactured from rigid oxygen permeable materials by known manufacturing processes including lathe cutting. It is to be understood that lens for refractive tear shaping  20  may be manufactured by any known contact lens manufacturing process or contact lens manufacturing processes to be developed in the future. 
     Lenses for refractive tear shaping  20  are expected to be made in diameters ranging from approximately 5 mm to 16 mm. Certain features of lens for refractive tear shaping  20  such as the diameter of central opening  26 , the structure of tear shaping edge  28 , the appropriate length of long axis  36  and short axis  38  to achieve desired refractive correction are expected to be developed with a certain degree of experimentation. It is expected that this degree of experimentation will not be undue and that those of ordinary skill in the art based on the present application disclosure will be able to engage in such experimentation without significant difficulty. 
     It is expected that for formation of concave tear meniscus  54 , that smaller diameter central openings  26  will result in higher refractive power of concave tear meniscus  54 , thus permitting higher degrees of refractive correction for myopia. It is also expected that when the diameter of central opening  26  becomes sufficiently small, tear meniscus  66  will transition from concave tear meniscus  54  to convex tear meniscus  58 . Determination of this transition diameter for transition is expected to be achievable by reasonable levels of experimentation. 
     The effect of depth  56  of tear shaping edge  28  on refractive power of tear meniscus  66  also should be determinable by reasonable experimentation. It is expected that greater depth  56  will generally create a thicker periphery of tear meniscus  66  resulting in higher degrees to concavity of concave tear meniscus  54  and greater myopic correction. 
     Further, understanding of the effect of other features of the disclosed lenses including anterior acute tear shaping edge  60 , anterior obtuse tear shaping edge  62 , concave tear shaping edge  64 , convex tear shaping edge  74  and faceted tear shaping edge  76  are expected to be achieved by reasonable experimentation well within the ability of one of ordinary skill in the art. It is expected that such experimentation will not be undue. It is also expected that the effect of stellate opening  40  with indentations  42  as well as stellate opening with appendages  44  and appendages  46  can also be determined experimentally. 
     Referring now to  FIGS. 15-20 , according to another embodiment of the invention, lens with partial depth cavity  84  is depicted in various embodiments. 
     Referring to  FIG. 14 , in the depicted embodiment, lens with partial depth cavity  84  generally includes lens body  86  presenting peripheral edge  88 , central partial depth cavity  90 , tear shaping surface  92 , and cavity peripheral edge  94 . Lens with partial depth cavity  84  is depicted as resting adjacent corneal surface  96 .  FIG. 14  depicts lens with partial depth cavity  84  having tear shaping surface  92  that is flatter in curvature than corneal surface  96 , thus having a longer radius of curvature than corneal surface  96 . Accordingly, in the depicted embodiment, tears underlying lens with partial depth cavity  84  generally provide a negative refractive power in addition to that provided by lens with partial depth cavity  84  alone due to tear lens  98 . 
     Another example embodiment of lens with partial depth cavity  84  is depicted in  FIG. 15 . Structures labeled in  FIG. 15  are similar to those labeled in  FIG. 14  but tear shaping surface  92  of lens with partial depth cavity  84  depicted in  FIG. 15  is curved more steeply than corneal surface  96  thus having a radius of curvature less than corneal surface  96  resulting in a positive powered tear lens  98 . 
     Referring now to  FIGS. 16 and 17 , according to the depicted embodiment, lens with partial depth cavity  84  includes at least one hole or passage  100  through lens body  86  as depicted. In the depicted embodiments, lens with partial depth cavity  84  presents central passage  102 , first peripheral passage  104  and second peripheral passage  106 . Any number of central passages  102  and peripheral passages  104  and  106  can be defined by lens body  86 . 
     Referring to  FIG. 18 , another embodiment of lens with partial depth cavity  84  is depicted. In the depicted embodiment, tear shaping surface  92  presents small diameter, concave tear shaping surface  108 . In the depicted embodiment, cavity peripheral edge  94  includes generally parallel sides  110 . For the purposes of this application, generally parallel sides  110  are considered to be generally parallel when they are within five degrees of parallel with each other. 
     Referring now to  FIG. 19 , another embodiment of lens with partial depth cavity  84  is depicted. In the depicted embodiment, central, partial depth cavity  94  is bounded by tear shaping surface  92  presenting concave to plano tear shaping surface  112 . In the depicted embodiment, concave to plano tear shaping surface  112  is flatter in curvature and thus has a longer radius of curvature than corneal surface  96 . In the depicted embodiment, cavity peripheral edge  94  presents non-parallel sides  114 . Non-parallel sides  114  are considered to be non-parallel when the angle between non-parallel sides  114  is greater than five degrees relative to each other. In the depicted embodiment, central, partial depth cavity  94  has a cavity diameter  116  less than that of the pupil  118 . 
     Referring now to  FIG. 20 , in the depicted embodiment, central, partial depth cavity  90  presents convex tear shaping surface  120  and non-parallel sides  114 . Convex tear shaping surface  120  is not only flatter than corneal surface  96  but it is shaped so that an anterior surface of tear lens  98  is by concave, thus providing a stronger negative power to tear lens  98 . 
     According to another example embodiment, lens  86  further presents base curve  122 . Contrary to prior art base curve  121  is not the most central curve of lens body  86 . The most central curve here is that of tear shaping surface  92 . According to an example embodiment, base curve  122  is the curve of the posterior lens that immediately surrounds central partial depth cavity  90 . Depth  124  of central partial depth cavity  90  is measured from an imaginary extension of based curve  122  across central partial depth cavity  90  to a center of tear shaping surface  92 . 
     Referring to  FIG. 21 , according to another example embodiment the invention, lens for refractive tear shaping  20  includes lens body  124  presenting anterior partial thickness cavity  126 . According to the depicted example embodiment, soft contact lens  128  has overall diameter  130  of 14.0 mm. Central thickness  132  of soft contact lens  128  is approximately 0.50 mm. Note that central thickness  132  indicates what the central thickness of soft contact lens  128  would be absent the presence of partial thickness cavity  126 . These dimensions are presented as an example only and are not to be considered limiting. 
     According to the depicted example embodiment: 
     r 1  represents anterior corneal radius of curvature of the anterior corneal surface; 
     r 2  represents posterior contact lens radius of curvature of the posterior surface of the soft contact lens; 
     r 3  represents partial depth cavity radius of curvature of the base surface of the partial depth cavity; and 
     r 4  represents anterior contact lens radius of curvature of the anterior surface of the contact lens. 
     According to the depicted embodiment, posterior contact lens radius r 2  is approximately 8.00 mm and anterior contact lens radius r 4  is also approximately 8.00 mm. Partial depth cavity diameter  134  is approximately is approximately 5.00 mm. Partial depth cavity depth  136  is not specifically identified in this example but is less than central thickness  132  of 0.50 mm. 
     Soft contact lens  128  as discussed herein according to an example embodiment, presents anterior partial thickness cavity  126 . Partial depth cavity diameter  34 , according to example embodiments of the invention, is in a range between 2.0 mm and 6.0 mm, and according to another example embodiment is in a range of 3.0 mm to 5.0 mm. 
     Central thickness  132  is in a range of 50 μm to 500 μm according to an example embodiment. According to another example embodiment, central thickness  132  is in a range of 80 μm to 350 μm. Central thickness  132  indicates what the central thickness  132  of soft contact lens  128  would be absent the presence of partial thickness cavity  126 . 
     Referring now to  FIGS. 22A, 22B and 22C , for the purposes of these depictions it is assumed that the anterior corneal surface  138  and posterior contact lens surface  140  are coincident. In fact, a layer of tear film laser lies between the anterior corneal surface  138  and posterior contact lens surface  140  and can be taken into account by known optical methods. Base surface  142  of anterior partial thickness cavity  126  is also depicted. 
     According to  FIG. 22A , base surface  142  has curvature  144  greater than posterior contact lens service  140 . It is of note that curvature and radius of curvature are reciprocal quantities. 
     According to  FIG. 22B , base surface  142  has curvature  144  less than posterior contact lens surface  140 . 
     According to  FIG. 22C , base surface  142  presents diffractive surface relief  144 . 
     The diffractive surface relief  144  may, for example, include a phase plate surface for phase modulation or according to another example embodiment a phase wrapped surface for amplitude modulation. 
     Typically the diffractive optic according to example embodiments of the invention is designed according to equation 1. 
         r   n =2 nfλ   Eq (1)
 
     wherein r n  represents the radius of curvature of the diffractive element, n represents refractive index or the refractive index difference, if the diffractive optic is immersed in a fluid having a refractive index other than air, f represents focal length and λ is the wavelength of light. According to example embodiments of the invention, the diffractive optical element is immersed in a fluid, the tear film, having a known refractive index different than air. 
     Referring to  FIG. 23A , an example diffractive surface relief  144  is depicted. In the depicted embodiment, diffractive surface relief  144  includes Fresnel surface  146  and plano surface  148 . Wavelength of light λ is also depicted along with optical wavefronts  150 . 
     Referring to  FIG. 23B , soft contact lens  128  is depicted with anterior partial thickness cavity  126  wherein base surface  142  includes diffractive surface relief  144 . 
     Base thickness  152  extending from base surface  142  to posterior contact lens surface  140  may vary in a range between, for example, 10 μm and 100 μm. According to an example embodiment, base thickness  152  may be in the range of 25 μm to 75 μm. 
     Referring to  FIG. 24 , optical train  154  is depicted. Optical train  154  includes radii of curvature r 1  representing the corneal curvature, r 2  representing the curvature posterior contact lens surface  140  of tear shaping lens  20 , r 3  representing the radius of curvature of base surface  142  of anterior partial thickness cavity  126  and r 4  representing anterior radius of curvature of tear fluid reservoir  156 . Here, n 1  represents diffractive index of the tear film between lens body  124  and the cornea, n 2  represents refractive index of the contact lens material and the n 3  represents the refractive index of the tear fluid reservoir  156 . Optical train  154  can be modeled using an optical software program such as, for example, Zemax. 
     In operation, lens for refractive tear shaping  20  is placed on an eye overlying the cornea of the eye. Lens for refractive tear shaping  20  will typically center on the eye such that central opening  26 , central partial depth cavity  94  or anterior partial thickness cavity  126  is approximately centered on the cornea and is approximately aligned with the visual axis of the eye. Tear lens  98  forms within central opening  26 , central partial depth cavity  94  or anterior partial thickness cavity  126  as described above to provide desired refractive correction. 
     The present invention may be embodied in other specific forms without departing from the spirit of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention. 
     Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions. 
     Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. 
     Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim.