Patent Publication Number: US-2021178555-A1

Title: Mandrel for holding a lens blank and method of making a lens using the same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application claims priority from Provisional Application U.S. Application 62/947,339, filed Dec. 12, 2019, incorporated herein by reference in its entirety. 
    
    
     FIELD 
     This invention relates to a mandrel for holding a lens, such as an intraocular lens, and a method of making a lens, more specifically, a method of making a one-piece lens, such as an intraocular lens using the mandrel. 
     BACKGROUND 
     As set forth in commonly assigned U.S. Pat. No. 9,919,487 (the “&#39;487 patent”, which is hereby incorporated by reference for all purposes), intraocular lenses are typically produced by machining and milling a polymer disc (i.e., a lens “blank”) that is held in place typically by wax or water (ice) during the fabrication process. Wax, either water soluble wax or solvent soluble wax, is used for fabricating hydrophilic intraocular lenses and ice is used when cryogenically fabricating hydrophobic intraocular lenses, which are rubbers at room temperature and require low temperatures for machining. Each side of the polymer blank is machined and milled in turn, with the final product being a completed single piece intraocular lens. Specifically, milling is performed on a first side of the disc by holding the disc on a first-side mandrel. The partially machined blank is then held on a second-side mandrel so that the second side of the blank may be milled. 
     The &#39;487 patent discloses an improved mandrel that is particularly beneficial when used as a second-side mandrel for holding a partially machined and/or molded hydrophilic lens blank with blocking wax. In contrast, lenses made of hydrophobic materials typically are formed cryogenically, which presents particular challenges in terms of ensuring that the optic and the haptic are centered. 
     SUMMARY 
     In one exemplary embodiment, a mandrel for holding and positioning an intraocular lens blank during manufacturing includes a shank portion having a central axis and a lens blank holding section to hold the lens blank. The holding section includes a central cavity formed concentrically with the central axis of the mandrel. Projections are formed on the surface of the central cavity to support a first surface of the lens blank. A ring fits within the periphery of the lens blank holding section, and holds a second opposing surface of the lens blank. 
     In one exemplary embodiment, a space is formed between the first surface of a lens blank as the lens blank is supported by the projections and the surface of the central cavity. 
     In one exemplary embodiment, a hollow channel is formed within the central cavity, the hollow channel extending into the shank. 
     In one exemplary embodiment, the shank portion is configured to be received within a supporting collet. 
     In one exemplary embodiment, a second cavity is concentric with the central cavity and has a smaller cross-sectional diameter than the central cavity. 
     In one exemplary embodiment, an interference fit retains the ring portion within the lens holding section. 
     In one exemplary embodiment, the ring portion includes a plurality of holes formed along an inner peripheral surface thereof, the holes being configured to permit a liquid, preferably water, to be transferred into the space formed between the first surface of a lens blank as the lens blank is supported by the projections and the surface of the central cavity. The water may be frozen to support the lens blank as it is milled and/or machined. 
     According to one exemplary embodiment, a method for making an intraocular lens using the mandrel includes providing a mandrel, positioning an intraocular lens blank in the central cavity of the mandrel, and fitting the ring to the mandrel so as to hold the intraocular lens blank on the mandrel. 
     According to one exemplary embodiment, the optical center of the intraocular lens blank is positioned concentrically with the central axis of the mandrel shank. 
     According to one exemplary embodiment, the method further includes applying a liquid to a space formed between the first surface of a lens blank as the lens blank is supported by the projections and the surface of the central cavity, freezing the liquid so that it supports the lens blank, and forming a lens from the lens blank. 
     According to one exemplary embodiment, forming the lens comprises one or more of milling or machining a second surface of the lens as it is supported within the mandrel. 
     According to one exemplary embodiment, the liquid preferably comprises water and the lens blank preferably comprises a hydrophobic material. 
     According to one exemplary embodiment, the mandrel is held in a vacuum collet and the lens is formed with a laser. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain principles of the invention. 
         FIG. 1  shows a perspective view of a mandrel according to one embodiment. 
         FIG. 2  shows a perspective view of an embodiment of a ring for use with the mandrel according to  FIG. 1 . 
         FIG. 3  shows a cross-sectional view of a mandrel/optic disc assembly including the mandrel according to  FIG. 1  with the ring according to  FIG. 2  holding a lens blank onto the mandrel. 
         FIG. 4A  shows a cross-sectional view of a lens blank being placed on a mandrel according to one embodiment. 
         FIG. 4B  shows a cross-sectional view of a ring being positioned onto a mandrel to hold a lens blank/optic disc according to one embodiment. 
         FIG. 4C  shows a cross-sectional view of a mandrel/optic disc assembly positioned within a collet according to one embodiment. 
         FIG. 5A  shows a cross-sectional view of a mandrel/optic disc assembly according to one embodiment being inverted into a container of water so as to allow a space between the optic disc and the mandrel to be filled with water. 
         FIG. 5B  is an enlarged view of a portion of the mandrel/optic disc assembly according to  FIG. 5A  in which water fills the space between the optic disc and the mandrel. 
         FIG. 6A  shows a cross-sectional view of a mandrel/optic disc assembly positioned within a collet being cooled according to one embodiment. 
         FIG. 6B  shows a cross-sectional view of a mandrel/optic disc assembly positioned within a collet in which ice a frozen liquid is formed within a space between the optic disc and the mandrel so as to support the optic disc according to one embodiment. 
         FIG. 6C  shows a perspective view of a milling operation of an optic disc as it is positioned on a mandrel assembly positioned within a collet according to one embodiment. 
         FIG. 6D  shows a milled optic disc within a mandrel assembly according to one embodiment. 
         FIG. 7  shows a milled optic disc within a mandrel assembly according to one embodiment and the manner by which the haptic meridian may be aligned with the mandrel. 
         FIG. 8  shows a top view of an intraocular lens that is formed from an optic disc that is held by a mandrel assembly according to one embodiment. 
         FIG. 9  shows a perspective view of a mandrel/optic disc assembly in which a lens is formed with a laser while the mandrel is held in a vacuum collet according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Conventional techniques for machining a lens blank on a mandrel present several challenges. For example, it is critical to ensure that the blank is held in proper alignment, particularly when milling the second side surface so that the haptic of the blank is properly centered. With conventional techniques, it is difficult to ensure accuracy, especially with hydrophobic lens materials that are milled cryogenically. 
       FIG. 1  depicts a mandrel  100  according to one embodiment. The mandrel  100  is configured for holding a lens blank during manufacturing. Preferably, the mandrel  100  is a second-side mandrel, meaning that the mandrel  100  is a mandrel to which a lens blank is transferred to from a first-side collet or a first-side mandrel, after a first side of the lens blank is partially machined. The second side of the lens blank may then be machined on the second-side mandrel. The mandrel  100  may be fabricated from, for example, a polymer, preferably, a glassy polymer material. 
     The mandrel  100  includes a hollow mandrel shank  150  that is configured to fit precisely within a collet during milling of a lens blank. The mandrel  100  may be formed, for example, by injection molding. Preferably, the mandrel  100  is formed with precise dimensions to maintain a precise height of a lens blank to be milled when the mandrel  100  is received in a collet, as discussed further below. Preferably, the diameter of the mandrel shank  150  is precisely controlled (for example, ±≤0.01 mm), as is the roundness of the mandrel shank  150  (for example, ±≤0.01 mm TIR). 
     According to an exemplary embodiment, the top or head portion  102  of the mandrel  100  has one or more substantially planar side surfaces  104 . These side surfaces  104  may be used advantageously to locate the meridian of haptics (M) to be formed from a lens blank. In certain non-limiting embodiments, information pertaining to the lens blank may be positioned on the side surfaces  104 . For example, a bar code (not shown) may be applied to one or both substantially planar side surfaces  104  of the mandrel  100  containing identifying information, such as part number, optical power, type of material used, testing and/or quality control information. 
     The mandrel  100  includes a lens blank holding section  105  configured to hold a lens blank. In this embodiment, the lens blank holding section  105  includes a central cavity  110  having a sidewall  118  and a bottom surface  120 . The sidewall  118 , in this embodiment, is substantially parallel to the central axis (X) of the mandrel  100 . Formed on the bottom surface  120  of the lens blank holding section  105  of the mandrel  100 , within the central cavity  110 , are a plurality of projections  112 . The plurality of projections  112  are configured to support a lens blank at a predetermined distance above the bottom surface  120  of the central cavity  110 . In this embodiment, the plurality of projections  112  are disposed radially from the central axis (X) of the mandrel  100 . Preferably, the plurality of projections  112  are positioned at locations such that they do not interfere with the milling of a lens blank to form the haptics of an intraocular lens. 
     In this embodiment, the lens blank holding section  105  further includes a second cavity  114 . The second cavity  114  is formed within the central cavity  110 . The second cavity  114  is concentric with the central cavity  110  and the central axis (X) of the mandrel  100 . The second cavity  114  has a smaller cross-sectional diameter than the central cavity  110 . A hollow center channel  116  is formed within the second cavity  114 . The hollow center channel  116  is configured to provide an outlet through which air, liquid, and/or a frozen liquid may pass through as discussed further below. The central cavity  110  may be rounded, may have a conical shape, or may have a truncated conical shape. Additionally, the second cavity  114  may be rounded, may have a conical shape, or may have a truncated conical shape. 
       FIG. 2  shows an embodiment of a ring  200  configured to be received within a periphery of the central cavity  110  of the lens blank holding section  105  of the mandrel  100 . In this embodiment, the ring  200  has a sidewall  218  that is configured to fit against the sidewall  118  of the central cavity  110  to form an interference fit between the ring  200  and the mandrel  100  when the ring  200  is received within the central cavity  110  of the mandrel  100  as depicted in  FIG. 3 . In an exemplary embodiment, the ring  200  may preferably comprise a polymer material and may be thin enough to be deformed and fit within a perimeter  122  of the central cavity  110 . Of course, other methods of retaining the ring  200  within the mandrel  100  may be employed. 
       FIG. 3  shows a mandrel/optic disc assembly  10  according to one embodiment including the mandrel  100  according to  FIG. 1  and the ring  200  according to  FIG. 2  holding a lens blank  204  onto the mandrel  100 . The ring  200  is formed with a ledge portion  202  on its inner circumference. The ledge portion  202  is configured to hold a lens blank  204  onto the mandrel  100  by pressing down on a top surface, second surface  210 , of the lens blank  204  while the bottom surface, first surface  208 , of the lens blank  204  is supported by the plurality of projections  112  of the mandrel  100 . As shown in  FIG. 3 , the central axis of the lens blank  204  is received concentrically with the central axis (X) of the mandrel  100  and is disposed over the hollow channel  116 . The lens blank  204  is preferably configured to occupy at least a portion of space formed by the central cavity  110  and a portion of space formed by the second cavity  114 . 
     In an exemplary embodiment, the ring  200  has a plurality of holes  212  formed along its inner periphery on an inner peripheral surface  201 . In this embodiment, the plurality of holes  212  are formed along the portion of the inner peripheral surface  201  that forms the ledge portion  202 . Preferably, the plurality of holes  212  are disposed symmetrically around the center of the ring  200 . In this embodiment, eight holes  212  are formed at approximately 45 degree intervals along the inner periphery of the ring  200  along the ledge portion  202 . In one exemplary embodiment, the diameter of each of the plurality of holes  212  is approximately 0.75 mm. 
     As discussed further below, the plurality of holes  212  form channels through which a liquid, preferably water, may be introduced into a space  405  formed below the first surface  208  of the lens blank  204  as the lens blank  204  is supported by the plurality of projections  112  of the mandrel  100  and held by the ring  200 . For the manufacturing of hydrophobic lenses from the lens blank  204  according to an exemplary embodiment, water is introduced through the plurality of holes  212  into the space  405  formed between the first surface  208  and the mandrel  100 . The water filled mandrel  100  is then cooled so that the water freezes to ice. The resulting ice provides stability to the lens blank  204  as the lens blanked  204  is milled. 
     A method of using the mandrel  100  for manufacturing a lens, such as an intraocular lens will now be described. 
     As shown in  FIG. 4A , a mandrel  100  according to one embodiment is placed in an ultra-precision collet  400 . In this exemplary embodiment, a lens blank  204 , for example, a hydrophobic optic disc  404 , is placed precisely on the central axis (X) of the mandrel  100 . The hydrophobic optic disc  404  described herein may be configured as described above with regard to the lens blank  204 . Placement of the hydrophobic optic disc  404  may be performed using an optical centering device, such as that described in commonly assigned U.S. Pat. No. 8,854,611, the entire contents of which are hereby incorporated by reference. 
     As shown in  FIGS. 4B and 4C , a compression ring  200  is then applied over the top surface  410  of the optic disc  404 , so as to hold the optic disc  404  in its precise location on the mandrel  100 . The bottom surface  408  of the optic disc  404  is supported on the mandrel  100  by the plurality of projections  112  formed on the bottom surface  120  of the central cavity  110  of the mandrel  100  to create a space  405 . In an exemplary embodiment, the space  405  is formed below the flat portion  412  of the optic disc  404  that will be milled to become the haptic of the intraocular lens and the top surface of the lens blank holding section  105  of the mandrel  100 . In one exemplary embodiment, the space  405  has a height of 0.250 mm. 
     The top surface  410  of the optic disc  404  may now be milled to form a lens such as an intraocular lens. One advantage provided by the embodiments described herein is that the mandrel/optic disc assembly comprising the mandrel  100  and the optic disc  404  (held precisely with the compression ring  200 ) can be packaged and shipped to other locations for completion of manufacturing to form lenses having desired optical characteristics. Additionally, because the mandrel/optic disc assembly is shelf-stable, it can be held in inventory for prolonged periods of time before completion of manufacturing. 
     At a desired time for manufacturing, the space  405  between the optic disc  404  and the surface of the lens blank holding section  105 , including the central cavity  110 , of the mandrel  100  is filled with a suitable liquid, preferably water  502 . For example, as illustrated in the embodiment depicted  FIGS. 5A and 5B , the mandrel/optic disc assembly may be inverted and the space  405  filled by submerging at least a portion of the head portion  102  of the mandrel  100  (in which the optic disc  404  is held) in a container  504  configured to hold water  502 . In this embodiment, water  502  may flow through the plurality of holes  212  in the ring  200  into the space  405  between a surface of the mandrel  100  and the optic disc  404 . The central channel  116  provides an outlet for air forced out of the space  405  as water  502  fills the space  405 . The hollow center channel  116  may be configured to communicate with an internal volume  130 . The filled mandrel/optic disc assembly may then be placed into a precision collet  400 , for example a milling collet  600 , for further processing. In this embodiment, water  502  is retained in the space  405  by surface tension as the mandrel  100  is removed from the container  504 . 
     As shown in  FIG. 6A , the liquid filled mandrel/optic disc assembly according to one embodiment is then cooled in order to freeze the liquid  502  in the space  405  between the optic disc  404  and the mandrel  100 . In this exemplary embodiment, the liquid filled mandrel  100  may be placed in a milling collet  600  and cooled with a cooling apparatus  605  configured to blow cold air over the mandrel/optic disc assembly in order to freeze the liquid  502  contained within the mandrel/optic disc assembly. In an alternative embodiment, the mandrel/optic disc assembly may be placed in a freezer. 
     The liquid  502  is frozen to form a solid surface (e.g., ice  607 ) within the mandrel/optic disc assembly as illustrated in  FIG. 6B . As the water  502  freezes and expands, it may flow through the plurality of holes  212  in the ring  200  and/or into the center channel  116  of the mandrel  100 . In this embodiment, the ice  607  surrounds at least the bottom surface  408  of the optic disc  404  and side surfaces  414  of the optic disc  404 , thereby holding the optic disc  404  firmly in place. The ice  607  provides enhanced stability for the optic disc  404  during milling. 
     As illustrated in the exemplary embodiment depicting a method of using the mandrel  100  for the manufacturing of a lens shown in  FIGS. 6C and 6D , the top (second) surface  410  of the optic disc  404  is milled with a precision mill  610 , such as a diamond end mill, to form haptic portions  614  and to complete the lens  612  including haptic portions  614  and optic portion  616 . Milling may include cutting through the optic disc  404  to form the haptic portions  614 . Preferably, the mill  610  is configured to cut through the optic disc  404  and into the ice  607  at defined locations to avoid damaging the underlying plurality of projections  112  configured to support the optic disc  404 . The ice  607  provides enhanced stability during milling. After milling, the water  502  is allowed to melt, and the finished lens  612  may be cleaned with more water, inspected, packaged and sterilized. 
     It will be appreciated by those of skill in the art that embodiments of the disclosed invention provides several advantages. For example, the mandrel  100  maintains the lens blank  204 , or optic disc  404 , in precise alignment to facilitate subsequent manufacturing of a lens  612 . Further, the mandrel  100  permits a lens blank  204 , or optic disc  404 , to be positioned on the mandrel  100  such that the position of the lens blank  204 , or optic disc  404 , may be maintained over a prolonged period of time before the completion of a lens  612 . Additionally, the lens blank holding section  105 , including the central cavity  110  and second cavity  114  formed within the mandrel  100 , may accommodate the formation of ice  607  to support the optic disc  404  during cryogenic milling. 
       FIG. 7  is a perspective view illustrating a finished lens  612  formed from a lens blank  204 , or optic disc  404 , and held within a mandrel  100  by a ring  200  according to one embodiment. As shown in  FIG. 7 , the meridian of haptics (M) formed by milling the optic disc  404  runs through the center of the surface of the mandrel  100  at a central axis (X) of the mandrel  100  and is parallel to one or more substantially planar side surfaces  104  of the mandrel head  102 . In an exemplary embodiment, the central axis (X) of the mandrel  100  may also include the central axis of the hollow mandrel shank  150  and/or the central axis of the lens blank  204 , optic disc  404 , or finished lens  612 . In this embodiment, the mandrel  100  has two parallel, planar side surfaces  104  including parallel lines P 1  and P 2 , respectively, as depicted in  FIG. 7 . 
       FIG. 8  is a top plan view illustrating the relative position of a finished lens  612  formed from a lens blank  204 , or optic disc  404 , as it is held within the mandrel  100  according to one embodiment. As shown in this embodiment, the optic disc  404  is centered precisely on the mandrel  100  and retained by the ring  200 . The plurality of projections  112  of the mandrel  100  are located outside of the portions of the finished lens  612  formed from the optic disc  404  that are milled or machined to form the intraocular lens  612 . For example, the haptic portions  614  extend between the plurality of projections  112 , which are disposed radially from the central axis (X) of the mandrel  100 . 
     While the mandrel  100  according to one embodiment may be used advantageously to cryogenically mill a lens  612 , the invention is not limited to the above described embodiments and a lens  612  may be formed in other ways using the mandrel  100 . As illustrated in the embodiment depicting a method of using the mandrel  100  for the manufacturing of a lens shown in  FIG. 9 , a mandrel/disc assembly according to some embodiments may be inserted into a vacuum collet  900 . In this embodiment, a lens  612  may be manufactured with a laser  910 . 
     In such an alternative process, it may not be necessary to introduce a liquid, such as water  502 , into the mandrel  100 . Accordingly, mandrels  100  according to this alternative embodiment may be used with lens blanks  204  formed of either a hydrophilic or a hydrophobic material. By affixing the lens blank  204  to the mandrel  100  with a ring  200  and supporting the lens blank  204  with a plurality of projections  112 , the use of a blocking material, such as wax (i.e., for use with hydrophilic lens materials) or ice  607  (i.e., for use with hydrophobic lens materials) may not be necessary. 
     From the foregoing description, it will be understood that mandrels according to the invention may be used to hold a lens blank with precise alignment for later manufacturing. Mandrels according to certain embodiments of the invention are particularly useful in holding an optic disc in which the optic has been preformed, whereby haptics can be formed with precision and surface features milled to adjust optical characteristics. However, it will be understood that mandrels according to the invention can be used to position and hold universal lens blanks or other lens materials. Although specific features of the invention are shown in some drawings and not others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject of the application are not to be taken as the only possible embodiments. 
     The construction and arrangement of the apparatuses and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g. variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangement of the exemplary embodiments without departing from the scope of the patent disclosure. 
     In addition, any amendment presented during the prosecution of the patent application for this invention is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant cannot be expected to describe certain insubstantial substitutes for any claim element amended. 
     REFERENCE NUMERALS 
     
         
           10  mandrel/optic disc assembly 
           100  mandrel 
           102  top/head portion the mandrel 
           104  planar side surfaces of mandrel 
           105  lens blank holding section 
           110  central cavity 
           112  plurality of projections 
           114  second cavity 
           116  center channel 
           118  sidewall of central cavity 
           120  bottom surface of central cavity 
           122  perimeter of the central cavity 
           130  internal volume 
           150  mandrel shank 
           200  compression ring 
           201  inner peripheral surface 
           202  ledge portion of ring 
           204  lens blank 
           208  first surface of lens blank 
           210  second surface of lens blank 
           212  ring holes 
           218  sidewall of ring 
           400  collet 
           404  optic disc  405  space formed below lens blank to receive liquid 
           408  bottom surface of optic disc 
           410  top surface of optic disc 
           412  flat portion of optic disc 
           414  side surface of optic disc 
           502  water 
           504  container 
           600  milling collet 
           605  cooling apparatus 
           607  ice 
           610  precision mill 
           612  lens 
           614  haptic portions 
           616  optic portion 
           900  vacuum collet 
           910  laser 
         X central axis of mandrel 
         M meridian of haptics 
         P 1  first parallel line 
         P 2  second parallel line