U.S. patent application number 12/371996 was filed with the patent office on 2009-06-11 for deformable molds and methods for their use in the manufacture of ophthalmic lenses.
Invention is credited to Zaffir A. Chaudhry, Mark A. Esley, Gregory J. Hofmann, Larry G. Jones, David Pearson, Jacqueline M. Roche, Jeffrey H. Roffman, Thomas R. Rooney.
Application Number | 20090146331 12/371996 |
Document ID | / |
Family ID | 33490947 |
Filed Date | 2009-06-11 |
United States Patent
Application |
20090146331 |
Kind Code |
A1 |
Hofmann; Gregory J. ; et
al. |
June 11, 2009 |
DEFORMABLE MOLDS AND METHODS FOR THEIR USE IN THE MANUFACTURE OF
OPHTHALMIC LENSES
Abstract
The present provides deformable molds and methods for
manufacturing ophthalmic lenses using deformable molds. The molds
of the invention may be used in the custom manufacture of
ophthalmic lenses.
Inventors: |
Hofmann; Gregory J.;
(Jacksonville Beach, FL) ; Rooney; Thomas R.;
(Jacksonville, FL) ; Pearson; David; (Hudson,
MA) ; Chaudhry; Zaffir A.; (South Glastonbury,
CT) ; Roche; Jacqueline M.; (Lunenburg, MA) ;
Roffman; Jeffrey H.; (Jacksonville, FL) ; Jones;
Larry G.; (Jacksonville, FL) ; Esley; Mark A.;
(Littleton, MA) |
Correspondence
Address: |
PHILIP S. JOHNSON;JOHNSON & JOHNSON
ONE JOHNSON & JOHNSON PLAZA
NEW BRUNSWICK
NJ
08933-7003
US
|
Family ID: |
33490947 |
Appl. No.: |
12/371996 |
Filed: |
February 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10881773 |
Jun 29, 2004 |
7516937 |
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12371996 |
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09649635 |
Aug 28, 2000 |
6830712 |
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10881773 |
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Current U.S.
Class: |
264/2.2 |
Current CPC
Class: |
B29D 11/00125 20130101;
Y10T 74/20582 20150115; B29D 11/00557 20130101; Y10T 74/165
20150115; B29D 11/00432 20130101; Y10S 425/808 20130101; B29D
11/023 20130101 |
Class at
Publication: |
264/2.2 |
International
Class: |
B29D 11/00 20060101
B29D011/00 |
Claims
1. A process for manufacturing an ophthalmic lens, comprising the
steps of: a.) providing a casting cup comprising: (i) a non-molding
surface and a molding surface, wherein at least a portion of the
molding surface is capable of being reversibly deformed and (ii.)
adjustment means for reversibly deforming the deformable portion of
the molding surface; and b.) deforming the deformable portion of
the molding surface to a shape suitable for imparting one or more
optical characteristics onto a lens surface.
2. The process of claim 24, further comprising the steps of: c.)
depositing a lens-forming material on the molding surface; and d.)
curing the lens-forming material under conditions suitable to form
the ophthalmic lens.
3. The process of claim 24, further comprising: c.) measuring a
wavefront shape for the molding surface; d.) using the adjustment
means to change the shape of the molding surface; e.) depositing a
lens-forming material on the molding surface mold; and f.) curing
the lens-forming material under conditions suitable to form the
ophthalmic lens.
4. The process of claim 25, wherein the lens-forming material is
selected from the group consisting of acquafilcon, etafilcon,
genfilcon, lenefilcon, senefilcon, balafilcon, lotrafilcon, and
galyfilcon.
5. The process of claim 26, wherein the lens-forming material is
selected from the group consisting of acquafilcon, etafilcon,
genfilcon, lenefilcon, senefilcon, balafilcon, lotrafilcon, and
galyfilcon.
6. The process of claim 24, further comprising the step of
attaching a plurality of pusher pins to the non-molding
surface.
7. The process of claim 24, further comprising attaching a
plurality of pusher pads to the non-molding surface.
8. The process of claim 29, further comprising attaching a
plurality of pusher pads to the non-molding surface.
9. A process for manufacturing a contact lens, comprising the steps
of: a.) providing a casting cup comprising: (i) a non-molding
surface and a molding surface, wherein at least a portion of the
molding surface is capable of being reversibly deformed and (ii.)
adjustment means for reversibly deforming the deformable portion of
the molding surface; b.) deforming the deformable portion of the
molding surface to a shape suitable for imparting one or more
optical characteristics onto a lens surface c.) measuring a
wavefront shape for the molding surface; d.) using the adjustment
means to change the shape of the molding surface; e.) depositing a
lens-forming material on the molding surface mold; and f) curing
the lens-forming material under conditions suitable to form the
ophthalmic lens.
10. A process for manufacturing a contact lens, comprising the
steps of: a.) providing a casting cup comprising: (i) a non-molding
surface and a molding surface, wherein at least a portion of the
molding surface is capable of being reversibly deformed and (ii.)
adjustment means for reversibly deforming the deformable portion of
the molding surface; b.) deforming the deformable portion of the
molding surface to a shape suitable for imparting one or more
optical characteristics onto a lens surface c.) depositing a
lens-forming material on the molding surface; and d.) curing the
lens-forming material under conditions suitable to form the
ophthalmic lens.
Description
RELATED APPLICATIONS
[0001] This application is a Divisional Application of co-pending
U.S. patent application Ser. No. 10/881,773 filed on Jun. 29, 2004,
which is a continuation-in-part of U.S. Pat. No. 6,830,712 granted
Aug. 28, 2000.
FIELD OF THE INVENTION
[0002] The present invention relates to the manufacture of
ophthalmic lenses. In particular, the invention provides deformable
molds and methods for manufacturing ophthalmic lenses using
deformable molds.
BACKGROUND OF THE INVENTION
[0003] The use of ophthalmic lenses, including spectacle lenses,
contact lenses, intraocular lenses, and the like for the correction
of ametropia is well known. Production of the lenses requires the
use of molds that impart the desired corrective characteristics
onto the lens surfaces. Typically, a large inventory of molds is
required corresponding to each sphere, add, and cylinder power and
combinations thereof desired for the finished lens. Production and
maintenance costs for the mold inventory are high. Therefore, a
need exists for a mold to produce ophthalmic lenses that permits
reduction of mold inventory.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a plan view of a mold of the invention.
[0005] FIG. 2 is an elevated cross-sectional view of the mold of
FIG. 1.
[0006] FIG. 3 is an elevated side view of a portion of the mold of
FIG. 1.
[0007] FIG. 4 is an elevated side view of an embodiment of a
casting cup used in the mold of FIG. 1.
[0008] FIG. 5 is a cross section of another embodiment of a casting
cup used in the mold of FIG. 1.
[0009] FIG. 6 is an elevated side view of a mold tray useful in the
mold of FIG. 1.
[0010] FIG. 7 is a flow diagram of a process for molding a lens
using the mold of FIG. 1.
[0011] FIG. 8 is a diagram of electronic equipment used in one
embodiment of a method for using the mold of FIG. 1.
[0012] FIG. 9 is a second embodiment of a mold of the
invention.
[0013] FIG. 10 is a flow diagram of a process for using the mold of
the invention.
DESCRIPTION OF THE INVENTION AND ITS PREFERRED EMBODIMENTS
[0014] The present invention provides deformable molds, and methods
using the molds, for producing ophthalmic lenses. The invention
permits the production of a full prescriptive range of lenses while
reducing the number of molds required. Further, the molds of the
invention may be used in a method for the delivery of customized
ophthalmic lenses to a lens wearer.
[0015] In one embodiment, the invention provides a mold for use in
the manufacture of ophthalmic lenses comprising, consisting
essentially of, and consisting of: a.) at least one mold half
comprising, consisting essentially of, and consisting of a
non-molding surface and a molding surface, wherein at least a
portion of the molding surface is capable of being reversibly
deformed; and b.) adjustment means for reversibly deforming the
deformable portion of the molding surface. For purposes of the
invention, by "ophthalmic lens" is meant a spectacle lens, a
contact lens, an intraocular lens, or the like.
[0016] The non-molding surface of the mold half is contacted with
the adjustment means and the molding surface contacts an ophthalmic
lens-forming material. At least a portion of the molding surface is
capable of being reversibly deformed and has a first shape that may
be of any shape, but conveniently is of a concave or convex shape
having a first radius of curvature R.sub.1. This deformable portion
of the molding surface is capable of being reversibly deformed by
action of the adjustment means against the non-molding surface so
that the deformable portion assumes a shape that is desired to be
imparted to at least a portion of one surface of the ophthalmic
lens to be produced in the mold. The assumed shape is such that it
can impart the desired optical characteristics to the lens.
[0017] By "optical characteristics" is meant one or more of
spheric, aspheric, toric, or cylindric curvature, high order
aberration correction, corneal topography aberration corrections,
and the like and combinations thereof. The optical characteristic
imparted will depend on the aberrations of the lens wearer's eye
desired to be corrected. The mold of the invention is suitable for
producing lenses for correction of either or both low and high
order wavefront aberrations of the eye, meaning any departure from
a spherical wavefront. These aberrations include, without
limitation, astigmatism, defocus, coma, spherical aberrations,
distortion, and the like. These aberrations may be mathematically
defined using known methods including, without limitation, using
Zernike polynomials.
[0018] The molding surface may be formed by any material capable of
being reversibly deformed, capable of withstanding the stresses
imposed by the lens manufacturing process selected and capable,
when deformed, of maintaining a shape suitable for imparting the
desired optical characteristics to the lens surface to be molded.
If the lens is to be formed using an ultra-violet or visible light
cure, the material preferably is transmissive of light between
about 250 and 500 nm. Additionally, the molding surface must be
compatible with the material from which the lens is to be molded.
Factors for determining whether the mold surface material is
compatible include, without limitation, whether the material
adheres to the lens-forming material and whether the material
chemically reacts with the lens-forming material.
[0019] Suitable molding surface materials include, without
limitation, metals, polymers, metalized polymers and the like and
combinations thereof. Exemplary of these materials are: aluminum,
gold, brass, and nickel metals; polyolefin polymers including,
without limitation, polyethylene and polypropylene, polyethylene
terphthalate; poly(vinylidene fluoride); poly(vinyl chloride);
polystyrenebutadiene; silicone polymers; electro-active polymers
such as polyanilines, polypyrroles, ion exchange polymer metal
matrix compositions and the like; shape-memory polymers such as
segmented polyurethanes, norbornene homopolymers and copolymers of
norbornene and alkylated, cyano, alkoxylated, mono- or diesterified
imides, or carboxylic acid derivatives and the like; shape-memory
alloys such as nitinol, and the like; ceramics such as silicon
carbide; and combinations thereof. These materials are commercially
available or methods for their production are known.
[0020] The molding surface must have an optical quality surface
finish meaning that it is sufficiently smooth so that a lens
surface formed by the polymerization of a lens forming material in
contact with the molding surface is optically acceptable. The
non-molding surface need not have an optical quality finish.
However, the non-molding surface must be sufficiently pliant,
flexible, and durable to enable its repeated contact with, and
action upon it by the adjustment means selected.
[0021] The size, shape, and thickness of the molding surface,
singly or in combination with the non-molding surface, will be
dependent on the type of lens to be produced. Preferably, the
molding surface, singly or in combination with the non-molding
surface, is in the form of a membrane, more preferably a polymeric
membrane. In a most preferred embodiment, the molding surface is a
membrane of a size and shape suitable for production of a soft
contact lens and is about 0.5 to about 5000, preferably 1 to about
1000 microns in thickness.
[0022] Adjustment means contact the non-molding surface of the mold
of the invention under conditions suitable to deform the deformable
portion of the molding surface to the desired shape. Adjustment
means may be any means capable of manipulating and deforming the
deformable portion of the molding surface to the degree necessary
to obtain the desired molding surface configuration. Examples of
such adjustment means include, without limitation, fluids,
micro-actuators, such as piezo-electric, micro-motorized, or
hydraulic micro-actuators, magneto-restrictive actuators,
electrostatic actuators, elector-restrictive actuators,
electro-active polymers, and the like that move in response to an
input signal. For example, by varying the voltage applied to a
series of piezo-electric micro-actuators, the deformable portion of
the molding surface may be displaced so that it assumes a desired
shape.
[0023] Preferably, the actuators are made of a suitable
electro-restrictive material including, without limitation,
lead-magnesium-niobate, lead-magnesium-niobate-titanate, and
electrorestrictive polymers including, without limitation,
poly(vinylidene fluoride-trifluoroethylene), and the like and
combinations thereof.
[0024] In embodiments in which micro-actuators are used, spacing of
the actuators may be determined by the resolution requirement of
the lens surface to be formed. The resolution requirements will be
determined by the features desired to be imparted onto the lens
surface. The adjustment means may be used in combination with heat
to alter the molding surface's shape. In this embodiment, heat is
used so as to raise the temperature of the molding surface to above
its glass transition temperature, the heat being provided into the
mold by any convenient known means. However, it is preferred that
only the adjustment means are used.
[0025] As an alternative to the micro-actuators, the adjustment
means may be a mechanical magnetic field deformation means. In this
embodiment, a first magnetic surface contacts the non-molding
surface. Preferably, the magnetic surface is of a shape that is
complementary to the non-molding surface. The magnetic surface may
be constructed of any magnetic material capable of withstanding the
molding process environment and, preferably, is of a material that
is capable of being physically or chemically bonded to the
non-molding surface. Suitable materials include, without
limitation, magnetic ferrous steels, cast or sintered alnicos,
bonded or sintered ferrites, lodex, P-6 alloy, cunife, cunico,
vicalloy, remalloy, platinum cobalt, cobalt-rare earth blends, and
the like and combinations thereof.
[0026] A second magnetic surface is brought into sufficient
proximity to the first magnetic surface to exert a magnetic force
upon the first surface that is effective to impart a desired shape
to the first magnetic surface and, through that surface, to the
molding surface. The second magnetic surface may be positioned by
any convenient positioning means including, without limitation, a
robotic arm, a gripper, an adjustable mechanical arm, or the like
or a combination thereof. Either or both the first and second
magnetic surfaces may be a formed of a series of
electromagnets.
[0027] Conditions suitable to deform any of the adjustments means
used in the invention will depend upon a number of factors. These
factors include the type of adjustment means used, the materials
selected to form the molding and non-molding surfaces, and the
shape desired to be imparted to the lens surface by the molding
surface.
[0028] In the molds of the invention, input signals to the
adjustment means may be, and preferably are, the distortions or
aberrations of the eye for which the lens is being manufactured to
correct. Clinical wavefront sensors, such as aberroscopes,
Hartmann-Shack devices and mirror arrays capable of measuring these
high order aberrations, as well as conventional low order
aberration measurement equipment such as a phoropter, are
commercially available. The wavefront data, or measured
aberrations, may be represented by a set of mathematical
coefficients, such as Zernike coefficients, that may be used to
form the input signals that drive the adjustment means. The
adjustment means contact a portion or the whole of the non-molding
surface and, by action on that surface, deform the deformable
portion of the molding surface so that the surface is capable of
imparting one or more optical characteristics onto all or a portion
of a surface of the lens to be formed within the mold.
Configuration of software suitable for processing and inputting the
signals for purposes of driving the adjustment means is within the
skill of one ordinarily skilled in the art.
[0029] The data obtained through the use of the wavefront sensors
may be reported in mathematical, as for example by Zernike
coefficients. This data then is converted mathematically into an
elevation map above and below a designated mean sphere value to
obtain the optical path difference. These elevations are then used
to determine the shape to be imparted to a surface of the lens. For
the manufacture of contact lenses, these elevations preferably will
be used to determine the shape of the front or object side surface
of the lens.
[0030] In addition to optical characteristics, the molding surface
may be used to impart a geometry to a surface of a contact lens
that substantially inversely corresponds with that of the lens
wearer's cornea. This function of the mold of the invention may
find its greatest utility in the manufacture of contact lenses. The
corneal topographic data for the lens wearer may be acquired using
conventional topographers. Preferably, these data are used to
produce a back surface design for a contact lens that is a
substantial mirror image of the corneal topography. By "mirror
image" is meant that the back surface substantially inversely
corresponds to the corneal topography and is superimposable on the
corneal topography. Alternatively, the data may be applied to a
soft contact lens model in an unflexed state and then by taking
into account lens flexure when the lens is placed onto the wearer's
eye.
[0031] For contact lenses, preferably, corneal data is used to
determine the elevation map of the lens' back surface. Mapping of
the corneal elevation onto the lens surface may be carried out by
any known method. For soft contact lens production, preferably,
mapping is carried out so that the error introduced by flexure of
the lens is minimized. In this method, the corneal elevation data
is applied to a soft contact lens in the unflexed state. The
elevation data is then transformed by taking into account lens
flexure.
[0032] In this method, for practical considerations, it is assumed
that the ideal cornea is spherical and that the actual corneal
elevations and their best spherical fit are denoted f(x) and g(x),
the function g(x) being part of a sphere having radius R.sub.a. In
general, the radius R.sub.b of an unflexed soft contact lens is
spherical and is larger than that of the best spherical fit g(x).
The first step is to transform the corneal elevations f(x) into a
larger scale for which the best spherical fit will have a radius
equal to R.sub.b. One approach in simplifying the transformation is
to represent the function f(x) in polar coordinates as f(.theta.).
Then using the scale factor .alpha.=R.sub.b/R.sub.a, the scaled
version of the corneal elevation may be expressed as
f.sup.(1)(.theta.)=.alpha.f(.theta.) (I)
[0033] In the second stage, the scaled corneal elevation,
f(.theta.), is scaled down so that the area covered by the soft
contact lens corresponds to the area of the cornea. In a two
dimensional case, this scaling down is obtained according to the
following relationship:
f.sup.(2)(.theta.)=.alpha..sup.-1f.sup.(1)[(.theta.)-.pi./2]+R.sub.b(1-1-
/.alpha.) (II)
[0034] The mapping transformations given in the above equations are
not restricted to the case in which the cornea and the back surface
of the contact lens are spherical. Rather, the true corneal and
lens curvatures may be used to calculate the scale parameter
.alpha. as a ratio between the lens and the corneal radius of
curvature. In the general case, the scale parameter will be a
function of .theta., i.e.,
.alpha.=R.sub.b(.theta.)/R.sub.a(.theta.)=.alpha.(.theta.).
[0035] The mapping transformation discussed above may be
generalized to the case of three dimensional transformation. In
such a case, the corneal elevations may be represented by a
function, f(.theta.,.phi.) where .theta. and .phi. represent the
azimuth and elevation angle, respectively. The original elevation
data is scaled up from the radius of curvature R.sub.a
(.theta.,.phi.) using the following transformation
relationship:
f.sup.(1)(.theta.,.phi.)=.alpha.f(.theta.,.phi.) (III)
where .alpha.=R.sub.b (.theta.,.phi.)/R.sub.a (.theta.,.phi.)
[0036] To obtain a desired back surface of the lens, the functional
f.sup.(1)(.theta.,.phi.) is scaled back down. However, in the three
dimensional case, there are a number of options to choose from in
performing the scaling operation such that the area is preserved.
For example, if it is assumed that the deformation of the material
is uniformly radial, the scaling mat be performed by scaling the
elevation angle only, leaving the original azimuth angle. This is
expressed in the following relationship:
f.sup.(2)(.theta.,.phi.)=.alpha..sup.-1f.sup.(1)[.theta.,
(.phi.-.pi./2)/.alpha.+.pi./2]+R.sub.b(1-1/.alpha.) (IV)
[0037] Once the molding surface is deformed to the desired shape,
the surface may be used to mold the desired lens. Therefore, in
another embodiment, the invention provides a process for
manufacturing an ophthalmic lens comprising, consisting essentially
of, and consisting of the steps of: a.) providing a mold, at least
one half of the mold comprising, consisting essentially of and
consisting of (i.) a non-molding surface and a molding surface,
wherein at least a portion of the molding surface is capable of
being reversibly deformed and (ii.) adjustment means for reversibly
deforming the deformable portion of the molding surface; b.)
deforming the deformable portion of the molding surface to a shape
suitable for imparting one or more optical characteristics onto a
lens surface; c.) depositing a lens-forming material on the molding
surface mold; and d.) curing the lens-forming material under
conditions suitable to form the ophthalmic lens.
[0038] Lens-forming material may be deposited on the molding
surface by any suitable means. The volume of lens-forming material
dispensed into the cavity will be a lens forming amount which is an
amount effective to form the desired ophthalmic lens. Typically,
the amount of material deposited used will be about 0.01 mg to
about 100 g.
[0039] The lens-forming material may be any material suitable for
forming an ophthalmic lens. Exemplary spectacle lens-forming
materials include, without limitation, polycarbonates, such as
bisphenol A polycarbonates, allyl diglycol carbonates, such as
diethylene glycol bisallyl carbonate (CR-39.TM.), allylic esters,
such as triallyl cyanurate, triallyl phosphate and triallyl
citrate, acrylic esters, acrylates, methacrylates, such as methyl-
ethyl- and butyl methacrylates and acrylates, styrenics,
polyesters, and the like and combinations thereof. Additionally,
the lens forming material may be one or more of the phosphine
oxides disclosed in U.S. Pat. No. 6,008,299 incorporated herein in
its entirety by reference.
[0040] Suitable lens-forming materials for contact lenses are any
materials useful for forming hard or soft contact lenses.
Preferably, the lens-forming material is suitable for forming a
soft contact lens. Illustrative materials for formation of soft
contact lenses include, without limitation silicone elastomers,
silicone-containing macromers including, without limitation, those
disclosed in U.S. Pat. Nos. 5,371,147, 5,314,960, and 5,057,578
incorporated in their entireties herein by reference, hydrogels,
silicone-containing hydrogels, and the like and combinations
thereof. More preferably, the material is a siloxane, or contains a
siloxane functionality, including, without limitation, polydimethyl
siloxane macromers, methacryloxypropyl polyalkyl siloxanes, and
mixtures thereof, silicone hydrogel or a hydrogel, made of monomers
containing hydroxy groups, carboxyl groups, or both or be made from
silicone-containing polymers, such as siloxanes, hydrogels,
silicone hydrogels, and combinations thereof. Materials for making
soft contact lenses are well known and commercially available.
Preferably, the material is acquafilcon, etafilcon, genfilcon,
lenefilcon, senefilcon, balafilcon, lotrafilcon, or galyfilcon.
[0041] Suitable materials for forming intraocular lenses include,
without limitation, polymethyl methacrylate, hydroxyethyl
methacrylate, inert clear plastics, silicone-based polymers, and
the like and combinations thereof.
[0042] Curing of the lens forming material deposited within the
mold may be carried out by any means known including, without
limitation, thermal, irradiation, chemical, electromagnetic
radiation curing and the like and combinations thereof. Preferably,
molding is carried out using ultraviolet light or using the full
spectrum of visible light.
[0043] More specifically, the conditions suitable for curing the
lens-forming material will depend on the material selected and the
lens to be formed. For formation of spectacle lenses, a preferred
curing condition is a two-stage UV cure in which the mold assembly
is exposed to low intensity and then high intensity ultraviolet
light. Low intensity UV light is UV light with an intensity of
about 0.5 to about 50, preferably about 1 to about 5 mW/cm.sup.2.
High intensity UV light is of an intensity of about 50 to about
2000, preferably 500 to about 1500 mW/cm.sup.2. The wavelengths at
which the exposures are carried out may be, and preferably are, the
same. Suitable wavelengths are about 300 to about 450, preferably
about 360 to about 400 nm. The time for the low intensity exposure
will depend on the lens-material selected, the type and amount of
any initiator used, material viscosity and the nature of its
reactive groups, and the intensity of the UV light. Subsequent to
the termination of the low intensity exposure, the mold assembly is
exposed to high intensity UV light under conditions suitable to
complete through-cure of the lens-forming. The same factors
determinative for low intensity exposure time are determinative for
the high intensity exposure time. Both high and low intensity
exposure may, and preferably are, carried out as single, continuous
exposures.
[0044] However, the exposures also may be carried out using
alternating periods of UV exposure and non-exposure periods. The
low and high intensity polymerization steps may be carried out at a
temperature between about 10 to about 50.degree. C. and atmospheric
pressure, preferably at ambient temperature. The UV exposure may be
used alone or in combination with heat.
[0045] Polymerization processes for contact lenses are well known.
Suitable processes are disclosed in U.S. Pat. No. 5,540,410
incorporated herein in its entirety by reference. For formation of
contact lenses, a preferred curing condition is to pre-cure the
mold assembly using UV light with an intensity of about 2 to about
10 mW/cm.sup.2. Following the pre-cure, the mold assembly is
exposed to UV light of an intensity of about 0 to about 4.0
mW/cm.sup.2. Suitable wavelengths are about 300 to about 500 nm.
The time for the low intensity exposure will depend on the
lens-material selected, the type and amount of any initiator used,
material viscosity and the nature of its reactive groups, and the
intensity of the UV light. Both pre-cure and subsequent UV exposure
may, and preferably are, carried out as single, continuous
exposures. However, the exposures also may be carried out using
alternating periods of UV exposure and non-exposure periods. The
polymerization steps preferably is carried out at a temperature
between about 40 to about 75.degree. C. and atmospheric pressure
preferably under a blanket of nitrogen gas. Total cure time is
between about 300 to about 500 seconds.
[0046] Once the curing is completed and the formed lens is removed
from the mold, the adjustment means may be manipulated so that the
molding surface returns to its original shape or assumes another
shape for use in molding of a lens of another prescription.
Alternatively, in the case that the molding surface is a polymeric
membrane, all or a portion of the molding surface first may be
deformed by the adjustment means, heated to above the molding
surface material's Tg, subsequently cooled, and then used in lens
molding. The cooled molding surface may be removed from the
adjustment means for use. Once molding is completed, the molding
surface may be disposed of or, and preferably, reused by use of
heat and the adjustment means to configure the surface to the
original shape or another desired shape.
[0047] In FIG. 1 is depicted a preferred mold half of the
invention. An outer cover, which is not shown, preferably surrounds
the mold half The mold half includes flexure mounting plate 14 and
mounting plate 17 which are connected by a plurality of standoffs
16. Mold tray 12, which holds lens casting cup 28, is mounted onto
flexure mounting plate 14. Clamping plate 13 is attached to mold
tray 12 and clamping plate 13 holds mold tray 12 against lens
casting cup 28. Mounting plate 17 is seated within back cover 18.
An electrical connector 19 extends outwardly from the inferior-most
portion of back cover 19. Electrical links to the micro-actuators
15 are fed through back cover 18 into electrical connector 19. For
purposes of attaching mold parts together, preferably nuts, bolts,
machine screws, tapped holes, and the like are used.
[0048] FIG. 2 is a cross-sectional view of the mold of FIG. 1. At
either end of micro-actuators 15 are attached mounting tabs 24. At
the inferior end of actuator 15, mounting tab 24 attaches to
actuator mounting bracket 25, which is attached to mounting plate
17. Preferably, mounting bracket 25 is removably attached to
mounting plate 17 allowing for removal of individual actuators from
the mold half. At the superior end of the actuator 15, mounting tab
24 attaches the actuator to mechanical lever 21, which mechanical
lever 21 is shown in close-up in FIG. 3.
[0049] For purposes of this embodiment of the invention, the
micro-actuators preferably are made from an electro-restrictive
material. Electro-restrictive materials are materials that are
capable of expanding, or exhibiting strain, when an electric field
is applied across the material.
[0050] As shown in FIG. 3, mechanical lever 21 contains pivot point
27 that attaches lever 21 to flexure mounting plate 14. Micro-clamp
20 in mechanical lever 21 is used to hold pusher pin 26 in place so
that when the mold is being utilized, mechanical lever 21 can make
a connection between pusher pin 26 and actuator 15 through flexure
plate 14. More specifically, in response to the actuator,
mechanical lever 21 moves the pusher pin upwardly so that the
pusher pin exerts pressure on the non-molding surface of the
casting cup.
[0051] In FIG. 4 is shown lens casting cup 28 used in the mold half
of FIG. 1. The shown casting cup 28 has a front to back surface
thickness of approximately 0.6 mm. Casting cup 28 has lens molding
surface 11 and a non-molding surface opposite the molding surface.
Pusher pins 26 are removably attached to the non-molding surface of
casting cup 28 prior to use of the mold. In the embodiment shown,
the pusher pins are evenly spaced along a 9 mm diameter circle that
is concentric with the optical axis of casting cup 28. However, one
ordinarily skilled in the art will recognize that the number of
pusher pins 26 used will be determined by a consideration of a
variety of factors including the design desired to be imparted to
molding surface 11, size of the pusher pins 26, thickness of the
casting cup 28, and the molding surface 11 material.
[0052] Casting cup 28, molding surface 11, and the non-molding
surface preferably are made from STYROLUX.TM., a
polystyrenebutadiene available commercially from BASF. Preferably
molding surface 11, and more preferably the entire casting cup 28,
are made from a material that is compatible with the lens forming
material to be used and has the following properties: an elastic
modulus of about 1,250 psi to about 5,250 psi (according to ASTM D
638-01, cross head speed 0.2 to 2 in./min., yield stress determined
at yield point, elongation determined at yield point, and modulus
measured between 0.0005 and 0.005 strain); a yield point such that
at the material recovers its original shape after being subjected
to strains that change the original shape by at least 5%; a yield
stress of greater than about 1500 psi, preferably greater than
about 5000 psi, more preferably greater than about 16,000 psi
measured according to ASTM D 638-01; and a light transmittance in
the range of about 100 to about 400 nm, preferably about 290 to
about 400 nm. Suitable materials meeting these criteria include,
without limitation, STYROLUX, polypropylene, poly(vinylidene
fluoride), poly(vinyl chloride), and the like and combinations
thereof. Molding surface 11 preferably has a RMS roughness of about
25.+-.5 nm or less and a surface energy of about 30.+-.2 dynes/cm
or less. Casting cup 28 may be made by any convenient manufacturing
method, but preferably is injection molded.
[0053] In a preferred embodiment, casting cup 28 includes pusher
pads 31 on non-molding surface 29 as shown in FIG. 5. In this
embodiment, each of pusher pins 26 attaches to casting cup 28 at a
pusher pad 31. The pusher pads provide increased surface area to
facilitate connection of the pusher pins to casting cup 28.
[0054] In operating the mold half of FIG. 1, pusher pins 26 are
attached to non-molding surface 29 of casting cup 28. The desired
number and placement of the pusher pins will depend upon the lens
geometry desired. The casting cup is then seated in opening 34, of
mold tray 12, and the lower portions of the pusher pins are put
through holes 33 of mold tray 12 and into a micro-clamp 20, which
opening 34 and holes 33 are shown in the elevated side view of mold
tray 12 in FIG. 6. Clamping plate 13 is then attached and cam screw
32 of micro-clamp 20 is tightened to a desired torque to hold
pusher pin 26. Preferably, micro-actuators 15 are biased to about
1/2 of their full voltage before the cam screw is tightened so that
the actuators will contract and a pulling force will be exerted on
molding surface 11 when the voltage is lowered.
[0055] A flow diagram of a process for molding a lens using lens
mold 10 is shown in FIG. 7. Once the casting cup 28 is in place
(701), a measurement of the global deformation, or influence
function, of the mold surface is carried out (702) using an
interferometer. In step 703, the desired lens design is uploaded
and a first measurement is made of molding surface 11 using any
suitable measuring device. Referring to FIG. 8, a preferred device
for measuring molding surface 11 is a phase-shifting interferometer
such as a Zygos HS GPI 1000. Interferometer 40 measures the shape
of the wave front associated with molding surface 11 and provides
this information to a mold computer 42. The computer may be any
commercially available computer equipped with a National
Instruments Board PCI6703 Static Analog Voltage Output 16 bit 110V.
Mold computer 42 compares the measured shape with the desired shape
and, in step 704, calculates the commands for amplifier 43 to
provide the appropriate voltage to micro-actuators 15 to change the
shape of molding surface 11. Once the voltage has been sent, step
705, to micro-actuators 15, in step 706 a second measurement of
molding surface 11 is made using interferometer 40. A determination
is made in step 707 as to whether molding surface 11 is the desired
shape. If the desired shape has been attained, mold 10 is ready to
be used to cast lenses in step 708. If the desired shape has not
been attained, steps 704 through 707 are repeated until that shape
is attained. The software useful for carrying out this process is
known as, for example, commercially available software such as
MATLAB.TM..
[0056] It may be assumed that each point on molding surface 11
overlaying a micro-actuator 15 would be moved to a location
dictated solely by the desired molding surface design and location
of the actuator. In that case, many actuators would be necessary
and the molding surface would need to be of a stiffness such that
the surface deformations brought about by the actuators are local.
However, it is one discovery of the invention that one need not
rely on moving each micro-actuator to a location coincident with
the design being replicated on the molding surface. Rather, by
selecting the molding surface so that it has a modulus and
thickness that, when deformation is caused by a micro-actuator, the
deformation is not local, complicated surfaces may be replicated on
the molding surface through the linear combination of the
deformations of a few micro-actuators, or degrees of freedom.
[0057] To determine how much each micro-actuator is to be moved so
that the sum of the deformations combines to replicate the desired,
shape, or design, on the molding surface, the design may be treated
as a vector and the deformations of each actuator as a basis
vector. The extent to which the micro-actuators need to be moved,
or voltage required, thus can be determined using linear algebra
and Least-Squares curve fitting. In carrying out this method, first
the deviation of each actuator as a function of the applied bias
voltage is measured. Typically, this curve is non-linear, but can
be made linear using a high order polynomial transfer function that
maps the actual applied bias voltage to a dummy voltage with the
deviations being a linear function of the dummy voltage.
[0058] The deformation of the entire molding surface due to a
particular actuator is measured as a function of the dummy voltage.
The shape of this global deformation, or influence function,
depends on the mechanical properties and thickness of the casting
surface along with the manner in which the actuator is attached to
the non-molding surface, the molding surface geometry, and the
location of the actuator. It is assumed that the influence function
varies linearly with the dummy voltage.
[0059] As an example, it is desired to replicate a design inversely
corresponding to an individual eye's corneal topography using a
mold employing eight micro-actuators. In this case, the molding
surface's design may be described as a grid that is composed of 28
equally spaced concentric circles and 24 radial meridians. This
grid is selected based on a consideration of the resolution of the
device used to measure the topography of the eye, 28 circles used
by the Keratron, and the device used to make mold inserts, 24
meridians used by VariForm lathe.
[0060] Each design may be thought of as a 672 row vector
(28.times.24=672), which is referred to as D. The influence
functions may be thought of as a set of basis vectors from which,
in principle, the design may be constructed by a proper choice of
coefficients. For example, consider each of the eight influence
vectors, based on the use of 8 actuators, as a 672.times.1 column
vector and that these may be arranged as the columns of a
672.times.8 matrix, referred to as R, the influence factors being a
response to a limit value of the dummy voltage. Thus, a particular
design may be given as:
D=RA (V)
and is solved for A using a Least-Squares method that determines
the values of A that minimize the norm of the vector D-RA. For
purposes of the equation, A is an 8 by 1 column vector of the dummy
voltages. To generate a particular design D, each actuator i is
biased at a voltage given by the Equation:
V.sub.i=g.sup.-1(A.sub.i) (VI)
wherein A.sub.i is the elements of the matrix A given by
A=(R.sup.TR).sup.-1 D; and g is a function that maps the real
voltage to a dummy voltage. The above Least-Squares problem also
may be solved using QR or singular value decomposition.
Alternatively, the problem may be reformulated as a weighted
Least-Squares problem with weight given to particular points on the
grid.
[0061] Alternatively, actuator movement may be determined by
techniques useful in controlling deformable mirrors. The
deformation of the molding surface due to an individual
micro-actuator, or influence function, may be measured and
decomposed into Zernike components so that:
INF.sub.i=.SIGMA.s.sub.jZ.sub.j (VII)
wherein INF is the influence function; i is the ith micro-actuator
influence function; s.sub.j is the coefficient of the jth Zernike
polynomial; and the sum is over N Zernike terms.
[0062] Each influence function can be though of as a 1.times.N
vector in which the corresponding Zernike coefficients are the
vector components. These influence functions may be arranged into a
matrix, R, in which the columns of the matrix are the transpose of
the INF vectors:
R=(INF.sub.1.sup.T INF.sub.2.sup.T . . . INF.sub.N.sup.T)
(VIII)
A particular mold design, D, may be thought of a N.times.1 vector
similar to that described for the influence functions. That is, the
design is decomposed into N Zernike terms and the Zernike
coefficients are then the vector components where the Zernike
coefficients are not necessarily the same as those found for the
influence functions.
[0063] The voltage that needs to applied to each micro-actuator may
be found by determining the components of the vector, V, that
minimize the norm of the vector equal to RV-D, where V is a
N.times.1vecotr the components of which are the voltages to which
each micro-actuator is to be set in order to replicate the design.
This may be carried out by using any convenient method including,
without limitation, QR decomposition or singular value
decomposition.
[0064] In practice, the influence functions may not be linearly
independent. Additionally, there may be some hysteresis in the
stroke of the actuator and some creep in the molding surface
material. Thus, a feedback loop between a device suitable for
measuring the surface, or associated surface wavefront, such as an
interferometer, and the routine that controls the actuators may be
used to alleviate these problems.
[0065] The fit for a design is performed over some aperture,
typically about 6 mm to about 7 mm. The solution to the above
equation is arrived at iteratively with the convergence criteria
set by either a minimum RMS error or maximum number of
iterations.
[0066] The molds of the invention may be composed of two mold
halves, each of which has a deformable molding surface.
Alternatively, one mold half may have a deformable mold surface and
the other mold half may have a fixed molding surface. For the mold
half of FIG. 1, the complementary mold half preferably is a
polypropylene mold half. Suitable methods and materials for forming
such fixed molding surfaces are well known in the art. The mold
halves may be brought into contact for purposes of molding the lens
using any suitable contacting means including, without limitation,
stepper motors, screw drives, or the like, and combinations
thereof. When positioned for molding of the lens, the mold halves
may contact one another. In this case, preferably a sealing means
is used to seal the molds so that an acceptable lens edge is
formed. Suitable sealing means include, without limitation, a
gasket, o-ring, and the like, and combinations thereof. If the mold
halves do not contact each other, preferably a mask is used to
expose only those areas at which polymerization is desired
[0067] The mold halves and molds of the invention may be supported
by any suitable support means. Supporting means include, without
limitation, a pallet, a support frame, a case, or the like, and
combinations thereof.
[0068] In FIG. 9 is shown mold 50, an alternative embodiment of the
invention in which a the adjustment means is a magnetic field
deformation means. Molding surface 51 has deformable portion 52
thereon. Non-molding surface 53 has in contact with it first
magnetic material 54. Second magnetic material 55 is brought into
proximity of first magnetic material 54 by mechanical arm 56, which
arm is movably mounted so that it can be manipulated in the
directions shown by the arrows. A magnetic force is exerted by
second magnetic material 55 resulting in the deformation of first
magnetic material 54 and deformable molding surface 52.
[0069] Preferably, the molds of the invention are contained within
a structure, such as a chamber, in which temperature, atmosphere,
and pressure are controlled. Additionally, the enclosure will
contain the source for curing of the lens material, such as a UV
light source. Also preferably, a feed back mechanism, such as an
interferomic technique, is used to feed information back to the
adjustment means regarding the position and shape of the molding
surface, the non-molding surface, or both.
[0070] The mold of the invention may be used to provide any
ophthalmic lenses suitable to correct visual acuity defects.
However, the molds of the invention may find particular utility in
providing lenses customized to correct the aberrations, both low
and high order, of a specific lens wearer. FIG. 10 is a flow
diagram of a method for providing such lenses using the molds of
the invention.
[0071] In step 601 of the method, a lens wearer's prescription
information is determined. By "prescription information" is meant
information necessary to correct the low order aberrations of the
lens wearer. This information includes, without limitation, sphere,
cylinder, axis, add power, and the like, and combinations thereof.
The information may be obtained using conventional ocular measuring
devices or and preferably, by use of wavefront sensors. Optionally
and preferably, in step 602, optical data is determined for the
lens wearer. "Optical data" means measurement of higher order
ocular aberrations. Such data is obtained using wavefront sensors.
Finally, optionally and preferably, patient fit data is determined
in step 603. For contact lenses, such data will include, without
limitation, corneal topographic measurements of the lens wearer's
cornea. For spectacle lenses, such information will include,
without limitation, fitting height, distance zone pupillary
distance, and the like, and combinations thereof.
[0072] The prescription information, optical data, and patient fit
data (collectively, the "order information") is then sent to the
lens manufacturer (604) by any convenient ordering means including,
without limitation, telephone, facsimile transmission, internet
website, and the like and combinations thereof. In a preferred
embodiment, ordering is carried out via the lens manufacturer's
internet website by the customer using any means capable of
communicating with the lens manufacturer's server system (web
server or web site). Suitable means for communicating with the
website include, without limitation, a personal computer and modem.
Thus, in yet another embodiment the invention provides a method for
producing customized ophthalmic lenses comprising, consisting
essentially of, and consisting of the steps of: a.) transmitting,
by a customer using a computer system, to a lens manufacturer's
server system lens order information; b.) manufacturing by the lens
manufacturer the lenses using a mold for comprising, consisting
essentially of, and consisting of i.) at least one mold half
comprising, consisting essentially of and consisting of a
non-molding surface and a molding surface, wherein at least a
portion of the molding surface is capable of being reversibly
deformed and ii.) adjustment means for reversibly deforming the
deformable portion of the molding surface (605); and c.) delivering
by the lens manufacturer directly to the customer the lenses
(606).
[0073] In carrying out manufacturing of the lenses, the lens
manufacture uses the order information, in whole or in part, to
drive the adjustment means of the deformable molds of the invention
to manufacture the wearer's lens. By "customer" is meant an orderer
of spectacle lenses. Examples of lens orderers include, without
limitation, ophthalmologists, optometrists, opticians, lens
retailers, lens wearers, and the like. Preferably, the method of
the invention is carried out so that it is a business-to-business
system.
* * * * *