Note: Descriptions are shown in the official language in which they were submitted.
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ACTIVELY CONTROLLABLE MULTIFOCAL LENS
The present invention relates to a multifocal lens containing a holographic
element
and providing at least two optical powers.
Various bifocal lens design concepts for ophthalmic lenses, which are placed
on or in
the eye to correct visual defects, e.g., contact lenses and intraocular
lenses, are available.
One conventional bifocal ophthalmic lens design is the concentric simultaneous
vision type.
A concentric simultaneous bifocal lens has alternating optical zones that are
concentrically
placed. The concentric alternating optical zones have different radii of
curvature to provide
separate powers for near images and far images and, thus, focus near and far
images onto
a common focal region. Although concentric simultaneous bifocal lenses have
been
available for some time, they have not been used widely. This is because
images projected
on the retina by a concentric simultaneous bifocal lens are composed of both
near and far
images, and the overlapping images make neither of the near and far images
completely
clear. For example, when a distant object is viewed through a concentric
simultaneous
bifocal lens, images of near objects are simultaneously present, veiling or
fogging the image
of the distant object. In addition, because the light entering the concentric
simultaneous
bifocal lens is shared by the two optical zones, contrast and intensity of the
focused images
are sacrificed, especially under low light conditions.
Another conventional bifocal ophthalmic lens design is the diffractive
simultaneous
vision type. These lenses have a diffractive optical element and a refractive
optical
element, and utilize both optical elements to simultaneously project distant
and near images
on the retina. As with concentric simultaneous bifocal lenses, a diffractive
simultaneous
bifocal lens splits the light entering the eye into near and far images and
projects the
images simultaneously on the retina. Consequently, neither of the near and far
images is
completely clear and creates the contrast and intensity problem under low
light conditions.
Yet another conventional bifocal ophthalmic lens design is the translating
type. A
translating bifocal constant lens generally follows the design of a
conventional bifocal lens
for eye glasses. A translating lens has two distinct localized viewing
sections that have
different optical powers. The position of the bifocal lens on the eye must
shift from one
section to the other when the wearer wishes to see objects that are located at
a distance
different from the objects currently in focus. One major problem inherent in a
conventional
translating bifocal ophthalmic lens is the difficulty encountered when the
wearer tries to shift
the position of the lens on the eye. The lens must move or shift a relatively
large distance
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on the eye to change from one viewing section to the other, and the shift from
one viewing
section to the other must be complete before clear vision can be realized.
Recently, actively controllable approaches for providing a bifocal function in
an
ophthalmic lens have been proposed. A simultaneous vision type bifocal lens
having
sectionally applied thermochromic coatings is an example. The bifocal lens is
designed to
activate the thermochromic coating on the distant optical zone of the lens,
when the wearer
looks down to focus on a near object. The activated thermochromic section of
the lens
blocks light from going through the distant optical zone, thereby preventing
the veiling or
fogging affect of the tight originating from near objects. This approach is
not highly practical
in that currently available thermochromic coating materials do not activate
and deactivate
fast enough for the concept to be practical. Another approach uses a lens that
changes its
focal length with an aid of a switchable battery or photocell. This approach
also is not
currently practical in that the electronic circuitry and the power source must
be made small
enough to be packaged in an ophthalmic contact lens and must be highly
reliable and
durable.
There remains a need for an ophthalmic lens that reliably provides multifocal
functions
without the deficiencies of prior art multifocal lenses. There additionally
remains a need for
optical materials that can be easily processed to produce a holographic
optical element.
There is provided in accordance with the present invention a multifocal lens
containing
a volume holographic optical element, which provides an optical power. The
lens has more
than one optical power, and one of the optical powers can be actively and
selectively
controlled by the wearer of the lens to allow the wearer to see clear and
unimpaired images.
The lens is suitable for various optical lenses, including contact lenses,
spectacle lenses
and intra-ocular lenses.
One embodiment of the present invention provides a multifocal optical lens
having a
first optical element and a volume holographic optical element, wherein the
first optical
element provides a first optical power at a first focal point and the
holographic optical
element or the holographic optical element in combination with the first
optical element
provides a second optical power at a second focal point. Another embodiment
provides a
multifocal lens having a volume holographic optical element, wherein the
holographic optical
element has a programmed activating angle, and the optical element provides a
first optical
power, e.g., corrective power or piano, for light entering the optical element
at an angle
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outside the activating angle and provides a second optical power for tight
entering the
optical element at an angle within the activating angle.
The present invention also provides a method for correcting visual defects.
The
method has the steps of providing a multifocal lens on an eye and moving the
multifocal
lens on the eye such that an appropriate focal point is placed on the fovea of
the eye. The
multifocal lens can be characterized in that the multifocal fens has a first
optical element
and a volume holographic optical element, wherein the first optical element
provides a first
optical power at a first focal point and the holographic optical element or
the holographic
optical element in combination with the first optical element provides a
second optical power
at a second focal point. As another embodiment of the invention, the
multifocal lens can
be characterized in that the multifocal lens has a holographic optical element
which has a
programmed activating angle, wherein the optical element provides a first
optical power for
light entering the optical element at an angle outside the activating angle
and provides a
second optical power for light entering the optical element at an angle within
the activating
angle.
The muttifocal lens of the present invention is a highly efficient corrective
lens that that
does not have the disadvantages of simultaneous vision lenses and conventional
translating lenses.
There is provided in accordance with the present invention a biocompatible
holographic element produced from a crosslinkable or polymerizable prepolymer.
The
prepoiymer is selected from crosslinkable or polymerizabie optical materials
that are
capable of forming a non-fluid or solid biocompatible optical element within 5
minutes of
irradiation by a UV source. The duration of crosslinking or polymerization is
measured by
placing the prepolymer between bottom and top quartz slides and providing a UV
source
which is a 200 watt medium pressure mercury arc lamp and placed 18 cm above
said top
quartz slide. Preferably, the biocompatible holographic element is a
transmission volume
holographic element. The invention also provides a hydrogel holographic
element that is
produced from the prepoiymer. Additionally provided is a process for producing
a
holographic element from a fluid composition of a prepolymer or monomer.
The holographic element can be used as medical devices, for example, as
optical
lenses and ophthalmic lenses. The optical and ophthalmic lenses having the
present
holographic optical element are relatively simple to produce and highly
suitable for
correcting various ametropic conditions.
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Fig. 1 illustrates an active ophthalmic lens of the present invention.
Fig. 2 illustrates the diffraction function of the holographic optical element
for an active
lens of the present invention.
Fig. 3 illustrates an active ophthalmic lens of the present invention.
Fig. 4 illustrates the transmission function of the holographic optical
element.
Fig. 5 illustrates the diffraction function of the holographic optical element
when the
element is activated.
Fig. 6 illustrates an exemplary method for producing the holographic optical
element.
Fig. 7 illustrates the optical power of the holographic optical element.
Figs. 8-8B illustrate a combination holographic optical element of the present
invention.
Fig. 9 illustrates a spectacle composite lens of the present invention.
The present invention provides active multifocal ophthalmic lenses. The
present
invention additionally provides active multifocal lenses for spectacles.
Hereinafter, the term
"optical lenses" is used to indicate both ophthalmic lenses and spectacle
lenses, unless
otherwise indicated. The active optical lens of the invention provides more
than one optical
power. More specifically, the lens provides at least one optical power and at
least one
additional optical power that can be activated. Unlike conventional bifocal
lenses, the
present active multifocal lens can be actively and selectively controlled to
provide one
desired optical power at a time without or substantially without optical
interferences from the
other optical powers of the lens.
The active optical lens contains a holographic optical element (HOE), and
suitable
HOEs for the active optical lens are transmission volume HOEs. A volume HOE
contains
interference fringe patterns that are programmed or recorded as a periodic
variation in the
refractive index of the optical material. The periodic variation in refractive
index creates
planes of peak refractive index, i.e., volume grating structure, within the
optical material.
The planes of interference fringe pattern in the HOE is further discussed
below.
Turning to Fig. 1, the figure illustrates an exemplary active bifocal tens 10
of the
present invention. It is to be noted that the invention is disclosed herein in
reference to a
bifocal optical lens for illustration purposes although the active optical
lens of the present
invention can have more than two optical powers. The lens 10 is a contact lens
having a
first optical element 12 and an HOE 14. The HOE 14 is embedded or encapsulated
in the
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first optical element 12 to form the composite lens 10 such that the HOE 14
moves in
conjunction with the lens 10. The first optical element 12 provides a first
optical power,
which corrects ametropia, e.g., myopia. Alternatively, the first optical
element 12 can be a
piano lens that functions as a carrier for the HOE 14. As for the HOE 14, the
optical
element is designed to modify the path of light only when the light enters the
HOE 14 at a
pre-programmed angle or within a pre-programmed angle range, i.e., activating
angle, that
activates the optical element. Accordingly, when the light enters at an angle
that is outside
the activating angle, the HOE 14 completely or substantially completely
transmits the
incoming light without significantly modifying or without modifying the path
of the light.
Alternatively stated, the HOE 14 may act as a piano lens except when the
incident angle of
the incoming light comes within the pre-programmed activating angle. When the
HOE 14 is
activated, the fringe patterns or volume grating structure programmed in the
HOE 14
modifies the path of the light to provide an optical power that is different
from the first
optical power of the lens 10. In addition to the activatable optical power,
the HOE 14 may
also provide an optical power that results from the shape of the HOE 14 and
the refractive
index of the composition of the HOE 14. Such additional optical power
complements the
first optical material to provide the first optical power of the active lens
10 when the
incoming light enters the lens 10 at an angle that does not active the HOE 14.
The term
"activating angle" as used herein indicates an incident angle of incoming
light, which is
defined by the angle formed by the advancing direction of incoming light and
the axis
normal to the HOE surface, that satisfies the Bragg condition such that the
incoming light is
diffracted by the interference fringe grating structure of the HOE, which is
further discussed
below. It is to be noted that the activating angle does not have to be a
single value and can
be a range of angles. The Bragg condition is well known in the optics art, and
it is, for
example, defined in ~u_~led Wave Theor~r for Thick Hologram Gratings, by H.
Kogelnik,
The Bell System Technical Journal, Vol. 48, No. 9, p 2909-2947 (Nov. 1969).
The
description of the Bragg condition disclosed therein is incorporated by
reference. The
Bragg condition can be expressed as
cos (~ - 9) = K/2B
wherein K = 2zr/A, A= the grating period of the interference fringes, 8 is the
incident angle
of incoming light, ~ is the slant angle of the grating and B is the average
propagation
constant, which can be expressed as B = 2nn/~,, wherein n is the average
refractive index
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and ~, is the wavelength of the light. When the Bragg condition is met, up to
100% of
incoming light can be coherently diffracted.
Fig. 2 further illustrates the function of the HOE 14 of the bifocal active
lens 10 of Fig.
1. The z-axis, which is normal to the planar surface of the HOE 14, and the
advancing
direction of the incoming light R form the incident angle a. When the incoming
light R
enters the HOE 14 at an incident angle that is within the activating angle of
the HOE 14, the
light R is diffracted by the pre-programmed interference fringe pattern, i.e.,
the volume
grating structure, of the HOE 14 and exits the HOE 14 as outgoing light S with
an exiting
angle p which is different from the incident angle a.
Figure 3 illustrates another embodiment of the active bifocal lens of the
present
invention. The bifocal active lens 16 is a composite lens which has a first
optical lens 17
and an HOE lens 18, which completely covers the first optical lens 17.
Alternatively, the
HOE lens 18 can be of a size that covers only the pupil of the eye. The first
optical lens 17
and the HOE lens 18 can be fabricated separately and joined, e.g., adhesively
or thermally.
Alternatively, the first optical lens 17 and the HOE lens 18 can be
sequentially or
simultaneously fabricated one over the other such that a composite lens is
produced. This
sequential or simultaneous approach is particularly suited when the first
optical lens and the
HOE lens are produced from one basic material or two chemically compatible
materials.
Although the active lens 16 is illustrated with a lens having an inner half
first optical lens
and an outer half HOE lens, other combinations of various optical elements can
be
produced in accordance with the present invention.
Yet another embodiment of the active bifocal lens is a non-composite active
HOE
bifocal lens. In this embodiment, the active HOE bifocal active lens is
produced from an
optical material that forms an HOE. The combination of the shape of the active
lens and
the refractive index of the HOE material provides a first optical power and
the programmed
volume grating structure in the HOE lens provides a second optical power. This
non-
composite active HOE lens embodiment is particularly suitable when the HOE
material
employed is a biocompatible material and, thus, does not adversely interact
with the ocular
tissues of the eye. The term "biocompatible material" as used herein refers to
a polymeric
material that does not deteriorate appreciably and does not induce a
significant immune
response or deleterious tissue reaction, e.g., toxic reaction or significant
irritation, over time
when implanted into or placed adjacent to the biological tissue of a subject.
Preferably, a
biocompatible material does not deteriorate and does not cause immune response
or
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deleterious tissue reaction over at least 6 months, more preferably at least 1
year, most
preferably at least 10 years. Suitable biocompatible optical materials are
highly
photocrosslinkable or photopoiymerizable optical materials. Suitable
biocompatible
materials include derivatives and copolymers of a polyvinyl alcohol,
polyethyleneimine, or
polyvinylamine. Exemplary biocompatible materials that are particularly
suitable for
producing the HOE of the present invention are disclosed in U.S. Pat. No.
5,508,317 to
Muller and International Patent Application No. PCT/EP96/00246 to Miihlebach,
which
patent and patent application are herein incorporated by reference and further
discussed
below.
The present HOE is designed or programmed to have one activating angle or a
range
of activating angles within which the HOE is activated, and the HOE diffracts
the incoming
light to focus the light on a desired location. Figs. 4 and 5 illustrate the
function of the HOE
21 of the composite active lens 20, which contains an HOE lens element that is
programmed to focus light originating from a near distance. When light 22 from
a distant
object enters the lens at an angle that does not activate the HOE 21, the
tight 20 is focused
in accordance with the optical power of the first optical element 23 of the
lens 10, in
combination with the optical power of the crystalline lens of the eye (which
is not shown), to
a focal point 24 on the retina of the eye, more specifically on the fovea. For
example, the
first optical element 23 can have a corrective power in the range between +10
diopters and
- 20 diopters. It is to be noted that the HOE lens 21 may have an inherent
optical power
that comes from the shape of the HOE lens 21 and the refractive index of the
HOE
composition. Consequently, the HOE lens 21 may contribute to the refractive
optical power
of the active lens 20. Notwithstanding, hereinafter, the inherent optical
power of the HOE
lens 21 is ignored in order to simplify the illustration of the diffractive
function of the present
HOE lens since the inherent optical power can be easily factored into the
teaching of the
present invention. When the HOE lens 21 is not activated, the HOE lens 21 does
not
interfere with the light 22 from traveling the normal refractive path caused
by the first optical
lens element 23. However, when the light enters the HOE lens 21 at an angle
that activates
the HOE lens 21 (i.e., enters within the activating angle), the light is
diffracted by the HOE
lens 21. As illustrated in Figure 5, when the incoming light enters the active
lens 25 at an
angle that activates the HOE lens 26, the lens, in conjunction with the first
optical lens 27
and the crystalline lens of the eye, focuses the light on the retina, more
specifically on the
fovea. For example, light 28 originating from a near object 29 forms an image
30 on the
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fovea, when the light enters the HOE lens 26 at an angle that is within the
programmed
activating angle.
The incident angle of incoming light with respect to the active bifocal lens,
more
specifically to the HOE portion of the active lens, can be changed by various
means. For
example, the active lens can be tilted to change the incident angle of the
incoming light, i.e.,
the wearer of the lens can change the incident angle of the light by looking
down while
maintaining the position of the head. Alternatively, the active lens may have
a position
controlling mechanism that can be actively controlled by the wearer of the
lens with one or
more muscles in the eye. For example, the active lens can be shaped to have a
prim
ballast such that the movement of the lens can be controlled with the lower
eyelid. It is to
be noted that the activating angle of the active lens 25 illustrated in Fig. 5
is exaggerated to
more easily explain the present invention, and thus, the activating angle of
the active lens
does not have to be as large as the tilted angle illustrated in Fig. 5. In
fact, HOEs suitable
for the present invention can be programmed to have a wide range of different
activating
angles in accordance with HOE programming methods known in the holographic
art.
Accordingly, the degree of movement required for the active lens to switch
from one optical
power to another can be easily changed depending on the design criteria and
the needs of
each lens wearer.
Although the active lens of the present invention provides more than one
optical
power, the active lens forms clearly perceivable images that are focused by
one optical
power at a time. Consequently, the active lens does not produce blurred or
fogged images,
unlike conventional bifocal tenses such as concentric simultaneous bifocal
lenses.
Returning to Fig. 5, when the active lens 25 is positioned to view a near
object 29 (i.e., the
incident angle of the light originating from the object 29 is within the
activating angle of the
HOE lens 26), the light from the object 29 is focused by the HOE lens 26, in
conjunction
with the first optical lens 27 and the crystalline lens of the eye, onto the
fovea 30. At the
same time, the incident angle of the light originating from distant objects is
not within the
activating angle of the active lens 25. Accordingly, the path of the incoming
light from
distant objects is not modified by the HOE lens 26, but the path of the
incoming light from
distant objects is modified, i.e., refracted, by the first optical lens 27 and
the crystalline lens
of the eye. The incoming light from the distant objects is, therefore, focused
to forms an
image at an area 31 which is outside the fovea. Consequently, the focused
images of the
near and distant objects are not concentrically or axially aligned. It has
been found that the
image, which is formed outside the fovea 31, is not clearly perceived by the
wearer of the
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active lens 25 and is easily disregarded as peripheral vision. Consequently,
the wearer of
the active lens 25 is able to clearly view the near object 29 without having
blurring
interferences from the light originating from distant objects.
Similarly, when the active lens is position to view a distant object, for
example, as
illustrated in Fig. 4, the light 22 from distant objects enters the lens at an
angle outside the
activating angle of the HOE 21. Therefore, the path of the light is not
affected by the HOE
21, and is only affected by the first optical element 23 and the crystalline
lens of the eye,
thereby forming an image of the distant object .on or near the fovea 24. At
the same time,
the light originating from a near object is diffracted and focused by the HOE
21 and is
projected onto an area outside the fovea. Accordingly, the wearer of the
active lens clearly
views the distant object without significant interferences.
The non-blurring advantage of the present active lens is a result of the
design of the
active lens that utilizes the inherent anatomy of the eye. It is known that
the concentration
of the retinal receptors outside the fovea is drastically lower than that in
the fovea.
Consequently, any image focused substantially outside of the fovea is not
clearly perceived
since the image is undersampled by the retina and easily disregarded by the
brain of the
lens wearer as peripheral vision or images. In fact, it has been found that
the visual acuity
of a human eye drops to about 20/100 for objects only 8° off the line
of sight. In the above-
described actively controlling manner, the present active lens provides clear
images from
one optical power at a time by utilizing the inherent anatomy of the eye.
Utilizing the
inherent retinal receptor anatomy of the eye and the ability to program
different ranges of
activating angles in the HOE lens, the present active lens uniquely and
selectively provides
clear images of objects that are located at different distances. In contrast
to various
simultaneous bifocal lenses, the active lens provides unimpeded clear images,
and in
contrast to translating bifocal lenses, the active lens can be easily designed
to require only
a small movement of the lens to selectively provide images from different
distances.
HOEs suitable for the present invention can be produced, for example, from a
polymerizable or crosslinkable optical material, especially a fluid optical
material. Suitable
polymerizable and crosslinkable HOE materials are further discussed below.
Hereinafter,
for illustration purposes, the term polymerizabie material is used to indicate
both
polymerizable and crosslinkable materials, unless otherwise indicated. An
exemplary
process for producing an HOE of the present invention is illustrated in Fig.
6. Point-source
object light 32 is projected to a photopolymerizable optical material 33
(i.e.,
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photopolymerizable HOE), and simultaneously collimated reference light 34 is
projected to
the photopolymerizable HOE 33 such that the electromagnetic waves of the
object light 32
and the reference light 34 form interference fringe patterns, which are
recorded in the
polymerizable material as it is polymerized, thereby forming a volume grating
structure in
the tens 33. The photopolymerizable HOE 33 is a photopolymerizable material
that is
polymerized by both the object tight and the reference light. Preferably, the
object light and
the reference light are produced from one light source, using a beamsplitter.
The two split
portions of the light are projected toward the HOE 33, in which the path of
the object light
portion of the split light is modified to form a point-source light 32. The
point-source object
light 32 can be provided, for example, by placing a conventional convex
optical lens some
distance away from the photopolymerizable HOE 33 so that the light is focused
on a
desirable distance away from the HOE 33, i.e., on the point-source light
position 32. A
preferred light source is a laser source, more preferred is a UV laser source.
Although the
suitable wavelength of the light source depends on the type of HOE employed,
preferred
wavelength ranges are between 300nm and 600nm. When the photopolymerizable HOE
33
is fully exposed and polymerized, the resulting HOE contains a pattern of
refractive index
modulation, i.e., the volume grating structure 35. In addition, when a fluid
polymerizable
optical material is used to produce the HOE, the light source transforms the
fluid optical
material to a non-fluid or solid HOE while forming the volume grating
structure. The term
"fluid" as used herein indicates that a material is capable of flowing like a
liquid.
Turning to Fig. 7, the polymerized HOE 36 has a focal point 38 which
corresponds to
the position of the point-source object light 32 of Fig. 6 when light 39
enters the HOE 36
from the opposite side of the focal point and matches or substantially matches
the reversed
path of the collimated reference light 34 of Fig. 6. Figs 6 and 7 provide an
exemplary
method for producing an HOE having a positive corrective power. As can be
appreciated,
HOEs having a negative corrective power can also be produced with the above-
described
HOE production set up with small modifications. For example, a convergent
object light
source that forms a focal point on the other side of the HOE away from the
light source can
be used in place of the point-source object light to produce an HOE having a
negative
corrective power. In accordance with the present invention, active multifocal
lenses having
various corrective powers can be readily and simply produced to correct
various ametropic
conditions, e.g., myopia, hyperopia, prebyopia, regular astigmatism, irregular
astigmatism
and combinations thereof. For example, the corrective powers of the HOEs can
be
changed by changing the distance, position and/or path of the object light,
and the
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activating angle of the HOEs can be changed by changing the positions of the
object light
and the reference light.
in accordance with the present invention, suitable HOEs can be produced from
polymerizable and crosslinkable optical materials that can be relatively
rapidly
photopolymerized or photocrosslinked. A rapidly polymerizable optical material
allows a
periodic variation in the refractive index can be created within the optical
material, thereby
forming a volume grating structure while the optical material is being
polymerized to form a
solid optical material. Preferably, suitable polymerizable and crosslinkable
optical materials
are selected from biocompatible optical materials, and preferably, suitable
optical materials
are selected from fluid biocompatible optical materials that crosslink or
polymerize to form a
non-fluid, solidified optical element having a defined shape in equal to or
less than 5
minutes, more preferably equal to or less than 3 minutes, yet more preferably
equal to or
less than 1 minute, most preferably equal to or less than 30 seconds, e.g.,
between 5 and
30 seconds. The duration of crosslinking or polymerization is determined by
placing a
crosslinkable or polymerizable optical material between two quartz slides,
which have the
dimensions of a microscope slide and are separated by 100 im with spacers. A
sufficient
amount of the optical material is applied on a first quartz slide to form a
circular drop having
a diameter of about 14 mm, and a second slide is placed over the optical
material.
Alternatively, a spacer can be used to provide the cylindrical space between
the slides for
the optical material. The optical material between the slides is irradiated
with a 200 watt
medium pressure mercury arc lamp which is placed 18 cm above the top quartz
slide.
An exemplary group of biocompatible polymerizable optical materials suitable
for the
present invention is disclosed in U.S. Pat. No. 5,508,317 to Muller. A
preferred group of
polymerizable optical materials, as described in U.S. Patent No. 5,508,317,
are those that
have a 1,3-diol basic structure in which a certain percentage of the 1,3-diol
units have been
modified to a 1,3-dioxane having in the 2-position a radical that is
poiymerizable but not
polymerized. The polymerizable optical material is preferably a derivative of
polyvinyl
alcohol having a weight average molecular weight, M",, of at least about 2,000
that, based
on the number of hydroxy groups of the polyvinyl alcohol, has from about 0.5%
to about
80% of units of formula I
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CH2
CH HC
(z)
O /O
iH 1
~R
~ ~ R2
wherein:
R is lower alkylene having up to 8 carbon atoms,
R' is hydrogen or lower alkyl and
R2 is an olefinically unsaturated, electron-attracting, copolymerizable
radical preferably
having up to 25 carbon atoms. R2 is, for example, an olefinically unsaturated
acyl radical of
formula R3-CO-, in which
R3 is an olefinically unsaturated copolymerizable radical having from 2 to 24
carbon
atoms, preferably from 2 to 8 carbon atoms, especially preferably from 2 to 4
carbon atoms.
Exemplary olefincally unsaturated copolymerizable radicals include ethenyl, 2-
propenyl, 3-
propenyl, 2-butenyl, hexenyl, octenyl and dedecanyl.
As a desirable embodiment, the radical R2 is a radical of formula II
[-CO-NH-(R4-NH-CO-O)q-RS-O]P--CO-R3 (II)
wherein
p is zero or one, preferably zero;
q is zero or one, preferably zero;
R° and R5 are each independently lower alkylene having from 2 to 8
carbon atoms,
arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic
group having
from 6 to 10 carbon atoms, arylenealkyiene or alkylenearylene having from 7 to
14 carbon
atoms, or arylenealkylenearylene having from 13 to 16 carbon atoms; and
R3 is as defined above.
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Lower alkylene R preferably has up to 8 carbon atoms and may be straight-
chained or
branched. Suitable examples include octylene, hexylene, pentylene, butylene,
propylene,
ethylene, methylene, 2-propylene, 2-butylene and 3-pentylene. Preferably lower
alkylene R
has up to 6 and especially preferably up to 4 carbon atoms. Methylene and
butylene are
especially preferred. R' is preferably hydrogen or lower alkyl having up to
seven, especially
up to four, carbon atoms, especially hydrogen.
As for R4 and R5, lower alkylene R" or RS preferably has from 2 to 6 carbon
atoms and
is especially straight-chained. Suitable examples include propylene, butylene,
hexylene,
dimethylethylene and, especially preferably, ethylene. Arylene R4 or RS is
preferably
phenylene that is unsubstituted or is substituted by lower alkyl or lower
alkoxy, especially
1,3-phenylene or 1,4-phenylene or methyl-1,4-phenylene. A saturated divalent
cycloaliphatic group R° or R5 is preferably cyclohexylene or
cyclohexylene-lower alkylene,
for example cyclohexylenemethylene, that is unsubstituted or is substituted by
one or more
methyl groups, such as, for example, trimethylcyclohexylenemethylene, for
example the
divalent isophorone radical. The arylene unit of alkylenearyiene or
arylenealkylene R4 or R5
is preferably phenylene, unsubstituted or substituted by lower alkyl or tower
alkoxy, and the
alkylene unit thereof is preferably tower alkylene, such as methylene or
ethylene, especially
methylene. Such radicals R4 or R5 are therefore preferably phenylenemethylene
or
methylenephenylene. Arylenealkylenearylene R° or R5 is preferably
phenylene-lower
alkylene-phenylene having up to 4 carbon atoms in the alkylene unit, for
example
phenyleneethylenephenylene. The radicals R4 and RS are each independently
preferably
lower alkylene having from 2 to 6 carbon atoms, phenylene, unsubstituted or
substituted by
Power alkyl, cyclohexylene or cyclohexylene-lower alkylene, unsubstituted or
substituted by
lower alkyl, phenylene-lower alkylene, lower alkylene-phenylene or phenylene-
lower
alkylene-phenylene.
The polymerizable optical materials of the formula I is produced, for example,
by
reacting a polyvinyiaicohol with a compound III,
R' R"
I I
O\CH R1
R-N
~R2
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wherein R, R' and R2 are as defined above, and R' and R" are each
independently
hydrogen, tower alkyl or lower alkanoyl, such as acetyl or propionyl.
Preferably, between
about 0.5 and about 80%, more preferably between about 1 and about 50%, most
desirably
between about 2 and about 15%, of the hydroxyl groups of the resulting the
polymerizable
optical material are replaced by the compound III.
Suitable poiyvinylaicohols for the present derivatized polyvinylalcohol have a
weight
average molecular weight between about 2,000 and about 1,000,000, preferably
between
10,000 and 300,000, more preferably between 10,000 and 100,000, and most
preferably
10,000 and 50,000. The polyvinylalcohols have less than about 50%, preferably
less than
about 20%, of unhydrolyzed vinylacetate units. In addition, the polyvinyl
alcohols may
contain up to about 20%, preferably up to about 5%, of one or more of
copolymer units,
such as, ethylene, propylene, acrylamide, methacrylamide, dimethacrylamide,
hydroxyethyl
methacrylate, methyl methacrylate, methyl acrylate, ethyl acrylate,
vinylpyrrolidone,
hydroxyethyl acrylate, allyl alcohol and styrene.
The polyvinylalcohol derivative are polymerized in a solvent by a
photocrosslinking
process, e.g., using a UV laser, to produce an HOE. A suitable solvent is any
solvent that
dissolves polyvinyl alcohol and vinylic comonomers. Exemplary solvents include
water,
ethanol, methanol, propanol, dimethyfformamide, dimethyl sulfoxide and
mixtures thereof.
To facilitate the photocrosslinking polymerization process, it is desirable to
add a
photoinitiator, which can initiate radical crosslinking. Exemplary
photoinitators suitable for
the present invention include benzoin methyl ether, 1-hydroxycyclohexylphenyl
ketone,
Durocure~ 1173 and Irgacure~ photoinitators. Preferably, between about 0.3 and
about
2.0%, based on the total weight of the polymerizable formulation, of a
photoinitiator is used.
In accordance with the present invention, suitable concentrations of the
polyvinylalcohol
derivative in the solvent to produce the HOE are preferably between about 3
and about 90
by weight, more preferably between about 5% and 60%, most preferably between
about
10% and about 50%, especially when the HOE is designed to be used as an
ophthalmic
lens.
Another group of exemplary biocompatible polymerizable optical materials
suitable for
the present invention is disclosed in U.S. Patent Application Serial No.
08/875,340,
(International Patent Application No. PCT/EP96/00246 to Muhlebach). The
description of
the polymerizable optical materials in the U.S. patent application is herein
incorporated by
reference. The suitable optical materials include azalactone-moiety containing
derivatives
of polyvinyl alcohol, polyethyleneimine or polyvinylamine which contain from
about 0.5 to
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about 80%, based on the number of hydroxyl groups in the polyvinyl alcohol or
the number
of imine or amine groups in the polyethyleneimine or polyvinylamine,
respectively, of units
of the formula IV and V:
CH2- H2
Ra
C O
R~ C-R2
O R3
NH-C-C=CH2
CHZ CH2-N
C=O
R~ C-R2
O R3
NH-C-C=CHZ
wherein R, and R2 are, independently of one another, hydrogen, a C~-CB alkyl
group, an aryl
group, or a cyclohexyl group, wherein these groups are unsubstitued or
substituted; R3 is
hydrogen or a C,-Ce alkyl group, preferably is methyl; and R4 is an -O- or -NH-
bridge,
preferably is -O-. Polyvinyl alcohols, polyethyleneimines and polyvinylamines
suitable for
the present invention have a number average molecular weight between about
2,000 and
1,000,000, preferably between 10,000 and 300,000, more preferably between
10,000 and
100,000, and most preferably 10,000 and 50,000. A particularly suitable
polymerizable
optical material is a water-soluble derivative of a polyvinyl alcohol having
between about 0.5
to about 80%, preferably between about 1 and about 25%, more preferably
between about
1.5 and about 12%, based on the number of hydroxyl groups in the polyvinyl
alcohol, of the
formula IV that has methyl groups for R, and R2, hydrogen for R3, -O- (i.e.,
an ester link) for
R4.
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The polymerizable optical materials of the formulae IV and V can be produced,
for
example, by reacting an azalactone of the formula VI,
i 3 // -C-R2
CH2 C-C~
O C O
wherein R,, R2 and R3 are as defined above, with a polyvinyl alcohol,
polyethyleneimine or
polyvinylamine at elevated temperature, between about 55°C and
75°C, in a suitable
organic solvent, optionally in the presence of a suitable catalyst. Suitable
solvents are
those which dissolve the polymer backbone and include aproctic polar solvents,
e.g.,
formamide, dimethylformamide, hexamethylphosphoric triamide, dimethyl
suifoxide,
pyridine, nitromethane, acetonitrile, nitrobenzene, chlorobenzene,
trichloromethane and
dioxane. Suitable catalyst include tertiary amines, e.g., triethylamine, and
organotin salts,
e.g., dibutyltin dilaurate.
In addition to the azalactone moiety, the azalactone-moiety containing optical
materials can have other hydrophobic and hydrophilic vinylic comonomers,
depending on
the desired physical properties of the polymerized HOE. Exemplary suitable
hydrophobic
comonomers include C,-C,e alkyl acrylates and methacrylates, C3-Cog
alkylacrylamides and
methacrylamides, acrylonitrile, methacrylonitrile, vinyl C~-C,e alkanoates, C2-
Cte alkenes,
styrene, vinyl alkyl ethers, C2-C,o perffuoroalkyl acrylates and
methacrylates, C3-C,2
perfluoroallcyl ehtylthiocarbonylaminoethyl acrylates and methacrylates,
acryloxy- and
methacryioxy-lakylsiloxanes, N-vinylcarbazole, C~-C,2 alky esters of malefic
acid, fumaric
acid, itaconic acid and the like. Exemplary suitable hydrophilic comonomers
include
hydroxyalkyl acrylates and methacrylates, acrylamide, methacrylamide,
methoxylated
acrylates and methacrylates, hydroxyalkyl amides and methacrylamides, N-
vinylpyrrole, N-
vinylsuccinimide, N-vinylpyrrolidone, vinylpyridine, acrylic acid, methacrylic
acid and the like.
The azalactone-moiety containing optical materials are polymerized in a
solvent by a
photocrosslinking process, e.g., using a UV laser, to produce an HOE. A
suitable solvent is
any solvent that dissolves the polymer backbone of the optical materials.
Exemplary
solvents include aproctic solvents disclosed above in conjunction with the
azlactone
modification, water, ethanol, methanol, propanol, glycols, glycerols,
dimethylformamide,
dimethyl sulfoxide and mixtures thereof. To facilitate the photocrosslinking
polymerization
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process, it is desirable to add a photoinitiator, which can initiate radical
crossfinking.
Exemplary photoinitators suitable for the present invention include benzoin
methyl ether, 1-
hydroxycyclohexylphenyl ketone, Durocure~ 1173 and Irgacure~ photoinitators.
Preferably,
between about 0.3 and about 2.0%, based on the total weight of the
polymerizable
formulation, of a photoinitiator is used. In accordance with the present
invention, suitable
concentrations of the azalactone-moiety containing optical material in the
solvent to
produce the HOE are preferably between about 3 and about 90 % by weight, more
preferably between about 5% and 60%, most preferably between about 10% and
about
50%, especially when the HOE is designed to be used as an ophthalmic lens.
Yet another group of biocompatible polymerizable optical materials suitable
for the
present invention is a functionalized copolymer of a vinyl lactam and at least
one additional
vinyl monomer, a second vinyl monomer. The copolymer is functionalized with a
reactive
vinyl monomer. The vinyl lactam of the present invention is a five to seven
membered
lactam of formula VII
Rb Ra
Rc N (VII)
wherein
Re is an alkylene bridge having from 2 to 8 carbon atoms;
Rb is hydrogen, alkyl, aryl, aralkyl or alkaryl, preferably hydrogen, lower
alkyl having
up to 7 carbon atoms, aryl having up to 10 carbon atoms, or aralkyl or alkaryl
having
up to 14 carbon atoms; and
R~ is hydrogen or lower alkyl having up to 7 carbon atoms, preferably methyl,
ethyl
or propyl.
Exemplary vinyl lactams suitable for the invention include N-vinyl-2-
pyrrolidone, N-
vinyl-2-caprolactam, N-vinyl-3-methyl-2-pyrrolidone, N-vinyl-3-methyl-2-
piperidone, N-vinyl-
3-methyl-2-caprolactam, N-vinyl-4-methyl-2-pyrrolidone, N-vinyl-4-methyl-2-
caprolactam, N-
vinyl-5-methyl-2-pyrrolidone, N-vinyl-5-methyl-2-piperidone, N-vinyl-5,5-
dimethyl-2-
pyrrolidone, N-vinyl-3,3,5-trimethyl-2-pyrrolidone, N-vinyl-5-methyl-5-ethyl-2-
pyrrolidone, N-
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vinyl-3,4,5-trimethyl-3-ethyl-2-pyrrolidone, N-vinyl-6-methyl-2-piperidone, N-
vinyl-6-ethyl-2-
piperidone, N-vinyl-3,5-dimethyl-2-piperidone, N-vinyl-4,4-dimethyl-2-
piperidone, N-vinyl-7-
methyl-2-caprotactam, N-vinyl-7-ethyl-2-caproiactam, N vinyl-3,5-dimethyl-2-
caprolactam, N-
vinyl-4,6-dimethyl-2-caprolactam, N-vinyl-3,5,7-trimethyl-2-caprolactam and
mixtures
thereof. Preferred vinyl lactams are heterocyclic monomers of formula VII
containing from 4
to 6 carbon atoms in the heterocycltc ring. More preferred vinyl lactams have
a heterocyclic
monomer of formula VII, in which the heterocyclic ring has 4 carbon atoms and
Rb and R
are independently selected from hydrogen and.lower alkyl moieties. A highly
suitable vinyl
lactam is N-vinyl-2-pyrrolidone.
Suitable second vinyl monomers include functional vinyl monomers that have in
addition to the vinyl group a functional group, for example, hydroxy, amino,
lower alkyl-
substituted amino, carboxyl, esterified caboxyl, alkoxycarbonyl, epoxy or
sulfo (-S03H). The
functional group is retained when the vinyl group of the second vinyl monomer
is reacted
with the vinyl lactam to produce a polymer chain, and can be used to modify or
functionalize
the polymer.
Suitable functional vinyl monomers include hydroxy-substituted lower alkyl
acrylates
and methacrylates, ethoxylated acrylates and methacrylates, epoxy-lower alkyl
acrylates
and methacrylates, epoxycycloalkyl-lower alkyl acrylates and methacrytates,
hydroxy-
substituted lower alkyl acrylamtdes and methacrylamides, hydroxy-substituted
lower alkyl
vinyl ethers, amino- or hydroxy-substituted styrenes, sodium
ethylenesulfonate, sodium
styrenesulfonate, 2-acrylamido-2-methytpropanesulfonic acid, acrylic acid,
methacrylic acid,
amino-lower alkyl and alkylamino-lower alkyl acrylates and methacrylates,
acryloxy- and
methacryloxy-lower alkylmalemides, and allyl alcohol. The term "lower alkyl"
as used herein
refers to an alkyl radical having up to 7 carbon atoms, preferably up to 4
carbon atoms.
Particularly suitable functional vinyl monomers include 2-hydroxyethyl
methacrylate, 3-
hydroxypropyl methacrylate, acrylic acid, methacrylic acid, 4-aminostyrene, 3-
methacryloxymethyl-7-oxa-bicyclo [4.1.0] heptane, N-methacryloxyethyl-
maleimide, glycidyl
methacrylate, ammonium ethyl methacrylate hydrochloride and ammonium propyl
methacrylate hydrochloride.
A copolymer of the vinyl lactam and the second vinyl monomer is produced with
or
without a solvent in a known manner. The copolymer can also be a statistical
polymer. A
process for producing a statistical polymer is disclosed in, for example, U.S.
Pat. No.
5,712,356. A suitable solvent dissolves and is substantially inert towards the
monomers
and the polymer produced from the monomers. Exemplary suitable solvents
include water;
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alcohols, e.g., methanol, ethanol and propanol; carboxylic acid amides, e.g.,
dimethylfom~amide and dimethyl sulfoxide; ethers, e.g., diethyl ether, THF and
diglymes;
and mixtures thereof. Suitable copolymers have a weight average molecular
weight
between about 2,000 and about 1,000,000, preferably between 10,000 and
300,000, more
preferably between 10,000 and 100,000, and most preferably 10,000 and 50,000.
The copolymer is further modified with a reactive vinyl monomer to produce a
rapidly
crosslinkable polymer. Suitable reactive vinyl monomers have in addition to
the vinyl group
a reactive moiety, which reacts with a functional group present in the
copolymer to form a
covalent bond while retaining the vinyl group of the monomer. Exemplary
suitable reactive
vinyl monomers include hydroxy-substituted lower alkyl acrylates and
methacrylates,
hydroxy-substituted lower alkyl acrylamides and methacrylamides, hydroxy-
substituted
lower alkyl vinyl ether, 2-acrylamido-2-methylpropanesulfonic acid, amino-
lower lakyl and
mono-lower alkylamino-lower alkyl acrylates and methacrylates, allyl alcohol,
epoxy-lower
alkyl acrylates and methacrylates, isocyanato-lower alkyl acrylates and
methacrylates,
vinylically unsaturated carboxylic acids having 3 to 7 carbon atoms and acid
chlorides and
anhydrides thereof, amino-, hydroxy- or isocyanate-substituted styrenes, and
epoxycycloalkyl-lower alkyl acrylates and methacrylates. Preferred reactive
vinyl monomers
include hydroxyethyl acrylate and methacrylate, hydroxypropyl acrylate and
methacrylate,
isocyantoethyl acrylate and methacrylate, acrylic and methacrylic acid
chloride, ammonium
ethyl methacrylate hydrochloride, and ammonium propyl methacrylate
hydrochloride.
The functionalized copolymer is typically crosslinked or polymerized in a
solvent by a
photocrosslinking process, e.g., using a UV laser, to produce an HOE, although
the
copolymer can be crosslinked or polymerized in the absence of a solvent. A
suitable
solvent is any solvent that dissolves the polymer backbone of the polymer.
Exemplary
solvents include water; alcohols, e.g., methanol and ethanol; carboxylic acid
amides, e.g.,
dimethylformamide and dimethyl sulfoxide; and mixtures thereof. The
photocrosslinking
process is facilitated by a photoinitiator, which can initiate radical
crosslinking. Exemplary
photoinitators suitable for the present invention include benzoin methyl
ether, 1-
hydroxycyclohexylphenyl ketone, Durocure~ 1173 and Irgacure~ 2959. Preferably,
between
about 0.3 and about 2.0%, based on the total weight of the polymerizable
formulation, of a
photoinitiator is used. In accordance with the present invention, suitable
concentrations of
the functionalized vinyl lactam copolymer in the solvent to produce the HOE
are preferably
between about 3 % and about 90 % by weight, more preferably between about 5%
and
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60%, most preferably between about 10% and about 50%, especially when the HOE
is
designed to be used as an ophthalmic fens.
Another group of HOEs suitable for the present invention can be produced from
conventional and other volume transmission holographic optical element
recording media.
As with the above-described polymerizable materials for HOEs, object light and
collimated
reference light are simultaneously projected onto an HOE recording medium such
that the
electromagnetic waves of the object and reference light form interference
fringe patterns.
The interference fringe patterns, i.e., volume grating structure, are recorded
in the HOE
medium. When the HOE recording medium is fully exposed, the recorded HOE
medium is
developed in accordance with a known HOE developing method. Suitable volume
transmission holographic optical element recording media include commercially
available
holographic photography recording materials or plates, such as dichromatic
gelatins.
Holographic photography recording materials are available from various
manufacturers,
including Polaroid Corp. Other holographic media suitable for the present
invention are
disclosed, for example, in International Patent Application No. PCT/US96/15600
to Polaroid
and U.S. Pat. No. 5,453,340 to Nippon Paint. When photographic recording
materials are
used as the HOE, however, toxicological effects of the materials on the ocular
environment
must be considered. Accordingly, when a conventional photographic HOE material
is used,
it is preferred that the HOE be encapsulated in a biocompatible optical
material. Useful
biocompatible optical materials for encapsulating the HOE include optical
materials that are
suitable for the first optical element of the present active lens, and such
suitable materials
are further discussed below.
As is known in the ophthalmic art, an ophthalmic lens should have a thin
dimensional
thickness to promote comfort of the lens wearer. Accordingly, a dimensionally
thin HOE is
preferred for the present invention. However, in order to provide an HOE
having a high
diffractive efficiency, the HOE has to be optically thick, i.e., the light is
diffracted by more
than one plane of the interference fringe pattern. One way to provide an
optically thick and
dimensionally thin HOE is programming the interference fringe pattern in a
direction that is
slanted towards the length of the HOE. Such slanted volume grating structure
renders the
HOE to have a large angular deviation between the incident angle of the
incoming light and
the exiting angle of the exiting light. However, an HOE having a large angular
deviation
may not be particularly suitable for an optical lens. For example, when such
an HOE is
used in an ophthalmic lens and the HOE is activated, the active line of sight
is significantly
bent away from the normal straight line of sight. As a preferred embodiment of
the present
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-21 -
invention, this angular limitation in designing an HOE lens is addressed by
utilizing a
multilayer combination HOE, especially a bilayer HOE. Figure 8 illustrates an
exemplary
multilayer HOE 40 of the present invention. Two dimensionally thin HOEs having
a large
angular deviation are fabricated into a combination HOE to provide a
dimensionally thin
HOE that has a small angular deviation. The combination HOE 40 has a
dimensionally thin
first HOE 42 and a thin second HOE 44. The first HOE 42 is programmed to
diffract the
incoming light such that when light enters the HOE at an activating angle a,
the light exiting
the HOE 42 forms an exiting angle Vii, which is larger than the incident angle
a, as shown in
Fig. 8A. Preferably, the first HOE has a thickness between about 10 Nm and
about 100 Nm,
more preferably between about 20 Nm and about 90 Nm, most preferably between
about 30
Nm and about 50 Nm. The second HOE 44 is programmed to have a activating
incident
angle (3 that matches the exiting angle (3 of the first HOE 42. in addition,
the second HOE
44 is programmed to focus the incoming light to a focal point 46 when the
light enters within
the activating angle (3. Fig. 8B illustrates the second HOE 44. Preferably,
the second HOE
has a thickness between about 10 Nm and about 100 Nm, more preferably between
about
20 Nm and about 90 Nm, most preferably between about 30 Nm and about 50 Nm.
When the first HOE 42 is placed next to the second HOE 44 and the incoming
light is
directed at an angle that corresponds to the activating angle a of the first
HOE 42, the light
exiting the multilayer HOE focuses the light to the focal point 46. By
utilizing a multilayer
combination HOE, a dimensionally thin HOE having a high diffractive efficiency
and a small
deviation angle can be produced. In addition to the high diffractive
efficiency and small
angular deviation advantages, utilizing a multilayer HOE provides other
additional
advantages, which include correction of dispersion aberration and chromatic
aberration. A
single HOE may produce images having dispersion and chromatic aberrations
since visual
light consists of a spectnrm of electromagnetic waves having different wave
lengths and the
differences in wavelengths may cause the electromagnetic waves to diffract
differently by
the HOE. It has been found that a multilayer, especially bilayer, HOE can
counteract to
correct these aberrations that may be produced by a single layer HOE.
Accordingly, a
multilayer combination HOE is preferred as the HOE component of the active
lens.
In accordance with the present invention, HOEs of the present invention
preferably
have a diffraction efficiency of at least about 70%, more preferably at least
about 80%,
most preferably at least 95%, over all or substantially all wavelengths within
the visible
spectrum of light. Especially suitable HOEs for the present invention have a
diffraction
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WO 99/34239 PCT/EP98/08465
efficiency of 100% over all wavelengths of the spectrum of visible light.
However, HOEs
having a lower diffraction efficiency than specified above can also be
utilized for the present
invention. Additionally, preferred HOEs for the present invention have a sharp
transition
angle between the activated and non-activated stages, and not gradual
transition angles,
such that activation and deactivation of the HOE can be achieve by a small
movement of
the active lens and that no or minimal transitional images are formed by the
HOE during the
movement between the activated and deactivated stages.
As for the first optical material of the active lens, an optical material
suitable for a hard
lens, gas permeable tens or hydrogel lens can be used. Suitable polymeric
materials for the
first optical element of the active ophthalmic lens include hydrogel
materials, rigid gas
permeable materials and rigid materials that are known to be useful for
producing
ophthalmic lenses, e.g., contact lenses. Suitable hydrogel materials typically
have a
crosslinked hydrophilic network and hold between about 35 % and about 75 %,
based on
the total weight of the hydrogel material, of water. Examples of suitable
hydrogel materials
include copolymers having 2-hydroxyethyl methacrylate and one or more
comonomers such
as 2-hydroxy acrylate, ethyl acrylate, methyl methacrylate, vinyl pyrrolidone,
N-vinyl
acrylamide, hydroxypropyl methacrylate, isobutyl methacrylate, styrene,
ethoxyethyl
methacrylate, methoxy triethyleneglycol methacrylate, glycidyl methacrylate,
diacetone
acrylamide, vinyl acetate, acrylamide, hydroxytrimethylene acrylate, methoxy
methyl
methacrylate, acrylic acid, methacrylic acid, glyceryl ethacrylate and
dimethylamino ethyl
acrylate. Other suitable hydrogel materials include copolymers having methyl
vinyl
carbazole or dimethylamino ethyl methacrylate. Another group of suitable
hydrogel
materials include polymerizable materials such as modified polyvinyl alcohols,
polyethyleneimines and polyvinylamines, for example, disclosed in U.S. Patent
No.
5,508,317, issued to Beat Muller and International Patent Application No.
PCT/EP96/01265.
Yet another group of highly suitable hydrogel materials include silicone
copolymers
disclosed in International Patent Application No. PCT/EP96/01265. Suitable
rigid gas
permeable materials for the present invention include cross-linked sitoxane
polymers. The
network of such polymers incorporates appropriate cross-linkers such as N,N'-
dimethy!
bisacrylamide, ethylene glycol diacrylate, trihydroxy propane triacrylate,
pentaerythtritol
tetraacrylate and other similar polyfunctional acrylates or methacrylates, or
vinyl
compounds, e.g., N-m,ethylamino divinyl carbazole. Suitable rigid materials
include
acrylates, e.g., methacrylates, diacrylates and dimethacrylates, pyrolidones,
styrenes,
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amides, acrylamides, carbonates, vinyls, acrylonitrieles, nitrites, sulfones
and the like. Of
the suitable materials, hydrogel materials are particularly suitable for the
present invention.
tn accordance with the present invention, the first optical element and the
HOE can be
laminated or the HOE can be encapsulated in the first optical element to form
the active
lens, when one of the composite active lens embodiments is practiced. In
addition, when
an ophthalmic active lens is produced using a non-biocompatible HOE, the HOE
preferably
is encapsulated in the first optical element such that the HOE does not make
direct contact
with the ocular environment since the HOE may adversely affect the long-term
corneal
health. Alternatively, as discussed above, the active lens can be produced
from a
biocompatible HOE such that an HOE can provide both diffractive and refractive
functions
of the active lens.
Figure 9 illustrates another embodiment of the present invention. A bifocal
spectacle
lens 50 is formed by laminating a layer of a first optical material having a
first optical power
52, which provides an optical power, and a layer of an HOE 54, which provides
a second
optical power. The two layers are fabricated separately and then joined, e.g.,
thermally or
adhesively. The composite lenses can be subsequently machined to fit a
spectacle frame
to provide a pair of bifocal glasses. The first optical material 52 is a
conventional optical
material that has been used to produce eyeglasses, e.g., glass, polycarbonate,
polymethylmethacrylate or the like, and the HOE is any holographic optical
material that can
be programmed to focus the incoming light, as previously described.
Alternatively, the
bifocal spectacle tens can be produced from a shaped HOE such that the optical
shape of
the HOE provides a refractive power when the HOE is not activated and the
volume grating
structure of the HOE provides a diffractive power when it is activated.
The present multifocal optical lens can be actively and selectively controlled
to provide
one desired optical power at a time without or substantially without optical
interferences
from the other optical powers of the lens, unlike conventional bifocal lenses.
In addition, the
programmable nature of the HOE of the active lens makes the lens highly
suitable for
correcting ametropic conditions that are not easily accommodated by
conventional
corrective optical lenses. For example, the active lens can be programmed to
have
corrective measures for the unequal and distorted corneal curvature of an
irregular
astigmatic condition by specifically designing the object and reference light
configurations.
The present invention is further illustrated with the following examples.
However, the
examples are not to be construed as limiting the invention thereto.
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Examples
Beispiel 1: Example 1
About 0.06 ml of the Nelfilcon A lens monomer composition is deposited in the
center
portion of a female mold half, and a matching male mold half is placed over
the female
mold half, forming a lens mold assembly. The male mold half does not touch the
female
mold half, and they are separated by about 0.1 mm. The lens mold halves are
made from
quartz and are masked with chrome, except for the center circular lens portion
of about 15
mm in diameter. Briefly, Nelfilcon A is a product of a crosslinkable modified
polyvinyl
alcohol which contains about 0.48 mmoUg of an acryamide crosslinker. The
polyvinyl
alcohol has about 7.5 mol % acetate content. Nelfilcon A has a solid content
of about 31
and contains about 0.1 % of a photoinitiator, Durocure~ 1173. The closed lens
mold
assembly is placed under a laser set up. The laser set up provides two
coherent collimated
UV laser beams having 351 nm wavelength, in which one beam is passed through a
optical
convex lens so that the focal point is formed at 500 mm away from the lens
mold assembly.
The focused light serves as a point-source object light. The angle formed
between the
paths of the object light and the reference light is about 7°. The set
up provides an HOE
having an added corrective power of 2 diopters. The lens monomer composition
is exposed
to the laser beams having about 0.2 watts for about 2 minutes to completely
polymerize the
composition and to form interference fringe patterns. Since the lens mold is
masked except
for the center portion, the lens monomer exposed in the circular center
portion of the mold
is subjected to the object light and the reference light and polymerized.
The mold assembly is opened, leaving the lens adhered to the male mold half.
About
0.06 ml of the Nelfilcon A lens monomer composition is again deposited in the
center
portion of the female mold half, and the male mold half with the formed lens
is placed over
the female mold half. The male and female mold halves are separated by about
0.2 mm.
The closed mold assembly is again exposed to the laser set up, except that the
optical
convex lens is removed from the object light set up. The monomer composition
is again
exposed to the laser beams for about 2 minutes to completely polymerize the
composition
and to form a second layer of interference fringe patterns. The resulting
composite lens
has an optical power based on the shape of the lens and the refractive index
of the lens
material and an activatable additional corrective power of +2 diopters.
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Beispiel 2: Example 2
110 g of polyvinyl alcohol (MowiolT"" 4-88, which is available from Hoechst AG
and
has a 87.7% hydrolysis level and Mw (g/mol) of about 31,000) are dissolved at
90°C in 440
g of deionized water and cooled to 22°C. 100.15 g of a 20.6% aqueous
solution of
methacrylamidoacetaldehyde dimethylacetal, 38.5 g of concentrated hydrochtoric
acid (37
p.a., Merck) and 44.7 g of deionized water are added. The mixture is stirred
at room
temperature for 22 hours and then adjusted to pH 7.0 with a 5% NaHO solution.
The
solution is diluted to 3 titers with deionized water, filtered and
ultrafiltered using a 1-KD-
Omega membrane produced by Filtron. After the three-fold specimen volume is
repeated,
the solution is concentrated. 660 g of a 17.9% solution of
methacrylamidoacetaldehyde-
1,3-acetal of polyvinyl alcohol having a viscosity of 210 cp are obtained.
According to NMR
investigation, 11 mol% of the OH groups have been acetalized and 5 mot% of the
OH
groups acetylated concentration of the aqueous polymer solution under reduced
pressure
and with air draft yields a 30.8% solution having a viscosity of 3699 cp.
0.7 %, based on the polymer content, of Durocure~ 1173 is added to the 30.8%
solution. The solution is introduced into a transparent contact lens mold of
polypropylene,
which has a center cavity thickness about 100 im, and the mold is closed. The
solution is
irradiated for 6 seconds from a distance of 18 cm using a 200 watt Oriel UV
lamp. The
mold is opened and a transparent contact lens is removed. The contact lens is
biocompatible, i.e., the lens can be worn on the eye for an extended time
without causing a
deleterious effect on the ocular environment, and the modulus and the flexural
elongation of
the lens are 0.9 mPa and 50%.
Beispiel 3: Example 3
Azlactone modified polyvinyl alcohol is produced as follows. 25 g of polyvinyl
alcohol
(MowioIT"" 4-98, which is available from Hoechst AG and has a 98.4% hydrolysis
level and
Mw (g/mol) of about 27,000) are dissolved in 100 g DMSO at 65°C in a
200 ml round-
bottom flask with mechanical stirring under a nitrogen blanket. 0.5 g of a
catalyst (1,8-
diazabicyclo [5.4.0]-undec-7-ene) are added and 7.14 g (0.051 mol) of 2-vinyl-
4,4-dimethyl-
azlactone is then added. The mixture is continuously stirred for 24 hours at
65°C. The
resulting modified polymer is precipitated into 1 liter of acetone under
vigorous stirring. The
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precipitate is filtered and dried. The modified polymer has about 9 mol% of
the OH-groups
of the polyvinyl alcohol reacted with the azlactone. The modified polymer is
dissolved in
DMSO to provide an about 30% solution, and Irgacure~ 2959 is added to make a
0.1
solution of the photoinitiator.
About 0.6 ml of the modified crosslinkable polymer solution is placed on a
quartz
slide, which has dimensions of a microscope slide, and a second quartz slide
is placed over
the solution. With a spacer, a 100 im space is maintained between the slides.
The
crosslinkable solution placed between the slides is subjected to the HOE
recording process
as disclosed in the first recording step of Example 1. The resulting HOE has a
diffractive
efficiency of about 70 %.
The above examples demonstrate that the polymerizable optical materials of the
present invention, which are selected with the present selection criteria,
produce
holographic optical elements (HOEs), especially biocompatible HOEs, that can
be utilized in
various uses, including optical lenses, e.g., multifocal contact lenses.
