Note: Descriptions are shown in the official language in which they were submitted.
~L2~3~
l OPAQUE TINTING PROCESS
BACKGROUND OF THE INVENTION
This invention relates to a process for tinting or
coloring a hydrogel contact lens or other ophthalrnic
prosthetic device. The process is especially suitable for
practice with the lens tinting procedure and lens mounting
apparatus described in U.S. Patent No. 4,518,390 as more
10 fully discussed hereinafter.
Contact lenses can be tinted for cosmetic
appearance as well as to reduce light transmission therehy
providing the wearer with increased visual comfort. It is~
of course, important that the tinted, or colored, lens
15 impart a natural appearance to the wearer's eye. A natural-
appearing soft contact lens should have a clear central
area, a tinted intermediate area and a clear outer area so
that the tinted portion will not cover the sclera of the
eye. Moreover, the central portion of the lens should be
20 untinted to permit maximum light passage into the eye
interior.
Apart from the foregoing considerations, the
nature of the tinting procedure imposes still other require-
ments if a technically successful and cost efficient tinting
25 operation is to be realized. It is important that the
worker not handle the lens directly with his or her fingers
or fingertips because the minute amounts of oil contained on
the worker's fingertips will preven~ the dye from being
accepted or absorbed evenly by the lens. If the ~orker uses
30 gloves~ manipulation of the lens during the tinting
procedure can be rendered difficult.
. ~
--2--
~29~3~
1 IE the worker uses tweezers and manually mounts the lens on
a fixture, lens production can be slow and accuracy in the
mounting may be compromised.
As suggested above, it is important that the
tinted annLllar area of the lens, and correspondingly the
clear central portion, be precisely defined and accurately
located. Even slight fuzziness or running of dye colors
into otherwise uncolored areas of the lens will be
immediately apparent. Fuzziness or tint runs will
10 necessitate the rejection of the finished lens product.
By way of achieving a precise and economical
procedure for tinting a contact lens meeting the foreyoing
criteria, U.S. Patent No. 4,518,390 provides a lens tinting
method employing a lens mounting apparatus comprising a tube
15 having a body portion and a closed end portion defined
partially by a lens masking structure in communication with
the tube body. Suitably treated water, e.g., physiological
saline, is placed in the tube to form a column of liquid~
The lens to be tinted is dropped into this liquid column and
20 as it falls through the liquid, attains a state of dynamic
equilibrium, with the lens convex side down. Further, the
hydraulic forces acting on the lens as it passes through the
column of liquid will cause the lens to center itself with
respect to the interior of the tube body. Thus, as the lens
25 reaches the bottom of the tube r it will be centered as it
comes to rest upon the lens mask structure formed at the
tube bottom. In one embodiment, this mask structure
includes two coaxial seats defining an open annular lens
area therebetween. It is this annular area which is to be
30 tinted.
.,
~x~
When the lens is centered on the mask, a mandrel
clevice is inserted into the tube. This mandrel has a nose
which substantially conforms to the concave surface of the
lens. Thus, when the mandrel engages the lens concave side,
the convex side of the lens is pushed into firm engagement
with the mask structure. The mandrel ls then locked within,
and upon, the tube. As the mandrel passes through the
liquid column it also will be centered due to hydraulic
forces acting thereon which produce a state of dynamic
10 equilihrium. Thus, upon engaging the lens, the mandrel is
also centered relative to the tube body.
Thereafter, the fixture is inverted and the liquid
column in the tube drainecl away. Next, a tinting medium or
dye solution is introduced into a chamber formed in the tube
15 bottom proximate the mask structure. This tinting nledium is
exposed only to the unmasked portion of the lens and will
permeate the lens material of the unmasked portion to
provide the desired tint.
The foregoing lens-tinting procedure and apparatus
employed therein provides generally excellent results with
lenses to be worn by individuals having light colored eyes.
For example, a gray iris can be made to take on the color of
almost any tinted lens. However, for the estimated seventy
percent of the world7s population with dark irises, i.e.,
25 brown eyes, a change in color is obtained only with the
darkest of lens tints as the underlying color of the iris
tends to dominate the overall color effect. Such eyes can
only be made to appear darker, not lighter.
3o
~g~
1 SUMMARY OF THE INVENTION
The present invention provides a method for
tintinq a hydrogel contact lens whereby the visual effect of
the tint is not appreciably influenced or modified by the
color of the wearer's eyes.
In accordance with this method, a selected area of
a hydrogel contact lens is first rendered opaque and only
then is the opaqued area tinted employing known lens tinting
techniques, e.g., those described in U.S. Patent Nos.
~O 4,252,421 and 4,457,761 and particularly that of ~.S. Patent
No. 4,51~,390 referred to above, or the preferred tinting
procedure employing a water-soluble lenco ester of a vat dye
as hereinafter described. The initial opaquing step can be
achieved using a variety of chemical techniques such as
15 those described in ~.S. Patent Mo. 3,679,504.
The term "hydrogel" is descriptive of any water
absorptive, optically clear polymeric material which is
suitable for the fabrication of a contact lens~
Illustrative of such polymers are the water swellable,
20 water-insoluble shape-reatining hydrogels disclosed in U.S.
Patent Nos. 2,976,576; 3,220,960; 3,822,089; 4,208,364;
4,208,365; and, 4,517,139, among others. Contact lenses
formed from such materials, the so-called "soft" lens
variety, become soft and pliable upon the absorption of
25 water and in the hydrated state, are relatively comfortable
to wear. By employing the opaquing process of this
invention, selected areas of such lenses can be subsequently
tinted to provide a variety of desired color effects,
., .
whether for cosmetic reasons or otherwise, which are
30 unimpaired by, and independent of, the color of the wearer's
eyes.
,~
1~9130~)
-4a
Various aspects of this invention are as
~ollows:
A method of tintiny a hydrogel contact lens
such that the visual effect of the tint is not
appreciably influenced or moclified by the color of the
wearer's eyes which comprises:
(a) opaquing selected portion(s) of said lens with
an opaquing medium which is al metal salt which undergoes
reaction with a precipitating agent to provide a
metallic opaquing makerial selected from the yroup
consisting of silver, gold and platinum; and
(b) tinting only the opaqued portion(s) of the
lens wherein said tinting is carried out by exposing the
opaqued portion(s) of said lens to a solution of a
~5 water-soluble leuco ester of a vat dye whereby said dye
penetrates said opaqued portion(s) of the lens and
thereafter the dye is oxidized to regenerate the vast
dye.
The method of tinting a hydrogel contact lens
such that the visual effect of the tint is not
appreciably influenced or modified by the color of the
wearer's eyes which comprises:
(a) prov.iding a tube-like structure which is
closed at one end by structure which includes maslc means
and which is open at the other end;
(b) orienting the tube-like structure in a first
position with the open end upwardi
(c) adding a fluid column to the interior of said
tube structure;
(d) dropping the lens to be opaqued into the fluid
in the tube, and permitting the lens to sink through the
fluid column, so as to cause the lens to orient and
center itself relative to the tube;
-
12913~()
-4b-
(e) permitting the oriented and centered lens to
come to rest on mask means defined in the tub~ bottom;
(f) inserting a mandrel member into the tube and
fluid to secure the lens in place between the mandrel
and the mask structure;
(g) opaquing the unmasked portion(s) of the lens
with an opaguing medium which is a metal salt which
undergoes reaction with a precipitating ayent to provide
a meta].lic opaquing material selected from the group
consisting of silver, gold alnd platinum;
(h) retaining the opaqued lens within the tube-
like structure of step (a), or transferring the opaqued
lens to another tube-like structure of step (a) in which
case steps (b) and (f) are repeated; and,
(i) tinting the opaqued, unmasked portion(s) of
the lens wherein said tinting is carried out by exposing
the opaqued portion (5) of said lens to a solution of a
water-soluble leuco ester of a vat dye whereby said dye
penetrates said opaqued portion(s) of the lens and
thereafter the dye is oxidized to regenerate the vat
dye.
~ ~,
i29~30~
sCRIPTION OF THE DRAWINGS
Fig. 1 (3rd sheet of drawings) is an exploded view
of a known lens mounting apparatus employed in a
preferred embodiment of the lens tinting method of this
invention;
Fig. 2 is a sectional view showing the apparatus o~
Fig. 1 in its assembled condition and inverted;
Fig. 3 is a fragmentary sectional view showiny in
further detail the masking portion of the apparatus in a
position as per Fig. 1, and inverted from that shown in
Fig. 2:
Fig. 4 is a Eragmentary sectional view taken
substantially in the plane oP line 4 - 4 in Fig. 3;
Fiy. 5 is a sectional view taken substantially in
the planes o-E lines 5 - 5 in Fig. 4;
Fig. 6 is a fragmentary sectional view showing the
motion of a contact lens as it passes through a column
of liquid contained within a tube portion of the
fixture;
Fig. 7 is a fragmentary sectional view similar to
Fig. 6 and showing action of the liquid as a mandrel
member is inserted into the tube; and
Fig. 8 is a side elevational view of the fully
assembled lens mounting apparatus of Fi~s. 1-7 showing
lens L properly centered therein and ready for the
opaquing and tinting operations of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A. The Lens Mounting Apparatus
Turning first to Figs. 1 and 2, there is shown a
lens mounting apparatus 10 in accordance with U.S.
Patent No. 4,518,390 which is especially well suited for
use in the
. '
1~9~3C~)
1 practice of th~ opaque tinting process herein. In general,
apparatus 10 can be considered to inclucle an elongate tube
12 into which a hydrogel contact lens L can be dropped or
otherwise inserted. One end 16 of this tube 12 is generally
open while the other end 18 is closed by a specially
designed masking structure.
The tube-closing structure 18 includes a lens mask
structure 20. Here, this mask structure includes an outer,
annular seat or mask portion 22, and spaced apart therefrom
but coaxial therewith; an inner seat or mask portion 24. To
provide desired resiliency in supporting, engaging, and
masking portions of contact lens L, this inner seat or mask
24 is formed on nose 26 of a plunger 28 which is biased, as
by a spring 30, toward lens L. Thus, the sprin~ biasing
15 means 30 urges the inner mask seat 24 toward lens L and into
firm contact therewith. Plunger motion toward lens L is
halted or restrained by a shoulder 32 formed on the bottom
portion of tube 12; a mating shoulder 34 is formed on the
plunger 28. Spring 30 and plunger 28 are retained within
20 the tube structure 12 by any convenient device such as a cap
or plug 36.
A chamber 40 is provided at the closed end of tube
12 proximate mask structure 20 for sequentially providing
liquid opaquing and tinting media to the unmasked portions P
25 of lens L as hereinafter more fully explained. Chamber 40
includes a cylindrical cavity 42 surrounding plunger nose 26
and inner mask seat 24, and disposed inwardly of the outer
mask portion 22.
.,
3
1~9~;~0~)
1 To admit liquid opaquing medium, and thereafter,
liquicl tinting medium to chamber cavity 42, inlet and outlet
ports 50 and 52 are provided as shown in Figs. 1, 2, 4 and
5. These media are urged to swirl through chamber 40 and
past lens L by orienting inlet and outlet ports 50 and 52
substantially tangential to wall 5~ of cylindrical cavity
42. To encourage the removal of air bubbles and the
accumulation of any preliminary solution squeezed out of the
lens during lens capture, inlet port 50 is smaller than
10 outlet port 52, and inlet port 50 is located tangentially as
noted above, and also at an axially uppèr position relative
to outlet port 52.
Tube 12 includes an elongate body portion 62
capable of retaining a column o~ liquid. The diameter of
15 body portion 62 is just slightly greater than the diameter
of lens L. Preferably, the internal diameter, I~, of tube
body portion 62 is approximately 2 mm. larger than that of
the lens diameter, LD. The height of the column of liquid
and the height of body portion 62 are from one to three
20 times the lens diameter, LD, and pre~erably from two and
one-half times lens diameter LD. When lens L is dropped
into liquid-filled tube 12, it descends through the liquid
and attains a state of dynamic equilibrium, with a lens
convex side CV down, as shown in Fig. 6. As the lens falls
25 downwardly through the column of liquid, the hydraulic
forccs acting on the lens will operate to center the lens
with respect to the tube. Thus the lens will be in the
desired orientation and will be properly centered as it
engages mask means 20 for the opaquing and tinting
30 operations to follow.
:.,
--8--
~913~)0
1 To engage and secure lens L against the mask means
or structure 20 in a position to be contacted by the
opaquing and tinting media, a mandrel 66 is inserted into
tube 62 as shown in Figs. 2 and 7. This mandrel 66 is
provided with a rounded nose portion 68 adapted to engage
the concave side CC of lens L.
So that the column of liquid will not overflow the
open top 16 of the tube 12, mandrel 66 is hollow, and a port
or hole 72 is formed in mandrel nose 68 to permit liquid to
10 flow into the mandrel interior as illustrated in Fig. 7.
This permits mandrel 66 to sink into the liquid in the tube
means with a controlled ~lotion, the mandrel being centered
by the hydraulic forces in the same manner as was lens L.
In addition, external spacer ribs 74 are ormed on the
15 outside of mandrel 66 so as to space mandrel 66 from the
tube body wall and permit liquid to ~low between mandrel 66
and the tube body wall thus ~urther enhancing the centering
action.
When mandrel 66 has been fully inserted into tube
20 12, a mandrel lock mechanism 80 is inserted into tube 12 to
force mandrel 66 against lens L and force lens L against
mask structure 20. As illustrated in Figs. 1, 2, 3 and 4,
this locking mechanism 80 takes the form of a plunger 82
which is provided with a stem 84 surrounded by a compression
25 spring 86. A lock cap 88, which can conveniently be of the
plug type, is secured to plunger stem 84 here, plunger stem
84 is provided with an enlarged nose 90 to prevent loss of
cap 88 from stem 84.
It will be noted that plunger 82 is provided with
30 an enlarged base ~2 provided with several cut-away
formatlons 94. Further, cap 88 is provided with several
~Z'3130(~
1 drain holes 96. Thus, when the assembled tube and mandrel
arrangement are inverted from the initial or assembly
position shown in Fig. 1 to the operating position shown in
Figs. 2 and 8, the column of liquid will drain from the
5 tube.
B. The OPaquinq Procedure
As shown in Fig. 8, the fully assembled lens
mounting apparatus of Figs. 1-7 with its properly centered
10 hydrogel contact lens L is set within a stand 110. Port
plugs 102 and 104 (Fig. 1) have been replaced with flexible
inlet and outlet tubes 111 and 112 fitted to inlet port 50
and outlet port 52, respectively. Tubes 111 and 112 are
each provided with a clamp or other device to control the
flow of liquid therethrough. The lens mounting apparatus is
filled to an appropriate height with a receiving or
preparatory liquid such as physiological saline which
insures that the hydrogel lens will be maintained in a
sterile and hydrophilic condition. ~he clamps are released
20 to fill tubes 111 and 112 with liquid thereby expelling any
air bubbles. The apparatus is again filled with liquid
with removal of any air bubbles as previously described.
The lens to be opaqued and thereafter tinted is
picked up by tweezers or some other clean device and is
25 deposited in the receiving liquid and allowed to sink
freely toward the closed end of the tube assembly. As it
drops, the lens will orient and center itself as shown in
Fig. 6, and will finally come to rest on mask structure 20
as shown in Figs. 6 and 7, not only with the convex side
3O down, but properly centered relative to mask structure 20.
.
''~
--10--
1~9~L300
1 Thereafter, mandrel 66 is inserted into tube 12. The
mandrel will also center itself and mandrel nose 68 will
engage the concave side CC of the lens L. Fluid flows in
the interior portion of mandrel 66 through port 72, as
explained previously so as to permit mandrel 66 to sink
into the lens-engaging position and to avoid overflow and
spillage. Finally, in assembling the device, mandrel
locking assembly 82 is thereafter inserted into the open
top 16 of tube 12. By this action, mandrel 66 is pressed
into firm engagement with the lens L and lens L is pressed
into firm engagement with both ollter mask 22 and inner mask
24 of the masking structure 20. It will be recalled that
inner mask 24 can be displaced slightly by this mandrel
forcing action against the action of plunger biasing sprin~
15 3o.
The completely assembled device with the captured
lens is now visually inspected to make certain that lens L
has been properly seated an~ centered. To this end, tube
12 and other parts of the assembly are preferably formed of
20 transparent plastic or other suitable materials. However,
mandrel 66 is preferably formed of opaque plastic so as to
enable the operator to better view lens L. If the lens has
not been properly located and seated, mandrel locking
mechanism 82 and mandrel 66 are removed, and the lens is
25 then removed. The lens is then re-dropped and the
mechanism is reassembled as before. If the lens has been
properly captured and secured, plugs 102 and 104 are removed
to drain the preparatory fluid from chamber 40. Next the
entire assembly or fixture is inverted into the position
30 shown in Figs. 2 and 8. As explained above, this inversion
motion permits the fluid column on the side of the lens
opposite the tinting chamber 40 to be drained from the
assembled fixture.
-11~
1~91~
1 Preferably, the lens opaquing of this invention
is carried out at ambient temperature but temperatures
above or below this level can be employed provided they do
not impede the chemical mechanisms involved in the opaquing
procedure. Opaquing medium, advantageously in the form of a
precipitatable metal salt as more fully discussed below, i5
introduced into chamber 40 through inlet port 50 of the
inverted lens mounting assembly. Because of the size and
location of inlet port 50 and outlet port 52 described
10 above, the opaquing medium enters chamber 40 tangentially to
the walls thereof with a low pressure swirling action. This
liquid swirling action ensures an even application oE t~he
opaquing medium to the unmasked area of the lens. Also this
action causes any bubbles of air to be removed from convex
15 surface CV of lens L which constitutes the temporary bottom
surface of chamber 40. These air bubbles are then swept out
through the outlet port. Removal of air bubbles in this way
is highly desirable because the presence of bubbles on the
surface of lens L can cause voids or irregularities in the
20 finished tinted lens.
It will also be noted that any preparatory
solution on lens L which has been squeezed out of the lens
by the locking or securing action of the mandrel 66, will
also be swept out of chamber 40. If this solution were
25 allowed to accumulate in chamber 40, the opaquing medium
might be diluted and an uneven opaquing action might
result.
A variety of opaquing makerials, e.gf, those
described in U.S. Patent No. 3,476~499 referred to above,
30 can be used with good results. For example, metallic
~ilver, gold, and platinum, each of which can produce an
.,
-12-
~2~
1 opaque effect in a hydrogel lens, can be precipitated from
solution~ of their salts ~ithin the hydrogel by means of
hydrazine, reducing sugars, or formaldehyde, respectively.
Opaquing precipitates can also be formed by reacting
suitable impregnating and precipitating agents with the
reaction product then being selectively exposed to light.
A particularly useful impregnating ~gent is silver nitrate
which will react with a halide saltr e.g., sodium chloride,
to precipitate the corresponding silver halide salt which
10 is light sensitive. Thus, after a suitable period of
exposure to light, the silver halide will form an opaque
precipitate within the unmasked portion o~ the hydrogel
lens which is resistant to loss by tearing or the wiping
action o~ the eyelids. The amounts of impregnating and
15 precipitating agent employed, the duration of contact o~
these agents with the unmasked portion of the lens and khe
duration of exposure of the precipitated metal salt are not
critical and are readily determined by those skilled in the
art employing known and relatively simple procedures.
In preparation for exposure to a source of light
(or other actinic radiation), the lens is removed from the
mounting apparatus, placed in a transparent vial partially
filled with physiological saline and the vial is exposed to
light. The resulting selectively opaqued lens is then
25 ready ~or the tinting procedure described below.
The opaquing materials herein are physiologically
inert. They cannot chemically irritate the eye nor can
they actually come in contact ~ith it in significant
amounts as they are unable to migrate in the hydrogel
3O material.
~13-
~9~30~)
1 C ~he Tintinq Procedure
The opaqued lens is centered in another lens
mounting apparatus which is fitted out and assembled as
before and the entire assembly is mounted in the inverted
position as shown in Fig. 8. The tinting operations are
preferably carried out at elevated temperature, e.g., at
from about 50C to about 60C, for overall best results .
The preferred procedure for tinting the opaqued
lens comprises applying a solution of a water-soluble leuco
lO ester of a vat dye to the lens followed by treatment with an
oxidizing to regenerate the vat dye. While any leuco ester
of a vat dye can be used in accordance with this invention,
it is o~ten preferred to use such dyes which impart a
natural eye color appearance to the lens. In general, the
15 useful dyes are water-soluble sulfuric acid esters of leuco
vat dyes of the anthroquinone and indigoid series. Various
combinations of such dyes can also be used. A more detailed
description of such leuco esters of vat dyes can be found in
Lubs, "The Chemistry of Synthetic Dyes and Pigments", ACS
20 Monograph No. 127, Reinhold Publishing Corporation, 1955,
pages 534 to 546 and Vankataraman, nSynthetic Dyes",
Academic Press, 1952, pp. 1046-1059. A number of specific
water-soluble leuco esters which may be employed in the
process of the present invention are disclosed in Lubs. op.
25 cit., pp. 538 to 546 inclusiveO Commercially available
dyes which can be employed herein include the Eollowing:
Solubilized Vat Blue 6, C. I. 69826
Solubilized Vat Orange 1, C. I. 59106
Solubilized Vat Brown 1, C. I. 70801
Solubilized Vat Yellow 3, C. I~ 61726
Solubilized Vat Green 1, C.I. 59826
9~3~
1 The solution of the water-soluble leuco ester of
the vat dye is usually employed as an aqueous solution
having a concentration of the dye of frorn about 0.1% to
about 25% by weight. In addition to the employment of
aqueous solutions, the water-soluble leuco ester of the vat
dye may be dissolved in various organic solvents or
mixtures of such solvents, with water.
The organic solvents, if used, should be water-
miscible and of relatively high volatility for quick
10 evaporation~ These are exemplified by methanol, ethanol,
propanol, butanol, acetone~ dimethyl ~ormamide, Cellosolve
(ethyl ehter of ethylene glycol), butyl Cellusolve (butyl
ether of ethylene glycol), dimethyl sulfoxide and the like.
Other assistants may be present if desired.
Color intensity is affected by such factors as
concentration of the dye solution, the temperature and the
duration of contact of the dye solution with the lens, the
thickness of the unmasked portions of the lens ~to be
penetrated by the dye and the degree of oxidation brought
20 about when regenerating the original chromophore. Simple
and routine experimentation can be used to determine the
combination of dye concentration, temperature and contact
time, and the extent of oxidation necessary to produce a
desired color effect in a hydrogel lens of a given type.
25 The oxidation step can be carried out by adding the acid and
reducing agent together or sequentially in any order.
Suitable acids include the mineral acids and strong organic
acids such as chlorosulfonic acid, and the like. Sulfuric
acid provides entirely acceptable results. In general, any
30 known oxidizing agent can be used to regenerate the vat
129~300
1 dye. Suitable oxidi~ing agents include such compounds as
the peroxides, per-acids, chlorates, ferric salts, cuprous
nitric acid, nitrites, chromic acid, chromates, chlorates,
and the like. Sodium nitrite is advantageously used Eor
5 this purpose.
Following regeneration of the vat dye to the
desired state of color development, the acid is neutralized
to terminate the oxidation reaction and the lens is
thoroughly washed with distilled water to remove all traces
10 f reagents and unoxidized dyeO
The following example is further illustrative of
the invention in which the operations and liquid media are
at ambient temperature except where indicated~
~5
. .
3o
-16-
~2~3~3~`3
EXAMPLE
1 The lens mounting apparatus of Figs. 1-7 is
~itted with inlet and outlet tubes for respectively
conveying liquids to and away from chamber 40 and placed in
a stand. Clarnps are placed on the inlet and outlet tubes
5 and the apparatus is filled with physiological saline. The
clamps are released and filled with saline thereby
releasing any air bubbles. The apparatus is then topped
with saline and any air bubbles are removed from the
interior wall thereof.
The h~drogel contact lens to be tinted is removed
from its vial and dropped into the column of saline where-
upon it comes to rest, concave side up, on the central
portion o~ the mask. The mandrel is then inserted in the
apparatus and locked under spring tension against the
15 concave surface of the lens. The lens mounting assem~ly is
then inverted and placed in a stand. Employing a syringe, 2
ml of a 2.5 weight percent aqueous solution of silver
nitrate is introduced through the unclamped inlet tube into
chamber 40 while the terminal end of the clamped outlet tube
is placed within a beaker or other li~uid-receiving vessel.
The silver nitrate solution is permitted to remain in
contact with the unmasked portions of the lens for from 12
seconds or less to 240 seconds or more depending upon the
intensity of opaqueness desired. Thereafter, 20 ml of
5 physiological saline is introduced through the unclamped
inlet tube into chamber 40. Reaction of the silver nitrate
and sodium chloride component of the saline causes the
formation of a precipitate of silver chloride which, when
exposed to light, releases metallic silver, the actual
3 opaquing material. The lens is removed from the apparatus,
-17-
~9~3~)()
1 placed in a lens vial half-filled with saline and the via]
with its lens are placed in close proximity to a neon lamp
for at least about 8 hours with the result that the opaque
tint appears as a light beige color.
The tinted lens assembled in another lens mounting
apparatus and equipped with inlet and outlet tubes as before
is inserted in a stand in the inverted position as in Fig~
8. The stand is associated with a heater (not shown) which
is capable of maintaining the lens mounting apparatus and
10 its contents at an approximately constant temperature, in
this case, about 50C, to accelerate the dyeing procedure.
Once the lens mounting assembly has attained this
temperature, a syringe is used to inject an aqueous solution
of the water~soluble leuco ester of the selected vat dye.
15 A~ter the desired period of dye solution contact has
elasped, the clamp on the outlet tube is released to drain
excess dye solution, the syringe is removed ~rom the inlet
tube and another syringe is inserted in the inlet tube and
used to inject a sulfuric acid solution of sodium nitrite
20 oxidizing agent into chamber 40. Following the desired
period of contact between the dye-impregnated lens and the
oxidizing agent, the lens is removed from its mountin~
apparatus and placed in a solution of sodium bicarbonate
which neutralizes the sulfuric acid and halts any further
25 oxidation of dye. The opaqued, tinted lens is then placed
in distilled water for fifteen minutes or so, removed
therefrom and placed in saline and then autoclaved. Thirty
minutes following autoclaving, the pH of the lens is checked
to see that it meets specifications (pH 5.50 8.50).
3o
~9~30t~
1 It is anticipated that those skilled in the art
may devise various alternatives or modifications to the
disclosed embodiment~ once possessed of the present
disclosure. ~s such this disclosure is not intended to
5 limit the invention, but rather to illustrate a preferred
embodiment, the spirit and scope of the invention being
defined by the claimed appended hereto.
3
