Note: Descriptions are shown in the official language in which they were submitted.
113~i~341
METHOD AND COMPOSITION FOR TREATING CONTACT LENSES
FIELD OF THE INVENTIGN
The invention relates generally to a method and
composition for the treatment of contact lenses to remove inorganic
deposits and to prevent the formation of inorganic deposits on the
lenses.
BACKGROUND OF THE PRIOR ART
Soft contact lenses may be divided into two broad
categories, namely hydrophilic and hydrophobic lenses. Hydro-
phobic contact lenses are usually based on elastic and flexiblesilicone rubber (polyslloxane), and are generally made from
cross-linked dimethyl polysiloxane.
A typical preparation of a silicone contact lens is
disclosed in U.S. Patent No. 3,228,741 and comprises forming a
mixture of a suitable polymerization catalyst, up to 40g of a
silica filler, and the silicone polymer. Said mixture is then
molded and cured by heating to cross-link the polysiloxane
and to produce a finished clear lens. Increased consumer
acceptance of flexible silicone rubber lenses has created a need
for a cleaning solution which can be used effectively with such
lenses.
Hydrophilic soft contact lenses are hydrated gel
lenses which can be prepared by copolymerizing hydrophilic organic
monomers containing an olefinic double bond with a small amount of
a cross-linking agent which usually contains two polymerizab!e
olefinic double bonds. These lenses are usually based on
polyhydroxylated alkyl methacrylates and contain a polyhydroxyla-
ted alkyl methacrylate, such as polyhydroxyethyl methacrylate,
30 cross-linked with, for example, an hydroxyethyl dimethacrylate.
One of the problems connected with these types of
lenses is the formation, over a period of time, of insoluble
inorganic deposits on the lenses. These deposits are brought
to be primarily calcium based, e.g., calcium phospate and
35 calcium carbonate, but may also contain other inorganic
materials and associated organic materials, e.g., protein. The
presence of these insoluble inorganic deposits is a common
cause of lens intolerance and decreased visual acuity.
BRIEF SUMMARY OF INVENTION
1~ 40 I have now discovered a method and composition for the
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treatment of contact lenses, and especia11y silicone and hydro-
philic plastic contact lensesl ~o remove inorganic de?osits and to
prevent the formation of inorganic deposits on the lenses.
The method comprises contacting a contact lens with an
aqueous solution containing an effective amount of a sequestering
agent selected from the group consisting of a poly~letaphosphate,
gluconic acid and salts thereof for a period of time sufficient
to remove existing inorganic deposits and to prevent formation
of inorganic deposits.
The composition comprises a preserved saline so1ution
sontain~ng from about 0.01 to about 20% by weight of a sequester-
ing agent selected from the group consisting of a polyT~taphos-
phate, gluconic acid and salts thereof. The composition may
addit10nally contain an agent for sterilizing the lenses.
DETAILED DESCRIPTION OF THE INVENTION
The sequestering agents which may be used in th~s in-
vention are typically calcium sequesterins agents such as, for
example, polymetaptlosphates, ~luconic acid and salts thereof.
Su1table polymetaphosphates include sodium polymetaphosphate and
preferably sodium hexametaphosphate. Salts of gluconic acid which
may be used include common inorganic salts such as the sodium,
potasslum and calcium salts as well as other salts such as, for
example, calc;um borogluconate. The preferred sequestering agent
is sodium hexametaphosphate. All of the aforementioned compounds
are well-known in the art, are commercially available~ and have
been used heretofore for industrial processes such as, for example,
leather tanning, dying9 laundry and textile processing, water
softening, metal plating, mordanting fabrics and as photographic
processing aids. Therefore, it was surprising to discover that
periodic treatment of contact lenses with aqueous solutions of
these compounds prevent the formation of inorganic depost~s on the
lenses without harming ~he 7ens or the eye of the user of the lens.
The amount of sequestering agent which may be used in
the present invention ranges between about 0.01 and about 2~%
and preferably about 0.1 to about 5~ by weight.
The sequestering agents may be manufactured in a number
of convenient forms for use in the treatment described herein.
~or example9 the sequestering agent could be delivered in the fo~m
of a dry, unit dosage from such as a tablet wh~ch would be dissolved
1 1;36~3~l1
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in water prior to use. The sequesterinn agent could also forma part of a ~uffered or unt,uffered preserved or unpreserved sterile,
isotonic saline solution used to store the lenses. The sequesterin~
agents described herein may also be incGrporated into cold disin-
fecting systems containing lens preservatives and disinfectants.
The present invention may be further described and illus-
trated with reference to the following examples. It is to be under-
stood9 however, that the following examples are for the purpose of
illustration and the invention is not to be regarded as limited to
any of the specific compounds or formulations or conditions recited
therein. Unless otherwise stated, percents are by weight.
EXAMPLE I
A hydrophilic contact lens (Polymacon) ~Jhcih had been
worn for approximately two (2) years was examined and found to
have a heavy visible film de~osit. The lens was cleaned with an
enzymatic cleaner for ~4 hours ~ith little effect. The lens was
then asepticized (heated to lO~C for 15 minutes) for two (~)
cycles in a 20% solution of sodium hexametaphosphate in water.
The lens still retained some of the film-like material, bu~ after
one further treatment with the enzy~atic cleaner, the lens was
found to be free of film. This indicates that the ~eposit consisted
of both inorganic and protein materials since the enzymatic cleaner
rapidly (usually within four hours) and completely removes protein
films from hydroph~lic lenses.
EXAMPLE II
A hydrophilic human worn lens with an inorganic film was
cleaned with an enzymatic contact lens cleaner for 24 hours. A
heavy visible film remained on the lens. The lens was cut in half
and one-half was asepticized (heated to 80C for 20 minutes) for
30 four cycles in an aqueous solution containing 0.2% sodium hexameta- - phosphate, 0.1% boric acid, 0.01% disodium edetate, 0.85X sodium
chloride preserved with 0.~01% thimerosal at pll 7.4. Follo~in~
another three hour treatment with the enzyme cleaner solution, the
lens was free of Yisible deposits. The other half of the lens
treated in a similar manner9 except that ~he aseptor cycle was
omitted, still retaine~ its heavy inor~anic film.
EXAMPLE III
A hydroph~lic human worn lens w1th an inorganic film
was cleaned for four hours wit~l the enzyme cleaner. tlo chan~e in
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the film was noted. It was then alternately asepticized (heated
to ~0C for 20 Ininutes) in an aqueous solution containing ~1.2X
sodiun~ gluconate~ ~.1% boric acid, O.OlX disodium edetate, 0.85%
sodium chloride preserved with 0.001% thimerosal at p~ 7.4 (Formula
S No. 5945X) ~or 20 Minutes and cleaned for several hours with the
enzyme cleaner until three of these cycles had been cornpleted.
Photomicrographs taken ot` the same area of the lens at each step
show al~Dst complete removal of the heav~ inorganic deposit after
the three cycles. No visible deposi~s re~ained.
EXAMPLE IY
Hydrophilic contact lenses were soaked in a 1% aqueous
solution of calcium chloride for 30 minutes and then placed in test
solutions for 23.5 hours. This was repeated for 8D cycles. Test
Solution 1 was an aqueous 501ution containing ~.2% POLYSORBATE 80*
1.92% propylene glycol, 0.033~ alkyl triethanol ammonium chloride,
0.05% sodium bicarbonate, 0.002% sodium chlori~e, Q.0023% thimerosal,
and Test Solution 2 contained the same in~redients plus 0.~5% --
sodium hexametaphosphate.
Examination of the test lenses after 80 cycles revealed
calcium carbonate deposits on the lenses treated with Test Solution 1.
There were no deposits of calcium carbonate on lenses treated with
Tes~ Solution 2 demonstrating that the addition of sodium hexameta-
phosphate prevented the deposition of the insoluble calcium salts
on hydrophilic contact lenses.
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