Note: Descriptions are shown in the official language in which they were submitted.
104359~
The present invention relates to medicine, and more
particularly to a combined contact lens and a method of man-
ufacturing thereof. Said combined contact lens can be used to
correct vision in some diseases and pathological conditions
of the cornea, for example, keratoconus, astigmatism, cicatrices
of the cornea, etc.
Known in the prior art are rigid contact lenses made
mostly of polymethylmethacrylate. The method of manufacturing
the~e lenses consists in preparing a polymer blank and sub-
sequent mechanical processing thereof into the required shap~s.
Despite the fact that rigid lenses ensure the required
optical effect they are badly tolerated by patients due to
metabolic disorders in the cornea.
Also known in the prior art are contact lenses made of
soft hydrophilic materials, mainly of hydroxyethylmethacrylate
polymerization products. The method of manufacturing these
lenses consists in preparing a polymer blank by polymerization
of hydroxyethylmethacrylate in the presence of an initiating
agent, for example, benzoyl peroxide, dinitrilazo-bis-isobutyric
acid, etc., and also in the presence of a solvent, or without it,
and in the presence of a linking "D",agent, e.g. dimethylacrylate
ethylene glycol. The polymerization process is effected in a
mould, and
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the blank is then worked mechanically to impart the desired shape
thereto.
I The disadvantage inherent in soft contact lenses is
! that in cases with aspheric cornea (astigmatism, cicatrices of
the cornea, etc.) the soft contact lens fails to correct the
defect of vision since the surface of the lens follows the
defective curvature of the cornea.
¦ Known also is a combined contact lens consisting of
? a zone of hydrophilic material with a solid body of an opticallytransparent material fixed in the centre of the inner side of
the lens ~facing the eye). The method for manufacturing this
lens is similar to those for manufacturing rigid and soft
~ contact lenses. But the combined lens fails to keep the shape
! f the optical surface in cases with aspherical cornea. More-
I over, the presence of two refractive media in the optical zone
¦ impairs the image on the retina.
The object of this invention is to provide a combined
contact lens that will ensure high optical efficiency and can
be well tolerated by the patients.
Said object has been attained by a combined contact
lens which consists of a zone of hydrophilic material, an aperture
in the centre of said zone, and a solid body of an optically
transparent material fixed in said aperture, said solid body
being made as a rod bonded chemically with said zone, characterized
in that said hydrophilic material comprises a hydroxyl-containing
monomer and said transparent material comprises a polymer which
is inactive in water but which swells in the solution of said
hydroxyl-containing monomer said monomer being chemically bonded
to said polymer by fusion.
D
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1043598
¦ It i9 recommendable to use polyoxyalkylmethacrylate
as the hydrophilic material and polymethylmethacrylate as the
optically transparent material of the solid body in the proposed
! combined contact len~.
The method for manufacturing the proposed combined
contact lens comprise~: polymerizing a hydroxyl-containing
monomer in the presence of a polymerization initiator, a solvent,
¦ and a linking agent in the mould, disposing a rod in the centre
I o~ said mould, said rod being made from a polymer inactive in
water but swelling in the solution of starting hydroxyl-containing
monomer, thereby forming a blank comprising a peripheral zone
of a hydrophilic material chemically bonded to said rod, and
mechanically working said blank.
¦ It is recommendable that polymethylmethacrylate be
¦ used as the polymer to give the rod the required optical and
mechanical properties.
It is also recommendable that water should be used
as the solvent and that it should be added in a quantity
corresponding to the equilibrium swelling of the resulting
polymer.
In order to improve elasticity of the zone of the
hydrophilic material, hydroxyethylmethacrylate is recommended
to be used.
For a better understanding of the invention it will
be further illustrated with an exemplary description of the
process for preparing the proposed combined contact lens with
reference to the appended drawings in which:
D ~
1043S98
Fig. 1 shows a i~ectional view of a combined contact
lens according to the invention'
Fig. 2 is a top view of the same lens, and
Fig. 3 is a lens according to the invention fixed on
the eye of the patient.
The proposed combined lens consists of a zone of
hydrophilic material 2 (Figs 1 and 2) and a solid body 1 ~Figs 1
and 2) made in the form of a rod and chemically bonded to said
zone inside an aperture.
The proposed contact lens is a convexonconcave shell
having variouis radii of curvature of spherical surfaces Rl, R2,
R3 and R4 (Fig. 1).
The solid body made in the form of a rod is an optically
transparent polymer non-swelling in water, preferably polymethyl-
methacrylate, having good mechanical strength, adequate optical
properties, and non-toxic. It is recommendable that the material
for the hydrophilic zone should be iselected from a series of
polymer derivatives of acrylic or methacrylic esters of polyoxy
compounds. Preference should be given to polyoxyethylmethacrylate,
since it ensures high elasticity and good tolerance of the lens,
The hydrophilic zone can be made either of a material
having the same swelling ability, or of a combination of
materials having different swelling abilities, so that in order
to meet various requirements, the hydrophilic zone can be made
in the form
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of concentric zones.
The swelling ability of the hydrophilic material can
increase from the centre toward periphery to facilitate correct
fitting of the lens to the eye-ball and to ensure good tolerance.
The inner surface of the proposed lens should be made
so that a certain gap remained between the lens and the cornea
3 of the eye 5 (Fig. 3). The lens can be applied onto the eye
so that the hydrophilic material zone should contact the cornea
3 of the eye (Fig. 5), or the sclera 4 (Fig. 3), or both.
The proposed contact lens was tested on six patients
with various disea3es of the eye (high myopia, irregular
astigmatism, traumatic aphakia, keratoconus). The vision of the
patients had been corrected with rigid contact lenses. The
attempt proved to be effective from the optical aspect, but failed
due to bad tolerance. The effect was with the known hydrophilic
contact lenses from the point of view of tolerance, but the
acuity of vision remained inadequate.
We tried the proposed contact lenses with these patie~ts
and the acuity of ~ision in all cases was at the level only at-
tainable with the known rigid lenses (from 0.7 to 1.0 per cent)
while the tolerance was much better and the terms of wearing the
lenses were much longer.
Clinical tests of the combined contact lenses have
shown that they can be used effectively to attain optimum optical
effect in various abnormalties of refraction and in pathological
`` ~043598
states of the cornea that otherwise drastically impair the power
of vision. The tolerance of the proposed lenses i8 good.
The method for preparing the proposed combined contact
lens consists in the following. A mould is provided with a rod
fixed in its centre. The rod is made of a polymer that is inac-
tive toward water but swells well in a solution of the starting
hydroxyl-containing monomer. The hydroxyl-containing monomer
for example, hydroxyethylmethacrylate, is polymerized in the
presence of a linking agen~ taken in a quantity of 0~05 - 5
mole per cent of the solvent, and an initiating agent. Ethylene-
glycol dimethacrylate, diethyleneglycol dimethacrylate, or some
other linking agents can be used.
Any known initiating agents, e.g. acyl peroxides,
esters of peracids, etc., as well as ultraviolet and ionizing
radiation can be used to initiate the polymerization process.
Said rod is made from material, preferably polymethyl- -
methacrylate, that does not swell in water but swells in a sol-
ution of the starting hydroxyl-containing monomer, that ensures
fast diffuse union of the hydrophilic and non-hydrophilic
portions of the blank.
It is recommendable to use water as the solvent, although
mixtures of water with organic solvents, e.g. ethyleneglycol,
can also be used. It is aliso necessary that the concentration
of the monomer correspond to the concentration of the polymer
that is
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formed out of it in the equilibrium swollen "D" state, This
ensures absence of tension in the hydropilic zone and, hence,
absence of deformation.
The obtained polymerized blank is worked mechanically
by conventional methods into a combined contact lens.
For a better understanding of the invention, the
following examples of its practical embodiment are given by
way of illustration.
Example 1
A tetrafluoroethylene mould, 17 mm in diameter, with
a rod, 6.5 mm in diameter, made from plasticizer-free polymethyl-
methacrylate and fixed in the centre of the mould, is filled with
4.8 g of ethyleneglycol monomethacrylate containing 0.16 per cent
of ethyleneglycol dimethacrylate, and 8 mg of dicyclohexyl
peroxidicarbonate, and then 3.2 ml of water are added.
Polymerization is conducted for ten hours at a temp-
erature of 45C, the resulting polymer blank i~ then extracted
froln the mould and dried at a temperature of 80C. A combined
contact lens i~ manufactured from the blank by mechanical
processing.
Example 2
A tetrafluoroethylene mould sirnilar to that used in
Example 1 is filled with a mixture of 6.0 g of ethyleneglycol
monomethacrylateand 10 ml of dinitrile of azo-bis-isobutyric acid,
0.25 g of diethyleneglycol dimethacrylate, and 3.0 g of water, and
poly-
104;~598
merization is conducted for 24 hours at a temperature of 60C.The re~ulting blank is then extracted from the mould, dried
at a temperature of 80C, and worked mechanically into a com-
bined contact lens.
