Note: Descriptions are shown in the official language in which they were submitted.
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CONTACT LENS
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BACKGROUND OF THE INVENTION
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Field of the Invention:
This invention relates to contact lenses and
has particular reference to improvements in lenses
used for the correction of presbyopia.
Discussion of the Prior Art:
Multifocal contact lenses are presently of
two basic designs, namely the truncated base type
and annular reading power type. The former rests
on the lower lid so that the lens is pushed up with
lowering of the gaze bringing a reading power segment
over the optical axis of the eye.
While a number of embodiments of this type
~ 15 of lens can be found in tXe art (e.g. as in U.S.
; Patent No. 3,102,157 and discussed in U.S. Patent
No. 4,268,133) it is well-known to the artisan that
difficulties result from movement of the lens over
the cornea with blinking or rotation of the truncation
away from its operative position.
In connection with the annular reading power
lens design, adaptation is difficult since both distance
viewing and reading powers produce simultaneous retinal
- images requiring separation by the brain. An example
of this type of lens can be found in ~.S. Patent -
No. 3,270,099.
Other schemes for multifocal viewing wi~h -
contact lenses include lowered center of gravity
devices as in U.S. Patent No. 3,279,878 including
the use of weights embedded in the lens structure
for orientation of viewing segments as in U.S. Patent
No. 3,431,327, surface relief as in U.S. Patent
No. 4,268,133 and/or edge chamfering as in U.S. Patent
No. 4,095,878. These, in addition to producing
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structual complication and costliness, afford less
than optimum wearing comfort and little assurance
of proper reading segment alignment with each attempt
to use.
In view of the foregoing, it is an object
of this invention to provide a contact lens which
overcomes the drawbac~s of prior art devices and
enables a presbyope to view detail at nearpoint with
optimum comfort and reliability of continued use.
Another object is to accomplish the above
r.. with an optical effect analogous to that produced
by multifocal spectacles lenses.
Still another object is to provide a contact
lens which is designed for the correction of visual
deficiencies of both presbyopic emmetropes and presbyopic
ametropes.
Other objects and advantages of the invention
- will become apparent from the following description.
SUMMAP~Y OF T~IE INVENTION
Objects and advantages of the invention are
accomplished with provision of a contact lens having
a main concavo-convex refracting portion and one
or more laterally extending plano carriers. The
2~ lens is designed for positioning against the globe
of the eye with the carrier~s) disposed in the inferior
fornix as stabilizing means. Only with downward - -~
gaze (rotation of the eye) does light enter the pupil -~ -
- throu~h the lens for presbyopic near vision assistance.
~he lens is servicable to presbyopic emmetropes
who need only this one lens for reading assistance
and to presbyopic ametropes wearing separate distance
viewing spectacle or contact lenses. ~he l~teer
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would slide behind the lens of the invention with
lowering of the gaze whiie the former would function
as for emmetropes but behind single vision spectacles
lenses, avoiding the often objected to appearance
of multifocal segments in spectacle lenses.
Details of the invention will become apparent
from the following description when taken in conjunction
with the accompanying drawings in which:
Fig. 1 is a front elevational illustration
of a preferred embodiment of the invention;
Fig. 2 is a cross-sectional view of the contact
lens of Fig. 1 taken along line 2-2;
Fig. 3 illustrates the contemplated wearing
position of the lens of Figs. 1 and 2 in a right -
eye, dotted line illustration depicting the inferior
fornix into which the lens is intended to be seated; - --
Fig. 4 is a cross-section through the eye -
and lens of Fig. 3 taken approximately along line
~-4;
Fig. 5 is a cross-sectional view similar to
Fig. 4 but illustrating a downward rotation of the -eye, i.e. lowering of the gaze, for use of the lens
in near viewing situations; - - - -
Fig. 6 illustrates use of the lens of the
invention in conjunction with the wearing of a separate
distance viewing contact lens; and
Figs. 7 and 8 illustrate modifications of
the invention.
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DESCRIPTION OF THE PREFERRED EM80DIMENTS :
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Referring more particularly to the drawings, ;
lens 10 comprises body portion 12 and laterally extending
carrier 14. Portion 12 of concavo-convex configuration
is designed to fit against the globe 16 of an eye
18 ~Figs. 3-5) with carrier 14 in the inferior fornix
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20 and extending toward the lateral canthus 21.
Carrier 14, functioning as stabilizing means, prevents
ro~ational and/or upward displacement of body portion
12 during use of the lens 10 whereby the eye is clear
for distance viewing over lens 10 as in Fig. 4 and
rotatable downwardly behind lens 10 for near viewing
through lens 10 as depicted in Fig. 5. The near
vision refractive power or "add" req~ired for a particular
presbyope is provided in the usual fashion of lens
anterior and posterior surface design with consideration
of the refractive index and thickness of material
from which the lens is constructed. Those interested ~~
in this aspect of contact lens design may refer to
U.S. Patent Nos. 3,915,609; 4,054,624; 4,123,407
and/or 4,284,399 for exemplification.
It is also pointed out that, with avoidance
of lens rotation in the eye according to the invention,
visual astigmatic correction can be provided in body -
- portion 12 with an assurance of proper cylinder axis
orientation at all times during use of the lens 10.
The provision of cylinder correction can be accomplished
in the well-known manner of rendering either the
anterior or posterior side of the lens toric, i.e.
of compound curvature. Those desiring further details
of means and method of correcting for astigmatism
may refer to the above referenced U.S. Patent Nos. ~-
- 4,268,133 and 4,095,878.
As further illustrated in Fig. 5, lens 10
may be used in conjunction with the wearering of ~- --
~pectacle lenses such as lens 22 shown with broken
line illustration. Thus, a presbyopic ametrope may
be provided with spectacle lens distance viewing
correction and lens 10 near vision (reading) c~rrection
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whereby the sometimes objectional aesthetics of multifocal
spectacle lenses is avoided. Similarly, distance
vision correction may be accomplished with the wearing
of conventional distance viewing contact lenses 24
as depicted in Fig. 6 which, in turn, will slide
behind lens 10 with lowering of the gaze for réading
or other near vision applications.
As further illustrated in Fig. 7, it is herein
contemplated that lenses of the invention may comprise
an intermediate viewing power area 26 in addition
to a near viewing portion 28. Thus, in a manner
analogous to the use of spectacle trifocals, the
wearer of lens lOa may partially lower his/her gaze
for viewing interm~diate objects throuyh area 26
lS while further lowering the gaze for acco~plishing
the already discussed near or reading power correction
with portion 28.
It should be understood that lens 10 may,
alternatively, be provided with a progressively varying
power, e.g. along an umbilic, e.g. axis A-A, of ~ig.
- . 1, in a manner analogous to that used in such spectacles
lenses as those of either U.S. Patent No. 4,056,311
or U.S. Patent No. 3,687,528, for example. The man~facture
of contact lenses of continuously varying dioptric
power is discussed in U.S. Patent No. 3,471,976.
- -It should also be understood that axes A-A
- of lenses depicted herein may be downwardly inclined
toward the nasal area of a wearer or extended vertically,
whichever is desired. Furthermore, lenses produced
according to this invention may include a second
~tabilizing carrier 30 as shown on lens lOb in Fig.
8. It is preferred, however, that this second carrier
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30 be shorter than carrier 14a, at least to the extent,
'of not reaching the relatively sensitive medial canthus
32 (Fi~ 3) when used.
All lenses illustrated in Figs 1-8 of the
drawings are intended for use in the right eye of
a patient. For left eye use, carriers 14, 14a and
30 are merely oppositely directed as is the inclination
of axis A-A in e~ch case, if the inclination is used.
It will become readily apparent to those skilled
in the art that there are various other modifications ,''-
and adaptations of the precise forms of the invention
here shown. Accordingly, the foregoing illustrations
are not to be interpreted as restrictive of the invention
beyond that necessitated by the followin~ claims.
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