Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02278428 1999-07-23
MARKED CONTACT LENS BEARING OPTICAL MARKING ELEMENT
Field of the Invention
The present invention relates to a marked lens, and
more particularly to a marked contact lens and a method of
making same.
Background of the Invention
During the past 10 to 15 years, contact lenses have
tended to replace glasses for correcting vision problems.
These days, an entire industry exists for contact lens
manufacturing and retailing.
One of the problems associated with contact lenses is
marking the lens in order to allow the users to wear them
properly, in the right position. Some lenses have to be worn
in an "upright" orientation while soft lenses must be worn
without inverting them, i.e. wearing them inside-out.
Generally, identification and orientation marks applies to
all kinds of contact lenses.
Various methods of contact lens identification are
known in the prior art. One method is printing a visible
mark on the periphery of the lens. However, this method is
not suited for wet molded soft lenses since the printing
must be performed on a dry surface and the lenses are never
in a dry state. Furthermore, the dark mark printed on lenses
may be too visible, so observers may even see the mark when
the lens is worn by a person.
CA 02278428 1999-07-23
Another method is to engrave or impart a mark on a lens
producing an opaque surface. However, this surface is
necessarily rough and may be felt by the wearer, thus
producing discomfort. The engraved mark may also attract and
retain proteinaceous and other types of deposits creating
propitious conditions for an infection.
Another method of marking contact lenses is to mark
them using a laser. However, this method can not be employed
for wet molded soft contact lenses. It is also time-
consuming and expensive.
Summary of the Invention
It is therefore a broad object of the present invention
to provide a method of marking transparent and semi-
transparent thin surfaces by providing optical means by way
of varying the form of such surfaces on small areas.
It is a more specific object of the present invention
to provide a method of marking contact lenses using a number
of optical elements.
It is also an object of the invention to provide a
marked contact lens with markings appearing to be bright or
dark (depending on the focal length of the optical element
and the distance at which the lens is held by the viewer)
when viewing a light source through the lens.
According to the invention, it is an object of the
present invention to provide an identification, orientation
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or inversion marking method for contact lenses using at
least one optical element.
In a broad aspect of the present invention, the
identification method using optical elements is not
restricted to lenses. Even if the invention is applicable to
all kinds of lenses, including dry or wet lenses as well as
soft or rigid lenses, the present method may also be used
for marking any other kind of transparent or semi-
transparent material that needs to be marked.
For clarity, this text uses the term "surface
orientation" to designate the orientation of a lens with its
concave surface toward the wearer's eye, as it should be
worn. The main object of the present invention is to provide
an easy information to the lens user concerning the right
surface orientation of the lens, before the lens is applied
on the eye's surface.
Inversion identification is applicable to soft lenses,
where the concave side is frequently inverted outwardly into
a convex shape in which state the lens is not suitable to be
worn. However, such a state of the lens is not clearly
visible to the observer and often times people may
incorrectly wear their lenses.
According to the invention, instead of marking contact
lenses as in the prior art by adding a color on them such as
by printing or engraving a mark on them, the present
invention uses microstructure surface variations, such as
dot or cylindrical microlenses, having the form of concave
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or convex semi-spheres or semi-cylinders (the cross-section
may also be elliptical or aspheric), which are applied on
the surface of the contact lens in order to provide
identification and orientation marks for allowing the user
to wear the lenses in the adequate position. The surface
variations are small and their surface is smooth and highly
polished therefore these microlenses do not attract and do
not retain proteinaceous and other deposits. Furthermore,
these microlenses are not felt by the wearer's eyelid. The
dimensions of the microlenses are chosen so as to avoid any
irritation when worn by the user. However, when removed and
held up toward a light source, they permit to the user to
clearly see them, thus providing information on the right
position they have to be worn in.
In a preferred embodiment of the present invention,
such optical elements are used to form letters or other
distinctive signs at specific locations on the contact lens
surface and these letters or signs provide position
information to the user.
In another preferred embodiment of the invention, the
optical elements may be located on a single side of the
lenses or on both sides of the lenses. In the latter case,
the optical elements may be even smaller in depth or height
if they are applied in conjunction to one another, one on
each face of the lens, thus superposing the optical effect
seen by the human eye when looking to the lens toward a
light source.
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CA 02278428 2007-04-10
According to the invention, there is provided a marked
contact lens comprising at least one microlens optical marking
element integrally formed on a surface of the contact lens in
a peripheral area thereof. Preferably, each microlens optical
marking element comprises a cross-section having a single
concave or convex surface.
The invention also provides a method of manufacturing a
marked contact lens comprising the steps of: forming at least
one microformation in a contact lens manufacturing mold for
integrally forming a microlens optical marking element; and
molding a lens in the mold to obtain the marked contact lens.
Preferably, each microlens optical marking element comprises a
cross-section having a single concave or convex surface.
The invention further provides a marked lens comprising
at least one microlens optical marking element integrally
formed on a surface of the lens in a non-image forming area
thereof.
Brief Description of the Drawings
The invention will be better understood by reference to
the accompanying drawings in which:
Figures la to if illustrate prior art techniques of
marking contact lenses, specifically, Figure la is a front
view of a sphero-cylindrical contact lens having orientation
marks indicating the prism ballast on the lens for holding the
lens in a particular position; Figure lb is a front view of a
contact lens having printed or engraved marks; Figures lc, ld,
le and if are a plan and a side view of a non-inverted and an
inverted contact lens respectively having AL/JA inversion
marks;
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Figure 2 respectively illustrates the prior art
principal of a semi-cylindrical lens which forms a straight
line image when a person looks through it at a light source;
Figures 3a and 3b illustrate microlens optical elements
which are used in the preferred embodiment to mark the
contact lens, specifically, Figure 3a shows a number of
semi-spherical optical elements used for creating the two
letters AL on the lens surface, while Figure 3b shows semi-
cylindrical elements used to form the same two letters on
the lens surface; and
Figure 4 is a partial sectional view of the contact
lens according to the preferred embodiment of the present
invention wherein dual optical elements are used to create
an optical mark on both lens surfaces.
Description of the Preferred Embodiments
In the preferred embodiment, optical elements are used
to mark lenses. These marks are used to provide lens
position information to the lens user, so lenses may be worn
in the right position. Figure 1 shows printed and engraved
marks used in the prior art in order to provide position
information to the lens wearer.
According to the present invention, semi-spherical or
semi-cylindrical optical elements are provided on the
surface of the contact lens for providing lens position
information to the lens user. An important characteristic of
such marks is that they are not felt or seen by the wearer
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while the lenses are worn. They are, however, clearly
visible when the lens is examined visually, especially when
held toward a light source. As an example, a semi-
cylindrical optical element 20 is shown in Fig. 2; the
cylindrical element 20 is seen as a straight line 22 when a
user 24 looks through it at a light source 26.
The optical marks on the contact lenses are composed by
a plurality of microlens optical elements which are imparted
on the surface of the contact lens. Each of these optical
elements 20 acts as either a spherical lens 21 or a
cylindrical lens 20 (or a combination of them) applied on
the contact lens 10.
Figure 3 illustrates some optical marks 28 having the
form of two letters AL and which are composed of spherical
elements 21 (Fig. 3a) and cylindrical elements 20' (Fig.
3b) . In the case of a spherical element 21, the mark would
appear to the viewer as a bright or dark point (depending on
the focal length of the optical element and the distance at
which the lens is held by the viewer) on the contact lens
when the lens is held in front of a light source. In the
case of a cylindrical element, the mark appears as a bright
or dark line, as shown in Fig. 2.
In the preferred embodiment, the mark "AL" composed of
cylindrical elements is provided on a contact lens. When a
user examines such a contact lens 10, as the one shown in
Fig. 4, in the right way, i.e. the concave surface 30 of the
lens toward the eye, the user sees the letters "AL" and he
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knows this is the right orientation the lens is suppose to
have. If the lens has its inside part 30 facing outwardly
(i.e. it is inverted and its outer surface 32 is now toward
the eye) then the user sees the letters "JA", as better
shown in Figs. id and lf, and knows that this is the wrong
orientation of the lens, so he may invert it before applying
it onto the eye.
In the preferred embodiment of the present invention,
the size of the optical marks are of the order of 2 mm in
length and are located at the periphery of the contact lens.
Other sizes of marks as well as other locations may be
suitable as well, as long as they do not interfere with the
wearer's vision and are not visible to others when worn by
the wearer. The saggittal depth or the height of the optical
elements 20 and 21 is preferably not more than 1.5 microns
so the lens wearer can not feel them. The following table
shows approximate dimensions of the optical elements in the
preferred embodiments. These dimensions are provided as an
example only and are not limited to the values provided.
Table Saggittal Height/Depth of the Optical Elements
Width of Sphero-Cylindrical Elements
W=0.20mm W=0.30mm W=0.40mm
Dioptric Power of Element
+/- 5.00 D H/D=0.00061mm H/D=0.00138mm H/D=0.00245mm
+/-10.00 D H/D=0.00067mm H/D=0.00151mm H/D=0.00268mm
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+/-15.00 D H/D=0.00073mm H/D=0.00164mm H/D=0.00292mm
In another preferred embodiment of the present
invention, the depth or height of optical elements 20 and 21
are substantially reduced even further if the elements are
applied in conjunction with one another, one on each side of
the contact lens, as shown in Fig. 4. Concave or convex
elements of smaller depth or height may be used for
generating an optical mark having the same visibility as a
mark of greater height or depth applied on a single side of
a lens.
All optical elements disclosed in the present
application have a smooth surface and have no abrupt sides
so the surface transition from the optical element to the
contact lens is smooth and does not comprise any edges
irritating to the user's eyelid. This feature is an
improvement over the prior art because it does not retain
impurities, it is not felt by the wearer, and it is not
visible for an observer when worn on the eye, while
remaining clearly visible when removed and examined visually
by the user.
In a preferred embodiment of the present invention, the
method of imparting the optical elements 20 and 21 onto the
contact lens 1.0 for creating optical marks 28 is to
incorporate the mark 28 into the optical molds used to mold
the contact lenses so that no other step is added to the
lens manufacturing process. The molds may be micro-machined
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or precision etched to achieve the precise desired shape of
the microlens optical marking elements.
