Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND AND BRIEF SUMMARY OF THE INVENTION
This invention relates to the field of contact lenses and the
method of making them.
Basically, the invention relates to multisurface contact lenses
at least one of whose surfaces is contoured to satisfy a prescription
requirement of an individual patient. Whenever multisurface surfaces
are provided on a contact lens, some provision must be made to assure
that the lens orients itself naturally upon the eye so as to position
the lens for natural usage. To specify a particular case, the correc-
tive surface for far distances should be so oriented that it is within
the upper portion of the lens, the corrective surface for nearer
distance should be so oriented that it occupies a next lower position
of the lens, and so on, when the lens is in use on the patient's eye.
The lenses of this invention are characterized in that as a
natural consequence of making the lens, it is asymmetrically weighted
so that the aforesaid orientation of the various surfaces occurs. It
is to be noted that not all of the surfaces need provide optical
correction, this being a factor dependent upon the user's require-
ments.
In a broad aspect, then, the invention relates to contact lenses
of the multisurface type in which the lens will naturally orient
itself by rotation on the user's eye to position the nearest distance
zone of the lens in a lowermost position, the farthest distance zone
in an uppermost position and an intermediate distance zone, if any, in
a position intermediate these two, all in consequence of the physical
characteristics of the lens as obtained from the novel method dis-
closed herein.
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Stated otherwise, an object of the invention involves the method
of making a multisurface contact lens in which the lens is asymmetri-
cally weighted so as naturally to position the surfaces in predeter-
mined relation on the user's eye.
Another object of the invention resides in the novel method which
comprises the steps of providing a contact lens blank having a poster-
ior surface conforming to the corneal requirements of the user, form-
ing an initial anterior surface on the lens blank in generally cen-
tered relation to the optical axis thereof, then forming a second
anterior surface on the lens blank centered in offset relation to the
initial anterior surface to remove a portion of the initial surface
and intersect smoothly therewith to leave a residual portion of the
initial surface which defines a zone of the lens providing asymmetri-
cal weighting thereof, at least one of the surfaces being contoured in
conformity with a prescription reguirement of the user.
Another object of the invention resides in the method as afore-
said wherein the optical axis of the lens, the axis on which the
initial surface is centered and the axis on which the second surface
is centered all lie substantially in a common plane.
Another object of the invention is to provide a method of making
a contact lens having an asymmetrically positioned and weighted pres-
byopic correction zone so that the presbyopic zone naturally positions
itself lowermost in relation to the user's eye, the method involving
the steps of providing a contact lens blank having a posterior surface
conforming to the corneal reguirements of the patient, forming an
initial anterior surface on the lens blank corresponding to the re-
quired presbyopic correction, and then forming a second anterior
~urface on the lens blank in offset relation to the initial surface
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partially to remove the initial surface and intersect smoothly there-
with to form the presbyopic correction zone.
Another object of the invention is to provide a ~ethod of making
a multifocal contact lens which comprises the steps of forming the
anterior surface of a contact lens blank with a corrective surface
conforming with the nearest distance correction of a user's prescrip-
tion, and forming a second anterior surface portion of the lens blank
with a corrective surface conforming with a greater distance correc-
tion of a user's prescription than the aforesaid near distance correc-
tion and which smoothly intersects the first formed surface to leave a
residual of such first formed surface which is of generally crescent
shape.
In conformity with the preceding object, a further object of the
invention is to provide a method which includes the step of forming a
third anterior surface portion of the lens blank with a corrective
surface conforming with far distance correction of the user's pre-
scription which smoothly intersects the second formed surface portion
to leave a residual thereof between the first formed surface and the
far distance surface.
Anothér object of the invention is to provide a method of making
a multifocal contact lens which comprises providing a contact lens
blank having a posterior surface corresponding to the corneal require-
ments of a patient, forming an initial anterior corrective surface on
the lens blank in conformity with a relatively near distance require-
ment of the patient's prescription and in such relation to the pos-
terior surface as to determine the maximum thickness of the contact
lens to be produced, forming a second anterior surface on the lens
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blank in offset relation to the initial surface in accord with a
farther distance re~uirement of the patient's prescription so as to
remove a portion of the initial surface and intersect smoothly there-
with to leave a generally crescent-shaped initial zone of relatively
near distance correction surmounted by a second zone of the farther
distance correction.
Still another object of the invention is to provide a method as
above including the further step of forming a third anterior surface
on the lens blank in offset relation to the second anterior surface
and in accord with the farthest distance correction required by the
patient's prescription to intersect smoothly with the second surface
and leave a generally crescent-shaped second zone surmounted by a
third zone of the farthest distance correction.
It is also an object of this invention to provide novel contact
lenses having physical and corrective characteristics as described
above.
These and further objects of this invention will become more
apparent as this description proceeds with relation to the drawing
Figures in which:
. BRIEF DESCRIPTION OF THE DRAWING FIGURES
Figure 1 is a cross-sectional view taken along the plane of
section line 1-1 in Figure 2 and illustrating a lens blank provided
with a posterior surface and the initial anterior surface;
Figure 2 is a plan view of the lens blank as in Figure 1:
Figure 3 is a cross-sectional view taken along the plane of
section line 3-3 in Figure 4 and illustrating the provision of a
second anterior surface and its smooth intersection with the initial
anterior surface;
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Figure 4 is a plan view of the lens of Figure 3 illustrating the
interaction between the initial and second surfaces in producing a
crescent shape of the initial zone of the lens;
Figure 5 is a cross-sectional view taken along the plane of
section line 5-5 in Figure 6 and illustrating a third anterior surface
of the lens and its smooth intersection with the second anterior
surface;
Figure 6 is a plan view of the lens according to Figure 5 illus-
trating the interaction between the second and third anterior surfaces
in producing a generally crescent shape of the zone of the lens de-
fined by the second surface; and
Figure 7 is a view similar to Figure 6 but illustrating how
variations in rotational axis offset in forming the second and/or
third anterior surfaces may be used to shape and position the various
zones of the lens.
DETAILED DESCRIPTION OF THE INVENTION
With reference at this time to Figures 1 and 2, a lens blank is
illustrated in which the posterior surface 10 has been configured or
contoured ln conformi^ty with the corneal requirements of the particu-
lar patient for which the lens is being made, this surface being shown
for the sake of simplicity as a surface centered at 11 on the optical
axis 12 of the lens and about which optical axis the lens is rotated
to form the surface 10 as well as the surfaces 13 and 15 about to be
described. The anterior surface of the lens is provided with a margi-
nal surface region indicated by the reference character 13, shown as
centered at 14 on the optical axis of the lens, and the initial
anterior surface which is formed thereon is the surface 15 which, for
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convenience, is shown as centered at 16 on the optical axis of the
lens. At this time, the lens is incomplete and requires further
working in order to render it usable. However, Figures 1 and 2 illus-
trate the initial steps which must be taken in order to practice the
method of this invention. The various surfaces illustrated may be
formed in any conventional fashion such as by lathe cutting them in
accord with well known techniques employed for making contact lenses.
It is well at this point to note that the lens body may be made from
any conventional material usable for contact lenses and the lens made
in accord with this invention may be a hard contact lens or it may be
a soft contact lens. It also should be mentioned that the various
anterior surfaces mentioned herein need not be spherical surfaces as
illustrated but may be other and different surfaces in accord with
usual techniques. For example, toroidal surfaces for astigmatic cor-
rection may be employed where desirable or necessary. Moreover, the
anterior surface 15 need not be formed by rotating the lens about the
optical axis 12, but may be formed by rotating the lens about an axis
offset slightly from the optical axis 12.
The next step in the method of this invention resides in the
formation of the second anterior surface on the lens as is illustrated
in Figures 3 and 4 and it is this step which imparts at least the
major asymmetrical weight distribution for the lens so that it may
naturally rotate on the patient's eye when in use so as to position
the zone of the lens bounded by the margins of the initial surface 15
in a lowermost position on the patient's eye. This second surface is
illustrated at 17 in Figure 3 and its center 18 is located along the
line L perpendicular to the midpoint of the chord C which connects the
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points T and 19, the second anterior surface 17 being formed by rotat-
ing the lens about the axis 12' which is offset from and parallel to
the axis 12, as shown. In Figure 3, the second anterior surface 17 is
shown as spherical, but it need not be as is permitted by currently
known cutting techniques. In any event, the cutting is carried out
such that the second surface 17 smoothly intersects with the initial
anterior surface 15 and with the marginal surface 13 to provide a
smooth margin 20 as illustrated in Figure 4 which delineates the upper
boundary of the residual, crescent-shaped zone of the initial surface
15 and the lower boundary of the new zone provided by the surface 17,
see particularly Figure 4. The formation of the second anterior
surface removes some of the lens material as is most clearly shown in
Figure 3 wherein the lens portion so removed is bounded by the origi-
nal initial surface portion 15', the original margin surface 13' and
the second surface 17, the asymmetrical weight distribution being
plainly visible from the Figure.
Except for conventional polishing, if desired, to remove the
possibility of any disturbing effect to the wearer due to the margin
at 20, the lens as so far described may be a finished lens. For
example, if the lens surface 15 has been formed in conformity with the
near or reading distance prescription requirement of a presbyopic
patient and the surface 17 has been formed in conformity with the far
distance correction requirements in accord with the patient's pre-
scription, the contact lens so formed constitutes a bifocal contact
lens which the patient may use by employing eye movements as are
required for ordinary bifocal eyeglasses.
In any case, it is to be noted that the lens as formed in accord
with Figures 1-4 has, upon the formation of the initial lens surface
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15, determined the maximum thickness of the finished lens and has,
upon the formation of the second surface 17, determined at least the
major asymmetrical weight distribution for the lens.
Figures 5 and 6 illustrate the formation of a trifocal contact
lens. As illustrated, the secondary surface 17 is formed in accord
with an intermediate distance correction required by the patient's
prescription by rotation of the lens about the offset axis 12' as
noted above, and a third anterior surface 21 is formed in conformity
with the far distance correction required by the patient's prescrip-
tion, but by rotation of the lens about the axis 12". The center of
curvature of the tertiary surface 21 is located along a line perpen-
dicular to the midpoint of a chord connecting the points 22 and T. As
was the case for the intersection between the initial and second
surfaces along the margin or boundary 20, the tertiary surface 21
intersects smoothly with the second surface 17 as shown at the point
22 in Figure 5 and creates a margin 23 as illustrated in Figure 6
which delineates the upper boundary of the residual, generally cres-
cent-shaped intermediate distance zone 17. Because the axes of rota-
tion 12' and 12" for forming the second and third surfaces 17 and 21
lie in a common plane also containing the optical axis 12 of the lens,
the two residual crescent-shaped zones defined by the surfaces 15 and
17 and the generally circular zone defined by the surface 21 are
symmetrical with a vertical plane through the lens and containing the
optical axis thereof when in use on the user's eye. This left/right
symmetry is considered desirable in the contact lenses of this inven-
tion.
Lenses in accord with this invention are multisurfaced and multi-
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focal. The necessary and sufficient condition is that the second
anterior surface formed is offset in relation to the initial anterior
surface of the lens so as to impart the asymmetric weight distribution
noted above. It should also be noted that the formation of the third
anterior surface imparts an even greater degree of weight asymmetry as
is evident from Figure 5 wherein it will be seen that some of the lens
material is removed between the extension of the secondary surface 17'
and the third surface 21.
It is also within the realm of this invention that the initial
surface lS formed on the anterior surface of the lens be centered in
offset relation to the optical axis which, in and of itself, will lend
some degree of weight asymmetry ab initio. The secondary surface and
the third surface, if any, will of course emphasize this weight asym-
metry.
Any lens material may be used as it becomes available and tech-
niques for forming contact lenses are likewise usable. Currently, the
rapid advancement in the composition and variety of optical materials
offered for the fabrication of contact lenses has been followed by
technological advances in the equipment used in the production of
contact lenses. MicrQprocessor and computer controlled lathes have
found their place in high tech production methods of contact lenses
along with laser technology for precise control and reproducibility of
the lenses. These developments permit the variations as are suggested
in Figure 7 easily to be utilized. This Figure illustrates that
variations in decentering may be employed to control the positioning
and/or sizes of the various zones of the lenses. Also, it is possible
to truncate the lowermost edge of the lens as indicated at 24 to
afford a degree of relief with respect to the lower eyelid of the
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user, which may be desirable for reading.
Lenses formed by the method described above are produced to fit
like any other well fitting contact lenses. The reading part of the
final lens is chosen to provide the reading prescription needed for an
individual wearer for whom the lenses are being made. The lens body
may be made in virtually any prescription power needed and from any
material. If an intermediate prescription is needed, the correct
curve is next cut into the lens body and prior to the final cut which
provides the far distance correction. After all prescription powers
are provided, the lens is then polished if needed to provide wearable
lenses. This polishing partly or completely obliterates the divisions
between the different power zones which provide the multifocal effect.
The diameter of the lens as well as the secondary curve height and the
diameter of the distance power will vary with the height of the bifo-
cal segment and the intermediate distance segment if used. These
zones are all variable to accommodate the various segment or zone
heights needed to accommodate each patient's eyes. These zone heights
vary with the distance from the lower edge of the pupil to the top
edge of the lower lid of the eye. The height or size of these zones
is controlied by the amounts of decentration of the curves of the
various surfaces. As noted, the lens can be further adjusted by
truncation of the lowermost edge of the lens if the reading and/or the
intermediate zones need to be lowered.
Having described my invention, it is to be understood that it is
not to be limited by the precise terminology and language employed
either above or in the following claims, but in accord with the spirit
and intent of the coverage intended by the claims herein.
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