Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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PROGRESSIVE ADDITION LENSES WITH MODIFIED CHANNEL POWER
PROFILES
Field of the Invention
The present invention relates to multifocal ophthalmic lenses. In particular,
the
invention provides lenses in which channel power progression modification is
achieved
without a significant increase in unwanted astigmatism.
Background of the Invention
The use of ophthalmic lenses for the correction of ametropia is well known.
For
example, multifocal lenses, such as progressive addition lenses ("PALs"), are
used for
the treatment of presbyopia. Typically, a PAL provides distance, intermediate,
and
near vision zones in a gradual, continuous progression of increasing dioptric
power.
PALs are appealing to the wearer because the lenses are free of the visible
ledges
between the zones of differing optical power that are found in other types of
multifocal
lenses, such as bifocals and trifocals.
As the wearer's eyes move from the distance, through the intermediate, and
into
the near vision zones of a PAL, the wearer's eyes converge bringing the pupils
closer
together. Ideally, the design of a PAL would be such that the power
progression from
the distance zone, through the intermediate and to the near zone matches the
wearer's
requirements as the eye scans the lens. However, in the design of conventional
PAL's,
a trade-off is made between the power progression distribution and the level
of
unwanted astigmatism of the lens.
Unwanted astigmatism is astigmatism introduced or caused by one or more of
the lens surfaces resulting in image blurring, distorting, and shifting for
the lens wearer.
In order to reduce unwanted astigmatism, the power progression is distributed
over a
greater length in some designs. Due to this lengthened distribution, the power
distribution may not meet the wearer's requirements and the wearer may have to
alter
their natural viewing posture, or head and eye position, in order to use the
intermediate
and near vision zones of the lens. Additionally, a lens
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with a lengthened channel cannot fit into the smaller spectacle frames
currently
preferred by lens wearers. In those lens designs in which the power
progression
distribution is over a shorter length, the level of unwanted astigmatism is
increased
reducing the useable area of the lens. Thus, a need exists for a PAL that
provides a
modified channel power progression, but that does not significantly increase
the lens'
unwanted astigmatism.
Brief Description of the Drawings
FIG. 1 is a diagrammatic representation of the lens power profile of the lens
of
Example 1.
FIG. 2 is a diagrammatic representation of the surface and lens power profiles
of a lens of the invention.
FIG. 3 is a diagrammatic representation of the surface and lens power profiles
of a lens of the invention.
FIG. 4 is a diagrammatic representation of the surface and lens power profiles
of a lens of the invention.
FIG. 5 is a diagrammatic representation of the surface and lens power profile
of
a lens of the invention.
FIG. 6 is a diagrammatic representation of the surface and lens power profile
of
a lens of the invention.
FIG. 7 is a diagrammatic representation of the surface and lens power profile
of
a lens of the invention.
FIG. 8 is a diagrammatic representation of the surface and lens power profile
of
a lens of the invention.
FIG. 9 is a diagrammatic representation of the surface and lens power profile
of
a lens of the invention.
Description of the Invention and its Preferred Embodiments
The present invention provides progressive addition lenses, as well as methods
for their design and production, in which the power distribution between
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the distance and near vision zones is modified. This modified distribution
permits the
requirements of the lens wearer's eye path to be met. Further, the modified
distribution
may be used to permit the lens to be used in spectacle frames of any
dimensions. The
modified channel power distribution of the lenses of the invention is obtained
without
reducing the useable lens surface by introducing a significant amount of
additional
unwanted astigmatism.
In one embodiment, the invention provides a lens comprising, consisting
essentially of, and consisting of: a.) at least one first surface that is a
progressive
addition or regressive surface, the at least one first surface having a first
channel with a
first channel length and a channel power profile and; b.) at least one
modifying surface
having a power profile, wherein the channel power profile of the lens is the
vector sum
of the first surface's channel power profile and modifying surface's power
profile and
the lens channel power profile, channel length, or both is modified relative
to the first
surface's channel power profile and channel length. By " lens" is meant any
ophthalmic lens including, without limitation, spectacle lenses, contact
lenses,
intraocular lenses and the like. Preferably, the lens of the invention is a
spectacle lens.
By "progressive addition surface" is meant a continuous, aspheric surface
having distance and near viewing or vision zones, and a zone of increasing
dioptric
power connecting the distance and near zones. By "regressive surface" is meant
a
continuous, aspheric surface having zones for distance and near viewing or
vision, and
a zone of decreasing dioptric power connecting the distance and near zones. By
"channel" is meant the corridor of vision that is free of unwanted astigmatism
of about
0.75 diopters or greater when the wearer's eye is scanning through the
intermediate vision zone to the near vision zone and back. By "channel power
profile"
is meant the power distribution along the channel length. By "channel
length" is meant the distance from the lens' fitting point to a point along
the channel at
which the dioptric add power is about 85 percent of the dioptric add power of
the
surface. By "fitting point" is meant the point on a lens aligned with the
wearer's
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pupil in its distance viewing position when the wearer is looking straight
ahead. By
"power profile" is meant the power distribution along a modifying surface. By
"modified" is meant one or both of a change in the channel power profile or a
change
in the channel length.
It is one discovery of the invention that a channel power profile of one or
more
progressive addition or regressive surface may be modified by combining the
surface
with one or more modifying surfaces. A modifying surface, for purposes of this
invention, is a continuous, aspherical surface having a power profile, the
power
profile with one or more power maxima along its length, one or more power
minima
along its length, or a combination thereof. The modifying surface may be a
rotationally symmetric surface without a channel, but preferably is a
progressive or
regressive surface. The modifying surface power profile is designed so that,
when the
modifying surface is combined with one or more of a progressive addition or
regressive surface, the channel power profile, the channel length, or a
combination
thereof of the progressive addition surface or regressive surface is altered.
The
alteration may be of the power distribution along the channel, while the
original
channel length is maintained. Alternatively, the channel power profile may
change
and the channel length may be lengthened or shortened. The modifying surface
power
profile, preferably, is continuous and exhibits no abrupt power changes to
avoid
introduction of unwanted astigmatism or image jumps into the lens.
One ordinarily skilled in the art will recognize that any of a variety of
positions of the modifying surface power profile in relation to the
progressive addition
or regressive surfaces' channel power profile may be used in order to achieve
the
desired modification of the channel power profile. For example, the top and
bottom of
the modifying surface's power profile and progressive addition or regressive
surface
channels may be aligned. As an alternative example, in the case in which the
modifying surface has a minimum in the power profile and the surface is used
in
combination with a progressive surface, preferably the start of the modifying
surface
power profile will be aligned with the top portion of the progressive addition
or
regressive surface channel. This alignment acts to subtract power from the
progressive
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surface power profile and shorten the channel length of the resulting lens. As
yet
another alternative, a modifying surface is combined with a progressive
surface, the
modifying surface with a maximum in its power profile preferably is situated
so that the
end of the modifying surface power profile will be aligned with the with the
lower
portion of the progressive addition surface's channel so that it adds power
to, or
increases, the power in the channel's lower portion. This alignment serves to
result in
a lens that reaches full near vision power using a shorter length. For the
previously
described alternatives, the alignment will be reversed in case in which the
modifying
surface is used in combination with a regressive surface. Finally, in the case
in which
the modifying surface power profile has both a maximum and a minimum, the
start of
the modifying surface's power profile may be aligned with the progressive or
regressive surface's channel's top portion. This alignment may be used to
increase or
decrease the power over substantially all of the channel length or to form a
plateau of a
specified power within the channel.
The modifying surface may or may not provide additional dioptric add power to
the lens. By "dioptric add power" is meant the amount of dioptric power
difference
between the distance and near vision zones. Preferably, the modifying surface
provides
less than about 3.50 diopters, more preferably less than about 1.00 diopters,
most
preferably less than about 0.50 diopters. By limiting the dioptric add power
contribution of the modifying surface, the introduction of unwanted
astigmatism into
the lens is minimized.
The progressive addition, regressive, and modifying surfaces useful in the
invention may be designed and optimized using any known method including,
without
limitation, the use of commercially available design software. The progressive
addition, regressive, and modifying surfaces may be on a convex
surface, a concave surface, a surface intermediate a convex and concave
surface, or any
combination thereof.
One ordinarily skilled in the art will recognize that one or more progressive
addition or regressive surfaces may be used in combination with a modifying
surface.
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Additionally, the features resulting from the physical combination of a
modifying and
progressive addition or regressive surface may be incorporated into a single
lens
surface. More than one modifying surface also may be used with one or more
progressive addition and regressive surfaces. For example, a modifying surface
with a
power maximum in combination with a modifying surface having a power minimum
may be used in combination with one or more of a progressive surface,
regressive
surface, or a combination thereof.
The channel power profiles and power profiles for each surface used in the
lenses of the invention may be selected from a variety of profiles including,
without
limitation, linear, spline, trigonometric, and the like. In the case in which
one or more
progressive addition or regressive surfaces is used, the channel power profile
for each
such surface may be the same or different.
The dioptric add power of each surface used in the invention is selected so
that,
when the surfaces are combined, the add power of the lens is substantially
equal to that
needed to correct the lens wearer's near vision acuity. The dioptric add power
of each
progressive addition surface individually may be about 0.25 diopters to about
3.50
diopters, preferably about 0.50 diopters to about 3.25 diopters, more
preferably about
1.00 diopters to about 3.00 diopters. For each regressive surface,
the dioptric add power may be about -0.25 diopters to about -3.50 diopters,
preferably
about -0.50 diopters to about -3.25 diopters, more preferably about -0.75
diopters to
about -3.00 diopters.
The refractive power range over the power profile for each modifying surface
individually may be about -2.00 to about + 2.00 diopters, preferably about -
1.00 to
about + 1.00 diopters, more preferably about -0.50 to about +0.50 diopters.
The progressive addition, regressive, and modifying surfaces each additionally
may
contain spherical power, cylinder power and axis, or combinations thereof.
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The lenses of the invention may be fabricated by any convenient means and
constructed of any known material suitable for production of ophthalmic
lenses.
Suitable materials include, without limitation, polycarbonate, allyl diglycol,
polymethacrylate, and the like, and combinations thereof. Such materials are
either
commercially available or methods for their production are known. Further, the
lenses
may be produced by any conventional fabrication technique including, without
limitation, grinding, whole lens casting, molding, then-noforming, laminating,
surface
casting, and the like, and combinations thereof. Casting may be carried out by
any
means including, without limitation, as disclosed in United States Patent Nos.
5,147,585, 5,178,800, 5,219, 497, 5,316,702, 5,385,672, 5,480,600, 5, 512,371,
5,531,940, 5,702,819, and 5,793,465.
The lenses of the invention may be manufactured to stock or in a custom
manufacturing system. If custom manufacturing is used, the modifying surface
to be
used for a particular prescription may be selected from an inventory of
modifying
surfaces to produce the desired channel power profile most suitable to a
particular
lens wearer.
The invention will be clarified further by the following, non-limiting
examples.
Exammples
Example 1
A conventional progressive lens is provided with a convex progressive
addition surface and a concave spherical surface. The convex surface distance
vision
zone curvature is 6.00 diopters and the near vision zone curvature is 8.00
diopters.
The channel length is 18 mm. The concave surface curvature is 6.00 diopters.
The
lens distance power is 0.00 diopters and the dioptric add power is 2.00
diopters. The
power profile for the lens is depicted in FIG. 1.
Example 2
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A lens of the invention is provided with a convex progressive addition surface
with a distance vision zone curvature of 6.00 diopters, a near vision zone
curvature of
7.80 diopters and a channel length of 18 mm. The convex surface power profile
is
depicted in FIG. 2. The lens concave modifying surface's power profile, also
depicted
in FIG. 2, starts at 0.00 diopters, decreases to -0.31 diopters, and then
increases to 0.20
diopters. The beginning of the convex and concave surface power profiles are
aligned.
The resulting, combined power profile, the lens power profile, is shown in
FIG. 2. The
lens channel length is 13 mm and the lens dioptric add power is 2.00 diopters.
Example 3
A lens of the invention is provided with a convex progressive addition surface
with a distance zone curvature of 6.00 diopters, a near zone curvature of 8.00
diopters
and a channel length of 18 mm. The convex surface power profile is depicted in
FIG.
3. The lens concave modifying surface's power profile, also depicted in FIG.
3, starts
at 0.00 diopters, decreases to -0.31 diopters, and then
increases to 0.00 diopters. The convex and concave surface power profiles are
aligned
so that the modifying surface power decrease is aligned with the top portion
of the convex surface's channel. The resulting, combined power profile, the
lens power
profile, is shown in FIG. 3. The lens channel length is 14 mm. The lens
dioptric add
power is 2.00 diopters and is contributed entirely by the convex progressive
surface.
Example 4
A lens of the invention is provided with a convex progressive addition surface
made of
a material with a 1.65 refractive index. The convex surface has a distance
zone
curvature of 6.00 diopters, a near zone curvature of 7.34 diopters and a
channel length
of 18 mm. The convex surface power profile is depicted in FIG. 4. The concave
surface is made of a material with a 1.50 refractive index and is also a
progressive surface. The distance curvature of the concave surface is 6.00
diopters, the
near curvature is 5.33 diopters, the dioptric add power is 0.67 diopters and
the channel
length of 18 mm. The concave power profile is shown in FIG. 4. The modifying
surface is intermediate the convex and concave surfaces and the power profile,
shown
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in FIG. 4, begins at 0 diopters, decreases to - 0.27 diopters and then
increases to 0
diopters.
The minimum curvature of the modifying surface ("MC") is 7.17 and is derived
as follows:
MC=DC-MPxnl-1.00
nl - n2
wherein nl and n2 are the refractive indices of the convex and concave surface
materials
and DC is the distance curvature, 6.00 diopters. The resulting lens, the power
profile of
which is shown in FIG. 4, has a distance power of 0.00 diopters, and add power
of 2.00
diopters, and a channel length of 14 mm.
Example 5
A lens of the invention is provided with a convex progressive surface with a
distance zone curvature of 6.00 diopters, a near zone curvature of 8.00
diopters and a
channel length of 18 mm. The convex surface power profile is depicted in FIG.
5. The
lens concave modifying surface's power profile, also depicted in FIG. 5,
starts at 0.00
diopters, increases to 0.20 diopters, and then decreases to 0.00 diopters. The
concave
surface power increase is aligned with the lower portion of the convex surface
power
profile. The resulting, combined power profile, the lens power profile, is
shown in
FIG. 5. The lens channel length is 16 mm and the lens dioptric add power is
2.00
diopters.
Example 6
A lens of the invention is provided with a convex progressive addition surface
with a distance zone curvature of 6.00 diopters, a near zone curvature of 0
diopters and
a channel length of 18 mm. The convex surface power profile is depicted in
FIG. 6.
The lens concave modifying surface's power profile, also depicted in FIG. 6,
starts at
0.00 diopters, decreases to -0.20 diopters, increases to 0.20 diopters, and
finally
decreases to 0.00 diopters. The beginning of the convex and concave surface
power
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profiles are aligned. The resulting, combined power profile, the lens power
profile, is
shown in FIG. 6. The lens channel length is 12 mm and the lens dioptric add
power is
2.00 diopters.
Example 7
A lens of the invention is provided with a convex progressive addition surface
with a distance zone curvature of 6.00 diopters, a near zone curvature of 8.00
diopters
and a channel length of 19 mm. The convex surface power profile is depicted in
FIG.
7. The lens concave modifying surface's power profile, also depicted in FIG.
7, starts
at 0.00 diopters, increases to 0.34 diopters, decreases to
-0.15 diopters, and finally increases to 0.00 diopters. The beginning of the
convex and
concave surface power profiles are aligned. The resulting, combined power
profile, the
lens power profile, is shown in FIG. 7. The lens channel length is maintained
at 19
mm, the channel power profile of the lens having an intermediate plateau at
1.00
diopters over a length of 4 mm, and the lens dioptric add power is 2.00
diopters.
Example 8
A lens of the invention is provided with a convex progressive addition surface
with a distance zone curvature of 6.00 diopters, a near zone curvature of 8.00
diopters
and a channel length of 19 mm. The convex surface power profile is
depicted in FIG. 8. The lens concave modifying surface's power profile, also
depicted
in FIG. 8, starts at 0.00 diopters, increases to 0.19 diopters, decreases to
-0.20 diopters, and finally increases to 0.00 diopters. The beginning of the
convex and
concave surface power profiles are aligned. The resulting, combined power
profile, the
lens power profile, is shown in FIG. 8. The lens channel length is increased
to 21 mm
and the lens dioptric
add power is 2.00 diopters.
Example 9
A lens of the invention is provided with a convex progressive addition surface
with a distance zone curvature of 6.00 diopters, a near zone curvature of 8.00
diopters
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and a channel length of 19 mm. The convex surface power profile is depicted in
FIG.
9. The lens concave modifying surface's power profile, also depicted in FIG.
9, starts
at 0.00 diopters, increases to 0.26 diopters, and finally decreases to 0.00
diopters. The
beginning of the convex and concave surface power profiles are aligned. The
resulting,
combined power profile, the lens power profile, is shown in FIG. 9. The lens
channel
length is reduced to 18 mm, the channel power
profile of the lens is increased over the entire channel length, and the lens
dioptric add
power is 2.00 diopters.
