U.S. patent application number 17/308944 was filed with the patent office on 2021-08-19 for soft contact lens with new stabilization zones for improved angular stability and comfort.
The applicant listed for this patent is Johnson & Johnson Vision Care, Inc.. Invention is credited to Pierre-Yves Gerligand, Philippe F. Jubin, Gary Richardson.
Application Number | 20210255484 17/308944 |
Document ID | / |
Family ID | 1000005567774 |
Filed Date | 2021-08-19 |
United States Patent
Application |
20210255484 |
Kind Code |
A1 |
Gerligand; Pierre-Yves ; et
al. |
August 19, 2021 |
SOFT CONTACT LENS WITH NEW STABILIZATION ZONES FOR IMPROVED ANGULAR
STABILITY AND COMFORT
Abstract
Ophthalmic lenses are described herein. An example ophthalmic
lens may comprise a first surface. The example ophthalmic lens may
comprise a second surface disposed opposite the first surface. The
second surface may be configured to abut at least a portion of an
eye of a wearer. The example ophthalmic lens may comprise a lens
stabilization zone disposed adjacent the first surface. At least a
contour of the lens stabilization zone may be configured to
minimize a recovery time for the ophthalmic lens to orient to a
resting position from a misaligned position.
Inventors: |
Gerligand; Pierre-Yves; (St.
Johns, FL) ; Jubin; Philippe F.; (Fernandina Beach,
FL) ; Richardson; Gary; (Jacksonville, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Johnson & Johnson Vision Care, Inc. |
Jacksonville |
FL |
US |
|
|
Family ID: |
1000005567774 |
Appl. No.: |
17/308944 |
Filed: |
May 5, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16411406 |
May 14, 2019 |
11029537 |
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17308944 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02C 7/048 20130101 |
International
Class: |
G02C 7/04 20060101
G02C007/04 |
Claims
1-45. (canceled)
46. An ophthalmic lens comprising: a first surface; a second
surface disposed opposite the first surface, wherein the second
surface is configured to abut at least a portion of an eye of a
wearer; and an active region disposed adjacent the first surface,
wherein the active region is positioned based on an expected
interaction with the at least one eyelid of the wearer, and wherein
the position is determined based on one or more eyelid profiles,
wherein at least a contour of the active region is configured based
on a distribution of terrain slope of a target one or more
eyes.
47. The ophthalmic lens of claim 46, wherein the contour comprises
a cumulative terrain slope.
48. The ophthalmic lens of claim 46, wherein the contour is
configured for interactions with only upper eyelids or only lower
eyelids.
49. The ophthalmic lens of claim 46, wherein the ophthalmic lens
has a generally round shape.
50. The ophthalmic lens of claim 46, wherein the ophthalmic lens
has a non-round shape.
51. The ophthalmic lens of claim 46, further comprising a second
active region disposed adjacent the first surface.
52. The ophthalmic lens of claim 51, wherein at least a contour of
the second active region is configured based on a distribution of
terrain slope of a target one or more eyes.
53. The ophthalmic lens of claim 51, wherein the active regions are
symmetrical with respect to the sagittal plane.
54. The ophthalmic lens of claim 51, wherein the active regions are
symmetrical with respect to the tangential plane.
55. The ophthalmic lens of claim 51, wherein the active regions are
symmetrical with respect to the sagittal plane and the tangential
plane.
56. The ophthalmic lens of claim 51, wherein the active regions are
not symmetrical with respect to the sagittal plane.
57. The ophthalmic lens of claim 51, wherein the active regions are
not symmetrical with respect to the tangential plane.
58. The ophthalmic lens of claim 51, wherein the active regions are
not symmetrical with respect to the sagittal plane and the
tangential plane.
59. The ophthalmic lens of claim 46, wherein the expected terrain
slope is determined based on an individual eye shape of a target
wearer.
60. The ophthalmic lens of claim 46, wherein the terrain slope is
determined based on a plurality of sample eyes.
61. The ophthalmic lens of claim 46, wherein the one or more eyelid
profiles comprise a Cartesian coordinate system by a second order
polynomial of the form: a0+a1x+a2x2, where a0 represents the
superior/inferior palpebral aperture, the distance between the
pupil center to the edge of the upper/lower eyelid in primary gaze,
a1 is the slope of the eyelid at the location of the
superior/inferior palpebral aperture and a2 is the curvature at
that same location, and x is the distance along the horizontal
direction of the Cartesian coordinate system with its origin at the
center of the pupil.
Description
BACKGROUND
[0001] Mechanical aspects related to an angular position of a soft
toric contact lens may be useful for vision performance. A first
mechanical aspect may comprise the speed at which a contact lens
returns to a final angular position. An angular misalignment may
occur during an initial lens insertion or from a mechanical
intervention, such as rubbing an eye or intensive blinking (induced
by the presence of foreign matter, for example). The faster a lens
reaches a final resting position, the faster a wearer (e.g., user,
etc.) wearing the lens may receive vision correction.
[0002] A second mechanical aspect may comprise the ability of a
contact lens to maintain a same angular position on an eye. Similar
lenses prescribed to multiple wearers may preferably rest angularly
in a same position on each wearer's eye, which may reduce
occurrences of selecting a next available cylinder axis by
maintaining a lens angular position proximate to a horizontal axis.
The horizontal axis may be used as a reference for the cylinder
axis. The tighter a distribution of a resting angular position of a
lens, the more stable the lens may be angularly. Providing a
tighter distribution of the resting angular position of the lens,
may provide less vision fluctuation, especially for wearers
requiring large astigmatism correction.
[0003] Stability may also be useful for wearers requiring vision
corrections that are more complex than astigmatism, such as high
order aberration corrections. Keratoconus condition is a good
example of an eye disease that may benefit from such a design, if a
vision deficiency related to the condition is corrected with the
use of contact lenses.
[0004] Improvements are needed.
SUMMARY
[0005] Ophthalmic lenses are described herein. An exemplary
ophthalmic lens may comprise a first surface. The exemplary
ophthalmic lens may comprise a second surface disposed opposite the
first surface. The second surface may be configured to abut at
least a portion of an eye of a wearer. The exemplary ophthalmic
lens may comprise a lens stabilization zone disposed adjacent the
first surface. At least a contour of the lens stabilization zone
may be configured to minimize a recovery time for the ophthalmic
lens to orient to a resting position from a misaligned
position.
[0006] Another exemplary ophthalmic lens may comprise a first
surface. The exemplary ophthalmic lens may comprise a second
surface disposed opposite the first surface. The second surface may
be configured to abut at least a portion of an eye of a wearer. The
exemplary ophthalmic lens may comprise an active region disposed
adjacent the first surface. At least a contour of the active region
may be configured based on a distribution of terrain slope of a
target one or more eyes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The following drawings show generally, by way of example,
but not by way of limitation, various examples discussed in the
present disclosure. In the drawings:
[0008] FIG. 1 illustrates a radial thickness contour plot of an
example soft contact lens.
[0009] FIG. 2 illustrates an example of a misaligned toric contact
lens. The solid black lines represent the upper and lower eyelid
profiles of an arbitrary eye. The circles represent the active
regions of the contact lens that drive the lens rotation.
[0010] FIG. 3 illustrates a representation of the wedge effect. On
the left section of the drawing is depicted the eyelid exerting
pressure in a normal direction of the surface of the lens. As the
pressure is perpendicular to the front surface of the lens no
lateral motion is generated. On the right section of the drawing is
depicted the eyelid exerting pressure in a direction different from
the normal to the surface. The direction of the pressure generates
a lateral motion in the active region providing the required torque
that rotates the lens.
[0011] FIG. 4 illustrates an example of a toric contact lens in its
resting position. The solid black lines represent the upper and
lower eyelid profiles of an arbitrary eye. The circles represent
the active regions of the contact lens that drive the lens
stability in rotation.
[0012] FIG. 5 illustrates a schematic representation of an average
eyelid on a right eye and its pressure band interacting with a
toric lens using DSZS approach for stability. The toric lens is
represented by radial thickness contours. The grey box represents
the active region that is the region of interest.
[0013] FIG. 6 illustrates average responses in rotation of three
lenses, Lens #1, Lens #2 and Lens #3 calculated over a 3.0 min
period (36 blinks each lasting 5 seconds). Each average response
was calculated from a set of 16 individual responses.
[0014] FIG. 7 illustrates standard deviations of the angular
position of three lenses, Lens #1, Lens #2 and Lens #3 calculated
over a 3.0 min period (36 blinks each lasting 5 seconds). Each
standard deviation response was calculated from a set of 16
individual responses.
[0015] FIG. 8 illustrates the standard deviation obtained for
Lenses #1, #2 and lens #3 plotted against the average lens angular
position.
[0016] FIG. 9 illustrates a cumulated histogram of the terrain
slope, calculated over the active region, for a set of 100 human
eyes.
[0017] FIG. 10 illustrates a histogram of the terrain slope,
calculated over the active region, of the front surface of the
Lenses #1, #2 and #3 when each lens is perfectly aligned with the
horizontal axis.
[0018] FIG. 11 illustrates a histogram of the terrain slope,
calculated over the active region, of the front surface of the
lenses #1, #2 and #3 when each lens is misaligned by 10 degrees in
the nasal direction.
[0019] FIG. 12 illustrates a standard deviations of Lenses #1, #2,
and #3 for varying lens misalignments ranging from 0 degree to 10
degrees in the nasal direction versus the cumulated distribution of
the terrain slope below 45 degrees in the active region.
DETAILED DESCRIPTION
[0020] A contact lens described herein may comprise one or more
stabilization zones. The stabilization zones may be contoured in
such a manner that pressure from an eyelid may secure the contact
lens to a location relative to a pupil of an eye. A first contoured
area may be to the left of the pupil of the eye. A second contoured
area may be to the right of the pupil of the eye. A contoured area
may comprise an outer perimeter and an inner perimeter. Moving from
the outer perimeter towards the inner perimeter, a contoured area
may generally increase in thickness. Having a contoured area with
generally increasing thickness to the left and the right of the
pupil of the eye may allow pressure from an eyelid to stabilize the
contact lens relative to the pupil at a horizontal location of the
first contoured area similar to a horizontal location of the second
contoured area.
[0021] An ophthalmic lens may comprise a first surface. The
ophthalmic lens may have a generally round shape. The ophthalmic
lens may also have a non-round shape.
[0022] The ophthalmic lens may comprise a second surface disposed
opposite the first surface. The second surface may be configured to
abut at least a portion of an eye of a wearer.
[0023] The ophthalmic lens may comprise a lens stabilization zone
disposed adjacent the first surface. At least a contour of the lens
stabilization zone may be configured to minimize a recovery time
for the ophthalmic lens to orient to a resting position from a
misaligned position.
[0024] The ophthalmic lens may comprise a second lens stabilization
zone disposed adjacent the first surface. At least a contour of the
second lens stabilization zone may be configured to minimize a
recovery time for the ophthalmic lens to orient to a resting
position from a misaligned position due to interaction with at
least one eyelid of the wearer. The lens stabilization zones may be
symmetrical with respect to the sagittal plane. The lens
stabilization zones may be symmetrical with respect to the
tangential plane. The lens stabilization zones may be symmetrical
with respect to the sagittal plane and the tangential plane. The
lens stabilization zones may not be symmetrical with respect to the
sagittal plane. The lens stabilization zones may not be symmetrical
with respect to the tangential plane. The lens stabilization zones
may not be symmetrical with respect to the sagittal plane and the
tangential plane.
[0025] The lens may comprise an area for a pupil. The first lens
stabilization zone may be to the left of the area for the pupil
when the lens is in a correct position. The second lens
stabilization zone may be to the right of the area for the pupil
when the lens is in the correct position. The lens stabilization
zones may be an equal distance from the area for the pupil. The
lens stabilization zones may not be an equal distance from the area
for the pupil.
[0026] The lens stabilization zones may each comprise a respective
outer parameter. The lens stabilization zones may each comprise a
respective inner parameter. A first thickness may be associated
with a respective outer parameter. A second thickness may be
associated with a respective inner parameter. The lens
stabilization zones may be contoured so as to smoothly and/or
gradually transition from the first thickness to the second
thickness. The first thickness, the second thickness, and/or the
contoured area between the first thickness and the second thickness
may be configured so that pressure from an eyelid causes the lens
to achieve a correct position relative to the area for the
pupil.
[0027] The lens stabilization zone may be disposed at least
partially within an active region of the lens based on an expected
interaction with the at least one eyelid of the wearer. The
expected interaction with the at least one eyelid of the wearer may
be based on an individual eye shape of a target wearer. The
expected interaction with the at least one eyelid of the wearer may
be based on a plurality of sample eyes. The expected interaction
with the at least one eyelid of the wearer may be based on one or
more eyelid profiles. The expected interaction with the at least
one eyelid may comprise one or more blinks. The expected
interaction with the at least one eyelid may comprise an open
position. The expected interaction with the at least one eyelid may
comprise a closed position. The expected interaction with the at
least one eyelid may comprise a resting position.
[0028] The one or more eyelid profiles may comprise a Cartesian
coordinate system by a second order polynomial of the form:
a0+a1x+a2x.sup.2, where a0 represents the superior/inferior
palpebral aperture (the distance between the pupil center to the
edge of the upper/lower eyelid in primary gaze), a1 is the slope of
the eyelid at the location of the superior/inferior palpebral
aperture, a2 is the curvature at that same location, and x is the
distance along the horizontal direction of the Cartesian coordinate
system with its origin at the center of the pupil.
[0029] The recovery time may be below 2 minutes for a misalignment
of 45 degrees. The misaligned position may be greater than 5
degrees measured angularly from a horizontal axis. The misaligned
position may be greater than 10 degrees measured angularly from a
horizontal axis.
[0030] The ophthalmic lens may comprise one or more silicone
hydrogels. The ophthalmic lens may comprise one or more traditional
hydrogels.
[0031] A wearer of contact lenses may insert a contact lens into an
eye of the wearer. The contact lens may comprise two contoured
stabilization zones. The contact lens may initially be out of
position relative to a pupil of the eye. The wearer may blink the
eye, causing pressure from an eyelid to be placed on the contact
lens. The pressure from the eyelid may cause the contact lens to
achieve a correct position relative to the pupil.
[0032] An ophthalmic lens may comprise a first surface. The
ophthalmic lens may have a generally round shape. The ophthalmic
lens may also have a non-round shape.
[0033] The ophthalmic lens may comprise a second surface disposed
opposite the first surface. The second surface may be configured to
abut at least a portion of an eye of a wearer.
[0034] The ophthalmic lens may comprise an active region disposed
adjacent the first surface. At least a contour of the active region
may be configured based on a distribution of terrain slope of a
target one or more eyes. The contour may comprise a cumulative
terrain slope. The contour may be configured for interactions with
only upper eyelids or only lower eyelids.
[0035] The ophthalmic lens may comprise a second active region
disposed adjacent the first surface. At least a contour of the
second active region may be configured based on a distribution of
terrain slope of a target one or more eyes. The active regions may
be symmetrical with respect to the sagittal plane. The active
regions may be symmetrical with respect to the tangential plane.
The active regions may be symmetrical with respect to the sagittal
plane and the tangential plane. The active regions may not be
symmetrical with respect to the sagittal plane. The active regions
may not be symmetrical with respect to the tangential plane. The
active regions may not be symmetrical with respect to the sagittal
plane and the tangential plane.
[0036] The lens may comprise an area for a pupil. The first active
region may be to the left of the area for the pupil when the lens
is in a correct position. The second active region may be to the
right of the area for the pupil when the lens is in the correct
position. The active regions may be an equal distance from the area
for the pupil. The active regions may not be an equal distance from
the area for the pupil.
[0037] The active regions may each comprise a respective outer
parameter. The active regions may each comprise a respective inner
parameter. A first thickness may be associated with a respective
outer parameter. A second thickness may be associated with a
respective inner parameter. The active regions may be contoured so
as to smoothly and/or gradually transition from the first thickness
to the second thickness. The first thickness, the second thickness,
and/or the contoured area between the first thickness and the
second thickness may be configured so that pressure from an eyelid
causes the lens to achieve a correct position relative to the area
for the pupil.
[0038] The active region may be configured based on an expected
interaction with the at least one eyelid of the wearer. The
expected interaction with the at least one eyelid of the wearer may
be based on an individual eye shape of a target wearer. The
expected interaction with the at least one eyelid of the wearer may
be based on a plurality of sample eyes. The expected interaction
with the at least one eyelid of the wearer may be based on one or
more eyelid profiles. The expected interaction with the at least
one eyelid may comprise one or more blinks. The expected
interaction with the at least one eyelid may comprise an open
position. The expected interaction with the at least one eyelid may
comprise a closed position. The expected interaction with the at
least one eyelid may comprise a resting position.
[0039] The one or more eyelid profiles may comprise a Cartesian
coordinate system by a second order polynomial of the form:
a0+a1x+a2x2, where a0 represents the superior/inferior palpebral
aperture (the distance between the pupil center to the edge of the
upper/lower eyelid in primary gaze), a1 is the slope of the eyelid
at the location of the superior/inferior palpebral aperture, a2 is
the curvature at that same location, and x is the distance along
the horizontal direction of the Cartesian coordinate system with
its origin at the center of the pupil.
[0040] At least a contour of the active region may be configured to
minimize a recovery time for the ophthalmic lens to orient to a
resting position from a misaligned position. The recovery time may
be below 2 minutes for a misalignment of 45 degrees. The misaligned
position may be greater than 5 degrees measured angularly from a
horizontal axis. The misaligned position may be greater than 10
degrees measured angularly from a horizontal axis.
[0041] The ophthalmic lens may comprise one or more silicone
hydrogels. The ophthalmic lens may comprise one or more traditional
hydrogels.
[0042] A wearer of contact lenses may insert a contact lens into an
eye of the wearer. The contact lens may comprise two contoured
active regions. The contact lens may initially be out of position
relative to a pupil of the eye. The wearer may blink the eye,
causing pressure from an eyelid to be placed on the contact lens.
The pressure from the eyelid may cause the contact lens to achieve
a correct position relative to the pupil.
[0043] FIG. 1 describes a standard dual stabilization zone system
on an exemplary lens. FIG. 1 represents a contour plot of the
radial thickness of a -3.00 D/-0.75 D @ 180 degrees Rx lens. The
stabilization zones located in the outer region of the lens, also
called peripheral region, present a larger thickness centered along
the horizontal direction than the thickness in the vertical
direction of the peripheral region. The geometry of the
stabilization zones follows the outer contour of the lens.
[0044] The re-orientation and stability of such lens is driven from
the pressure exerted by the upper and lower eyelids on the front
surface of the lens. When the lens is angularly misaligned (FIG.
2), the eyelids will exert pressure on the lens in the active
regions where large gradient thickness is present, acting as a
wedge (FIG. 3), resulting in a torque that will rotate the lens in
the clockwise direction as provided in the example. The region of
the lens in contact with the eyelid that does not present large
thickness gradient will not contribute to the lens rotation due to
the lack of wedge effect. Once the lens reaches its final angular
position (FIG. 4), all four active regions balance each other
within an eyelid (temporal and nasal regions) and between eyelids
(superior and inferior regions) resulting in maintaining the lens
in its resting position.
[0045] Described herein is a new toric lens design where the
angular stabilization is provided with a dual stabilization zone
system (DSZS) where the active regions of the contact lens, when
such lens reached its final angular resting position, have been
optimized for angular stability.
[0046] An average eyelid profile was obtained from the measurement
of multiple profiles collected on the right eye over a population
of 100 subjects representing different ethnicities (Caucasian, East
Asian, Indian/Middle Eastern). Each eyelid profile was described in
a cartesian coordinate system by a second order polynomial of the
form:
a0+a1x+a2x.sup.2
[0047] Where a0 represents the superior/inferior palpebral
aperture, the distance between the pupil center to the edge of the
upper/lower eyelid in primary gaze, a1 is the slope of the eyelid
at the location of the superior/inferior palpebral aperture and a2
is the curvature at that same location, and x is the distance along
the horizontal direction of the cartesian coordinate system with
its origin at the center of the pupil. Table 1 below provides the
coefficients of the polynomials describing the average geometry of
the upper and lower eyelid calculated over 100 subjects of
different ethnicities.
TABLE-US-00001 TABLE 1 Average geometry of the upper and lower
eyelid calculated over 100 subjects. Upper Eyelid Lower Eyelid a0
[mm] a1 [mm] a2 [mm] a0 [mm] a1 [mm] a2 [mm] 4.302 0.032 -0.037
-6.285 0.016 0.025
[0048] The region of interaction between the upper eyelid and the
lens was defined as a band following the contour of the upper
eyelid (FIG. 5). The band width below the upper eyelid contour was
set to 0.25 mm and the band width above the eyelid contour was set
to 0.50 mm providing a total band width of 0.75 mm representing the
eyelid pressure band along with the eyelid is exerting pressure
directly to the eye or to a contact lens when such lens is
worn.
[0049] It should be obvious to the person who is familiar with such
work that the average eye lid contour could be replaced by an
individual contour or an average contour representative of a
specific ethnicity. For example, the average contour could be
representative of the Caucasian population or of the Asian
population who have very distinctive eyelid geometries.
[0050] The lens rotation of toric lenses is mostly driven by the
pressure exerted by the upper and lower eyelid and the motion of
the upper eyelid during a blink cycle and more particularly the
interaction of the upper eyelid with the stabilization zones of the
soft contact lens. The active region (FIG. 5) is defined as the
region of the upper eyelid interacting directly with the lens
stabilization zone. In the provided examples, the start of the
active region was defined at the horizontal coordinate of 4.00 mm.
For horizontal coordinates below 4.00 mm the upper eyelid does not
have any interaction with the lens stabilization zone. At this
location the blending region connecting the outer edge of the optic
zone to the inner region of the periphery may usually be found. It
should be obvious to someone familiar with toric soft contact
lenses that the starting point of the active zone should be
adjusted according to the dimension of the soft contact lens and
the location of the stabilization zone built into that contact
lens.
[0051] In one aspect, the stabilization zone contours are modified
such that the distribution of the slope within the active region
interacting with the eyelid pressure band better matches that
distribution calculated over a set of eyes when the orientation of
the contact lens corresponds to its final resting position (lens
aligned with the horizontal axis).
[0052] In another aspect, the stabilization zone contours are
modified such that the distribution of the slope within the active
region interacting with the eyelid pressure band better matches
that distribution calculated over a set of eyes when the contact
lens is misaligned by 10 degrees from its final resting position in
a counter clockwise direction.
[0053] A better slope match means a more natural lens eyelid
interaction in comparison with the eye eyelid interaction when no
lens is present on the eye. This implies less eyelid deformation
and thus a lens that is more comfortable to wear.
Examples
[0054] In a first example, a soft toric contact lens (Lens #1) is
first evaluated for lens rotation and stability. The assessment was
performed using a population of 16 eyes for which the eye
topography and eyelid geometry were measured. The rotation and
stability data were obtained using a rotation and centration
simulation model (U.S. Pat. No. 8,403,479). A toric lens of Rx
-3.00 D/-0.75 D@180 deg. was nasally misaligned by 25 degrees, the
lens re-orientation was observed over 36 blinks cycles, each blink
cycle lasting 5 seconds. The average lens rotation (FIG. 6) and
standard deviation (FIG. 7) were calculated over the entire time
frame.
[0055] In a second example a soft toric contact lens (Lens #2) of
the same prescription of the Lens #1 was evaluated using the same
conditions and eye population as of the lens of example 1. The
average lens rotation (FIG. 6) and standard deviation (FIG. 7) were
also calculated over the entire time frame.
[0056] In a third example a soft toric contact lens (Lens #3) of
the same prescription of the Lens #1 was evaluated using the same
conditions and eye population as of the lens of example 1. The
average lens rotation (FIG. 6) and standard deviation (FIG. 7) were
also calculated over the entire time frame.
[0057] All three lenses present similar responses in lens
re-orientation. All lenses converge to a final angular resting
position close to the horizontal direction. To better compare those
lenses to each other the standard deviation was plotted against the
average lens angular position (FIG. 8). FIG. 8 thus provides the
standard deviation of each lens for the same average angular
position.
[0058] Lenses #2 and #3 were designed with the same base curve
geometry, center thickness, maximum peripheral thickness located
along the horizontal meridian, and same minimum peripheral
thickness located along the vertical meridian as Lens #1. The only
geometry influencing the rotation and stability performance is the
front surface geometry of the stabilization zone located in the
peripheral region.
[0059] FIG. 9 is the cumulated histogram of the terrain slope
calculated over a set of 100 eyes in the active region. Those eyes
are a mix of Caucasian eyes, East Asian eyes and Indian/Middle
Eastern eyes. The terrain slope is defined as the steepest slope
calculated at a single location. The slope ranges from about 25
degrees to 45 degrees.
[0060] FIG. 10 displays the terrain slope in the same active region
of the front surface of the Lenses #1, #2 and #3 when each lens is
perfectly aligned with the horizontal axis that is the optimum
angular position a contact lens can take when it reaches its
resting position. FIG. 11 displays the terrain slope in the same
active region of the front surface of the Lenses #1, #and #3 when
each lens is misaligned by 10 degrees in the nasal direction. As
the cylinder axis for toric lenses is usually provided every 10
degrees, toric lenses resting on the eye with a misalignment
greater than 5 degrees from the required prescribed cylinder axis
will usually be adjusted by selecting the next cylinder axis to
reduce the axis error below 5 degrees. Thus, considering the case
where the lens is misaligned by 10 degrees is very conservative as
it should never occur with a lens correctly fitted on a
patient.
[0061] In one aspect, the stabilization zones of the Lens #3 was
designed such that the front surface in the active region better
matches the cumulated terrain slope calculated for a set of 100
human eyes. Specifically, the cumulated distribution of the terrain
slope below 45 degrees in the active region presents a higher
percentage that of the cumulated distribution of the terrain slope
of Lens #1 (Table 2 below). In other terms, the higher the
cumulated distribution of the terrain slope below 45 degrees is,
the larger the area matching the cornea slope is in the active
region. In the second example, the stabilization zones of the Lens
#2 was designed such that the front surface in the active region
does not match the cumulated terrain slope and that the cumulated
distribution of the terrain slope below 45 degrees in the active
region presents a lower percentage that of the cumulated
distribution of the terrain slope of Lens #1.
[0062] It should be obvious to someone familiar with toric soft
contact lenses that the threshold angle might be changed based on
the eye population the lens is designed for. In the proposed
examples the threshold angle is based on a mix population of eyes.
The threshold angle can also be ethnicity specific or other type of
criterion if the toric soft contact lens is designed for a specific
type of eyes.
TABLE-US-00002 TABLE 2 Cumulated distribution in percentage of the
terrain slope below 45 degrees. Lens misalignment 0 deg. 5 deg. 10
deg. Lens #1 37.7 37.7 38.7 Lens #2 26.5 28.6 30.6 Lens #3 53.4
52.3 51.5
[0063] The average angular response obtained for Lens #3 over a 3.0
min period of lens re-orientation closely matches that of the Lens
#1 with a better lens angular stability provided the standard
deviation is smaller. The average angular response obtained for
Lens #2 over a 3 min period of lens re-orientation still matches
that of the Lens #1 but with a worse lens angular stability
provided the standard deviation is larger.
[0064] FIG. 12 displays the standard deviation of each lens for
varying lens misalignments ranging from 0 degree to 10 degrees in
the nasal direction versus the cumulated distribution of the
terrain slope below 45 degrees in the active region. FIG. 12. shows
that a toric lens with a front surface terrain slope for which the
cumulated distribution is larger than 38% will provide a better
angular stability than toric lenses where the terrain slope
cumulated distribution is below 38%. Preferably the cumulated
distribution needs to be above 48%.
[0065] Although shown and described in what is believed to be the
most practical and preferred embodiments, it is apparent that
departures from specific designs and methods described and shown
will suggest themselves to those skilled in the art and may be used
without departing from the spirit and scope of the invention. The
present invention is not restricted to the particular constructions
described and illustrated but should be constructed to cohere with
all modifications that may fall within the scope of the appended
claims.
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