U.S. patent application number 16/043574 was filed with the patent office on 2018-11-15 for multifocal lens design and method for preventing and/or slowing myopia progression.
The applicant listed for this patent is Johnson & Johnson Vision Care, Inc.. Invention is credited to Noel A. Brennan, Khaled A. Chehab, Xu Cheng, Kurt John Moody, Xin Wei.
Application Number | 20180329229 16/043574 |
Document ID | / |
Family ID | 54012118 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180329229 |
Kind Code |
A1 |
Brennan; Noel A. ; et
al. |
November 15, 2018 |
MULTIFOCAL LENS DESIGN AND METHOD FOR PREVENTING AND/OR SLOWING
MYOPIA PROGRESSION
Abstract
Contact lenses incorporate multifocal power profiles that at
least one of slow, retard or preventing myopia progression. The
lens includes a first zone at a center of the ophthalmic lens and
at least one peripheral zone surrounding the first zone. The at
least one peripheral zone has a different width and dioptric power
than the first zone. The first zone and at least one peripheral
zone are stepped or discontinuous. The multifocal power profile has
substantially equivalent foveal vision correction to a single
vision lens and has a depth of focus and reduced retinal image
quality sensitivity that slows, retards, or prevents myopia
progression.
Inventors: |
Brennan; Noel A.;
(Jacksonville, FL) ; Chehab; Khaled A.;
(Jacksonville, FL) ; Cheng; Xu; (St. Johns,
FL) ; Moody; Kurt John; (St. Augustine, FL) ;
Wei; Xin; (Jacksonville, FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Johnson & Johnson Vision Care, Inc. |
Jacksonville |
FL |
US |
|
|
Family ID: |
54012118 |
Appl. No.: |
16/043574 |
Filed: |
July 24, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14472481 |
Aug 29, 2014 |
10061143 |
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16043574 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/16 20130101; G02C
2202/24 20130101; G02C 7/044 20130101; G02C 7/06 20130101; G02C
7/041 20130101; A61F 2/145 20130101 |
International
Class: |
G02C 7/06 20060101
G02C007/06; G02C 7/04 20060101 G02C007/04; A61F 2/14 20060101
A61F002/14; A61F 2/16 20060101 A61F002/16 |
Claims
1. An ophthalmic lens for at least one of slowing, retarding or
preventing myopia progression, the ophthalmic lens comprising: a
central zone at a center of the ophthalmic lens; and at least two
peripheral zones surrounding the central zone, said at least two
peripheral zones having different widths and dioptric powers than
said central zone, wherein the central zone and at least two
peripheral zones are stepped or discontinuous, thereby providing a
multifocal lens power profile having equivalent foveal vision
correction to a single vision lens, and having a depth of focus and
reduced retinal image quality sensitivity that slows, retards, or
prevents myopia progression, wherein the power is equal to 0.26 D
for a radial range of between 0 mm to less than 1.15 mm, equal to
-0.32 D for a radial range of greater than or equal to 1.15 mm to
less than 2.19 mm, and equal to -0.95 D for a radial range of
greater than or equal to 2.19 mm to less than 3.43 mm.
2. The ophthalmic lens according to claim 1, wherein the at least
one peripheral zone comprises two zones.
3. The ophthalmic lens according to claim 1, wherein the multifocal
power profiles are adjustable based upon pupil size to achieve a
balance between foveal vision correction and an effective depth of
focus and reduced retinal image quality sensitivity for treating
myopia progression.
4. The ophthalmic lens according to claim 1, wherein the central
zone comprises a width in the range from about 0.5 mm to about 1.2
mm.
5. The ophthalmic lens according to claim 1, wherein the at least
one peripheral zone comprises a width in the range from about 0.5
mm to about 1.6 mm.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 14/472,481, filed Aug. 29, 2014.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] The present invention relates to ophthalmic lenses, and more
particularly, to contact lenses designed to slow, retard, or
prevent myopia progression. The ophthalmic lenses of the present
invention comprise multifocal power profiles that provide foveal
vision correction, an increased depth of focus and an optimized
retinal image at a range of accommodative distances that makes the
degradation of retinal image quality less sensitive to blur during
near work activities, thereby preventing and/or slowing myopia
progression.
Discussion of the Related Art
[0003] Common conditions which lead to reduced visual acuity
include myopia and hyperopia, for which corrective lenses in the
form of spectacles, or rigid or soft contact lenses, are
prescribed. The conditions are generally described as the imbalance
between the length of the eye and the focus of the optical elements
of the eye. Myopic eyes focus in front of the retinal plane and
hyperopic eyes focus behind the retinal plane. Myopia typically
develops because the axial length of the eye grows to be longer
than the focal length of the optical components of the eye, that
is, the eye grows too long. Hyperopia typically develops because
the axial length of the eye is too short compared with the focal
length of the optical components of the eye, that is, the eye does
not grow long enough.
[0004] Myopia has a high prevalence rate in many regions of the
world. Of greatest concern with this condition is its possible
progression to high myopia, for example greater than five (5) or
six (6) diopters, which dramatically affects one's ability to
function without optical aids. High myopia is also associated with
an increased risk of retinal disease, cataracts, and glaucoma.
[0005] Corrective lenses are used to alter the gross focus of the
eye to render a clearer image at the retinal plane, by shifting the
focus from in front of the plane to correct myopia, or from behind
the plane to correct hyperopia, respectively. However, the
corrective approach to the conditions does not address the cause of
the condition, but is merely prosthetic or intended to address
symptoms. More importantly, correcting the myopic defocus error of
the eye does not slow or retard myopia progression.
[0006] Most eyes do not have simple myopia or hyperopia, but have
myopic astigmatism or hyperopic astigmatism. Astigmatic errors of
focus cause the image of a point source of light to form as two
mutually perpendicular lines at different focal distances. In the
following discussion, the terms myopia and hyperopia are used to
include simple myopia or myopic astigmatism and hyperopia and
hyperopic astigmatism respectively.
[0007] Emmetropia describes the state of clear vision where an
object at infinity is in relatively sharp focus with the
crystalline lens relaxed. In normal or emmetropic adult eyes, light
from both distant and close objects and passing though the central
or paraxial region of the aperture or pupil is focused by the
crystalline lens inside the eye close to the retinal plane where
the inverted image is sensed. It is observed, however, that most
normal eyes exhibit a positive longitudinal spherical aberration,
generally in the region of about +0.50 Diopters (D) for a 5.0 mm
aperture, meaning that rays passing through the aperture or pupil
at its periphery are focused +0.50 D in front of the retinal plane
when the eye is focused to infinity. As used herein the measure D
is the dioptric power, defined as the reciprocal of the focal
distance of a lens or optical system, in meters.
[0008] The spherical aberration of the normal eye is not constant.
For example, accommodation (the change in optical power of the eye
derived primarily though changes to the crystalline lens) causes
the spherical aberration to change from positive to negative.
[0009] As noted, myopia typically occurs due to excessive axial
growth or elongation of the eye. It is now generally accepted,
primarily from animal research, that axial eye growth can be
influenced by the quality and focus of the retinal image.
Experiments performed on a range of different animal species,
utilizing a number of different experimental paradigms, have
illustrated that altering retinal image quality can lead to
consistent and predictable changes in eye growth.
[0010] Furthermore, defocusing the retinal image in both chick and
primate animal models, through positive lenses (myopic defocus) or
negative lenses (hyperopic defocus), is known to lead to
predictable (in terms of both direction and magnitude) changes in
eye growth, consistent with the eyes growing to compensate for the
imposed defocus. The changes in eye length associated with optical
blur have been shown to be modulated by changes in scleral growth.
Blur with positive lenses, which leads to myopic blur and a
decrease in scleral growth rate, results in development of
hyperopic refractive errors. Blur with negative lenses, which leads
to hyperopic blur and an increase in scleral growth rate, results
in the development of myopic refractive errors. These eye growth
changes in response to retinal image defocus have been demonstrated
to be largely mediated through local retinal mechanisms, as eye
length changes still occur when the optic nerve is damaged, and
imposing defocus on local retinal regions has been shown to result
in altered eye growth localized to that specific retinal
region.
[0011] In humans there is both indirect and direct evidence that
supports the notion that retinal image quality can influence eye
growth. A variety of different ocular conditions, all of which lead
to a disruption in form vision, such as ptosis, congenital
cataract, corneal opacity, vitreous hemorrhage and other ocular
diseases, have been found to be associated with abnormal eye growth
in young humans, which suggests that relatively large alterations
in retinal image quality do influence eye growth in human subjects.
The influence of more subtle retinal image changes on eye growth in
humans has also been hypothesized based on optical errors in the
human focusing system during near work that may provide a stimulus
for eye growth and myopia development in humans.
[0012] One of the risk factors for myopia development is near work.
Due to accommodative lag or negative spherical aberration
associated with accommodation during such near work, the eye may
experience hyperopic blur, which stimulates myopia progression as
discussed above.
[0013] Moreover, the accommodation system is an active adaptive
optical system; it constantly reacts to near-objects, as well as
optical designs. Even with previously known optical designs placed
in front of the eye, when the eye accommodates interactively with
the lens+eye system to near-objects, continuous hyperopic defocus
may still be present leading to myopia progression. Therefore, one
way to slow the rate of myopia progression is to design optics that
reduces the impact of hyperopic blur on retinal image quality. With
such designs, for each diopter of hyperopic defocus the retinal
image quality is less degraded. In another sense, the retina is
therefore relatively desensitized to hyperopic defocus. In
particular, depth of focus (DOF) and image quality (IQ) sensitivity
may be used to quantify the susceptibility of the eye to myopia
progression as a result of hyperopic defocus at the retina. An
ophthalmic lens design with a larger depth of focus and low image
quality sensitivity will make the degradation of retinal image
quality less sensitive to hyperopic defocus, hence slowing down the
rate of myopia progression.
[0014] In object space, the distance between the nearest and
farthest objects of a scene that appear acceptably sharp is called
depth of field. In image space, it is called depth of focus (DOF).
With a conventional single vision optical design, a lens has a
single focal point, with image sharpness decreasing drastically on
each side of the focal point. With an optical design with extended
DOF, although it may have a single nominal focal point the decrease
in image sharpness is gradual on each side of the focused distance,
so that within the DOF, the reduced sharpness is imperceptible
under normal viewing conditions.
[0015] Image quality (IQ) sensitivity can be defined as the slope
of the retinal IQ-defocus curve at an accommodative demand of 1 to
5 diopters. It indicates how image quality changes with defocus.
The larger the value of IQ sensitivity, the more sensitive image
quality is to defocus error during accommodation.
SUMMARY OF THE INVENTION
[0016] The multifocal lens design of the present invention
overcomes the limitations of the prior art by ensuring comparable
or better distance vision correction with an increased depth of
focus and reduced IQ sensitivity, thereby providing myopic
treatment.
[0017] In accordance with one aspect, the present invention is
directed to an ophthalmic lens for at least one of slowing,
retarding or preventing myopia progression. A first zone is at a
center of the ophthalmic lens. At least one peripheral zone
surrounds the first zone and has a different width and dioptric
power than the first zone. The first zone and at least one
peripheral zone are stepped or discontinuous, thereby providing a
multifocal lens power profile having substantially equivalent
foveal vision correction to a single vision lens, and having a
depth of focus and reduced IQ sensitivity that slows, retards, or
prevents myopia progression.
[0018] In accordance with another aspect, the present invention is
directed to a method for at least one of slowing, retarding or
preventing myopia progression. An ophthalmic lens is provided with
a multifocal power profile having substantially equivalent foveal
vision correction to a single vision lens, and having a depth of
focus and reduced IQ sensitivity that slows, retards, or prevents
myopia progression. The multifocal lens power profile comprises a
first zone at a center of the lens and at least one peripheral zone
surrounding the first zone. The at least one peripheral zone has a
different width and dioptric power than the first zone. The first
zone and the at least one peripheral zone are stepped or
discontinuous. Accordingly, the growth of the eye is altered.
[0019] The contact lens of the present invention is designed with a
multifocal power profile. As set forth herein, it has been shown
that a lens design with larger depth of focus and low image quality
sensitivity will make the degradation of retinal image quality less
sensitive to hyperopic blur, hence slowing down the rate of myopia
progression. Accordingly, the present invention utilizes lenses
having a multifocal power profile to provide foveal vision
correction, and a depth of focus and low image quality sensitivity
that treats or slows myopia progression.
[0020] The multifocal lens design of the present invention may also
be customized to achieve both good foveal vision correction and
higher treatment efficacy based on the subject's average pupil
size.
[0021] The multifocal contact lens design of the present invention
provides a simple, cost-effective and efficacious means and method
for preventing and/or slowing myopia progression.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The foregoing and other features and advantages of the
invention will be apparent from the following, more particular
description of preferred embodiments of the invention, as
illustrated in the accompanying drawings.
[0023] FIGS. 1A, 1B and 1C, illustrate the change of Defocus
Z.sup.0.sub.2, Spherical Aberration Z.sup.0.sub.4 terms, and
entrance pupil diameter as a function of vergance for myopic and
emmetropic population.
[0024] FIGS. 2A, 2B, and 2C are illustrations of power profiles for
a spherical lens, an aspheric lens with +1.50 D positive
longitudinal spherical aberration (LSA) at 5.0 mm pupil aperture,
and an ACUVUE.RTM. bifocal lens (a multiconcentric alternating
distance and near zone lens) with +1.50 D add power,
respectively.
[0025] FIG. 3A is an illustration of a power profile for a first
multifocal lens design in accordance with the present
invention.
[0026] FIG. 3B is a graph showing the neural sharpness and depth of
focus for the multifocal lens design of FIG. 3A.
[0027] FIG. 3C is a graph showing neural sharpness at various
accommodative states for the multifocal lens design of FIG. 3A.
[0028] FIG. 4A is an illustration of a power profile for a second
multifocal lens design in accordance with the present
invention.
[0029] FIG. 4B is a graph showing the neural sharpness and depth of
focus for the multifocal lens design of FIG. 4A.
[0030] FIG. 4C is a graph showing the neural sharpness at various
accommodative states for the multifocal lens design of FIG. 4A.
[0031] FIG. 5A is an illustration of a power profile for a third
multifocal lens design in accordance with the present
invention.
[0032] FIG. 5B is a graph showing the neural sharpness and depth of
focus for the multifocal lens design of FIG. 5A.
[0033] FIG. 5C is a graph showing the neural sharpness at various
accommodative states for the multifocal lens design in FIG. 5A.
[0034] FIG. 6A is an illustration of a power profile for a fourth
multifocal lens design in accordance with the present
invention.
[0035] FIG. 6B is a graph showing the neural sharpness and depth of
focus for the multifocal lens design of FIG. 6A.
[0036] FIG. 6C is a graph showing the neural sharpness at various
accommodative states for the multifocal lens design in FIG. 6A.
[0037] FIG. 7A is an illustration of a power profile for a fifth
multifocal lens design in accordance with the present
invention.
[0038] FIG. 7B is a graph showing the neural sharpness and depth of
focus for the multifocal lens design of FIG. 7A.
[0039] FIG. 7C is a graph showing the neural sharpness at various
accommodative states for the multifocal lens design of FIG. 7A.
[0040] FIG. 8 is a diagrammatic representation of an exemplary
contact lens in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0041] FIGS. 2A, 2B, and 2C are illustrations of power profiles for
a spherical lens, an aspheric lens with +1.50 D of positive
longitudinal spherical aberration (LSA) at 5.0 mm pupil aperture,
and an ACUVUE.RTM. bifocal (a multiconcentric lens having
alternating distance and near zones) lens with +1.50 D add power,
respectively. There have been observations that the aspheric lens
and ACUVUE.RTM. bifocal +1.50 lens both may have an effect on
treating myopia. Thus, a mechanism beyond changing spherical
aberration, as disclosed in U.S. Pat. No. 6,045,578, is needed for
describing lenses for preventing, treating, or slowing myopia
progression.
[0042] According to the present invention, multifocal power
profiles are developed for ophthalmic lenses that provide foveal
vision correction, and have an increased depth of focus and reduced
IQ sensitivity that treats or slows myopia progression.
[0043] In accordance with one exemplary embodiment, a multifocal
power profile may be described by:
P ( r ) = P Seg ( r ) + 24 5 .times. SA .times. r 2 3.25 4 - 12 5
.times. SA 3.25 2 , ( 1 ) ##EQU00001##
[0044] wherein P represents the dioptric power (D);
r represents a radial distance from a geometric lens center; SA
represents an amount of spherical aberration; and P.sub.Seg(r)
represents a step function that has a number of zones with
different magnitudes.
[0045] To measure vision correction, neural sharpness at 4.5 mm EP
(entrance pupil) and 6.5 mm EP is utilized as a determinant of
retinal image quality. It is important to note that any other
suitable means and/or methods (for example, area under the MTF
curve, Strehl ratio, and the like) that measure the goodness of
retinal image quality may be utilized.
[0046] Neural sharpness is given by the following equation:
NS = .intg. - .infin. .infin. .intg. - .infin. .infin. psf ( x , y
) gn ( x , y ) dxdy .intg. - .infin. .infin. .intg. - .infin.
.infin. psf DL ( x , y ) gn ( x , y ) dxdy , ( 2 ) ##EQU00002##
[0047] wherein psf or point-spread function is the image of a point
object and is calculated as the squared magnitude of the inverse
Fourier transform of the pupil function P(X,Y) where P(X,Y) is
given by
P(X,Y)=A(X,Y)exp(ikW(X,Y)), (3)
[0048] wherein k is the wave number (2.pi./wavelength) and A(X, Y)
is an optical apodization function of pupil coordinates X,Y,
psf.sub.DL is the diffraction-limited psf for the same pupil
diameter, and g.sub.N (X,Y) is a bivariate-Gaussian, neural
weighting function. For a more complete definition and calculation
of neural sharpness see Thibos et al., Accuracy and precision of
objective refraction from wave front aberrations, Journal of Vision
(2004) 4, 329-351, which discusses the problem of determining the
best correction of an eye utilizing wavefront aberrations. The
wavefront W(X, Y) of the contact lens and the eye is the sum of
each as given by:
W.sub.CL+eye(X,Y)=W.sub.CL(X,Y)+W.sub.eye(X,Y). (4)
[0049] To determine image quality sensitivity or slope of a
lens+eye system for an object at a specific target vergence, three
major steps are required: identification of coupling effect of
ocular accommodation system, estimation of the corresponding
accommodating state for the object, and calculation of the image
quality sensitivity.
[0050] Step 1: Identification of Coupling Effect of Ocular
Accommodation System:
[0051] As the human eye accommodates from distance to near, two
ocular structures change simultaneously: the iris aperture becomes
smaller; the crystal lens becomes bulkier. These anatomical changes
leads to three optical related parameters change in a coupled
manner in the lens+eye system: entrance pupil diameter, defocus
(e.g. Zernike defocus Z.sub.2.sup.0), and spherical aberration
(e.g. Zernike spherical aberration Z.sub.4.sup.0). Note in
particular, since the pupil size decreases as the target moves
closer and conventional Zernike defocus and spherical aberration
highly depends on the pupil sizes, it is challenging to specify the
these Zernike aberration terms in a conventional manner. As an
alternative, to gauge the Zernike defocus and aberration across
different pupil sizes, these terms were sometimes presented in a
`diopter` manner. To convert to the classic Zernike coefficients
via equations as follows:
Z.sub.20.sup.microns=Z.sub.20.sup.Diopter*(EPD/2).sup.2/(4* 3)
Z.sub.40.sup.microns=Z.sub.40.sup.Diopter*(EPD/2).sup.4/(24* 5)
[0052] wherein EPD is the diameter the entrance pupil,
Z.sub.20.sup.Diopter (unit: D) and Z.sub.40.sup.Diopter (unit:
D/mm.sup.2), note sometimes in the figures, as well as in some
literatures, the unit of this term is also specified as `D` in
short) are the Zernike defocus and spherical aberration terms
specified in `diopter` manner, and Z.sub.20.sup.microns and
Z.sub.40.sup.microns are corresponding conventional Zernike
terms.
[0053] Ghosh et al 2012 (Axial Length Changes with Shifts of Gaze
Direction in Myopes and Emmetropes, IOVS, September 2012, VOL. 53,
No. 10) measured the change of these three parameters in relation
to target vergence for emmetropes and myopes. FIG. 1A is a
graphical representation of defocus vs. target vergence, FIG. 1B,
is graphical representation of Spherical Aberration vs. Target
Vergence and FIG. 1C, is a graphical representation of enterance
pupil diameter vs. target vergence. As the target vergence changes,
these three parameters change simultaneously. Since these data were
measured on the human subject eyes without contact lens, the
relation between these optical parameters and target vergence with
lens+eye system differs. Nevertheless, the coupling relation among
the optical parameters (entrance pupil size, defocus, and spherical
aberration) remains the same because their changes originates from
the same anatomical source. Different interpolation techniques
could then be used to model such coupling relations among the three
parameters from the experimental data.
[0054] Step 2: Estimation of the Corresponding Accommodating State
for the Object at Near:
[0055] Once the coupling relation among the entrance pupil, defocus
and spherical aberration during the accommodation is modeled at
step 1, it could then be used to estimate the resting accommodating
state of lens+eye system for a target at any given distance. The
scientific essence of this step is to find how the eye accommodates
to the near target in the presence of contact lens. For example, a
target at specific distance at near (e.g. 2 D) results blurs for a
distance corrected lens+eye system (e.g. the system that combines
the lens in FIG. 3A and an eye model 0.06 D/mm.sup.2 SA). To
determine the resting accommodating state of this system, the
entrance pupil, defocus, and spherical aberration of the eye were
systematically adjusted per the coupling model in step 1 so that
the corresponding image quality improves to a threshold. For
example, in FIG. 3C, the entrance pupil, defocus, and spherical
aberration are found to be 5.3 mm, 1.5 D, 0.03 D/mm.sup.2 to boost
the image quality (NS) to be -1.6 (roughly 20/25 VA).
[0056] Calculation of the image quality sensitivity for the
specific target vergence: Once the accommodating state, and the
corresponding entrance pupil, defocus, and spherical aberration are
determined, the retina image quality sensitivity or slope could be
readily calculated as follows:
IQ sensitivity=d.NS/d.Rx (5)
[0057] wherein d.NS/d.Rx is the derivative of Neural Sharpness to
defocus value. For example, for design 3A with the standard eye
model and target 2 D away, the corresponding IQ sensitivity is
calculated to be 0.7.
[0058] By setting ranges for the number of zones, width of the
zones, magnitudes of the zones, and spherical aberration in
Equation (1), different multifocal power profiles can be obtained.
Exemplary, non-limiting ranges of these variables are listed below
in Table 1.
TABLE-US-00001 TABLE 1 Zone1 Zone2 Zone3 Zone4 Zone1 Zone2 Zone3
Zone4 width width width Width mag mag mag mag SA (mm) (mm) (mm)
(mm) (D) (D) (D) (D) (D/mm.sup.2) max 1.2 1.6 1.5 1.0 0.5 0.8 0.6
0.2 0 min 0.5 0.5 0.6 0 -0.8 -0.5 -1 -0.2 -0.5
[0059] Resulting multifocal power profiles are illustrated in FIGS.
3A, 4A, 5A, 6A, and 7A. The parameters for the first three
multifocal lens designs or embodiments 1-3, and as illustrated in
FIGS. 3A, 4A, and 5A, respectively, are listed below in Table
2.
TABLE-US-00002 TABLE 2 Zone1 Zone2 Zone3 Zone4 Zone1 Zone2 Zone3
Zone4 width width width width mag mag mag mag SA Design (mm) (mm)
(mm) (mm) (D) (D) (D) (D) (D/mm.sup.2) #1 1.15 1.04 1.24 NA 0.26
-0.32 -0.95 NA -0.31 FIG. 3A #2 0.98 1.65 0.80 NA 0.04 -0.39 0.56
NA -0.48 FIG. 4A #3 0.53 0.60 1.37 0.79 -0.63 0.56 -0.17 0.06 -0.16
FIG. 5A
[0060] FIG. 3A shows a power profile for a three-zone lens design,
which is stepped or discontinuous. The Rx or prescription for the
ophthalmic lens is -3.00 D. In FIG. 3B, image quality (as measured
by neural sharpness) for the ophthalmic lens would be sharpest at
0.00 diopter defocus, indicating that the optic system carries the
sharpest image when it is well focused. As refractive error (both
positive and negative) is introduced into the optical system, the
image quality starts to drop. A threshold neural sharpness value of
-2.2 is chosen to quantify DOF. When the neural sharpness value is
larger than -2.2, patients still have reasonably good near vision
for reading. In FIG. 3B, a horizontal threshold line at -2.2 is
drawn. The line intersects the through-focus curve. The width
between the two intersections corresponds to DOF. In this
embodiment, the DOF is 1.18 D.
[0061] FIG. 3C is a graph of neural sharpness at 2 D, 3 D, 4 D and
5 D accommodative states (target vergence) and a calculated defocus
error of -0.40 D to -1.10 D, which is typically associated with
accommodation lag, for the lens design of FIG. 3A. Each curve is
characterized by a shoulder at a neural sharpness threshold value
of -1.6, having a specific defocus (Z20), spherical aberration
(Z40) and Entrance Pupil size (EP). The slope of the shoulder is
indicative of reduced retinal IQ sensitivity. In this embodiment,
the IQ sensitivity is 0.67, 0.38, 0.70 and 0.95, respectively.
[0062] FIG. 4A shows a power profile for an alternate three zone
lens design, which is stepped or discontinuous. The Rx or
prescription for the ophthalmic lens is -3.00 D. In FIG. 4B, a
threshold neural sharpness value of -2.2 is chosen to quantify DOF.
The line intersects the through-focus curve. The width between the
two intersections corresponds to DOF. In this embodiment, the DOF
is 1.26 D.
[0063] FIG. 4C is a graph of neural sharpness at 2 D, 3 D, 4 D and
5 D target vergence and a calculated defocus error -0.50 D to -0.90
D, which is typically associated with accommodation lag, for the
lens design of FIG. 4A. The curves are characterized by a shoulder
at a neural sharpness threshold value of -1.6, having a specific
defocus (Z20), spherical aberration (Z40) and Entrance Pupil size
(EP). The slope of the shoulder is indicative of reduced retinal IQ
sensitivity. In this embodiment, the IQ sensitivity is 1.01, 0.66,
0.40 and 0.30, respectively.
[0064] FIG. 5A shows a power profile for a four zone lens design,
which is stepped or discontinuous. The Rx or prescription for the
ophthalmic lens is -3.00 D. In FIG. 5B, a threshold neural
sharpness value of -2.2 is chosen to quantify DOF. The line
intersects with through-focus curve. The width between the two
intersections corresponds to DOF. In this embodiment, the DOF is
1.04 D.
[0065] FIG. 5C is a graph of neural sharpness at 2 D, 3 D, 4 D and
5 D target vergence at a defocus error of -0.40 D to -1.00 D, which
is typically associated with accommodation lag, for the lens design
of FIG. 5A. The curves are characterized by a shoulder at a neural
sharpness threshold value of -1.6, having a specific defocus (Z20),
spherical aberration (Z40) and Entrance Pupil size (EP). The slope
of the shoulder is indicative of reduced retinal IQ sensitivity. In
this embodiment, the IQ sensitivity is 0.84, 0.33, 0.64 and 0.87,
respectively.
[0066] FIG. 6A shows a power profile for a four zone lens design,
which is stepped or discontinuous. The Rx or prescription for the
ophthalmic lens is -3.00 D. In FIG. 6B, a threshold neural
sharpness value of -2.2 is chosen to quantify DOF. The line
intersects the through-focus curve. The width between the two
intersections corresponds to DOF. In this embodiment, the DOF is
1.16 D.
[0067] FIG. 6C is a graph of neural sharpness at 2 D, 3 D, 4 D and
5 D target vergence and a calculated defocus error -0.50 D to -1.00
D, which is typically associated with accommodation lag, for the
lens design of FIG. 6A. The curves are characterized by a shoulder
at a neural sharpness threshold value of -1.6, having a specific
defocus (Z20), spherical aberration (Z40) and Entrance Pupil size
(EP). The slope of the shoulder is indicative of reduced retinal IQ
sensitivity. In this embodiment, the IQ sensitivity is 1.10, 0.47,
0.43 and 0.36, respectively.
[0068] FIG. 7A shows a power profile for a five zone lens design,
which is stepped or discontinuous. The Rx or prescription for the
ophthalmic lens is -3.00 D. In FIG. 7B, a threshold neural
sharpness value of -2.2 is chosen to quantify DOF. The line
intersects the through-focus curve. The width between the two
intersections corresponds to DOF. In this embodiment, the DOF is
1.03 D.
[0069] FIG. 7C is a graph of neural sharpness at 2 D, 3 D, 4 D and
5 D target vergence and a calculated defocus error of -0.50 D to
-0.90 D, which is typically associated with accommodation lag, for
the lens design of FIG. 7A. The curves are characterized by a
shoulder at a neural sharpness threshold value of -1.6, having a
specific defocus (Z20), spherical aberration (Z40) and Entrance
Pupil size (EP). The slope of the shoulder is indicative of reduced
retinal IQ sensitivity. In this embodiment, the IQ sensitivity is
1.14, 0.15, 0.66 and 0.83, respectively.
[0070] As shown below in Table 3, the neural sharpness at an
entrance pupil (EP) of 4.5 mm and 6.5 mm is calculated for the
multifocal lens designs. The depth of focus (DOF) and IQ
sensitivity are calculated at threshold neural sharpness values of
-2.2 and -1.6, respectively.
TABLE-US-00003 TABLE 3 IQ IQ IQ IQ Neural Neural Sensitivity
Sensitivity Sensitivity Sensitivity Sharpness Sharpness Depth at 2D
at 3D at 4D at 5D 4.5 mm EP 6.5 mm EP of Field vergence vergence
vergence vergence Sphere -0.40 -0.54 0.76 8.15 5.95 4.43 3.75
Aspheric -0.88 -1.62 1.16 1.10 1.31 3.91 5.62 ACUVUE .RTM. -1.34
-2.01 0.89 2.79 2.41 0.76 0.25 bifocal Design #1 -0.64 -1.46 1.18
0.67 0.38 0.70 0.95 FIG. 3A Design #2 -0.68 -0.93 1.26 1.01 0.66
0.40 0.30 FIG. 4A Design #3 -0.47 -0.38 1.04 0.84 0.33 0.64 0.87
FIG. 5A Design #4 -0.40 -0.77 1.16 1.10 0.47 0.43 0.36 FIG. 6A
Design #5 -0.41 -0.27 1.03 1.14 0.15 0.66 0.83 FIG. 7A
[0071] As shown in Table 3, the multifocal lens designs as
illustrated in FIGS. 3A, 4A, 5A, 6A, and 7A have better neural
sharpness than the aspheric and ACUVUE.RTM. bifocal +1.50 D lenses
and comparable or better myopia treatment efficacy as measured by
the depth of focus as illustrated in FIGS. 3B, 4B, 5B, 6B, and 7B
and by low IQ sensitivity as illustrated in FIGS. 3C, 4C, 5C, 6C,
and 7C.
[0072] Referring to FIG. 8, there is illustrated a diagrammatic
view of a contact lens 700 in accordance with an embodiment of the
present invention. The contact lens 700 comprises an optic zone 702
and an outer zone 704. The optic zone 702 comprises a first,
central zone 706 and at least one peripheral zone 708. In specific
embodiments, the diameter of the optic zone 702 may be selected to
be 8.0 mm, the diameter of the substantially circular first zone
706 may be selected to be 4.0 mm, and the boundary diameters of an
annular outer peripheral zone 708 may be 5.0 mm and 6.5 mm as
measured from the geometric center of the lens 700. It is important
to note that FIG. 8 only illustrates an exemplary embodiment of the
present invention. For example, in this exemplary embodiment, the
outer boundary of the at least one peripheral zone 708 does not
necessarily coincide with the outer margin of the optic zone 702,
whereas in other exemplary embodiments, they may coincide. The
outer zone 704 surrounds the optic zone 702 and provides standard
contact lens features, including lens positioning and centration.
In accordance with one exemplary embodiment, the outer zone 704 may
include one or more stabilization mechanisms to reduce lens
rotation when on eye.
[0073] It is important to note that the various zones in FIG. 8 are
illustrated as concentric circles, the zones may comprise any
suitable round or non-round shapes such as an elliptical shape.
[0074] It is important to note that as the entrance pupil size of
the eye and target vergence/accommodation varies among
subpopulations. In certain exemplary embodiments, the lens design
may be customized to achieve both good foveal vision correction and
myopic treatment efficacy based on the patient's average pupil size
and preferred target vergence. Moreover, as pupil size correlates
with refraction and age for pediatric patients, in certain
exemplary embodiments, the lens may be further optimized towards
subgroups of the pediatric subpopulation with specific age and/or
refraction based upon their pupil sizes. Essentially, the power
profiles may be adjusted or tailored to pupil size to achieve an
optimal balance between foveal vision correction, increased depth
of focus, and reduced IQ sensitivity.
[0075] Currently available contact lenses remain a cost effective
means for vision correction. The thin plastic lenses fit over the
cornea of the eye to correct vision defects, including myopia or
nearsightedness, hyperopia or farsightedness, astigmatism, i.e.
asphericity in the cornea, and presbyopia, i.e., the loss of the
ability of the crystalline lens to accommodate. Contact lenses are
available in a variety of forms and are made of a variety of
materials to provide different functionality.
[0076] Daily wear soft contact lenses are typically made from soft
polymer materials combined with water for oxygen permeability.
Daily wear soft contact lenses may be daily disposable or extended
wear disposable. Daily disposable contact lenses are usually worn
for a single day and then thrown away, while extended wear
disposable contact lenses are usually worn for a period of up to
thirty days. Colored soft contact lenses use different materials to
provide different functionality. For example, a visibility tint
contact lens uses a light tint to aid the wearer in locating a
dropped contact lens, enhancement tint contact lenses have a
translucent tint that is meant to enhance one's natural eye color,
the color tint contact lens comprises a darker, opaque tint meant
to change one's eye color, and the light filtering tint contact
lens functions to enhance certain colors while muting others. Rigid
gas permeable hard contact lenses are made from siloxane-containing
polymers but are more rigid than soft contact lenses and thus hold
their shape and are more durable. Bifocal contact lenses are
designed specifically for patients with presbyopia and are
available in both soft and rigid varieties. Toric contact lenses
are designed specifically for patients with astigmatism and are
also available in both soft and rigid varieties. Combination lenses
combining different aspects of the above are also available, for
example, hybrid contact lenses.
[0077] It is important to note that the multifocal lens design of
the present invention may be incorporated into any number of
different contact lenses formed from any number of materials.
Specifically, the multifocal lens design of the present invention
may be utilized in any of the contact lenses described herein,
including, daily wear soft contact lenses, rigid gas permeable
contact lenses, bifocal contact lenses, toric contact lenses and
hybrid contact lenses. In addition, although the invention is
described with respect to contact lenses, it is important to note
that the concept of the present invention may be utilized in
spectacle lenses, intraocular lenses, corneal inlays and
onlays.
[0078] Although shown and described is 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.
* * * * *