U.S. patent application number 11/973458 was filed with the patent office on 2008-04-10 for lens having an optically controlled peripheral portion and a method for designing and manufacturing the lens.
Invention is credited to Joseph Michael Lindacher, Ming Ye.
Application Number | 20080084534 11/973458 |
Document ID | / |
Family ID | 39276987 |
Filed Date | 2008-04-10 |
United States Patent
Application |
20080084534 |
Kind Code |
A1 |
Lindacher; Joseph Michael ;
et al. |
April 10, 2008 |
Lens having an optically controlled peripheral portion and a method
for designing and manufacturing the lens
Abstract
A contact lens or phakic IOC lens is provided with a peripheral
portion that has a power profile that provides optical control of
peripheral vision images. Typically, the central portion of the
lens is also provided with optical control. The power profile of
the lens at the boundary of the central and peripheral portions
meets certain boundary conditions that ensure that the lens
provides a desired or selected vision correction. Because the
peripheral portion of the lens provides optical control that
defocuses the peripheral vision image relative to the retina, the
lens can be used to prevent or inhibit growth of the eye, thereby
preventing or inhibiting myopia or the effects of myopia.
Inventors: |
Lindacher; Joseph Michael;
(Suwanee, GA) ; Ye; Ming; (Forth Worth,
TX) |
Correspondence
Address: |
CIBA VISION CORPORATION;PATENT DEPARTMENT
11460 JOHNS CREEK PARKWAY
DULUTH
GA
30097-1556
US
|
Family ID: |
39276987 |
Appl. No.: |
11/973458 |
Filed: |
October 9, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60828793 |
Oct 10, 2006 |
|
|
|
60829055 |
Oct 11, 2006 |
|
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|
Current U.S.
Class: |
351/159.08 |
Current CPC
Class: |
A61F 2/1613 20130101;
G02C 2202/24 20130101; G02C 7/04 20130101; A61F 2/1602 20130101;
G02C 7/028 20130101 |
Class at
Publication: |
351/161 |
International
Class: |
G02C 7/04 20060101
G02C007/04 |
Claims
1. A lens for controlling a location at which a peripheral vision
image is focused relative to a retina of an eye, the lens
comprising: a central portion having at least one optical zone that
provides optical control over light rays passing through the
central portion, the central portion having a power profile that
optically controls a location at which a center vision image is
focused relative to a retina of an eye: a peripheral portion having
at least one optical zone that provides optical control over light
rays passing through the peripheral portion, the peripheral portion
having a power profile that optically controls a location at which
a peripheral vision image is focused relative to a retina of an
eye.
2. The lens of claim 1, wherein the central portion extends a
radial distance from a center of the lens outwardly toward a
periphery of the central portion that is between about 3.5
millimeters (mm) and about 4.0 mm, and wherein the peripheral
portion extends a radial distance from a boundary where the
periphery of the central portion meets the peripheral portion to a
periphery of the peripheral portion of about 3.5 mm to about 4.0
mm.
3. The lens of claim 2, wherein the power profile of the peripheral
portion is defined by a mathematical function that is continuous at
the boundary where the periphery of the central portion meets the
peripheral portion such that it is possible to take a first
derivative of the function.
4. The lens of claim 3, wherein the mathematical function is a
polynomial.
5. The lens of claim 2, wherein the power profile of the peripheral
portion is defined by a mathematical function that is discontinuous
at the boundary where the periphery of the central portion meets
the peripheral portion such that it a first derivative of the
function is not obtainable, and wherein the optical power provided
by the power profile of the central portion at the boundary and the
optical power provided by the power profile of the peripheral
portion at the boundary differ by no more than about 8.0
Diopters.
6. The lens of claim 5, wherein the optical power provided by the
power profile of the central portion at the boundary and the
optical power provided by the power profile of the peripheral
portion at the boundary differ by no more than about 3.0
Diopters.
7. The lens of claim 5, wherein the mathematical function is a
piecewise function.
8. The lens of claim 2, wherein the power profile of the peripheral
portion is defined by a mathematical function that is continuous at
the boundary where the periphery of the central portion meets the
peripheral portion and that is not differentiable in a first
derivative at the boundary, and wherein the optical power provided
by the power profile of the central portion at the boundary and the
optical power provided by the power profile of the peripheral
portion at the boundary differ by no more than about 8.0
Diopters.
9. The lens of claim 8, wherein the optical power provided by the
power profile of the central portion at the boundary and the
optical power provided by the power profile of the peripheral
portion at the boundary differ by no more than about 3.0
Diopters.
10. The lens of claim 8, wherein the mathematical function is a
spline.
11. The lens of claim 1, wherein the lens is a soft contact
lens.
12. The lens of claim 1, wherein the lens is a hard contact
lens.
13. The lens of claim 1, wherein the lens is a phakic intraocular
(IOC) lens.
14. The lens of claim 1, wherein the lens, when worn on a person's
eye, provides myopic defocus of the peripheral vision image that
helps prevent or inhibit growth of the eye.
15. The lens of claim 1, wherein the lens, when worn on a person's
eye, ameliorates effects of myopia.
16. A method for providing a lens to be worn on a person's eye that
prevents or inhibits myopia by preventing or inhibiting eye growth,
the method comprising: selecting a power profile for a peripheral
portion of a lens to be designed, the power profile of the
peripheral portion optically controlling a location at which a
peripheral vision image is focused relative to a retina of an eye,
the lens having a central portion, the central portion having a
power profile that optically controls a location at which a center
vision image is focused relative to a retina of an eye; and
producing a design of a lens having the central portion and the
peripheral portion, the peripheral portion having the selected
power profile.
17. The method of claim 16, further comprising: manufacturing a
lens or a plurality of lenses having the lens design.
18. The method of claim 16, wherein the central portion extends a
radial distance from a center of the lens outwardly toward a
periphery of the central portion that is between about 3.5
millimeters (mm) and about 4.0 mm, and wherein the peripheral
portion extends a radial distance from a boundary where the
periphery of the central portion meets the peripheral portion to a
periphery of the peripheral portion of about 3.5 mm to about 4.0
mm.
19. The method of claim 18, wherein the power profile of the
peripheral portion is defined by a mathematical function that is
continuous at the boundary where the periphery of the central
portion meets the peripheral portion such that it is possible to
take a first derivative of the function.
20. The method of claim 18, wherein the power profile of the
peripheral portion is defined by a mathematical function that is
discontinuous at the boundary where the periphery of the central
portion meets the peripheral portion such that a first derivative
of the function is not obtainable, and wherein the optical power
provided by the power profile of the central portion at the
boundary and the optical power provided by the power profile of the
peripheral portion at the boundary differ by no more than about 8.0
Diopters.
21. The method of claim 20, wherein the optical power provided by
the power profile of the central portion at the boundary and the
optical power provided by the power profile of the peripheral
portion at the boundary differ by no more than about 3.0
Diopters.
22. The method of claim 18, wherein the power profile of the
peripheral portion is defined by a mathematical function that is
continuous at the boundary where the periphery of the central
portion meets the peripheral portion and that is not differentiable
in a first derivative at the boundary, and wherein the optical
power provided by the power profile of the central portion at the
boundary and the optical power provided by the power profile of the
peripheral portion at the boundary differ by no more than about 8.0
Diopters.
23. The method of claim 22, wherein the optical power provided by
the power profile of the central portion at the boundary and the
optical power provided by the power profile of the peripheral
portion at the boundary differ by no more than about 3.0 Diopters.
Description
[0001] This application claims the benefits under 35 USC 119(e) of
U.S. Provisional Patent Application Nos. 60/828,793 filed Oct. 10,
2006 and 60/829,055 filed Oct. 11, 2006, herein incorporated by
reference in their entireties.
TECHNICAL FIELD OF THE INVENTION
[0002] The invention relates to contact lenses and phakic
intraocular (IOC) lenses used to provide vision correction. More
particularly, the invention relates to providing contact lenses and
phakic IOC lenses with peripheral portions that are optically
controlled.
BACKGROUND OF THE INVENTION
[0003] A contact lens is a thin plastic or glass lens that is
fitted over the cornea of the eye to correct vision defects.
Various types of contact lenses exist that are designed to treat
various types of vision defects. A phakic IOC lens is a lens that
is implanted behind a person's cornea and works in conjunction with
the natural crystalline lens of the eye to provide vision
correction. Phakic IOC lenses are typically made of a material
called polymethylmethacrylate (PMMA). The term "phakic" means that
the eye with which the phakic IOC lens is used possesses the
natural crystalline lens of the eye.
[0004] Typical lenses, including both contact lenses and phakic IOC
lenses, are designed and manufactured to provide only the central
portion of the lens with optical control. The central portion of
the lens is deemed most important because it affects central
vision, which is much more accurate than peripheral vision. The
"central portion" of the lens, as that term is used herein, is
intended to denote the portion of the lens that is optically
controlled to provide an intended optical effect on a person's
central vision. The central portion of a typical soft contact lens
extends from the center of the lens outwardly to a distance of
approximately 3.5 to 4 millimeters (mm) at the periphery of the
central portion. This corresponds to a radial distance, r, that
ranges from r=0.0 mm at the center of the lens to r.apprxeq.3.5 or
4.0 mm at the boundary where the central and peripheral portions of
the lens meet. The peripheral portion of a typical contact lens has
a peripheral portion that starts where the central portion ends
(e.g., at r.apprxeq.3.5 or 4.0 mm) and extends outwardly a radial
distance from the lens center of r.apprxeq.7.0. Thus, the typical
soft contact lens has a total diameter of approximately 14.0
mm.
[0005] It is believed that central vision is more accurate than
peripheral vision due to the relatively high density of
photoreceptors in and around the center of the retina of the eye.
These photoreceptors, also known as "cones", are responsible for
daylight and color vision and are concentrated in a small
depression near the center of the retina known as the fovea
centralis. This dense concentration of cones provides this region
of the retina with the greatest visual acuity. Acuity drops
dramatically in the peripheral region of the retina. Central vision
allows a person to distinguish smaller features that are near or at
the center of the field of view, whereas features that are outside
of the center of the field of view must be larger for the person to
distinguish them through peripheral vision.
[0006] Soft contact lenses are not designed to provide optical
control over the peripheral portions of the lenses because the
peripheral portions do not affect the central vision of the eye.
The light rays that pass through the peripheral portion of a
typical soft contact lens are not focused in the central region of
the retina, and thus do not affect the central vision of the eye.
The peripheral portion of a typical soft contact lens sometimes
includes a blending or transitioning portion that connects the
central portion to the peripheral portion. This blending portion
does not designed to provide optical control, and therefore does
not provide vision correction except in cases where the pupils of
the eye are small. The purpose of the blending portion is simply to
connect the central and peripheral portions to each other.
[0007] Although an eye's corneal diameter typically ranges from
about 11 mm to about 12 mm, the central portion of a typical soft
contact lens typically ranges from about 7 mm to about 8 mm in
diameter (i.e., r.apprxeq.3.5 to 4 mm). The diameter of the central
vision zone of the eye is generally defined as the region that
provides central vision when the pupil is no larger than 7 mm in
diameter under scotopic viewing conditions. The term "scotopic"
means the ability to see in darkness or dim light, also referred to
as dark-adapted vision. Although a typical soft contact lens is
about 14 mm in total diameter, only the central 7 or 8 mm diameter
portion provides vision correction. The peripheral portion, also
commonly referred to as the lenticular portion, serves to stabilize
the lens and fit the lens comfortably over the limbus of the
eye.
[0008] While the peripheral portion of a typical soft contact lens
is not designed to provide optical control over light entering the
eye, it has been suggested that peripheral vision images may have
important effects on the vision system of the eye. For example, it
has been suggested that vision in the peripheral range drives
myopia. Myopia is the medical term for nearsightedness. People with
myopia see objects that are closer to the eye more clearly, while
distant objects appear blurred or fuzzy.
[0009] The manner in which peripheral vision may affect the vision
system of the eye is explained in, for example, U.S. Pat. No.
7,025,460 to Smith, et al. Specifically, in Column 3, lines 42-47
of Smith et al. states:
[0010] "The present invention is based on new learning from our
experiments that demonstrates that the peripheral retinal image
(i.e. peripheral vision) plays a major role in determining overall
eye length, and is an effective stimulus that promotes peripheral
and total eye growth that results in axial elongation, an overall
increase in eye size and myopia."
Smith et al. discloses various methods and devices for providing a
visual image that has "a peripheral field image location that is
positioned more anteriorly to (or in front of) the peripheral
retina (i.e. toward the cornea or the front of the eye) than
normally in the uncorrected condition, while the central field
image location is positioned near the central retina (i.e. the
fovea)". Smith et al. discloses that this arrangement minimizes or
eliminates the stimulus for eye axial elongation leading to
myopia.
[0011] U.S. Pat. No. 6,045,578 to Collins et al. discloses a method
for treating myopia that uses a lens having a central portion
(i.e., an optic zone) that causes paraxial light rays entering the
center region of the central portion of the lens to be focused on
the retina while causing light rays entering the peripheral region
of the central portion of the lens to be focused in a plane between
the cornea and the retina, thereby producing positive spherical
aberration of the image on the retina. Collins et al. states that
this positive spherical aberration has a physiological effect on
the eye that tends to inhibit growth of the eye, thus mitigating
the tendency of the myopic eye to grow longer.
[0012] Collins et al. also discloses an embodiment for mitigating
hyperopia by using a lens having a central portion (i.e., an optic
zone) that causes paraxial light rays entering the center region of
the central portion of the lens to be focused on the retina while
causing light rays entering the peripheral region of the central
portion of the lens to be focused in a plane behind the retina,
thereby producing negative spherical aberration of the image on the
retina. Collins et al. states that this negative spherical
aberration has a physiological effect on the eye that tends to
enhance growth of the eye, thus mitigating hyperopia.
[0013] While Smith et al. and Collins et al. both recognize the
importance of the peripheral vision image, these patents are
directed to the effects that light rays passing through the
periphery of the central portion of the lens have on the vision
system of the eye. In other words, these patents are not directed
to the effects that light rays passing through the peripheral
portion of the lens (i.e., the portion outside the approximately 7
or 8 mm diameter central portion of the lens) have on the eye.
Therefore, the effects that these light rays produce on the vision
system are limited by the ability of the central portion of the
lens to provide the necessary optical control.
[0014] For a variety of reasons, including those described in Smith
et al. and Collins et al., it would be desirable to provide a lens
having a peripheral portion that provides optical control. However,
because the peripheral portion of the lens is used to stabilize the
lens and to fit the lens to the surface of the eyeball, and is
normally the same for every lens of a given lens series, the
peripheral portion is normally not designed to provide optical
control. If the peripheral portion were to be designed to provide
optical control, it could not be kept the same for an entire lens
series. Rather, the peripheral portion would need to be varied from
lens to lens in order to ensure that the optical control it
provides works with the optical control provided by the central
portion. Consequently, the traditional view in the soft contact
lens industry is that because central vision is most important, and
because providing the peripheral portion of the lens with optical
control would require that different lenses of the same series be
manufactured with different peripheral portions, it is undesirable
to design contact lenses to have peripheral portions that provide
optical control.
[0015] Furthermore, increasing the diameter of the optical zone of
a contact lens presents certain problems that would need to be
solved by the contact lens industry. For example, for a typical
lens series comprising lenses ranging in optical power from -10 D
to +6 D and having 8 mm diameter central portions, the sagittal
depth (SAG) difference for different lenses of the series is
roughly 20 micrometers (.mu.m) per Diopter. Therefore, both the
thickness of the lens at the center of the central portion and at
the edge of the central portion vary over a lens series. If the
diameter of the central portion were to be increased, the SAG
difference across the series would increase to an even greater
extent. Because the front surface of the peripheral portion is
generally constant across the power range of the series, increasing
the diameter of the central portion would require that the slope
and curvature of the blending portion be varied to an even greater
extent from lens to lens across a given series. This presents even
greater difficulties in terms of lens design and manufacture.
[0016] Accordingly, a need exists for a contact lens having a
peripheral portion that provides optical control and that can be
easily designed and manufactured.
SUMMARY OF THE INVENTION
[0017] In accordance with the invention, a lens is provided that
has a peripheral portion that provides optical control. The
peripheral portion of the lens has a power profile that optical
controls a location at which a peripheral vision image is focused
relative to a retina of an eye. The lens also has a central portion
having at least one optical zone that provides optical control over
light rays passing through the central portion. The central portion
has a power profile that optically controls a location at which a
center vision image is focused relative to the retina of the
eye.
[0018] The invention also provides a method for providing a lens
that prevents or inhibits eye growth that leads to myopia. The
method comprises selecting a power profile for a peripheral portion
of a lens to be designed, and producing a design of a lens that has
a peripheral portion that provides optical control based on the
selected power profile. The power profile of the peripheral portion
optically controls a location at which a peripheral vision image is
focused relative to a retina of an eye. The lens design also
includes a central portion having a power profile that optically
controls a location at which a center vision image is focused
relative to the retina of the eye.
[0019] These and other features and advantages of the invention
will become apparent from the following description, drawings and
claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 illustrates a plan view of a lens in accordance with
an illustrative embodiment of the invention having a central
portion and a peripheral portion, wherein the peripheral portion is
optically controlled.
[0021] FIG. 2 illustrates a plan view of the central portion of the
lens shown in FIG. 1 in accordance with an embodiment having one or
more optical zones that are optically controlled.
[0022] FIG. 3 illustrates a plot that contains three different
power profiles that are suitable power profiles for the lens shown
in FIG. 1, and which all provide the peripheral portion of the lens
with optical control.
[0023] FIG. 4 illustrates a plot that contains three different
power profiles that are suitable power profiles for the lens shown
in FIG. 1, and which all provide the peripheral portion of the lens
with optical control.
[0024] FIG. 5 illustrates a flowchart that represents the method of
the invention in accordance with an embodiment.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0025] In accordance with the invention, the peripheral portion of
a contact lens or phakic IOC lens is provided with optical control
by controlling the power profile of the peripheral portion of the
lens. Typically, the central portion of the lens is also provided
with optical control, but because the invention is directed
primarily to the peripheral portion of the lens, the invention is
not limited with respect to the power profile of the central
portion of the lens. The power profile of the lens of the invention
at the boundary of the central and peripheral portions meets
certain boundary conditions necessary to ensure that the lens
provides a desired or selected vision correction, as will be
described below in detail with reference to FIGS. 3 and 4.
[0026] FIG. 1 illustrates a plan view of a contact lens 1 in
accordance with an embodiment of the invention. The lens 1
comprises a central portion 10 and a peripheral portion 20. The
peripheral portion 20 includes a blending portion 30 that
interconnects the central portion 10 and the peripheral portion 20.
The central portion 10 has a radius, r, that typically ranges from
0.0 mm at the center 2 of the lens 1 to about 3.5 or 4.0 mm at the
outer edge of the periphery 3 of the central portion 10. The
peripheral portion 20 has an inner radius, rI, that coincides with
the radius, r, of the central portion 10, and an outer radius, rO,
that coincides with the outer edge of the periphery 11 of the
peripheral portion 20 and is typically about 7.0 mm to about 8.0
mm.
[0027] FIG. 2 illustrates a plan view of the central portion 10 of
the lens 1 without the surrounding peripheral portion 20. The
central portion 10 of the lens 1 may be made up of a single optical
zone or a plurality of optical zones. The invention is not limited
with respect to the number of optical zones that make up the
central portion 10. The dashed circles 13, 14 and 15 are intended
to demark optional optical zones 16, 17, 18 and 19 that make up the
central portion. Although the dashed circles 13, 14 and 15 may
appear to indicate discrete boundaries between the optical zones,
any optical zones making up the central portion 10 will typically
be provided with smooth transition regions so that there are not
abrupt changes in optical power when transitioning from one zone to
another. However, the invention is not limited with regard to the
optical zone or zones provided by the central portion 10 or with
respect to the optical control provided by the central portion
10.
[0028] In one embodiment of the present invention, the power
profile that describes the optical control provided by the central
portion 10 and by the peripheral portion 20 of the lens 1 is any
power profile that is continuous in the first derivative across the
boundary (i.e., the blending portion 30) where the central portion
10 and the peripheral portion 20 meet. A large number of
mathematical functions exist that satisfy this boundary condition
and that are suitable for defining the power profile of the lens
1.
[0029] FIG. 3 illustrates a plot 40 of three different power
profiles 50, 60 and 70 that are suitable power profiles for the
lens 1 shown in FIG. 1. The vertical axis of the plot 40 represents
optical power in Diopters and the horizontal axis represents the
radial distance from the center 2 of the lens 1 outward toward the
periphery 11 of the peripheral portion 20 of the lens 1. In this
example, the outer periphery 11 of the peripheral portion 20 is a
radial distance of approximately 7 mm from the center 2 of the lens
1, but the plot 40 stops at r=6.0 mm because the profile beyond
this region is not important in this embodiment. In accordance with
this embodiment, the boundary between the central portion 10 and
the peripheral portion 20 is a radial distance of approximately 3.5
mm from the center 2 of the lens 1.
[0030] Each of the power profiles 50, 60 and 70 is defined by a
mathematical function that is differentiable in the first
derivative at least at the boundary where the central portion 10
and the peripheral portion 20 meet. In other words, the
mathematical functions are continuous at least at the boundary
where the central portion 10 and the peripheral portion 20 meet.
This means that the first derivative of each of the functions can
be taken at least at the boundary. In addition to being
differentiable in the first derivative at the boundary where the
central portion 10 and the peripheral portion 20 meet, these
functions may be, but need not be, differentiable in the second,
third and higher order derivatives at the boundary. Therefore, the
functions may be higher order functions such as polynomials, for
example. Other functions, such as, for example, linear functions
and continuous spline functions (e.g., cubic splines and bicubic
splines), may also be used to describe the power profiles. Linear
functions and cubic and bicubic spline functions are all
differentiable in at least the first derivative.
[0031] In the central portion 10, the power profiles 50, 60 and 70
are identical and are represented by the portion of the power
profile labeled with reference numeral 41. This portion of the
power profile corresponds to the typical Seidel, Zernike, conic and
biconic mathematical functions commonly used to define power
profiles for soft contact lenses prescribed for treating myopia and
hyperopia. The invention is not limited to the power profiles 50,
60 and 70 shown in FIG. 3, and is not limited with respect to the
power profile in the central portion 10 of the lens 1. The power
profiles shown in FIG. 3 are merely examples of power profiles that
are continuous in the first derivative and that are suitable power
profiles for the lens 1 shown in FIG. 1.
[0032] For most uncorrected eyes, the peripheral vision image is
formed behind the retina. Each of the power profiles 50, 60 and 70
has an ADD power in the peripheral portion 20 that is greater than
zero. Consequently, each of the power profiles 50, 60 and 70 will
provide a positive ADD power that will pull the peripheral vision
image in a direction toward the cornea from either behind the
retina, on the retina or in front of the retina. The power profile
selected for the peripheral portion will depend on the patient and
the amount of vision correction needed or desired. For example, in
some cases, the patient may have an uncorrected vision that results
in the peripheral vision image being focused behind the retina. In
this case, fitting the patient with a lens that has the profile 50
will provide a relatively large ADD power that will move the
peripheral vision image so that it is focused in front of the
retina.
[0033] If the patient has an uncorrected vision that results in the
peripheral vision image being focused on the retina, fitting the
patient with a lens that has the profile 60 will provide a lower
ADD power that will move the peripheral vision image from being
focused on the retina to being focused in front of the retina.
Similarly, if the patient has an uncorrected vision that results in
the peripheral vision image being focused slightly in front of the
retina, fitting the patient with a lens that has the profile 70
will provide a small ADD power that will move the peripheral vision
image a little more in the direction toward the cornea.
[0034] In all of these cases, the additional ADD power provided by
the lens results in myopic defocus in the peripheral region of the
retina. This myopic defocus helps prevent or inhibit eye growth,
thereby preventing or inhibiting myopia and/or ameliorating the
effects of myopia.
[0035] FIG. 4 illustrates a plot 110 that contains three different
power profiles 120, 130 and 140 that are suitable power profiles
for the lens 1 shown in FIG. 1. The power profiles 120, 130 and 140
are, in this example, mathematically identical in the central
portion 10, as indicated by portion 111 of the power profile, which
extends from the center 2 out to approximately 4.0 mm at the
boundary where the central and peripheral portions 10 and 20 meet.
In accordance with this embodiment, the power profiles 120, 130 and
140 may or may not be continuous over the boundary between the
central and peripheral portions 10 and 20. In other words, at the
boundary, the first derivative may not be able to be taken for any
of the mathematical functions that describe the profiles 120, 130
and 140.
[0036] For example, if the power profile is mathematically defined
by a piecewise function, the profile will typically not be
continuous at the boundary, and therefore, will not be
differentiable in the first derivative at the boundary. In
contrast, if the power profile is mathematically defined by a
spline function, the profile will typically be continuous at the
boundary, but will not be differentiable in the first derivative at
the boundary However, provided other boundary conditions are met, a
lens having any one of the profiles 120, 130 and 140 will work for
its intended purpose regardless of whether it is continuous or
discontinuous at the boundary and regardless of whether it is
differentiable in the first derivative at the boundary.
[0037] In particular, the only boundary condition that needs to be
met is that the difference between the optical power in the central
portion 10 at the boundary and the optical power in the peripheral
portion 20 at the boundary cannot be too great. Provided this
boundary condition is met, the lens peripheral portion 20 will
provide a positive ADD power that will pull the peripheral vision
image in a direction toward the cornea from either behind the
retina, on the retina or in front of the retina, depending on the
patient's uncorrected vision. Also, the discontinuity in the
profiles 120, 130 and 140 at the boundary will not result in
artifacts or other undesired effects on the vision system as long
as the boundary condition is met.
[0038] The difference in optical power in the central portion 10 at
the boundary and the optical power in the peripheral portion 20 at
the boundary should not be greater than about 8.0 Diopters, and
preferably is no greater than about 3.0 Diopters. In the plot 110
shown in FIG. 1, for profile 120, the difference in optical power
in the central portion 10 at the boundary and the optical power in
the peripheral portion 20 at the boundary is only about 1.6
Diopters, which easily meets the boundary condition. For profile
130, the difference in optical power in the central portion 10 at
the boundary and the optical power in the peripheral portion 20 at
the boundary is only about 0.7 Diopters, which easily meets the
boundary condition. Similarly, for profile 140, the difference in
optical power in the central portion 10 at the boundary and the
optical power in the peripheral portion 20 at the boundary is only
about 0.6 Diopters, which easily meets the boundary condition.
[0039] The power profile selected for the peripheral portion 20
will depend on the patient and the amount of vision correction
needed or desired. For example, if the patient has an uncorrected
vision that results in the peripheral vision image being focused
behind the retina, fitting the patient with a lens that has the
profile 120 will provide a relatively large ADD power that will
move the peripheral vision image so that it is focused in front of
the retina. If the patient has an uncorrected vision that results
in the peripheral vision image being focused on the retina, fitting
the patient with a lens that has the profile 130 will also provide
a relatively ADD power that will move the peripheral vision image
from being focused on the retina to being focused well in front of
the retina. Similarly, if the patient has an uncorrected vision
that results in the peripheral vision image being focused slightly
in front of the retina, fitting the patient with a lens that has
the profile 140 will provide a small ADD power that will move the
peripheral vision image a little more in the direction toward the
cornea.
[0040] In all of these cases, the additional ADD power provided by
the lens having the profiles shown in FIG. 4 results in myopic
defocus in the peripheral region of the retina. This myopic defocus
helps prevent or inhibit eye growth, thereby preventing or
inhibiting myopia and/or ameliorating the effects of myopia.
[0041] The profiles 120, 130 and 140 may be described by any type
of mathematical functions that meet the boundary condition
described above, including, for example, spline functions and
piecewise functions. The invention is not limited with respect to
the mathematical functions that are used to define the profiles in
the peripheral portions 20. It should be noted that although the
profiles may be discontinuous at the boundary (i.e., not
differentiable in the first derivative), the actual lens surfaces
preferably are continuous. The manner in which lenses having
profiles that are discontinuous at the boundary can be designed and
manufactured with continuous surfaces is known in the art. For
example, contact lenses having optical zones in the central
portions that are defined by splines or piecewise functions are
known.
[0042] Likewise, the manner in which lenses having profiles that
are continuous at the boundary can be designed and manufactured
with continuous surfaces is known in the art. For example, contact
lenses having optical zones in the central portions that are
defined by polynomials are well known.
[0043] The optical zone provided by the peripheral portion 20 may
be formed on the front surface of the lens or on anterior surface
of the lens. The manner in which lenses can be designed and
manufactured to meet all of these criteria is also known.
Therefore, in the interest of brevity, design and manufacturing
techniques that are suitable for use with the present invention
will not be described herein.
[0044] FIG. 5 illustrates a flowchart that represents the method of
the invention in accordance with an embodiment. A selection process
is first performed during which a power profile for the peripheral
portion of the lens is selected, as indicated by block 160. The
selected power profile may be for a single lens or for a lens
series. Each lens of a given lens series will have the same power
profile.
[0045] Once the power profile has been selected, a lens is designed
to have a peripheral portion that provides the optical control
provided by the selected power profile, as indicated by block 170.
During the design process, typically a software program executed by
a processor performs receives input from a designer and generates a
lens model having the surfaces that define the lens and the
selected power profile.
[0046] After the lens has been designed, the lens or the
corresponding series of lens are manufactured, as indicated by
block 180. A variety of manufacturing techniques may be used to
manufacture the lens or the lens series, and the technique used
will typically depend on the type of lens to be manufactured as
well as the types of surfaces that the lens or lenses are to have.
For example, in the case of soft contact lenses, the manufacturing
technique may use molds to manufacture the lens or lenses.
Typically, many soft contact lenses are manufactured on a
manufacturing line that uses processes, materials and equipment to
make the lens and inspect the lens to ensure it is suitable for
shipment to customers.
[0047] A different technique may be used to manufacture phakic IOC
lenses. Likewise, a different technique may be used to manufacture
hard contact lenses. In addition, the technique that is used to
manufacture the lens or lenses may depend on the selected power
profile. For example, the technique used to manufacture a soft
contact lens having a continuous power profile defined
mathematically by a polynomial may be different from the technique
used to manufacture a soft contact lens having a discontinuous
power profile defined mathematically by a piecewise function or
spline. Persons skilled in the art will know how to select the
appropriate manufacturing technique for the selected lens
design.
[0048] It should be noted that the entity that selects the power
profile for the peripheral portion may be, but need not be, the
same entity that designs and manufactures of the lens. Likewise,
the entity that manufactures the power profile for the peripheral
portion may be, but need not be, the same entity that designs the
lens. Thus, a single entity or three or more entities may perform
the process represented by the flowchart illustrated in FIG. 5
[0049] It should be noted that the invention has been described
with reference to certain illustrative embodiments and that the
invention is not limited to the embodiments described herein. For
example, FIGS. 3 and 4 show certain power profiles that have been
described herein for exemplary purposes, and the invention is not
limited to these profiles. Persons skilled in the art will
understand, in view of the disclosure provided herein, the manner
in which other power profiles can be selected that provide the
peripheral portion of the lens with a desired optical control.
* * * * *