U.S. patent application number 10/073081 was filed with the patent office on 2003-05-22 for contact lens for correcting myopia and/or astigmatism.
Invention is credited to Mitsui, Iwane.
Application Number | 20030095232 10/073081 |
Document ID | / |
Family ID | 19163587 |
Filed Date | 2003-05-22 |
United States Patent
Application |
20030095232 |
Kind Code |
A1 |
Mitsui, Iwane |
May 22, 2003 |
Contact lens for correcting myopia and/or astigmatism
Abstract
The present invention provides a myopia and/or
astigmatism-correcting contact lens for correcting myopia and/or
astigmatism based on the alteration in the shape of a patient's
cornea. The myopia and/or astigmatism-correcting contact lens
comprises a pressure zone having a first surface defined by the
inner surface of the contact lens located on the side of the
patient's cornea and positioned at the center of the contact lens.
The first surface is formed in a concave shape having a curvature
less than that of the central surface of the patient's cornea. The
contact lens further includes a relief zone having a concave-shaped
second surface defined by the inner surface of the contact lens
located on the side of the patient's cornea and positioned at the
periphery of the pressure zone, and an anchor zone having a
concave-shaped third surface defined by the inner surface of the
contact lens on the side of the patient's cornea and positioned at
the periphery of the relief zone. The first surface has a curvature
determined based on the shape of the patient's cornea to induce a
specific desired alteration in the shape of the patient's cornea.
Further, each of the curvatures of the first, second and third
surfaces is arranged to satisfy the following formulas,
RC=BC+7.0.about.9.0 D (diopter), and AC=BC+2.0.about.4.0D where BC
is the curvature of the first surface, RC is the curvature of the
second surface, and AC is the curvature of the third surface.
Inventors: |
Mitsui, Iwane; (Tokyo,
JP) |
Correspondence
Address: |
Edward G. Greive
Renner, Kenner, Greive, Bobak, Taylor & Weber
Fourth Floor
First National Tower
Akron
OH
44308-1456
US
|
Family ID: |
19163587 |
Appl. No.: |
10/073081 |
Filed: |
February 12, 2002 |
Current U.S.
Class: |
351/159.07 |
Current CPC
Class: |
G02C 7/047 20130101;
A61F 9/0017 20130101 |
Class at
Publication: |
351/176 |
International
Class: |
G02C 007/04; G02C
007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2001 |
JP |
2001-351257 |
Claims
What is claimed is:
1. A myopia and/or astigmatism-correcting contact lens for
correcting myopia and/or astigmatism based on the alteration in the
shape of a patient's cornea, said myopia and/or
astigmatism-correcting contact lens comprising; a pressure zone
having a first surface defined by the inner surface of said contact
lens located on the side of the patient's cornea and positioned at
the center of said contact lens, said first surface being formed in
a concave shape having a curvature less than that of the central
surface of the patient's cornea; a relief zone having a second
surface defined by the inner surface of said contact lens located
on the side of the patient's cornea and positioned at the periphery
of said pressure zone, said second surface being formed in a
concave shape; and an anchor zone having a third surface defined by
the inner surface of said contact lens on the side of the patient's
cornea and positioned at the periphery of said relief zone, said
third surface being formed in a concave shape,wherein said first
surface has a curvature determined based on the shape of the
patient's cornea to induce a specific desired alteration in the
shape of the patient's cornea, and each of the curvatures of said
first, second and third surfaces is arranged to satisfy the
following formulas,RC=BC+7.0.about.9.0 D (diopter),
andAC=BC+2.0.about.4.0 Dwhere BC is the curvature of the first
surface, RC is the curvature of the second surface, and AC is the
curvature of the third surface.
2. A myopia and/or astigmatism-correcting contact lens as defined
in claim 1, wherein each of the curvatures of said first, second
and third surfaces is arranged to satisfy the following
formulas,RC=BC+7.5.about.8.- 5 D, andAC=BC+2.5.about.3.5 D
3. A myopia and/or astigmatism-correcting contact lens as defined
in claim 1, wherein each of the curvatures of said first, second
and third surfaces is arranged to satisfy the following
formulas,RC=BC+about 8.0 D, andAC=BC+about 3.0 D
4. A myopia and/or astigmatism-correcting contact lens as defined
in either one of claim 1, which has a diameter ranging from about
9.0 to about 11.0 mm.
5. A myopia and/or astigmatism-correcting contact lens as defined
in either one of claim 1, which has a diameter ranging from about
9.5 to about 10.5 mm.
6. A myopia and/or astigmatism-correcting contact lens as defined
in either one of claim 1, which has a diameter of about 10 mm.
7. A myopia and/or astigmatism-correcting contact lens for
correcting myopia and/or astigmatism based on the alteration in the
shape of a patient's cornea, said myopia and/or
astigmatism-correcting contact lens comprising; a pressure zone
having a first surface defined by the inner surface of said contact
lens located on the side of a patient's cornea and positioned at
the center of said contact lens, said first surface being formed in
a concave shape having a curvature less than that of the central
surface of the patient's cornea; a relief zone having a second
surface defined by the inner surface of said contact lens located
on the side of the patient's cornea and positioned at the periphery
of said pressure zone, said second surface being formed in a
concave shape; a first anchor zone having a third surface defined
by the inner surface of said contact lens on the side of the
patient's cornea and positioned at the periphery of said relief
zone, said third surface being formed in a concave shape; and a
second anchor zone having a fourth surface defined by the inner
surface of said contact lens on the side of the patient's cornea
and positioned at the periphery of said first anchor zone, said
fourth surface being formed in a concave shape, wherein said first
surface has a curvature determined based on the shape of the
patient's cornea to induce a specific desired alteration in the
shape of the patient's cornea, and each of the curvatures of said
first, second, third and fourth surfaces is arranged to satisfy the
following formulas,RC=BC+11.00-13.0 DAC 1=BC+3.0-5.0 D, andAC
2=BC+4.0-6.0 D where BC is the curvature of the first surface, RC
is the curvature of the second surface, AC 1 is the curvature of
the third surface, and AC 2 is the curvature of the fourth
surface.
8. A myopia and/or astigmatism-correcting contact lens as defined
in claim 7, wherein each of the curvatures of said first, second,
third and fourth surfaces is arranged to satisfy the following
formulas,RC=BC+11.5-12.5 D,AC 1=BC+3.5-4.5 D andAC 2=BC+4.5-5.5
D
9. A myopia and/or astigmatism-correcting contact lens as defined
in claim 7, wherein each of the curvatures of said first, second,
third and fourth surfaces is arranged to satisfy the following
formulas,RC=BC+about 12 D,AC 1=BC+about 4 D, andAC 2=BC+about 5
D
10. A myopia and/or astigmatism-correcting contact lens as defined
in claim 7, which has a diameter ranging from about 9.6 to about
11.6 mm.
11. A myopia and/or astigmatism-correcting contact lens as defined
in claim 7, which has a diameter ranging from about 10.1 to about
11.6 mm.
12. A myopia and/or astigmatism-correcting contact lens as defined
in claim 7, which has a diameter ranging from about 10.6 to about
11.2 mm.
13. A myopia and/or astigmatism-correcting contact lens as defined
in claim 7, which has a diameter of either one of about 10.2, 10.4,
10.6, 10.8, and 11.0 mm.
14. A myopia and/or astigmatism-correcting contact lens for
correcting myopia and/or astigmatism based on the alteration in the
shape of a patient's cornea, said myopia and/or
astigmatism-correcting contact lens comprising; a pressure zone
having a first surface defined by the inner surface of said contact
lens located on the side of a patient's cornea and positioned at
the center of said contact lens, said first surface being formed in
a concave shape having a curvature less than that of the central
surface of the patient's cornea; a relief zone having a second
surface defined by the inner surface of said contact lens located
on the side of the patient's cornea and positioned at the periphery
of said pressure zone, said second surface being formed in a
concave shape; a first anchor zone having a third surface defined
by the inner surface of said contact lens on the side of the
patient's cornea and positioned at the periphery of said relief
zone, said third surface being formed in a concave shape; and a
second anchor zone having a fourth surface defined by the inner
surface of said contact lens on the side of the patient's cornea
and positioned at the periphery of said first anchor zone, said
fourth surface being formed in a concave shape, wherein said first
surface has a curvature determined based on the shape of the
patient's cornea to induce a specific desired alteration in the
shape of the patient's cornea, and each of the curvatures of said
first, second, third and fourth surfaces is arranged to satisfy the
following formulas,RC=BC+12.5-14.5 D,AC 1=BC+3.0-5.0 D, andAC
2=BC+4.0-6.0 D where BC is the curvature of the first surface, RC
is the curvature of the second surface, AC 1 is the curvature of
the third surface, and AC 2 is the curvature of the fourth
surface.
15. A myopia and/or astigmatism-correcting contact lens as defined
in claim 14, wherein each of the curvatures of said first, second,
third and fourth surfaces is arranged to satisfy the following
formulas,RC=BC+13.0-14.0 D,AC 1=BC+3.5-4.5 D, andAC 2=BC+4.5-5.5
D
16. A myopia and/or astigmatism-correcting contact lens as defined
in claim 14, wherein each of the curvatures of said first, second,
third and fourth surfaces is arranged to satisfy the following
formulas,RC=BC+about 13.5 D,AC 1=BC+about 4 D, andAC 2=BC+about 5
D
17. A myopia and/or astigmatism-correcting contact lens as defined
in claim 14, which has a diameter ranging from about 9.6 to about
11.6 mm.
18. A myopia and/or astigmatism-correcting contact lens as defined
in claim 14, which has a diameter ranging from about 10.1 to about
11.6 mm.
19. A myopia and/or astigmatism-correcting contact lens as defined
in claim 14, which has a diameter ranging from about 10.6 to about
11.2 mm.
20. A myopia and/or astigmatism-correcting contact lens as defined
in claim 14, which has a diameter of either one of about 10.2,
10.4, 10.6, 10.8, and 11.0 mm.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a contact lens for
correcting myopia and/or astigmatism. More specifically, the
present invention relates to a myopia and/or astigmatism-correcting
contact lens for reshaping the cornea based upon corneal topography
to effect correction of visual defects.
BACKGROUND OF THE INVENTION
[0002] Visual or optical defects which prevent parallel light rays
entering the eye from focusing clearly on the retina exist in
several varieties. In hyperopia (farsightedness), the point of
focus lies behind the retina, generally because the axis of the
eyeball is too short. In myopia (nearsightedness), the image is
focused in front of the retina, generally because the axis of the
eyeball is too long. In astigmatism, refraction is unequal on the
different meridians of the eyeball, generally due to asymmetry in
the shape of the eye.
[0003] Corrective glasses or contact lenses have been used to
correct these defects, including convex (plus) lenses for
hyperopia, concave (minus) lenses in myopia, and cylindrical lenses
in astigmatism. More recently, a surgical technique, myopic or
hyperopic keratomileusis has been used to alter cornea curvature
and thereby improve refractive error. This method cuts and removes
a predicted thickness of the corneal disk with a microkeratome.
Additional surgical procedures such as radial keratotomy use
microincisions in the cornea to surgically modify the curvature of
the cornea and thereby reduce or eliminate myopia or
astigmatism.
[0004] Photorefractive keratectomy (PRK) uses a laser to ablate the
center of the cornea and thus change the cornea. In Automated
Lamilar Keratectomy (ALK) pressure is placed on the cornea to bulge
the central dome. A flap in the dome is then opened, layers of
corneal tissue are removed and the flap is then closed. Procedures
combining aspects of ALK/PRK are sometimes used, called LASIK
(laser in situ keratectomy).
[0005] While these surgical procedures effect long lasting
correction of visual defects, they present an inherent risk of
permanent damage to a patient's eye. However slight this risk might
be, many patients are unwilling to undergo these surgical
procedures to correct the curvature of the cornea. Thus, there has
existed a need to provide a non-surgical method for reshaping the
cornea and thereby effecting correction of visual defects.
[0006] As one technique for satisfying such a demand, U.S. Pat. No.
5,695,509 provides an optical contact lens (contact lens) for
non-surgically reshaping and altering the curvature of the cornea.
When applied to the cornea of a patient, this optical contact lens
(hereinafter, sometime referred to as "contact lens") exerts a
selective pressure on the cornea causing displacement of corneal
tissue away from a pressure zone to a relief zone, thereby
reshaping the patient's cornea and improving the patient's vision
without surgical intervention. In general, the design of the
optical contact lens induces change in the corneal topography of
the patient's eye to make the cornea of a myopic eye more
oblate.
[0007] This optical contact lens is tooled in response to the
specific contour or topography of a patient's cornea and to affect
a desired reshaping or correction of the eye's curvatures. When the
contact lens is placed on the patient's cornea, a pressure zone of
the contact lens exerts a relative selective pressure on the
underlying or engaged region of the cornea to effect displacement
of corneal tissue away from the region of pressure. A relief zone
adjacent to the pressure zone does not contact the cornea and does
not exert pressure on the cornea, but is an area where the contact
lens is raised above the corneal surface. This area serves to
receive corneal tissue which is displaced from the cornea
underlying the pressure zone. An anchor zone adjacent to the relief
zone and between the relief zone and the periphery of the contact
lens controls or guides the reshaping of the corneal tissue,
directing displaced tissue to the relief zone. The anchor zone also
ensures good centration and maintenance of centration of the
contact lens on the cornea thus providing predictability of the
result and preventing overshooting the desired correction.
[0008] A contact lens of this invention useful in the treatment of
myopia contains a central pressure zone, an adjacent annular relief
zone, and an annular anchor zone adjacent to the relief zone and
located between the relief zone and the periphery of the contact
lens. When the contact lens is positioned on the patient's cornea,
pressure is exerted by the central pressure zone on the approximate
center of the corneal dome, thereby effecting displacement of
corneal tissue away from the center of the dome and to the adjacent
annular relief area. The pressure exerted at the anchor zone
controls reformation of the corneal surface by guiding the
displaced tissue into the relief zone. With time, the steep
curvature of the myopic eye's corneal dome is flattened or reduced,
and light incident over the central cornea will more correctly
converge on the retina, thereby improving the patient's vision.
[0009] In order to effect the treatment of astigmatism for a
patient's corneal dome having one or more curvatures, the contact
lens' curvature is arranged in each of given axes to allow the
pressure zone to be positioned so as to apply pressure at the
steepest meridian, thereby reducing the steep meridian and
minimizing or eliminating the difference in curvature. The
characteristics of a contact lens for treating astigmatism are
similar to those of a contact lens for correcting myopia.
[0010] The contact lens provided by the above U.S. Patent can be
summarized as follows.
[0011] A myopia and/or astigmatism-correcting contact lens for
correcting myopia and/or astigmatism based upon the alteration in
the shape of a patient's cornea, comprising;
[0012] a pressure zone having a first surface defined by the inner
surface of the contact lens located on the side of a patient's
cornea and positioned at the center of the contact lens, wherein
the first surface is formed in a concave shape having a curvature
than that of the central surface of the patient's cornea;
[0013] a relief zone having a second surface defined by the inner
surface of the contact lens located on the side of the patient's
cornea and positioned at the periphery of the pressure zone,
wherein the second surface is formed in a concave shape; and
[0014] an anchor zone having a third surface defined by the inner
surface of the contact lens located on the side of the patient's
cornea and positioned at the periphery of the relief zone and,
wherein the third surface is formed in a concave shape.
[0015] More specifically, in order to induce a specific desired
alteration in the shape of the patient's cornea, the first surface
has a curvature determined based on the shape of the patient's
cornea, and each of the curvatures of the first, second and third
surfaces is arranged to satisfy the following formulas,
RC=BC+3.00 D (diopter), and
AC=BC+0.0-1.0 D
[0016] where BC is the curvature of the first surface, RC is the
curvature of the second surface, and AC is the curvature of the
third surface.
[0017] The contact lens having the RC and AC arranged as above
could achieve some positive results. However, it was significantly
effective only for European and American but less effective for
Asian. Thus, the inventors have researched the shape of the cornea
of Asian, particularly of Japanese, and have found out a desirable
curvature of each of the aforementioned surfaces of the contact
lens most effective for Asian, particularly for Japanese.
DISCLOSURE OF THE INVENTION
[0018] Based on this knowledge, it is an object of the present
invention to provide a myopia and/or astigmatism-correcting contact
lens having a curvature effective for Asian, particularly for
Japanese.
[0019] According to the first aspect of the present invention, a
myopia and/or astigmatism-correcting contact lens for correcting
myopia and/or astigmatism based on the alteration in the shape of a
patient's cornea, said myopia and/or astigmatism-correcting contact
lens comprising;
[0020] a pressure zone having a first surface defined by the inner
surface of said contact lens located on the side of the patient's
cornea and positioned at the center of said contact lens, said
first surface being formed in a concave shape having a curvature
less than that of the central surface of the patient's cornea;
[0021] a relief zone having a second surface defined by the inner
surface of said contact lens located on the side of the patient's
cornea and positioned at the periphery of said pressure zone, said
second surface being formed in a concave shape; and
[0022] an anchor zone having a third surface defined by the inner
surface of said contact lens on the side of the patient's cornea
and positioned at the periphery of said relief zone, said third
surface being formed in a concave shape, wherein
[0023] said first surface has a curvature determined based on the
shape of the patient's cornea to induce a specific desired
alteration in the shape of the patient's cornea, and
[0024] each of the curvatures of said first, second and third
surfaces is arranged to satisfy the following formulas,
RC=BC+7.0.about.9.0 D (diopter), and
AC=BC+2.0.about.4.0 D
[0025] where BC is the curvature of the first surface, RC is the
curvature of the second surface, and AC is the curvature of the
third surface.
[0026] It is preferred that, in the above myopia and/or
astigmatism-correcting contact lens, each of the curvatures of said
first, second and third surfaces is arranged to satisfy the
following formulas,
RC=BC+7.5.about.8.5 D, and
AC=BC+2.5.about.3.5 D
[0027] Alternatively, each of the curvatures of said first, second
and third surfaces is preferably arranged to satisfy the following
formulas,
RC=BC+about 8.0 D, and
AC=BC+about 3.0 D
[0028] The myopia and/or astigmatism-correcting preferably has a
diameter ranging from about 9.0 to about 11.0 mm, and more
preferable, about 9.5 to about 10.5 mm, and especially preferable,
about 10 mm.
[0029] According to the second aspect of the present invention, a
myopia and/or astigmatism-correcting contact lens for correcting
myopia and/or astigmatism based on the alteration in the shape of a
patient's cornea, said myopia and/or astigmatism-correcting contact
lens comprising;
[0030] a pressure zone having a first surface defined by the inner
surface of said contact lens located on the side of a patient's
cornea and positioned at the center of said contact lens, said
first surface being formed in a concave shape having a curvature
less than that of the central surface of the patient's cornea;
[0031] a relief zone having a second surface defined by the inner
surface of said contact lens located on the side of the patient's
cornea and positioned at the periphery of said pressure zone, said
second surface being formed in a concave shape;
[0032] a first anchor zone having a third surface defined by the
inner surface of said contact lens on the side of the patient's
cornea and positioned at the periphery of said relief zone, said
third surface being formed in a concave shape; and
[0033] a second anchor zone having a fourth surface defined by the
inner surface of said contact lens on the side of the patient's
cornea and positioned at the periphery of said first anchor zone,
said fourth surface being formed in a concave shape, wherein
[0034] said first surface has a curvature determined based on the
shape of the patient's cornea to induce a specific desired
alteration in the shape of the patient's cornea, and
[0035] each of the curvatures of said first, second, third and
fourth surfaces is arranged to satisfy the following formulas,
RC=BC+11.00-13.0 D
AC 1=BC+3.0-5.0 D, and
AC 2=BC+4.0-6.0 D
[0036] where BC is the curvature of the first surface, RC is the
curvature of the second surface, AC 1 is the curvature of the third
surface, and AC 2 is the curvature of the fourth surface.
[0037] It is preferred that, in the above myopia and/or
astigmatism-correcting contact lens, each of the curvatures of said
first, second, third and fourth surfaces is arranged to satisfy the
following formulas,
RC=BC+11.5- 12.5 D,
AC 1=BC+3.5-4.5 D and
AC 2=BC+4.5-5.5 D
[0038] Alternatively, each of the curvatures of said first, second,
third and fourth surfaces is preferably arranged to satisfy the
following formulas,
RC=BC+about 12 D,
AC 1=BC+about 4 D, and
AC 2=BC+about 5 D
[0039] According to the third aspect to the present invention, a
myopia and/or astigmatism-correcting contact lens for correcting
myopia and/or astigmatism based on the alteration in the shape of a
patient's cornea, said myopia and/or astigmatism-correcting contact
lens comprising;
[0040] a pressure zone having a first surface defined by the inner
surface of said contact lens located on the side of a patient's
cornea and positioned at the center of said contact lens, said
first surface being formed in a concave shape having a curvature
less than that of the central surface of the patient's cornea;
[0041] a relief zone having a second surface defined by the inner
surface of said contact lens located on the side of the patient's
cornea and positioned at the periphery of said pressure zone, said
second surface being formed in a concave shape;
[0042] a first anchor zone having a third surface defined by the
inner surface of said contact lens on the side of the patient's
cornea and positioned at the periphery of said relief zone, said
third surface being formed in a concave shape; and
[0043] a second anchor zone having a fourth surface defined by the
inner surface of said contact lens on the side of the patient's
cornea and positioned at the periphery of said first anchor zone,
said fourth surface being formed in a concave shape, wherein
[0044] said first surface has a curvature determined based on the
shape of the patient's cornea to induce a specific desired
alteration in the shape of the patient's cornea, and
[0045] each of the curvatures of said first, second, third and
fourth surfaces is arranged to satisfy the following formulas,
RC=BC+12.5-14.5 D,
AC 1=BC+3.0-5.0 D, and
AC 2=BC+4.0-6.0 D
[0046] where BC is the curvature of the first surface, RC is the
curvature of the second surface, AC 1 is the curvature of the third
surface, and AC 2 is the curvature of the fourth surface.
[0047] It is preferred that in the above myopia and/or
astigmatism-correcting contact lens as defined in claim 10, wherein
each of the curvatures of said first, second, third and fourth
surfaces is arranged to satisfy the following formulas,
RC=BC+13.0-14.0 D,
AC 1=BC+3.5-4.5 D, and
AC 2=BC+4.5-5.5 D
[0048] Alternatively, each of the curvatures of said first, second,
third and fourth surfaces is preferably arranged to satisfy the
following formulas,
RC=BC+about 13.5 D,
AC 1=BC+about 4 D, and
AC 2=BC+about 5 D
[0049] The myopia and/or astigmatism-correcting contact lens may
have a diameter ranging from about 9.6 to about 11.6 mm, preferable
about 10.1 to about 11.6 mm, more preferable, about 10.6 to about
11.2 mm, and especially preferable, about 10.2, 10.4, 10.6, 10.8,
and 11.0 mm.
[0050] As with the optical contact lens of the aforementioned U.S.
Patent, in a myopia and/or astigmatism-correcting contact lens of
the present invention, application of this contact lens to a
patient's cornea results in reshaping of the cornea and provides
improved visual acuity. In a preferred embodiment, once a patient's
cornea has achieved an optimal shape, as determined by functional
visual acuity, the contact lens of the present invention may be
temporarily removed without loss of visual correction. However, a
patient may maintain the desired shape of the cornea by wearing the
optical contact lens for a short period of time, e.g.,
approximately three to eight hours per day. For example, in some
instances, a patient may wear the contact lens one or two nights a
week or every night during sleep to maintain the desired shape and
functional vision.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a schematic side sectional view of an average
normal eye;
[0052] FIG. 2 is a schematic sectional view of a myopic eye;
[0053] FIG. 3 is a schematic sectional view of an astigmatic
eye;
[0054] FIG. 4 is a schematic sectional view of a contact lens
according to a first embodiment of the present invention suitable
for treating the myopic eye of FIG. 2; and
[0055] FIG. 5 is a schematic sectional view of a contact lens
according to second and third embodiments of the present invention
suitable for treating the myopic eye of FIG. 2.
BEST MODE FOR CARRYING OUT THE INVENTION
[0056] In order to help understanding of a myopia and/or
astigmatism-correcting contact lens according to a preferred
embodiment of the invention, the general state of eyes will be
first described with referred to FIGS. 1 to 3.
[0057] FIG. 1 shows a normal eye containing a normal cornea 2. The
portion of the cornea 2 which projects over the lens 5 is termed
the corneal dome 4. The corneal dome 4 is generally considered
rotationally symmetrical and aspherical in shape, with the
approximate dome center 6 having essentially the highest projection
away from the center of the eye. A generally circular optical zone
o transmits incident light which normally converges on the retina
7.
[0058] Defects in visual acuity are correlated with distortions in
the shape of the cornea. As shown in FIG. 2, convergence occurs in
front of the retina in a myopic eye (nearsighted), and is
associated with an elongated axis a and a steepened or heightened
corneal dome 4. In an eye having astigmatism, multiple curvatures
of the cornea cause multiple areas of convergence as shown in FIG.
3.
[0059] The degree of corneal distortion and precise location and
size of a patient's corneal dome center 6 and dome periphery 8 may
be determined by one of skill in the art using a videokeratoscope
or corneal topographer. As described in pending U.S. application
Ser. No. 08/046,619, measurements of the contour of the cornea of
the human eye have been used to facilitate the design and fit of
contact lenses, as well as for use and performance of surgical
procedures.
[0060] In a conventional videokeratoscope used to measure the
cornea, concentric rings of light from a source of light within a
housing are directed onto a cornea and reflected by the cornea onto
the film of a camera as an image of the rings. The deviation of the
rings from their known concentricity is measured and this data is
processed mathematically to determine the actual contour of the
cornea, which is not a perfect sphere and which differs from one
individual to another. Conventional photokeroscopes are disclosed,
for example, in U.S. Pat. Nos. 3,248,162 and 3,598,478.
Videokeratoscopes or corneal topographers are disclosed for
example, in U.S. Pat. Nos. 4,978,213, 5,227,818 and U.S. patent
application Ser. No. 08/046,619. In general, a corneal topographer
includes a camera means, such as a charged coupled device camera
system for sensing the images of rings of light reflected from the
cornea. The camera apparatus sends standard video signals to a
computer, such as a conventional, commercially available image
processor, which digitize the video signals. The computer analyzes
the digital data and produces data useful in determining the
contour of the cornea of the human eye. A corneal topographer
apparatus which automatically centers and focuses the corneal image
reflected from a patient's cornea onto a charge coupled device
camera system is disclosed in U.S. patent application Ser. No.
08/046,619.
[0061] Any of the above-described methods, as well as others known
to those of skill in the art, may be used to determine the
topography of the cornea of a patient to be fitted with a contact
lens of the present invention. Whatever method is utilized, the
data is analyzed to determine the corneal condition, e.g., regular,
irregular, or astigmatism by methods generally known in the art.
The location and curvature of the corneal dome 4 and center 6 is
determined. Using these measurements, as well as the degree of
refractive error to be corrected, a contact lens or a lens of the
present invention is machined to apply selective pressure to areas
of the patient's cornea in order to effect a desired displacement
and reshaping of the cornea. Reformation or reshaping of the
patient's cornea results in improvement of the patient's
vision.
[0062] The contour and shape of the contact lens L1 according to a
first embodiment are shown in FIG. 4 in an exaggerated form. The
contour of the contact lens L1 is designed to treat myopia or
astigmatism. In FIG. 4, the contact lens L1 is symmetrical with
respect to the axis X.
[0063] The contact lens L1 includes at its center a pressure zone
10 which will overlay or engage a region of the corneal surface
where alteration is desired. When the contact lens L1 is placed on
the eye, the pressure zone 10 will apply a relative pressure to the
underlying or engaged region of the cornea. It is understood that
the contact lens L1 is separated from the cornea by fluid, e.g.,
tears present between the lens and the surface of the cornea but
the fluid follows the contour of the cornea.
[0064] The contact lens L1 also includes an annular relief zone 12
positioned at the periphery of the pressure zone 10. The relief
zone 12 is an area adjacent to the pressure zone 10 that creates a
space or void between the surface of cornea and the contact lens.
No pressure is applied from the relief zone 12 onto the underlying
region of the cornea. In contrast to the pressure zone 10, the area
between the relief zone 12 and the underlying corneal surface is
sufficiently spacious to receive corneal tissue displaced by
pressure applied at the pressure zone 10. An annular anchor zone 14
is located adjacent to the periphery of the relief zone 12. The
anchor zone 14 is in contact with the cornea and exerts minimal
pressure on the cornea for purposes of anchoring the contact lens
on the corneal surface to achieve and maintain good centration or
positioning. By applying relative pressure adjacent to the relief
zone 12, the anchor zone 14 guides the displaced corneal tissue
into the area under the relief zone 12.
[0065] The position of the pressure zone 10 on the cornea is
important to the contact lens's function of providing useful
reshaping of the cornea. Referring to FIG. 4, in a contact lens
designed to treat myopia, the pressure zone 10 is positioned to
apply pressure at the approximate center of the corneal dome. The
anchor zone 14 maintains the contact lens's position on the cornea
and controls the direction of corneal tissue displacement into the
relief zone.
[0066] Preferably, the contact lens L1 of the present invention
includes a second annular relief zone 16 at the periphery 18 of the
contact lens. The second relief zone 16 is raised away from the
cornea 2, e.g., to approximately 80-100 .mu.m at the periphery 18
of the contact lens, to assist in the movement of fluid and
nutrients under the contact lens, and also to permit easy removal
of the contact lens from the eye.
[0067] The specific location and size of the pressure zone, relief
zone, anchor zone, and second relief zone will differ with the
specific condition of the patient's eye and corneal topography, and
with the type of correction desired.
[0068] As shown in FIG. 4, when the contact lens is applied to an
eye, the pressure zone 10 engages the underlying corneal tissue.
The term "Engages" means that portion of the contact lens is
separated from the corneal tissue essentially only by tear fluid,
and the "engagement" causes pressure to be exerted by the pressure
zone 10 of the contact lens onto the underlying corneal tissue. The
pressure applied at the pressure zone 10 causes the underlying
cornea to be displaced away from the pressure zone.
[0069] The relief zone 12 is that portion of the contact lens
which, when positioned on an eye, does not "engage" the underlying
cornea, but in contrast, is recessed or raised away from the
cornea, creating an annular space or zone between the contact lens
and the corneal surface for receiving displaced corneal tissue.
[0070] When the contact lens is applied to an eye, the annular
anchor zone 14 engages the underlying cornea. The anchor zone 14
exerts a minimal pressure on the corneal surface underlying the
contact lens at a location adjacent to the relief zone 12 and
between the relief zone 12 and the periphery 18. The pressure
exerted by the anchor zone 14 cooperates with the central pressure
zone 10 and guides displaced corneal tissue into the space
underlying the contact lens at the relief zone 12. Pressure exerted
by the anchor zone 14 also stabilizes the contact lens on the
corneal surface and permits achievement and maintenance of good
centration of the contact lens on the cornea. Like the relief zone
12, a second relief zone 16 does not engage the underlying cornea.
The second relief zone 16 facilitates easy access of fluid and
nutrients under the contact lens and also permits easy "lift off"
or removal of the contact lens from the corneal surface. In
general, the periphery 18 of the contact lens has a sufficient
curvature to be raised away from the cornea for access of fluids,
e.g., approximately 80-100 .mu.m, and preferably about 90-100
.mu.m.
[0071] The design of a contact lens to correct astigmatism of the
eye as shown in FIG. 3 is in general similar to the contact lens of
FIG. 4 for treating a myopic eye.
[0072] The concave surface of the contact lens of the present
invention is formed with a continuous aspheric curvature from
center to periphery, that is with a gradual change of curvature
into each specified zone. The continuous curve is achieved by
machining the contact lens in accordance with a mathematical
analysis of the best curve fit for the desired distances between
the surface of the cornea at each of the specified zones and the
contact lens.
[0073] The contact lens of the present invention may be fabricated
from materials and using methods known to be useful, for example,
in the manufacture of conventional contact lenses. Such materials
include those useful in fabricating conventional gas (oxygen)
permeable contact lenses, e.g., fluroperm (Paragon Optical Co.) or
any oxygenated rigid plastic available and known to be useful in
fabrication of conventional contact lenses. An especially preferred
lens material is fluroperm 60 or 90, because it has high DK value
(oxygen transmissibility). In a preferred embodiment, the contact
lenses will also have optical properties to correct refractive
error during the reshaping of the cornea.
[0074] The contact lenses of the present invention are machined to
provide the appropriate reshaping of a particular patient's eye.
The eye's corneal topography is defined and mapped using
conventional corneal topography equipment as described above. The
refraction of the eye is measured by conventional techniques. A
diagnosis of the condition to be treated is made, e.g., myopia or
astigmatism, and the amount of refractive error is determined. The
patient's corneal topography is analyzed to select the appropriate
parameters for the patient's contact lens, including the position,
size and location of the corneal dome, the shape factor (e.g.,
deviation from a perfect sphere), and curvatures of the contact
lens to match the patient's topography.
[0075] Measurements of a patient's corneal topography are adjusted
for the desired correction and used to specify the dimensions of
the corrective contact lens. For the myopic eye shown in FIG. 2,
the approximate size of the optical zone o, or heightened area of
the corneal dome is measured as the radius (or diameter) from the
approximate center of the dome 6 to the approximate mid-periphery
8. Generally, for a contact lens having a total diameter of about
10 mm, the diameter of the optical zone will vary from about 4 to
about 7.5 mm. An area within the patient's optical zone o is
analyzed to determine the average diopter of the optical zone,
which determines the base diopter of the corrective contact lens.
As shown in FIG. 4, the relative size and position, e.g., annular
diameters of the pressure zone 10 and the diopter and annular
diameter of the relief zone 12 is determined in part by the
correction needed and the degree of the desired therapy.
[0076] The desired diopter of the pressure zone 10 is calculated to
apply a relative pressure to the underlying cornea according to the
diopter of cornea to be corrected, and is generally calculated by
subtracting a given value from the diopter of the cornea to be
corrected, in which the given value is preferable to be 1.5-4.5,
particularly about 3.
[0077] The factors disclosed in the aforementioned U.S. patent may
be used as factors in addition to those described above and
bellow.
[0078] The rate of curvedness (curvature) RC of the curve of the
annular relief zone 12 (the second surface) is machined to satisfy
the following formula, 1 RC = BC + 7.0 - 9.0 D = BC + 7.5 - 8.5 D (
preferably ) = BC + about 8.0 D ( more preferably )
[0079] where BC is the curvature of the curved surface of the
aforementioned pressure zone (the first surface).
[0080] The rate of curvedness (curvature) RC of the curve of the
anchor zone 14 (the third surface) is machined to satisfy the
following formula, 2 RC = BC + 2.0 - 4.0 D = BC + 7.5 - 8.5 D (
preferably ) = BC + about 8.0 D ( more preferably )
[0081] where BC is the curvature of the curved surface of the
aforementioned pressure zone (the first surface).
[0082] Then, the contact lens is machined to provide a continuous
curvature from the annular anchor zone 14 through the second relief
zone 16 to the raised periphery 18 of the contact lens. The
periphery 18 of the contact lens is machined to be raised
approximately 80-100 .mu.m from the surface of the cornea to
provide edge lift.
[0083] The general diameter of the contact lens of the first
embodiment is arranged in the range of about 9.0 to about 11.0 mm
(4.5 to 5.5 mm in radius), preferably about 9.5 to about 10.5 mm
(4.75 to 5.25 mm in radius), and most preferably about 10 mm (about
5 mm in radius).
[0084] The diameter of the central pressure zone 10 is arranged in
the range of about 4 to 7.5 mm (2 to 3.75 mm in radius), preferably
4.5 to 7.0 mm (2.25 to 3.5 mm in radius), and most preferably 5.8
to 6.5 mm (2.9 to 3.25 mm in radius). The annular radius of the
relief zone is arranged preferably in the range of 0.5 to 1.0 mm,
particularly at about 0.7 mm. The annular radius of the anchor zone
is arranged preferably in the range of about 0.6 to about 0.8 mm.
The annular radius of the second relief zone is arranged preferably
in the range of 0.3 to 0.6 mm.
[0085] The method of forming a contact lens for the treatment of
astigmatism is similar to that for forming a contact lens to treat
a myopic eye. The general diameter and average curvature of the
optical zone is determined. Next, the curvature of the pressure and
relief zones are calculated, as well as the anchor zone and second
relief zone curvatures.
[0086] The specific curvature of each contact lens is determined
from the topography of the eye and the desired level of visual
correction needed. One general method for calculating the
curvatures of a contact lens for treating a myopic eye is described
below. It is understood that several methods may be used to achieve
a contact lens of the present invention. Thus, the following
description is meant to be exemplary, and does not limit the
invention.
[0087] First, the patient's corneal topography is measured.
Examining a central portion of the cornea, e.g., the optical zone
at about 4-5 mm in central diameter (about 2-2.5 mm in central
radius), an average diopter is determined.
[0088] After determining the average diopter of the center portion
of the cornea, a desired diopter is arranged based on the
determined average diopter to provide a diopter of the pressure
zone 10 of the contact lens L1.
[0089] Each curvature of the relief zone and anchor zone of the
contact lens to treat myopia is determined using the aforementioned
formula.
[0090] The other factors may be determined by those described in
the aforementioned U.S. patent.
[0091] After the patient has worn a contact lens of the present
invention for a period of time, the patient is examined to record
progress in reaching an optimal shape or optimal level of
correction. For example, the patient may be examined approximately
weekly or monthly by measuring corneal topography and comparing new
measurements of corneal shape and visual acuity with prior records.
An optimal shape of the cornea is that shape which permits good
correction of the patient's visual defect to obtain functional
vision, e.g., that vision acceptable to the patient without contact
lenses.
[0092] For a very myopic patient, a plurality of contact lenses
having different correction diopters may be prepared to allow the
contact lens to be changeably worn depending on the progress in
correction.
[0093] Examples of such contact lenses will be described
bellow.
[0094] A contact lens L2 according to a second embodiment
comprises: a pressure zone 110 having a first surface defined by
the inner surface of the contact lens located on the side of a
patient's cornea and positioned at the center of the contact lens,
wherein the first surface is formed in a concave shape having a
curvature less than that of the central surface of the patient's
cornea; a relief zone 112 having a second surface defined by the
inner surface of the contact lens located on the side of the
patient's cornea and positioned at the periphery of the pressure
zone 111, wherein the second surface is formed in a concave shape;
a first anchor zone 114a having a third surface defined by the
inner surface of the contact lens on the side of the patient's
cornea and positioned at the periphery of the relief zone 112,
wherein the third surface is formed in a concave shape; and a
second anchor zone 114b having a fourth surface defined by the
inner surface of the contact lens on the side of the patient's
cornea and positioned at the periphery of the first anchor zone
114a, wherein the fourth surface is formed in a concave shape.
[0095] The contact lens L2 has the curved surfaces arranged to
satisfy the following formulas,
RC=BC+11.00-13.0 D
AC 1=BC+3.0-5.0 D, and
AC 2=BC+4.0-6.0 D
[0096] where BC is the curvature of the first surface, RC is the
curvature of the second surface, AC 1 is the curvature of the third
surface, and AC 2 is the curvature of the fourth surface.
[0097] Preferably, the above relationship is arranged as
follows,
RC=BC+11.5-12.5 D,
AC 1=BC+3.5-4.5 D, and
AC 2=BC+4.5-5.5 D
[0098] and, most preferably, the above relationship is arranged as
follows.
RC=BC+about 12 D,
AC 1=BC+about 4 D,
AC 2=BC+about 5 D
[0099] A contact lens L3 according to a third embodiment comprises
a pressure zone, a relief zone, a first anchor zone and a second
anchor zone as with the contact lens L2 of the second embodiment.
However, these are different in the relationship between respective
curvatures of the surfaces as follows.
[0100] The contact lens L3 has the curved surfaces arranged to
satisfy the following formulas,
RC=BC+12.5-14.5 D
AC 1=BC+3.0-5.0 D, and
AC 2=BC+4.0-6.0 D
[0101] where BC is the curvature of the first surface, RC is the
curvature of the second surface, AC 1 is the curvature of the third
surface, and AC 2 is the curvature of the fourth surface.
[0102] Preferably, the above relationship is arranged as
follows,
RC=BC+13.0-14.0 D,
AC 1=BC+3.5-4.5 D, and
AC 2=BC+4.5-5.5 D,
[0103] and, more preferably, the above relationship is arranged as
follows.
RC=BC+about 13.5 D,
AC 1=BC+about 4 D, and
AC 2=BC+about 5 D
[0104] The diameters of the contact lens L2 and L3 are
approximately the same and arranged preferably in the range of
about 9.6 to about 11.6 mm, more preferably about 10.1 to about
11.3 mm, further 10.6 to 11.2 mm, and are specifically arranged at
either one of about 10.2, 10.4, 10.6, 10.8, and 11.0 mm.
[0105] The diameter of the central pressure zone 110 is arranged in
the range of about 4 to about 7.5 mm (2 to 3.75 mm in radius),
preferably 4.5 to 7.0 mm (2.25 to 3.5 mm in radius), more
preferably 5.8 to 6.5 mm (2.9 to 3.25 mm in radius). The annular
radius of the relief zone 112 is arranged preferably in the range
of 0.5 to 1.0 mm, particularly at about 0.7 mm. The annular radius
of the first anchor zone 114a is arranged preferably in the range
of about 0.5 to about 0.9 mm, particularly at about 0.6 mm. The
annular radius of the second anchor zone 114b is arranged
preferably in the range of about 0.4 to about 0.9 mm, particularly
at about 0.6 mm. The second relief zone 116 is provided at the
outer periphery of the second anchor zone 114b, and an annular
radius of the second anchor zone 114b is arranged preferably in the
range of about 0.3 to about 0.6 mm, particularly at about 0.4
mm.
[0106] The following examples will be referred to help better
understanding of the invention.
EXAMPLES
Example 1 (with the Features of the Contact Lens L1 of the First
Embodiment)
[0107] A Japanese patient A initially wore a soft contact lens
every day to correct myopia. The patient was diagnosed with myopia
through the measurement of refractive error. According to the
measurement of the topography of central curves of the right and
left eyes, the diopter of the right eye was 38.50 (refractive
error: -4.25, uncorrected vision: 0.1) and the diopter of the left
eye was 39.00 (refractive error: -4.00, uncorrected vision:
0.1).
[0108] Based on the above measurements, BCs of the contact lenses
of the patient's right and left eyes were arranged at 35.50 D and
36.00 D, respectively.
[0109] Then, according to the present invention, RC and AC were
determined using the following two formulas.
RC=BC+8.0 D
AC=BC+3.0 D
[0110] As a result, RC and AC of the right eye's contact lens were
43.50 D and 38.50 D, respectively. Further, RC and AC of the left
eye's contact lens were 44.0 D and 39.00 D, respectively.
[0111] Then, the general diameter of the contact lens was arranged
at 10 mm, the diameter of the central pressure zone 10 being
arranged at 6.0 mm (3.00 mm in radius), the annular radius of the
relief zone 12 being arranged at 0.7 mm, the annular radius of the
anchor zone 14 being arranged at 0.7 mm, and the annular radius of
the second relief zone being arranged at 0.6 mm.
[0112] By using the above parameters, the contact lens L1 having
the configuration of the example 1 shown in FIG. 4 was
fabricated.
[0113] On the other hand, RC and AC were determined using the
following two formulas which have heretofore been used in U.S. as
described above.
RC=BC+3.0 D
AC=BC+0.0 D
[0114] As a result, RC and AC of the right eye's contact lens were
38.50 D and 35.50 D, respectively. RC and AC of the left eye's
contact lens were 39.00 D and 36.00 D, respectively.
[0115] Then, using the same diameters as those of the inventive
example, a contact lens as a comparative example was
fabricated.
[0116] The contact lenses of the inventive example and the
comparative example were worn by the patient A, and their results
were compared with each other.
[0117] More specifically, the contact lenses as the comparative
example were first worn by the myopic patient A at bedtime of night
for one week. As a result, the right and left eyes of the patient A
had 37.75 diopter (refractive error: -3.50, uncorrected vision:
0.2) and 38.00 diopter (refractive error: -3.25, uncorrected
vision: 0.3), respectively, and some improvement was observed.
However, once quitting the wearing, the original state was brought
back in a week.
[0118] After that, the contact lenses according to the example 1 of
the invention were worn by the patient A in the same way as that of
the comparative example. As a result, the right and left eyes of
the patient A had 37.00 diopter (refractive error: -1.75,
uncorrected vision: 0.9) and 37.00 diopter (refractive error:
-1.50, uncorrected vision: 1.0), respectively, and significant
improvement was observed. Then, after the patient A continued the
wearing under the above condition for a month, the effect was
measured. As a result, the right and left eyes of the patient A had
36.25 diopter (refractive error: -0.25, uncorrected vision: 1.5)
and 36.00 diopter (refractive error: -0.25, uncorrected vision:
1.5), respectively. Thus, the effect has been apparently
proved.
Examples 2 and 3 (with the Features of the Contact Lenses L2 and L3
of the Second and Third Embodiments)
[0119] A Japanese patient B initially wore a soft contact lens
every day to correct myopia. The patient was diagnosed with myopia
through the measurement of refractive error. According to the
measurement of the topography of central curves of the right and
left eyes, the diopter of the right eye was 41.25 (refractive
error: -6.25, uncorrected vision: 0.01) and the diopter of the left
eye was 41.50 (refractive error: -6.50, uncorrected vision: 0.01
).
[0120] Based on the above measurements, BCs of the contact lenses
of the patient's right and left eyes were arranged at 38.25 D and
38.50 D, respectively.
[0121] Then, according to the present invention, RC, AC 1 and AC 2
were determined using the following three formulas.
RC=BC+12.0 D
AC 1=BC+5.0 D
AC 2=BC+4.0 D
[0122] As a result, RC, AC 1 and AC 2 of the right eye's contact
lens of the example 2 were 50.25 D, 43.25 D and 42.25 D,
respectively. Further, RC, AC 1 and AC 2 of the left eye's contact
lens were 50.50 D, 43.50 D and 42.50 D, respectively.
[0123] Then, for the contact lens of the example 3, RC, AC 1 and AC
2 were determined using the following three formulas.
RC=BC+13.5 D
AC 1=BC+5.0 D
AC 2=BC+4.0 D
[0124] As a result, RC, AC 1 and AC 2 of the right eye's contact
lens of the example 3 were 51.75 D, 43.25 D and 42.25 D,
respectively. Further, RC, AC 1 and AC 2 of the left eye's contact
lens were 52.00 D, 43.50 D and 42.50 D, respectively.
[0125] Then, the general diameter of the contact lenses according
to the example 2 and 3 was arranged at 10 mm, the diameter of the
central pressure zone 10 being arranged at 6.0 mm (3.00 mm in
radius), the annular radius of the relief zone 12 being arranged at
0.7 mm, the annular radius of the first anchor zone 14 being
arranged at 0.6 mm, the annular radius of the second anchor zone
being arranged at 0.6 mm, and the annular radius of the second
relief zone being arranged at 0.4 mm.
[0126] By using the above parameters, the contact lenses L2 and L3
having the configurations of the examples 2 and 3 shown in FIG. 5
were fabricated.
[0127] On the other hand, RC and AC were determined using the
following two formulas which have heretofore been used in U.S. as
described above.
RC=BC+3.0 D
AC=BC+0.0 D
[0128] As a result, RC and AC of the right eye's contact lens were
41.25 D and 38.25 D, respectively. RC and AC of the left eye's
contact lens were 41.50 D and 38.50 D, respectively.
[0129] Then, using the same diameters as those of the example 1, a
contact lens as a comparative example 2 was fabricated.
[0130] The contact lenses of the examples 2 and 3 and the
comparative example 2 were worn by the patient B, and their results
were compared with each other.
[0131] More specifically, the contact lenses of the comparative
example 2 were worn by the patient B at bedtime of night for one
week. As a result, the right and left eyes of the patient B had
40.75 diopter (refractive error: -5.50, uncorrected vision: 0.08)
and 40.50 diopter (refractive error: -5.75, uncorrected vision:
0.07), respectively, and some improvement was observed. However,
once quitting the wearing, the original state was brought back in a
week.
[0132] After that, the contact lenses according to the example 2 of
the invention were worn by the patient B in the same way as that of
the comparative example. As a result, the right and left eyes of
the patient B had 39.75 diopter (refractive error: -4.25,
uncorrected vision: 0.2) and 39.50 diopter (refractive error:
-4.00, uncorrected vision: 0.3), respectively, and significant
improvement was observed. Then, after the patient B continued the
wearing under the above condition for a month, the effect was
measured. As a result, the right and left eyes of the patient B had
39.25 diopter (refractive error: -2.50, uncorrected vision: 0.7)
and 39.00 diopter (refractive error: -2.25, uncorrected vision:
0.8), respectively.
[0133] After that, the contact lenses according to the example 3 of
the invention were successively worn by the patient B in the same
way as that of the example 2. As a result, the right and left eyes
of the patient B had 38.25 diopter (refractive error: -0.50,
uncorrected vision: 1.5) and 38.50 diopter (refractive error:
-0.75, uncorrected vision: 1.2), respectively, and more significant
improvement was observed.
[0134] As above, the effect of the present invention has been
apparently proved. Further, when the contact lenses prepared by the
technique according to the present invention were worn by an
astigmatic patient, a similar same effect to that in the case of
myopia could be obtained
[0135] The above results demonstrate the effect of the present
invention.
* * * * *