U.S. patent application number 11/350437 was filed with the patent office on 2007-08-09 for intra-ocular device with multiple focusing powers/optics.
This patent application is currently assigned to Alcon Manufacturing, Ltd.. Invention is credited to Xin Hong, Richard J. Mackool, Michael A. Southard, Xiaoxiao Zhang.
Application Number | 20070182917 11/350437 |
Document ID | / |
Family ID | 38009748 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070182917 |
Kind Code |
A1 |
Zhang; Xiaoxiao ; et
al. |
August 9, 2007 |
Intra-ocular device with multiple focusing powers/optics
Abstract
An intraocular lens device that includes an intraocular lens
optics that provides at least two powers of magnification one being
near vision power and the other being distance vision power. The
lens optics has surface modulations that are responsible for
providing the near vision power. The zone structure provides an add
power of over 6 diopters. The add power indicative of an extent
that the near vision focusing power is greater than the distance
vision focusing power.
Inventors: |
Zhang; Xiaoxiao; (Fort
Worth, TX) ; Mackool; Richard J.; (Astoria, NY)
; Hong; Xin; (Arlington, TX) ; Southard; Michael
A.; (Arlington, TX) |
Correspondence
Address: |
ALCON
IP LEGAL, TB4-8
6201 SOUTH FREEWAY
FORT WORTH
TX
76134
US
|
Assignee: |
Alcon Manufacturing, Ltd.
|
Family ID: |
38009748 |
Appl. No.: |
11/350437 |
Filed: |
February 9, 2006 |
Current U.S.
Class: |
351/159.11 ;
351/159.74 |
Current CPC
Class: |
A61F 2/1654 20130101;
A61F 2/1618 20130101 |
Class at
Publication: |
351/159 |
International
Class: |
G02C 7/02 20060101
G02C007/02 |
Claims
1. An intraocular lens comprising, an optic that provides at least
two powers of magnification one being near vision power and the
other being distance vision power, the optic having a plurality of
surface modulations within a diffractive zone structure that are
configured to achieve light interference for creating add power
indicative of an extent that the near vision focusing power is
greater than the distance vision focusing power of the optic, the
diffractive zone structure providing the add power to be greater
than 6 diopters and having a plurality of diffractive zones
radially spaced from each other each with at least one of the
plurality of surface modulations, the diffractive zone structure
being defined as a function of the add power in accord with
r.sub.i.sup.2=(2i+1).lamda.f wherein r.sub.i denotes a radial
distance of each of the diffractive zones, i denotes a zone number
for which a central zone is denoted by i=0, .lamda. denotes a
design wavelength, and f denotes an add power.
2. The lens of claim 1, wherein the optic is either bifocal or
multifocal.
3. The lens of claim 1, wherein the lens is constructed to be
sulcus fixated.
4. The lens of claim 1, wherein the lens is constructed to be
implanted in a capsular bag.
5. The lens of claim 2, wherein the lens is constructed to be
sulcus fixated.
6. The lens of claim 1, whereas the lens is constructed to be
implanted in an anterior chamber.
7. The lens of claim 1, wherein the surface modulation is a
sawtooth configuration.
8. The lens of claim 7, wherein the sawtooth configuration has a
step height equal to .lamda. a .function. ( n 2 - n 1 ) .times. f
apodize ##EQU3## wherein .lamda. denotes the design wavelength
.alpha. denotes a parameter that can be adjusted to control
diffraction efficiency associated with various orders, n.sub.2
denotes the index of refraction of the optic, n.sub.1 denotes the
refractive index of a medium in which the lens optics is placed,
and f.sub.apodize represents a scaling function whose value
decreases as a function of increasing radial distance from an
intersection of an optical axis with an anterior surface of the
lens optics.
9. The lens of claim 8, wherein the scaling function f.sub.apodize
is in accord with f apodize = 1 - ( r i r out ) 3 ##EQU4## wherein
r.sub.i denotes the radial distance of an i.sup.th zone, r.sub.out
denotes an outer radius of a last diffractive zone.
10. The lens of claim 9, wherein a value of the f.sub.apodize is
one, a value of .alpha. is two.
11. The lens of claim 9, wherein the diffraction zone structure is
formed to resemble a series of ring configurations of different
diameters.
12. The lens of claim 1, wherein the diffraction zone structure is
further configured to direct images off-center so as to align the
line of sight with functional retina.
13. The lens of claim 1, wherein the optic is telescopic because of
the at least two powers with magnification, further comprising
optically aligning the telescopic optic with a non-telescopic
optic, the non-telescopic optic lacking multiple powers of
magnification.
14. A method for improving vision affected by age-related macular
degeneration (AMD), comprising the steps of: implanting an
intraocular lens with an optic that provides at least two powers of
magnification one being near vision power and the other being
distance vision power, the optic further having a plurality of
surface modulations within a diffractive zone structure that are
configured to achieve light interference for creating add power
indicative of an extent that the near vision focusing power is
greater than the distance vision focusing power of the intraocular
lens, the diffractive zone structure providing the add power
greater than 6 diopters and having a plurality of diffractive zones
radially spaced from each other each with at least one of the
plurality of surface modulations, the diffractive zone structure
being defined as a function of the add power in accord with
r.sub.i.sup.2=(2i+1).lamda.f wherein r.sub.i denotes a radial
distance of each of the diffractive zones, i denotes a zone number
for which a central zone is denoted by i=0, .lamda. denotes a
design wavelength, and f denotes an add power.
15. The method of claim 14, further comprising forming the optic to
be either bifocal or multifocal.
16. The method of claim 14, wherein the implanting includes
fixating the intraocular lens. optics in a sulcus.
17. The method of claim 14, wherein the implanting includes
fixating the intraocular lens in a capsular bag.
18. The method of claim 15, wherein the implanting further includes
fixating the intraocular lens in a sulcus.
19. The method of claim 15, wherein the implanting further includes
fixating the intraocular lens in an anterior chamber.
20. The method of claim 14, further comprising configuring the
surface modulations to be indicative of a sawtooth
configuration.
21. The method of claim 20, wherein the configuring includes
providing the sawtooth configuration with a step height equal to
.lamda. a .function. ( n 2 - n 1 ) .times. f apodize ##EQU5##
wherein .lamda. denotes the design wavelength .alpha. denotes a
parameter that can be adjusted to control diffraction efficiency
associated with various orders, n.sub.2 denotes the index of
refraction of the optic, n.sub.1 denotes the refractive index of a
medium in which the lens optics is placed, and f.sub.apodize
represents a scaling function whose value decreases as a function
of increasing radial distance from an intersection of an optical
axis with an anterior surface of the lens optics.
22. The method of claim 21, wherein the scaling function
f.sub.apodize is in accord with f apodize = 1 - ( r i r out ) 3
##EQU6## wherein r.sub.i denotes the radial distance of an i.sup.th
zone, r.sub.out denotes an outer radius of a last diffractive
zone.
23. The method of claim 22, wherein a value of the f.sub.apodize is
one, a value of .alpha. is two.
24. The method of claim 14, further comprising configuring the
diffraction zone structure to resemble a series of ring
configurations of different diameters.
25. The method of claim 14, further comprising configuring the
diffraction zone structure to direct images off-center so as to
align the line of sight with functional retina.
26. The method of claim 14, wherein the optic forms a telescopic
optical system.
27. The method of claim 14, further comprising performing macular
translocation surgery.
28. The method of claim 14, further comprising administering
ophthalmic pharmaceutically effective medications suited to at
least slow further development of AMD at a time subsequent to the
implanting.
29. The method of claim 28, wherein the administering includes
administering the ophthalmic pharmaceutically effective medication
suited to stop the further development of AMD.
30. An intraocular lens comprising, an optic that provides at least
two powers of magnification one being near vision power and the
other being distance vision power, the optic having a plurality of
surface modulations configured to achieve add power indicative of
an extent that the near vision focusing power is greater than the
distance vision focusing power of the optic, the surface
modifications providing the add power to be greater than 6 diopters
and having a plurality of zones radially spaced from each
other.
31. A method for improving vision affected by age-related macular
degeneration (AMD), comprising the steps of: implanting an
intraocular lens with an optic that provides at least two powers of
magnification one being near vision power and the other being
distance vision power, the optic having a plurality of surface
modulations that are configured to achieve light interference for
creating add power indicative of an extent that the near vision
focusing power is greater than the distance vision focusing power
of the intraocular lens, the surface modulations providing the add
power greater than 6 diopters and having a plurality of zones
radially spaced from each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a vision aid for the amblyopic
population, inclusive of patients with age-related macular
degeneration (AMD) or other low vision conditions. The vision aid
is an intra-ocular lens (IOL) device that has multiple focusing
powers or optics.
[0003] 2. Discussion of Related Art
[0004] Age-related macular degeneration (AMD) patients usually have
impaired central visual fields and often rely heavily on peripheral
vision for daily tasks. Peripheral retina has low receptors (cons
and rods) densities, which lead to their poor resolution ability.
Low vision patients, such as the amblyopic population, also have
poor retina resolutions. For these patients, the bottle neck of
visual resolution is at retina resolution. Improving optical
imagery in details does not solve the problem of poor visual
resolution.
[0005] AMD patients often have compromised fovea. However, there
are still functional retina receptors surrounding the compromised
receptors. These functional retina receptors are often peripherally
located and have larger spacing between each other. The increase
spacing leads to decreased image resolution ability of the retina.
For example, at 3 degrees nasal retina, the visual acuity is
reduced to 0.4 compared to the 1.0 visual acuity at 0 degrees; at 5
degrees nasal retina, the visual acuity is reduced to 0.34 compared
to the 1.0 visual acuity at 0 degrees (Millodot, 1966).
[0006] There are three basic types of vision aids available
conventionally either individually or in combination.
[0007] The first type is a single telescope as the visual aid. The
telescopes are often mounted on the spectacles, which are heavy and
are not appealing cosmetically. Implanted telescopes often require
very large incisions during surgery to implant. The main
disadvantage of using a telescope system alone is the resultant
narrow visual field of view and overall poor image quality, which
could cause a safety concern during motion.
[0008] The second type of vision aid is a prism. The prism is to
realign the line of sight to the peripheral retina. This
application needs to overcome a binocular fusion problem in order
to avoid double imagery. Also, the prism does not magnify the
retinal images. Therefore, the problem of low visual resolution due
to the larger peripheral retina receptor spacing is not
resolved.
[0009] The third type of vision aid is a magnifying glass,
sometimes combined with a prism. This visual aid is often used as a
desk mount device, which limits the application range for patients.
The handheld version of this visual aid has vision instability and
focus problems for patients with hand tremors.
[0010] Therefore, there are needs to 1) keep a larger visual field
of view, 2) increase portability for application, and 3) improve
cosmetics, and 4) increase the quality of vision and the stability
of the application.
[0011] FIG. 1 shows Peripheral Visual Acuity from Bennett and
Rabbetts "Clinical Visual Optics" page 37, Butterworth, Boston,
1984.
[0012] It is known that the peripheral vision can still provide
adequate resolution. The resolution, however, is progressively
reduced (FIG. 1). As shown in FIG. 1, visual acuity is reduced to
0.5 at 2 degrees nasally, to 0.4 at 3 degrees nasally, to 0.34 at 5
degree nasally, relative to the 1.0 visual acuity at 0 degrees.
Temporal, superior and inferior peripheral retinas are expected to
have similar behavior at similar small degree off axis range.
Accordingly, increasing or magnifying retina image size relative to
the size associated with 14 inches reading distance could allow the
peripheral retina to effectively resolve small text and objects
comparable to what normal eyes can do with central 0 degrees
retina. In particular, the magnification could be 2 times for using
2 degrees peripheral retina, 2.5 times for using 3 degrees
peripheral retina, or 3 times for using 5 degrees peripheral
retina.
[0013] Bifocal and multifocal optics are well known in the
ophthalmic optics field. Alcon's ReSTOR.RTM. lens optics is an
example. However, existing ophthalmic bifocal or multifocal optics
have much lower add power by design because they are obligated to
suit different patient needs. The ReSTOR.RTM. lens has a 4 D IOL
add power which is likely the highest add power known for
commercially available products. Table 1 indicates that with a 4 D
add power the magnification is only 1.2 times. That 1.2 times.
value is not likely to be adequate for AMD application according to
the needs shown in FIG. 1. That is, 1.2 times magnification is only
useful if the 0.5 degrees retina is not damaged by AMD.
SUMMARY OF THE INVENTION
[0014] One aspect of the invention pertains to a bifocal or
multifocal IOL or system that provides at least two focusing powers
or optics systems. While providing the distance power for normal
wide visual field needs of AMD and other low vision patients, the
IOL of the present invention enables such patients to focus reading
materials at near distances by employing surface modulations in
zone structure, preferably modulations is a diffractive zone
structure resembling a series of ring configurations of increasing
diameter.
[0015] Such near distances lead to clear retina images that are
magnified larger than 1.2 times of those normal reading retinal
images associated with reading distance of about 14 inches.
Preferably, the near distance power leads to clear retina images
that are magnified to 2-3 times of the normal reading retinal
images.
[0016] Reading needs of AMD patients can be met with the invention
preferably by bringing the magnified and focused retinal images to
the peripheral retinal receptors when patients position the normal
reading text to be focused via the near distance power. The
invention also provides the normal visual field of view needs that
can not be provided by telescopic devices used for AMD and other
low vision patients. This is achieved by making provisions to
incorporate a distance focus power capability. In addition, the
stable IOL position provides stable vision for patients with hand
tremors.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] For a better understanding of the present invention,
reference is made to the following description and accompanying
drawings, while the scope of the invention is set forth in the
appended claims.
[0018] FIG. 1 is a conventional graphical representation of visual
acuity as a function of eccentricity in the nasal retina.
[0019] FIG. 2 is a schematic representation of a bifocal/multifocal
on a sulcus fixed IOL carrier in accordance with an embodiment of
this invention.
[0020] FIG. 3 is a schematic representation of a bifocal/multifocal
IOL in a capsular bag accordance with a further embodiment of the
invention.
[0021] FIG. 4 is a schematic representation of a bifocal/multifocal
IOL in an anterior chamber or sulcus, plus an IOL in a capsular
bag, in accordance with another embodiment of the invention.
[0022] FIG. 5 is a conventional representation of different acuity
scales depicting a relationship between them.
[0023] FIG. 6 is a schematic elevation view of a diffractive
multifocal lens with a sawtooth surface modulation in accordance
with an embodiment of the invention.
[0024] FIG. 7 is a top plan view of the embodiment of FIG. 6,
revealing a ring diffractive zone structure.
[0025] FIG. 8 is a schematic side view representation of the eye
with an intraocular implant in accordance with an embodiment of the
invention.
[0026] FIG. 9 is a schematic front view representation of the eye
with the intraocular implant of FIG. 8.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] The inventors of the present invention are aware of sight
problems faced by patients with AMD or low vision and are aware
that such patients use add powers in reading glasses to help
improve their seeing ability.
[0028] Placing a strong add power in a reading glass will provide a
bigger magnified image, but such gives fewer photons per receptor
than would be the case if the same strong add power were placed in
an intraocular lens. By placing the strong add power into the
intraocular lens, such provides better contrast sensitivity for
patients with AMD or low vision disorders than would be the case if
the strong add power is in the reading glass instead--reason for
this difference is due to optics.
[0029] By placing the strong add power into the intraocular lens,
such provides a greater photon per receptor concentration as
compared to strong add power in the reading glass. The inventors
have determined that the add power of the lens implant be greater
than the current conventional level of 4 diopters on the lens
itself--the effect on the patient's vision is about 2.75 diopters.
Preferably, the add powers should be increased to any stronger add
power that would effect the patient's vision by as much as 5, 7.5
and 10 diopters and potentially higher.
[0030] There are at least the following three patient populations
that can potentially benefit from the invention.
[0031] Population 1: IOL patients that developed AMD
[0032] Population 2: Non-cataract presbyopic patients that
developed AMD.
[0033] Population 3: Non-cataract Non-presbyopic patients that
developed AMD or Low vision patients (amblyopic population).
[0034] Device approach for Population 1: Use a bifocal/multifocal
IOL10 on a sulcus fixed IOL carrier as shown in FIG. 2. The distant
power is plano or near plano for the patient's distance vision and
normal visual field size. The near add power will allow the patient
to see close enough (e.g. 6-7 inches) so that the retinal image
size of the normal reading text is resolvable by the good retinal
receptor array. As a placement alternative, this bifocal/multifocal
can also be on an anterior chamber IOL carrier and put into the
anterior chamber of the eye.
[0035] Device approach for Population 2: Use a bifocal/multifocal
IOL10 in a capsular bag as shown in FIG. 3. The distance vision
power is selected for the patient's distance vision needs and
normal visual field size. The near vision power will allow the
patient to see close enough (e.g. 6-7 inches) so that the retinal
image size of the normal reading text is resolvable by the good
retinal receptor array.
[0036] Device approach for Population 3: Use a bifocaimultifocal
IOL10 in an anterior chamber or sulcus fixed IOL carrier plus an
IOL12 in the capsular bag as shown in FIG. 4. The multilens
multifocal system has at least one telescopic view system (e.g.
IOL10) together with a non-telescopic view system (e.g., IOL 12).
The telescopic system provides magnified retina image for visual
acuity improvement. The non-telescopic view system provides the
normal visual field of view. In cases that the natural
accommodation of the natural crystalline lens is to be preserved, a
different embodiment can be used in which the natural crystalline
lens will be kept to work with a bifocal/multifocal IOL in an
anterior chamber or sulcus fixed IOL carrier. In such cases the
magnified retinal images are provided via the higher add power of
the bifocal/multifocal IOL.
[0037] Any other cross application of the three approaches to any
of the three populations is anticipated by the inventors. Also,
other forms of IOL lens carrier for the bifocal/multifocal IOL such
as iris fixated IOL carriers, is envisioned. This visual aid device
could also be used together with commercially available AMD drugs
and/or contact lenses and refractive ablations. The drug will
steady and stabilize the vision to help the device improve the
patient vision and the surgery or device can help to improve the
patient's vision.
[0038] In view of FIGS. 2-4, the present invention addresses the
need to keep a larger visual field of view than that provided by
the three basic types of vision aids available conventionally as
previously discussed by using bifocal or multifocal optics. The
present invention also addresses the needs for an increase in
portability for application and for an improvement in cosmetics
over such conventionally basic types and by implementing the optics
inside the eye in a conventional minimally invasive surgical
procedure, unlike implanted telescopes.
[0039] The inventive bifocal or multifocal device or IOL provides
at least two focusing powers. Patients' normal wide visual field
needs are met by the distance power of the device. Patients'
reading needs are met by allowing the patients to see focused
images at a closer sight distance than the normal 14 inches for
near distance. Image quality is also based on a focused image
rather that a patient having to orient his/her head or eyes.
[0040] With first order optics estimation, the retina Image size
magnification as a function of an IOL power can be found by using
equation 1 below.
.beta.=f.sub.1.times.f.sub.2/(f.sub.1.times.f.sub.1'-x.sub.1.times..DELTA-
.) Equation (1)
[0041] Where .beta. is the Image magnification of a optical system,
f.sub.1 is the object space focal length of the first optical lens
of the system, f.sub.2 is the object space focal length of the
second optical lens of the system, f.sub.1' is the image space
focal length of the first optical lens of the system, x.sub.1 is
the object distance from the object space focal point, .DELTA. is
the separation distance between the principal plane of the first
lens and the principal plane of the second lens.
[0042] Assuming the first lens is the cornea and has a power of 43
diopters, the .DELTA. is 4.3 mm, the refractive index in the image
space is 1.336, the distance power of the IOL is about +18
Diopters. Decreasing the object vergence distance increases the IOL
add power. Exemplary calculations using Equation (1) are tabulated
in Table 1.
[0043] Table 1 retina Image size change as a function of the IOL
power. TABLE-US-00001 Image size change relative to Distance
Distance IOL near that of 14.3 (mm) (in) power .beta. inches Note
-500 -19.7 21.0 0.081 0.7 -444 -17.5 21.3 0.092 0.8 -400 -15.7 21.5
0.103 0.9 -364 -14.3 21.8 0.114 1.0 Jager chart testing distance
-333 -13.1 22.0 0.126 1.1 -308 -12.1 22.3 0.137 1.2 ReSTOR
magnification -286 -11.2 22.5 0.149 1.3 -287 -10.5 22.8 0.161 1.4
-250 -9.8 23.0 0.173 1.5 -235 -0.3 23.3 0.185 1.6 -222 -8.7 23.5
0.197 1.7 -211 -8.3 23.8 0.210 1.8 -200 -7.9 24.0 0.222 1.9 -190
-7.5 24.3 0.235 2.1 see J1 text (Times New Roman N4 font) with 2
degree nasal retina -182 -7.2 24.5 0.247 2.2 -174 -8.8 24.8 0.260
2.3 -167 -8.8 25.0 0.273 2.4 -160 -8.3 25.3 0.286 2.5 See J1 text
(Times New Roman N4 font) with 3 degree nasal retina -154 -6.1 25.5
0.299 2.8 -148 -5.8 25.8 0.313 2.7 -143 -5.6 26.0 0.26 2.9 -138
-5.4 26.3 0.339 30. see J1 text (Times New Roman N4 font) with 5
degree nasal retina -133 -5.2 26.5 0.353 3.1 -129 -5.1 26.8 0.366
3.2 -125 -4.9 27.0 0.379 3.3
In the table note, the text font size estimation is based on FIG.
5.
[0044] Once the image size is magnified enough, the corresponding
focus power or imaging capability will bring a focused clear image
to the retina. Normal eye optics do not provide imaging capability
for bringing a focused clear image to retina at such close distance
except in very young children eyes.
[0045] While the accurate calculation could be done through ray
tracing, the above approximation should illustrate the concept.
With the present inventive device, AMD patients could have normal
visual field of view during motion except with a central Scotoma.
When they need to read text, reading ability is triggered by
bringing the text close to get a clearly focused image. Times New
Roman fonts of N4 or N5 are very small, and patients could read
these texts at 8 to 5.5 inches with retina adjacent to fovea
(depending on their Scotoma size).
[0046] Therefore, the invention modifies bifocal and multifocal
optics to provide an "add" power >+6 diopters in the IOL plane.
The preferred "add" power is >+6 to +8 diopters depending on
reading distance needs, although any greater power, such as 9
diopters or 10 diopters, is envisioned. The "add" power is the
difference between the near vision power and the distance vision
power of the bifocal or multifocal IOL.
[0047] The construction of the bifocal/mutifocal optics of the
present invention is a variation of constructions available
conventionally. Such conventional constructions provide a lesser
difference between the near vision power and the distance vision
power than 6 diopters. Some examples of conventional constructions
include that of U.S. Pat. No. 5,217,489 that mentions that the near
vision power is greater than the distance vision power by 2.0-5.0
diopters and whose contents are incorporated herein by reference
with respect to its bifocal intraocular lens structure.
[0048] U.S. Pat. No. 4,888,012 discloses an accommodative lens that
differs from the present invention in at least the following two
aspects. First, the said accommodative lens is a lens that
theoretically changes its power as the ciliary muscle compresses
it, instead of a predetermined multifocal lens. Second, the
accommodative lens only has a single focus instead of multiple foci
simultaneously. Therefore, U.S. Pat. No. 4,888,012 does not
disclose high add power values for multifocal lenses that have
simultaneously multiple foci which the present invention refers
to.
[0049] U.S. Pat. No. 6,432,246 B1 reveals a type of multifocal lens
known as progressive multifocal lens. Such a lens achieves power
variations across the lens optic by changing the surface radius of
curvature. This is based on the principle of geometric optics
instead of the diffractive optics principle. The progressive
multifocal lens has to deliver light over a wide range of foci and
thus reduces the available light energy for individual focus.
Therefore, it is not as effective as the diffractive optics
multifocal IOL in this regard. Therefore, U.S. Pat. No. 6,432,246
B1 does not disclose high add power values for multifocal lenses
that rely on diffractive optics principle to generated distinct and
highly efficient multiple foci, which the present invention refers
to.
[0050] Other conventional constructions include those of U.S. Pat.
No. 6,969,403 B2, U.S. Pat. No. 6,695,881 B2, and U.S. Published
Patent Application No. US 2005/0209692 A1, each of which being
incorporated herein by reference with respect to their structures
of an intraocular lens and carrier of the same.
[0051] Given the objective of providing low vision patients the
near reading ability as well as the normal field of view, light
energy is preferred to be concentrated at well defined specific
(i.e. distinct) foci such as distance focus and near focus, in some
cases also including an intermediate focus. Diffractive multifocal
lenses are more effective in this regard.
[0052] Diffractive multifocal lenses are often made with surface
modulation to achieve light interference for focus creation. The
add power of such lenses is related to the size of the concentric
rings of the surface modulation structure. By way of example, a
diffractive bifocal 20 can have a sawtooth shape surface modulation
22 as shown in FIG. 6. The ring structure 24 (also known as
diffractive zone structure) is better illustrated by FIG. 7. This
ring structure can be defined as a function of the add power needed
by equation 2 below, r.sub.i.sup.2=(2i+1).lamda.f Equation (2)
[0053] wherein [0054] r.sub.i denotes the radial distance of each
diffractive zone in the ring pattern [0055] i denotes the zone
number (i=0 denotes the central zone), [0056] .lamda. denotes the
design wavelength, [0057] f denotes an add power.
[0058] The sawtooth shape has a feature of step height 26 as shown
in FIG. 6. The step height 26 at each zone boundary of the bifocal
diffractive pattern can be defined by equation 3: Step .times.
.times. height = .lamda. a .function. ( n 2 - n 1 ) .times. f
apodize . Equation .times. .times. ( 3 ) ##EQU1## [0059] wherein
[0060] .lamda. denotes a design wavelength (e.g., 550 nm), [0061]
.alpha. denotes a parameter that can be adjusted to control
diffraction efficiency associated with various orders, e.g.,
.alpha. can be selected to be 2, [0062] n.sub.2 denotes the index
of refraction of the optic, [0063] n.sub.1 denotes the refractive
index of a medium in which the lens is placed. In embodiments in
which the surrounding medium is the aqueous humor having an index
of refraction of 1.336, the refractive index of the optic (n.sub.2)
can be selected to be 1.55. [0064] and f.sub.apodize represents a
scaling function whose value decreases as a function of increasing
radial distance from the intersection of the optical axis with the
anterior surface of the lens.
[0065] By way of example, the scaling function f.sub.apodize can be
defined by equation 4: f apodize = 1 - ( r i r out ) 3 . Equation
.times. .times. ( 4 ) ##EQU2## [0066] wherein [0067] r.sub.i
denotes the radial distance of the i.sup.th zone, [0068] r.sub.out
denotes the outer radius of the last bifocal diffractive zone. In
embodiments in which the near focus light energy need is high, the
f.sub.apodize scaling function can be assigned with other values.
For example, f.sub.apodize can be a constant of 1.0.
[0069] The step heights 26 provided by the above equations are only
examples, and other step heights can also be utilized.
[0070] The near vision focus power is provided by the diffraction
zone structure 24, while the distance vision focus power is
provided by the region 28 outside the diffraction zone structure 24
and by the diffraction zone structure 24. When there is an optimal
intermediate focus need for the AMD or low vision patients, a
trifocal-style multifocal lens can also be applied for as a low
vision aid use with high add power values.
[0071] Refractive multifocal lenses such as disclosed in U.S. Pat.
No. 5,217,489 can be changed upon higher add power and improved
light energy concentration at distance focus and near focus, as
anticipated by the inventors. The present invention has bifocal or
multifocal lenses with distinct foci that is as diffractive and
refractive as, although more diffractive and refractive than, that
disclosed in U.S. Pat. No. 5,217,489, but not utilizing progressive
multifocal lens in the manner of U.S. Pat. No. 6,432,246 B1.
[0072] Turning to FIGS. 9 and 10, a further embodiment is shown
illustrating the concept of deflecting an image 30 to functional
retina 32 and thereby avoid scotoma in the visual field. The
intraocular lens 34 is configured to effect the deflection as
shown, which is helpful for low vision patients such as those with
AMD and underwent Mascular Translocation surgeries.
[0073] Macular translocation is a surgical technique designed to
move the area of the retina responsible for fine vision (macula)
away from the diseased underlying layers (the retinal pigment
epithelium and choroid). The macula is moved to an area where these
underlying tissues are healthier. Consequently, safe treatment of
the sick blood vessels [choroidal neovascularization (CNV)] with,
for example, laser treatment can be performed without harming
central vision.
[0074] For patients who had Macular Translocation surgeries, their
normal line of sight are no longer aligned with their macula.
Consequently, the Macular Translocation treated eye could show the
undesirable "tropia" appearances such as "esotropia" or
"exotropia". Further, if patients had their both eyes treated with
Macular Translocation surgeries, there could be negative impact to
the intended vision function. For example, if the left eye needs to
look up to see better, and the right eye needs to look down to see
better, then patients can not performance the task because such
binocular eye movements are very difficult. This embodiment of
redirecting the retinal image location can reduce or correct the
"tropia" appearances by relocating the light of sight to the new
macular location. This will be even more helpful in the binocular
Macular Translocation cases.
[0075] In the binocular Macular Translocation cases, this
embodiment of the invention could achieve binocular summation,
which is at least about 40 percent more effective than monocular
vision. Different shift amounts of retinal image locations for the
paired eyes are allowed by adjusting the IOL of this embodiment. It
takes advantage of the availability of retinal portions with the
best neural functions. Neural learning and adaptation restructures
the visual pathway and forms image fusion for better vision.
[0076] The optics of this embodiment of the present invention to
achieve the redirection of images is based on diffractive optics so
that the IOL need not be thick and the implantation does not need
large incisions. The diffractive optics can be designed as an off
centered diffractive single focus and could have an appearance as
asymmetric diffractive rings on a centered IOL. In cases that the
line of sight is redirected to a new functional area, and the
retinal receptors in this area are less in density and large in
separations, the diffractive optics of the embodiment of FIGS. 8
and 9 can provide good and suitable optical imagery. Preferably,
the retinal imagery provided by this embodiment is no higher than
what is suitably resolved by receptors and thus avoids aliasing.
Aliasing constitutes false image signals that could provide wrong
movement direction to patients.
[0077] The embodiments of FIGS. 8 and 9 may be combined with that
of the embodiments of FIGS. 2-4 and 6-7 to provide features of
each. That is, the lens optics has a diffractive zone structure
such as that exemplified in FIGS. 6-7 with appropriate surface
modulations to provide an add power of at least 6 diopters and is
configured to deflect or redirect images based on diffractive
optics in the manner of FIGS. 8 and 9 toward the functional retina
to avoid scotoma in the visual field. Thus, an AMD patient can look
in the direction of objects to see them without the need to turn
away to do so. Further, such an intraocular lens may be implanted
in any of the positions shown in FIGS. 2-4 to attain improvement in
the ability to see objects when looking in the direction of the
object.
[0078] Preferably, the diffractive zone structure 24 is made of the
same lens material and is of uniform material composition.
[0079] To treat patients with AMD, any of the embodiments disclosed
may be used in conjunction with administration of an AMD drug to
stop and deter further development of AMD. The AMD drug may be an
ophthalmic pharmaceutical preparation for the treatment of advanced
macular degeneration.
[0080] While the foregoing description and drawings represent the
preferred embodiments of the present invention, it will be
understood that various changes and modifications may be made
without departing from the scope of the present invention.
* * * * *