U.S. patent application number 09/820832 was filed with the patent office on 2001-10-11 for methods and apparatus for presbyopia correction using ultraviolet and infrared lasers.
Invention is credited to Lin, J. T..
Application Number | 20010029363 09/820832 |
Document ID | / |
Family ID | 25231828 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010029363 |
Kind Code |
A1 |
Lin, J. T. |
October 11, 2001 |
Methods and apparatus for presbyopia correction using ultraviolet
and infrared lasers
Abstract
Presbyopia is treated by a system using various lasers to remove
a portion of the scleral tissue and increase the accommodation of
the presbyopic patient's eye. Stable accommodation is achieved by
the filling of the sub-conjunctiva tissue to the laser-ablated
scleral areas. The proposed laser wavelength ranges from
ultraviolet to infrared of (0.15-0.36) microns, (0.5-1.4) microns
and (0.9-3.2) microns. Both scanning and fiber delivered systems
are proposed to generate the ablation patterns. Laser ablation of
the sclera may be conducted with or without opening the conjunctiva
layer.
Inventors: |
Lin, J. T.; (Oviedo,
FL) |
Correspondence
Address: |
J. T. LIN
4532 Old Carriage Trail
Oviedo
FL
32765
US
|
Family ID: |
25231828 |
Appl. No.: |
09/820832 |
Filed: |
March 30, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09820832 |
Mar 30, 2001 |
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09303673 |
May 3, 1999 |
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6258082 |
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Current U.S.
Class: |
606/5 |
Current CPC
Class: |
A61F 9/00808 20130101;
A61F 9/00802 20130101; A61F 9/008 20130101; A61F 9/00804 20130101;
A61F 2009/00895 20130101; A61F 9/00817 20130101; A61F 9/00838
20130101; A61F 2009/00865 20130101; A61F 2009/00872 20130101 |
Class at
Publication: |
606/5 |
International
Class: |
A61B 018/18 |
Claims
I claim:
1. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing a portion of the scleral tissue of an eye in a
predetermined pattern and area, whereby the accommodation of the
presbyopic eye increases via the movement of the ciliary body and
zonular fiber connected to the corneal lens of the eye.
2. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing a portion of the scleral tissue of an eye in
accordance with claim 1 in which said movement of the ciliary body
is provided by the increase of the flexibility of said laser beam
ablated said scleral tissue which is filled in by the
subconjunctiva tissue.
3. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern
includes at least 3 radial lines around the area of the cornea
outside the limbus and each radial line has a dimension of about
(0.1-1.0) mm in width and (2.0-5.0) mm in length.
4. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined area defined by
the area outside the limbus and between two circles having diameter
of about 10 mm and 18 mm.
5. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern
includes at least 3 curved lines around the area of the cornea
outside the limbus.
6. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern
includes a dotted ring pattern around the area of the cornea
outside the limbus and each dot has a size of about (0.1-2.0) mm in
diameter.
7. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern is
generated by a scanning mechanism.
8. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern is
generated by a fiber-coupled device.
9. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern is
generated by a translation device.
10. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said predetermined pattern is
generated by a mask which is non-transparent to the said laser
beam.
11. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said laser beam is a ultraviolet
laser having a predetermined wavelength of about (0.15-0.36)
microns.
12. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said laser beam is an infrared
laser having a predetermined wavelength of about (0.9-6.0)
microns.
13. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing portion of the scleral tissue of an eye in
accordance with claim 1 in which said laser beam is a short pulse
solid state laser having a predetermined wavelength of about
(0.5-1.4) microns and a pulse width of about one femtosecond to one
nanoseconds.
14. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing a portion of the scleral tissue of an eye in
accordance with claim 1 in which said laser beam is delivered to
said predetermined area of the cornea by an optical fiber.
15. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing a portion of the scleral tissue of an eye in
accordance with claim 1 in which said scleral tissue is ablated by
said laser beam after the conjunctiva is open.
16. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing a portion of the scleral tissue of an eye in
accordance with claim 1 in which said scleral tissue is ablated by
said laser beam without opening the conjunctiva.
17. A laser beam ophthalmic surgery method for treating presbyopic
patient by removing a portion of the scleral tissue of an eye in
accordance with claim 12 in which said laser beam is tightly
focused to a spot size of about (1-500) microns to selectively
remove the sclera tissue underneath the conjunctiva layer.
Description
[0001] This is a Continuation-in-part of application Ser. No.
09/303,673 filed on May 3, 1999.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to apparatus and methods for
the treatment of presbyopia using ultraviolet and infrared lasers
to ablate the sclera tissue of an eye.
[0004] 2. Prior Art
[0005] Corneal reshaping, including a procedure called
photorefractive keratectomy (PRK) and a new procedure called laser
assisted in situ keratomileusis, or laser intrastroma
keratomileusis (LASIK), has been performed by lasers in the
ultraviolet (UV) wavelength of 193-213 nm. Commercial UV refractive
lasers include ArF excimer lasers at 193 nm and other non-excimer,
solid-state lasers, such as the one patented by the present
inventor in 1992 (U.S. Pat. No. 5,144,630). Precise, stable corneal
reshaping requires lasers with strong tissue absorption (or minimum
penetration depth) such that the thermal damage zone is at a
minimum (less than few microns). Furthermore, accuracy of the
procedure of vision correction depends on the amount of tissue
removed in each laser pulse, in the order of about 0.2 microns.
Therefore, lasers at UV wavelengths between 193 and 213 nm and at
the mid-infrared wavelengths between 2.8 and 3.2 microns are two
attractive wavelength ranges which match the absorption peak of
protein and water, respectively.
[0006] The above-described prior arts are however limited to the
use of reshaping the corneal surface curvature for the correction
of myopia, astigmatism and hyperopia. When a person reaches a
certain age (around 45), the eyes start to lose their capability to
focus for near vision and becomes presbyopia. Presbyopic problem is
not due to the cornea curvature but comes about as the lens loses
its ability to accommodate or focus for near vision as a result of
loss of elasticity that is inevitable as people age. Therefore the
existing lasers using corneal reshaping can not provide the
solution for presbyopia patients. In addition, corneal reshaping is
ablating the central portion of trhe corneal and change its
curvature.
[0007] To correct presbyopia, the present patent uses a "cold"
laser to remove sclera tissue (outside the limbus area) versus a
"thermal" lasers in Sand's patent (U.S. Pat. No. 5,484,432) to
shrink the corneal shape (inside the limbus area). The cold laser
of the present has a wavelength range of (0.15-0.36) microns and
(2.6-3.2) microns which are also different from that of the
"thermal" laser range of (1.80-2.55) microns proposed by Sand.
[0008] The prior arts of Ruitz (U.S. Pat. No. 5,533,997) and Lin
(U.S. Pat. No. 5,520,679) are all limited to the corneal central
portion and are designed to change the curvature of the cornea by
ablation the surface layer of the cornea. The present patent, on
the contrary, does not change the corneal central curvature and
only ablating tissue outside the limbus.
[0009] The technique used in the prior art of Bille (U.S. Pat. No.
4,907,586) is specified to below conditions: (a) quasi-continuous
laser having pulse duration less than 10 picoseconds and focused
spot less than 10 micron diameter; (b) the laser is confined to the
interior of a selected tissue to correct myopia, hyperopia or
astigmatism, and (c) the laser is focused into the lens of an eye
to prevent presbyopia. He also proposed to use laser to create a
cavity within the corneal stroma to change its viscoelastic
properties.
[0010] The "presbyopia" correction proposed by Ruitz using an
excimer (ArF) laser also required the corneal surface to be
reshaped to form "multifocal" effort for a presbyopia patents to
see near and far. However, Ruitz's "presbyopia" correction is
fundamentally different from that of the present patent which does
not change the corneal curvature and only ablate the scleral tissue
outside the limbus area. In the presnt patent, we propose that the
presbyopia patent is corrected by increasing patient's
accommodation rather than reshaping the cornea into
"multifocal".
[0011] To treat presbyopic patients, or the reversal of presbyopia,
using the concept of expanding the sclera by mechanical devices or
implantation of a band has been proposed by Schachar in U.S. Pat.
Nos. 5,489,299, 5,722,952, 5,465,737 and 5,354,331. These
mechanical approaches have the drawbacks of complexity and are time
consuming, costly and have potential side effects. To treat
presbyopia, the Schachar U.S. Pat. Nos. 5,529,076 and 5,722,952
propose the use of heat or radiation on the corneal epithelium to
arrest the growth of the crystalline lens and also propose the use
of lasers to ablate portions of the thickness of the sclera.
However, these prior arts do not present any details or practical
methods or laser parameters for the presbyopic corrections. No
clinical studies have been practiced to show the effectiveness of
the proposed concepts. The concepts proposed in the Schachar
patents regarding lasers suitable for ablating the sclera tissues
were incorrect because many of his proposed lasers are thermal
lasers which will cause thermal burning of the cornea, rather than
tissue ablation. Furthermore, the clinical issues, such as
locations, patterns and depth of the sclera tissue removal were not
indicated in these prior patents. In addition, Schachar's methods
also require the weakening of the sclera and increase the lens
diameter by band expansion, which is different from the theory
proposed in the present patent, where the sclera tissue becomes
more flexible than weakening after laser ablation.
[0012] Another prior art proposed by Spencer Thornton, Chapter 4,
"Survey for hyperopia and presbyopia", edited by Neal Sher
(Williams & Wilkins, MD, 1997) is to use a diamond knife to
incise radial cuts around the limbus areas. It requires a deep
(90%-98%) cut of the sclera tissue in order to obtain accommodation
of the lens. This method, however, involves a lot of bleeding and
is difficult to control the depth of the cut which requires
extensive surgeon's skill. Another major drawback for presbyopia
correction provided by the above-described non-laser methods is the
post-operative regression of about (30%-80%) caused by the healing
of the "incision" gap. And this regression is minimum in the laser
"excision" or "ablation" method proposed in the present
invention.
[0013] The important concept proposed in the present invention is
to support the present inventor's postoperative results which show
minimum regression. We proposed a theory based upon the fact that
the laser ablated sclera tissue "gap" will be filled in by the
sub-conjunctiva tissue within few days after the surgery. This
filled in sub-conjunctiva tissue is much more flexible than the
original sclera tissue. Therefore the filled-in gap in the sclera
area will cause the underlying ciliary body to have more space to
move. This in turn will allow the ciliary body to contract or
expand the zonular fiber which is connected to the lens, when the
presbyopic patient is adjusting his lens curvature to see near and
far. The above described subconjunctiva tissue filling effects and
the increase of "flexibility" of the sclera area are fundamentally
different from the scleral "expansion" (or weakening) concept
proposed by the prior arts of Schachar who proposed an implanted
slceral band. In the present invention, the laser ablated sclera
area is not weakening, it becomes more flexible instead.
[0014] Therefore one objective of the present invention is to
provide an apparatus and method to obviate these drawbacks in the
above described prior arts.
[0015] It is yet another objective of the present invention to use
a scanning device such that the degree of ciliary mussel
accommodation can be controlled by the location, size and shapes of
the removed sclera tissue.
[0016] It is yet another objective of the present invention to
define the non-thermal lasers for efficient tissue ablation.
[0017] It is yet another objective of the present invention to
define the optimal laser parameters and the ablation patterns for
best clinical outcome for presbyopia patients, where sclera
ablation will increase the accommodation of the ciliary mussel by
the increase of the flexibility in the laser-ablated areas.
[0018] It is yet another objective of the present invention to
provide the appropriate scanning patterns which will cause
effective ciliary body contraction and expansion on the zonules and
the corneal lens based upon a theory different from the prior
arts.
[0019] t is yet another objective of the present invention to
provide a new mechanism which supports the clinical results of
laser presbyopia correction with minimum regression. One important
concept proposed in the present invention is to support the
post-operative results which show minimum regression when
presbyopia is corrected by a laser ablation for the sclera tissue.
We proposed that the laser ablated sclera tissue "gap" is filled in
by the sub-conjunctiva tissue within few days after the surgery.
This filled-in sub-conjunctiva tissue is much more flexible than
the original sclera tissue. Therefore the flexible filled-in gap in
the sclera area will allow the ciliary body to contract and cause
the zonular fiber and the corneal lens to adjust its focusing power
and increase the accommodation of presbyopic patient.
[0020] The concept presented in the present patent is to remove, by
any methods including laser or non-laser methods, portion of the
sclera tissue which is then filled in by sub-conjunctiva tissue to
increase the flexibility of the scleral area and in turn causes the
movement of the ciliary body and zonular fiber to increase the lens
accommodation.
SUMMARY OF THE INVENTION
[0021] The preferred embodiments of the present surgical laser
consists of a combination of an ablative-type laser and delivery
unit. The ablative-type laser has a wavelength range of from 0.15
to 0.35 microns and from 2.6 to 3.2 microns and is operated in a
pulsed mode such that the thermal damage of the corneal tissue is
minimized.
[0022] It is yet another preferred embodiment of the present
surgical laser to provide a scanning mechanism to effectively
ablate the sclera tissue at a controlled depth by beam overlapping
or by controlling the number of laser pulses acting on the
sclera.
[0023] It is yet another embodiment of the present surgical laser
to provide an integration system in which the ablative laser may be
delivered by a scanner or by a fiber-coupled device which can be
manually scanned over the cornea.
[0024] It is yet another embodiment of the present surgical laser
to focus the laser beams to generate the sclera ablation patterns
in radial lines, curved lines, dotted rings, or a slit pattern.
[0025] It is yet another embodiment of the present surgical laser
to provide an integration system in which the sclera ablation leads
to the increase of the accommodation of the ciliary muscle for the
treatment of presbyopia.
[0026] Further preferred embodiments of the present surgical laser
will become apparent from the description of the invention which
follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 is the schematic drawing of the anterposterior
section through the anterior portion of a human eye showing the
sclera, ciliary muscle, zonule and the lens.
[0028] FIG. 2 is a schematics of scleral ablation area outside the
limbus.
[0029] FIG. 3 is a schematics of the structure of corneal including
conjunctiva, sub-conjunctiva and sclera area ablated by laser.
DETAILED DESCRIPTION OF THE INVENTION AND THE PREFERRED
EMBODIMENTS
[0030] FIG. 1 shows the lens of a human eye 12 connected to the
sclera tissue 13 and the ciliary body 14 by zonule fibers 15. The
lens power is given by contraction and expansion of the ciliary
mussel 14 and the movement of the zonular fiber 15 connected to the
lens 12.
[0031] FIG. 2 shows the laser ablated sclera area outside the
limbus 16 defined by the area between two circles, 17 and 18,
having diameter of about 10 mm and 18 mm. Various ablation patterns
within these two circle area are proposed in the present
invention.
[0032] Based on the proposed theory of the present invention and as
shown in FIG. 3, when a portion of the sclera tissue 13 is removed
by an ablative laser, this ablated "gap" 19 will be filled in by
the subconjunctiva tissue 21 which is much more flexible than the
original sclera tissue 13. This filled in subconjunctiva 21 will
allow the ciliary body 14 to contract or relax the zonular fiber 15
which is connected to the lens, when the presbyopic patient is
adjusting his lens curvature to see near and far. Ablation of the
sclera 13 will cause the ciliary body 14 to contract and the lens
12 becomes more spherical in topography with a shorter radii of
curvature for near objects. The reversed process of ciliary muscle
relaxation will cause a longer radii of curvature for distant
objects. Therefore, laser ablation of the sclera tissue will
increase the accommodation of the ciliary body for the presbyopic
patient to see both near and distance. Typically, we open the
conjunctiva tissue 20 first and then ablate the sclera tissue 13.
The conjunctiva 20 and sub-conjunctiva 21 layers may be remove
mechanically by the same laser used for scleral ablation. For
efficient accommodation, the depth of the laser ablation needs to
be approximately (60%-90%) of the sclera thickness which is about
(500-700) microns. For safety reasons, the ablation depth should
not cut through the choroid. It is therefore clinically important
that the patient's sclera thickness be measured pre-operatively and
the laser ablation depth controlled. A scanning laser is used to
control this depth by the number of scanning lines or pulses over
the selected area at a given set of laser parameters.
Alternatively, the surgeon may observe the color change of the
ablated sclera tissue to determine when the ablation depth reaches
the interface of the sclera and the ciliary.
[0033] The ablation patterns can be any symmetric shapes around the
limbus area, including radial lines, arc or curved line, dotted
rings. These are examples only but it can be more or less without
departing from the spirit and scope of the invention. Enhancement
may be performed by adding more ablation lines. The preferred
embodiment of the beam spot sizes are about (0.1-2.0) mm on the
cornea surface for a round beam and about (0.1-2.0) mm in width and
(2.0-5.0) mm in length for a line-spot. These round and slit spots
may be generated by a focusing spherical and a cylinder lens. These
beam spots may also be generated by a "mask" which blocks the laser
beam and produce the desired patterns on the cornea surface. The
mask shall be made by non-transparent materials at the laser
wavelength used for sclera ablation.
[0034] Ablation patterns described above may be generated by the
preferred embodiment of the present system including a
computer-controlled galvanometer, fiber-coupled hand piece (using a
manual scan), motorized mirrors, refractive optics, reflecting
mirror and any a translation device. A mask having various "holes"
or "slits" may also be used to generate various patterns proposed
in the present invention.
[0035] We are able to calibrate the ablation rate of various lasers
on the sclera tissue by comparing the clinical data. To avoid the
post-operative regression, the sclera tissue is permanently removed
by the ablative lasers and filled in by the sub-conjunctiva
tissues.
[0036] The preferred embodiment of the laser in the proposed system
includes an ablative laser such as a Er:YAG laser; Er:YSGG laser;
an optical parametric oscillation (OPO) laser at (2.6-3.2) microns;
a gas laser with a wavelength of (2.6-3.2) microns; an excimer
laser of ArF at 193 nm; a XeCl excimer laser at 308 nm; a
frequency-shifted solid state laser at (0.15-3.2) microns; the
harmonic generation of Nd:YAG or Nd:YLF or Ti:sapphire laser at
wavelength of about (190-220) nm; a CO laser at about 6.0 microns
and a carbon dioxide laser at 10.6 microns; a diode laser at
(0.8-2.1) microns, or any other gas or solid state lasers including
flash-lamp and diode-laser pumped, at (0.5-6.0) microns spectra
range. To achieve the ablation of the sclera tissue at the
preferred laser spot size of (0.1-2.0) mm requires an ablative
laser energy per pulse of about (0.1-30) mJ depending on the pulse
duration and the laser beam spot size.
[0037] For a typical pulse laser width of 100 nanoseconds to 500
microseconds, the preferred embodiments of FIG. 1 shall require the
ablative laser to meet the peaks of tissue absorption spectra such
as 0.98, 1.5, 2.1, 2.94 and 6.0 microns. However, for the case of
lasers with a very short pulse of about from 1 femtosecond to 100
picoseconds, the laser wavelength becomes non-critical in the
tissue interaction and the high peak laser intensity with small
laser spot are more important. Therefore, The preferred embodiment
of the laser should also include the short pulse lasers having
wavelength of about (0.5-1.4) microns, such as Nd:YAG or Nd:YLF
laser and their second harmonics operated in the range of
picosecond or femtosecond pulse width. These short pulse lasers
shall be able to remove sclera tissue and conjunctiva tissue easily
by focusing the laser beam on the surface of the tissue to be
removed. Another preferred embodiment of the present laser system
is to tightly focused underneath the conjunctiva layer and
selectively ablate the sclera tissue without damage or removing the
conjunctiva tissue. Focused spot size of about (1-500) microns and
accurate laser position of the depth will be needed for the
procedure. We noted that the tissue reaction is not critical to the
wavelength when the laser highly focused and achieve a high fluency
level such that tissue can be removed by interruption process.
Another preferred embodiment is to use an optical fiber or an
articulate arm to deliver the ablative laser beams such that the
presbyopia treatment may be conducted manually without the need of
a scanner or reflecting mirrors. For the fiber delivered system, a
fiber tip connected to the fiber hand piece is preferred such that
sterilization may be done only on the fiber tip.
[0038] The concept presented in the present patent is to remove, by
any methods laser or non-laser, portion of the sclera tissue which
is filled in by sub-conjunctiva tissue to increase the flexibility
of the scleral area and in turn causes the zonular fiber to
increase the lens accommodation. Therefore the laser ablation
effects on the scleral tissue may also be conducted by any
non-laser methods such as using a diamond knife which removes the
scleral tissue at a width about (0.5-2.0) mm and length of
(2.0-4.0) mm, as far as this area can be filled in by the
sub-conjunctiva tissue.
[0039] Another important concept proposed in the present invention
is to support the post-operative results which show minimum
regression. We proposed that the laser ablated sclera tissue "gap"
will be filled in by the sub-conjunctiva tissue within few days
after the surgery. This filled in sub-conjunctiva tissue is much
more flexible than the original sclera tissue. Therefore the
filled-in gap in the sclera area will cause the underlying ciliary
body to contract or expand the zonular fiber and the lens when the
presbyopic patient is adjusting the corneal lens power to see near
and far.
[0040] To remove the sclera tissue, we typically open the
conjunctiva first such that the underlying laser ablated area may
be protected by the conjunctiva during the healing period. The
preferred embodiment is to use mechanical method such as a knife or
a scissors. Alternatively, the same ablative laser for sclera
tissue ablation may be used to open (ablate) the conjunctiva.
Another preferred embodiment is to couple the laser to a fiber
which has a fiber tip having a size about (0.2-0.5) mm and can
easily penetrate into the conjunctiva layer and ablate the sclera
tissue underneath. Without opening the conjunctiva, the laser
ablation procedure will be much less invasive to the cornea,
because most of the bleeding during the procedure is caused by
cutting the conjunctiva.
[0041] The invention having now been fully described, it should be
understood that it may be embodied in other specific forms or
variations without departing from the spirit or essential
characteristics of the present invention. Accordingly, the
embodiments described herein are to be considered to be
illustrative and not restrictive.
* * * * *