Note: Descriptions are shown in the official language in which they were submitted.
V~4 93/0677 PC'~'/U592t0722~
2~223'~3
r~ETxoD a~ L~sxR ~xoTOAxL~~Ta~r ~~° LxrtTxe~R mssuE
F'~R THE CORRECTTON OF ~ISTOId PROELEP4s
EACh~,GROTJN17 OF' TxE TNVEN~°TON s
d',.eld of the ~~ye~t~ono
The present invention relates generally to the
fi~~ld of photoablation of ocular tissue to correct
vision deficiencies and treat other vision-impairing
ocular problems, and, more particularly, to treatment
of the natural ocular lens.
Backctround Discussion:
historically, and until only a few decades ago,
eye-glasses (i.e., spectacles) were exclusively used
2p for mast correctable vision deficiencies, including,
for example, hyperopia (wherein incident parallel rays
of light converge to foeus behind the retina), myopia
(wherein a.nci~ent parallel rays of light converge t~ a
focus a.n front of the retina) , and astigmatism (a
defect in vision ordinarily caused by irregularities
in the cornea) . ~iowever, in about the 19~L~s, contact
lenses started being used as a viable alternative, at
least fox° many individuals, to the use of spectacles
for correcting vision deficiencies, and provided--often
at a cost of some discomfort--freedom from many
annoyances and appearance problems associated with the
wearing of spectacles.
mother method for treating some types of problems
causing vision problems was introduced by Dr. Peter
Ridley just after the close of ~lorld liar TI. This new
(although there is some evidence tha°~ it had been tried
~~ 93/08b77 P~'/~JS92/07228
21~23~~3
2
,
several hundred years ago) method involved the
replacement of a diseased natural ocui~r~~lens, for
example, a natural lens which had been clouded because
of Cataract, with a plastic artificial or prosthetic
intraocular lenses (IOL). Such lens extraction and T~L
implantation is now a commonly-performed surgical
procedure. and is credited with saving the sight of many
individuals who were or would have become blind.
Vision correction can now be achieved on soave
pztients, especially those with myopia, by a surgical
procedure on the cornea called radial keratotomy (R~).
In an TtK procedure, several slits, for example about
give, are made radially inwardly toward the optical
axis from the peripheral edge of the cornea. These
x5 radial slits enable the cornea to flatten out a bit,
thereby decreasing. the . curvature of the cornea..
Candidates for RK procedures are typically near-sighted
individuals who cannot or who do not want to wear
either spectacles or contact lenses.
2p Corneal onlays or implants, which may be
constructed of synthetic materials or from donor
corneas, are surgically attached to or implanted into
patients' eyes, are also useful to enhance vision in
patients whose corneas have been damaged and/or scarred
~5 by corneal , diseases, such as ulcers. or cancer, or by
injury t~ the cornea.
Due to shortcomings associated with ~ surgery and
a desire to provide vision correction to many
i.rrdividuals without the necessity for those individuals
p to wear spectacles or contact lenses, considerable .
research and development has been directed over the
past several years to apparatus and techniques for
reshaping the anterior (forward) surface of the cornea.
Excimer lasers--lasers operating in the ultraviolet
!~V~ 93f08677 PL'~'fU~92f07228
~a.cz~~~~._.
(UV) .region of less than about 200, manometers
-'':, wavelength--have thus now been used ,to selectively
ablate regions of the cornea to resculpt the cornea of
patients an a manner correcting certain vision
problems. For example, regions of the cornea around
its optical axis are photoablated to a greater depth
than peripheral regions of the cora~ea, thereby
decreasing the curvature of the cornea to correct
;,
myopia. In contrast, photoablation of the cornea is
. concentrated near the periphery of the cornea to
:.;
increase the curvature of the cornea and thereby
correct for hyperopia. In a related manner,
ra astigmatism can be corrected by selectively varying the
: rate of laser photoablati~n of an astigmatic cornea in
a manner providing an appropriate vision correction.
In this regard, t7. S. patent No. 4, 784 ,135 to glum, et
", al., discloses a method for removing biological tissue
by irradiation the tissue with tTV radiation; while, for
iy;y
example, U.S. patent Nos. 4~665,91.3; 4,669,466;
~~r' 20 4,718,418; 4,721,379a 4,729,372, 4,732,149; ~,'770,1.'72~
~'ls:
~rrw 4,773,414; and 4,798,204 t0 hsperance disclose
apparatus and. methods for laser sculpting of Corneal
''7' tlSSUCy. t~ correct Vlslon defects. gn add~.t,~on, U. S.
i
~
t . patent ~o o 4 , 842 , 782 t~ Portney, et al . and N~ .
C:i
pi,r
4,856,513 to Muller (as well as one or more of the
above-c~.ted L ~sperance patents) disclose masks useful
,,q
for selectively controlling the laser beam intensity or
total laser beam energy to different regions to thereby
enable selective corneal ablation to effect the desired
~~'~~ 30 vision correction. Various of the above-cited patents
..a to laEsperance also disclose methods for determining
the required laser ablation profile for the Cornea; for
ra
example, patent No. 4,995,913 discloses computer
ewo 9~voss~~ ~crous9zvo~x~~
4
mapping of the cornea and computer-controlled scanning
of the cornea by the laser beam.
~n spite of reported short-term medical successes-
-both in clinical testing in the ~Tnited States and in
,.,
use in unregulated foreign countries---with laser
photoablation of corneal tissue to correct vision
; deficiencies, the verdict is still not .in concerning
:
;-
a the long-term effects and efficacy of corneal laser
.",.l
,
,.
,ra photoabl~tion. In particular, questions have been
y:~ ~
raised whether over a long term the vision correction
7,...rinitially provided by photoablation of the cornea will
r
remain effective because of the noraaal . regrowth of the
removed epithelium layer of the cornea over the ablated
~;~ area. In this regard, there seems to be at least some
',~ 15 natural tendency for the epithelium layer to regrow in
~
.b?
t' a manner that, in time, the pre-ablation contour of the
t:
. cornea may
be reestablished or sufficiently so that
vision re~correction is required. An ancillary
k,t
quest~On ,~~, therefore, hour many times and how
fre uentl can a laser
q Y photoablation process be
repeated. also there have been reports of hare forming
on the c~rnea after g~hotoablati.on; although this
M; appears to-be a relatwely transient phenomena-lasting
.
t '. only a. few anonths and ordinarily not too bothersome to
v
2s the pat~.ent~-at the present there has been insufficient
post~ablation time on any patients to determine long
rvh
tee effects. Moreover, a.t appears that there may be a
IDa~Clmllm dl~pter change--ar~und f a.~l'e d~lopters-that can
:.
f'
~
~
. presently be effectively and predictably made by
;
30 corneal photoablation. Still further, at least at
.y present, the laser ablation of corneal tissue is
4.';:
extremely painful to the patient on which the surgical
procedure is performed.
r ~ . ~" ~.. ,
.:
.. ,:-, . .: . ;; . ... ~: , ., .::. . ~ :,, . , ,.. . :., ~: .:r . .,. :. ;..
.via..':'.~,.:.'..~:~.....w. . ~ . .: ~.: ,. ,...... ...,..;..,. . , ,
...~..~.:..... :~..,.......v.,..;: :-.~::~ ,,..,:-::,. . ;.:.... , ..;::..'..
:-:.~ ,,.,..~
!W~ 93/t~8677 PC;~'/~JS92/0722~
S
further with respect to laser photoablation of the
cornea, it should be appreciated that alga~ugh in so
a
doing the cornea is sculpted in a manner correcting
',
vision, it is frequently the case that the cornea is
not itself responsible for the vision problems being
corrected. As an illustration, myopia nay more likely
,'r be caused by an increase in lens size, -usually as a
,,
natural effect of the human ageing process, of the
natural lens of the eye (located posteriorly of the
co'nea). ~ther vision defects or deficiencies may also
v'' originate at the natural lens, while the associated
cornea ~~y .itself bean a normal c~nd~t.~.on a
-' For these and other reasons, and for the reason
that because the lens is closer to the retina than is
the cornea, less material would have to be removed frown
v:? . ,
the lens to achieve a similar visaon correction, the
present .inventor has determined that it would often be
''" preferable to reprofile the natural lens over
:~ reprofiling the cornea. Such natural lens reprofiling
;;.
would eliminate many of the concerns presently raised
5
about corh~a3 photoablation and may result in reduced
risks to patients, and since the lens has no nerve
supply, the procedure should result in no sensation of
'~ pain to the patient. It is, therefore, a principle
,
,a
. objective of the present invention to provide a method
a5
'~ for laser ablation of selected regions of the natural
lens in order to correct vision problems and to correct
problems, such as incipient cataract, on the lens.
~~~ 6l'F ~~~ ~~~~~~~~ o
According to the present invention, there is
provided a method for the laser photoablation of ocular
lens tissue, the method comprising the steps of
VYO 931067? PU~'lUS9~10722~
~~.z2~~:~13
6
determining the region of the lens tassue to be
photoablated, end directing a pulsed laser beam at such -
region with an amount of ~ energy ef f active f or
photoablating the region without causing substantial
damage to surrounding tissue regions. preferably~ the
laser is a Nd:YLF laser having an operating frequency
in the infrared spectrum and more preferably having an
operating frequency of about 1053 nanometers. The
laser preferably has a repetition rate of between about
~ 1 and about 1000 Hertz, and more preferably about 1000
Hertz; and operates with. a pulse width of between about
1 femtosecond and about 1 millisecond and, more
preferably, about 60 picoseconds. Moreover, the laser
preferably operates at an energy level of between about
~. nanojoule and about 50 millijoules per pulse and,
more preferably, about 30 microjoules. Stil1 further,
the laser preferably operates with a beam spot diameter
of between about l micron and about 100 microns and,
more preferably, with a beam spot diameter of about 20
microns. The laser preferably operates with a zone of
effect of less than about 200 microns and, more
preferably with a zone of effect of less than about 50
m~cron~J' a ~ .
. In accordance with one embodiment of the
invention,- a method is provided for the laser
photoablation of ocular lens tissue for the correction
of myopia, hyperopia or presbyopia. In this case, the
method comprises the steps of determining the region of
the lens tissue to be photoablated, calculating the
amount of lens tissue to be photoablated from the
determined region; and directing the pulsed infrared
laser beam at the region with an amount of energy
effective for photoablating~the calculated amount of
lens tissue in the determined region without causing
,:, , ., .,; . . . - .. . __ _., - ~. ;,. . ..._~: :- - ~: .. . - . : - .~
8~V0 93/077 PG'I'/LIS92/072Z~
21~23'~~
substantial da~aage to lens tissue surrounding such
region.
7Cn another embodiment of the invention, a method
is provided for the laser photoablatian of ocular lens
tissue for the removal of incipient cataract, the
method comprising the steps of determining the region
of the lens tissue to be photoablated so ws to remove
the incipient cataract; calculating the amount of lens
tissue to be photoablated from the determined region so
as to remove the incipient cataract; and directing the
pulsed infrared laser beam at the region with an amount
of energy effective for photoablating the calculated
amount of lens tissue in the determined region so as to
remove the incipient cataract without causing
substantial damage to lens tissue surrounding, such
region.
~R~~F ~EaCRTP'~TON GF THE DFtAWIPdGS a
2~ . The present invention can be more readily
understood by a consideration of the following detailed
descripti~n when .taken in conjunction with the
accompanying drawings, In wh~chl
FIG. a is a longitudinal cross sectional drawing
of a representative eye showing, in simplified form,
the cornea, iris, natural lens and retina, and showing
the manner in which an image is focused on the retina
in a normal eye.
FIG. 2 is an enlarged, longitudinal cross
sectional drawing of a normal lens showing, in
simplified form, its composition; and
17V~3 931OF3677 fCI"/~JS92/fl722~
". ~~~~e~.D~r~9
8
FIG. 3 is a simplified, longitudinal cross
sectional draw~.ng_~-similar to FIG. 1-ashowing the
manner in which the natural lens has regions thereof
photoablated using, for example, a Nd:YLF laser
operating at a frequency of abou°~ 1053 manometers and
operating at a repetition rate of about 1000 pulses per
second, FIG. 3a showing the manner in which internal
regions of the lens are photoablated for the purpose of
correcting myopia, hyperopia or presbyopia, and FIG. 3b
showing the manner in which generally surfaee regions
of the lens are photoablated to remove incipient
cataract.
In the various FIGs. identical elements and
~ features are given the same reference number.
il.frdAILFrD ~ES~~~P~I~~ VF ~~~ .SiV V L1VTI0AY :
4:~ There is shown in FIG. 1, in greatly simplified
diagrammatic form, a longitudinal cross sectional
:a
drawing of a typical, normal eye 10, which is generally
., symmetrical about an optical axis 12. Shown comprising
'' eye iD, and in order from the front of the eye to the
.~' back, is a cornea 14, an iris 16, a natural lens 18 and
~'~k
a retina 20. 3n a normal eye, light from an object 22
:<
is refracted by cornea 14 and lens 1~ so as to form an
ima a 24 on retina 20
g (iris .15 being ,shown having an ,
open central aperture 26 permitting light to pass
through to the lens).
Shown more particularly in FIG. 2 (beat still in
:.:a
:3 greatly simplified form), lens 15 is a biconvex,
~'.~
somewhat flexible structure which is suspended behind
v~'. iris 16 and is connected t~ a peripheral chary body 30
of eye 10 by tonal fibers (zonules) 32. Since lens 13
W~ 93/08677 f('f/L1~92/07228
2~2~3.~~~ .__
is avascular, its pathology is more simple_than most
"~w other tissues of the body; primarx ~ inf lamination
J:t:
v'v'r processes do not occur and neoplastic growths in lens
;:
;
18 are unknown. However, trauma or injury to lens 18
' 5 results in passive and degenerative changes in the lens
:
~
'~~"' with consequent opacification.
:::;;~.
e,~, Focusing of lens 18 , which functions to transmit
.~ and refract light to retina 20, is (assuming the lens
,~~.
is in its normal, youthful condition) by contraction
a,
v~~ relaxed
and relaxation of tonal fibers 32. In the
'~~~~A,
, state of fibers 32, lens 18 assumes its maximum convex
.
:.,
,;
:
?:,',~curvature and thickness; as tension in tonal fibers
v,=~ increases, lens 18 is stretched and its convex
curvature and thickness is decreased. By this
, amechanism, called accommodation, the~shape of lens I8
;;-:<,is physically varied in a manner causing images 22 to
,:
:.a
'~'': be correctlx focused on retina 20 as' the distance, D,
vv:;.,
~; . between obj ect W 2 and cornea 14 changes between far and
near.
Lens 18 consists of about 65 percent water and
about 35 percent protein (known as crystallins), along
'~-.:'~with traces of minerals. Lens 18 is avascular,
containing no blood vessels, and has no nerve supply,
and comprises a thin, transparent capsule or bag 34, a
Sub~apsular ep~.thelium layer 3G, a cortex 38 of soft
fibres and a harder, dense nucleus 40 at the center.
During development of lens 18, surface ectoderm
invaginates to form the lens vesicle. The posterior
~el~.s of the lens vesicle then elongate to form the
~.;
primary lens fibres, which obliterate the cavity of the
'"~rt=~vesicle and abut on the anterior (forward) epithelium
layer 3~. This process is completed early in fetal
development. subsequently, secondary lens fibres are
~a~ added throughout life by the elongation and
W~ 93/08677 PvCI'/US92/~7228
2~.2~3~3
,a
differentiation of epithelial cells circumferentially '
f;
at the equator of lens ~,8. The net result is the
:r' progressive internalisation of previously-formed
,,
fibers. The older fibers are always found toward
i
r5 nucleus 4o and the younger fibers toward cortex 38.
i'
dens 18 continues to grow throughout an
,,.;1
individuals life in a process similar to that in which
the epidermal tissue of the skin renews itself.
However, unlike the skin where old cells are
fi% 1~ continually cast off from the surface
s older lens cells
,
accumulate centrally and cannot be cast off. The net
result is a progressive growth of lens ~8 with age,
associated with a decrease in elasticity and
~
rS
accommodative ability. The result is that the most
35 common degenerative condition of lens 18 as presbyopia,
y
a condition in which loss of elasticit of the lens
results ih the inability of eye ~.~ to focus sharply for
near vision, such that most individuals by about the
age of forty require some visual assistance, for
2!D exam le that rovided b s
P . P y pectacles, contact lenses or
~ suxgery:
Another common degenerative condition of lens 18
tYaat as g~ner~lly associated .with aging is cataract,
which is generally defined as any opacity in the lens.
~5 In the case of cataract, the extent of disability .
depends upon the location and severity of the opacity.
Thus, d relatively small posterior (i.e., rearward)
suboapsuZar cataract may be visually incapacitating
because it 'is situated near the nodal point of the
~' 30 dioptric system, while peripheral opacities that do not
,l
" impinge on optical axis
~ 12 may cause little visual
r~
inconvenience. In general, patients initially complain
of a visual disturbance, then a diminution of vision
and finally a complete failure of vision. For small
t~~ 93/~~677 PC:T/1J592/07228
._ _.
11
lens specifies and early disturbance or diminution of
~cr~s2c~n there is n~ proven therapeutgc modality ( ~ ~ a ~ ,
treatment). Ophthalmologists have long considered
removal of lens 1~ as the only treatment for cataract.
At present, the most commonly performed operation is an
extracapsular cataract extraction with ~ntraocular lens
implantation, the objective of the surgical procedure
being to remove as much of the lens as possible with
subsequent optical device correction. The concept or
ZO sESective removal of a small opacity or sections of the
lens was not heretofore considered nor would it have
been technically possible.
THE PRESENT INVENTION:
The present invention relates to methods t~
treat presbyopia, refractive errors, and cataract by
means of focusing high power pulse laser photoablation
of lens opacities and selected normal lens ffibers~ A
laser 50 ~F'IG. 3) which can advantageously be used for
such pure~se is preferably, but is not limited to, a
quasi-cantinuous NdtYLF picosecond laser which may be
purchased as ISL Model 200.1 MPII or ~0~1 OhS from
Intelligent Isaser Systems, Inc. of San Dieg~,
- ~5 ~al~f~rnlas In general, laser ~O pr~duce~J' a $h~~s~
wave ~n the t~.SSUe at whach its beam ~s focused, the
shock wave expanding radially from the point of focus
and dasintegrat~ng the target tissue (~pt~.cal
y
breakdown) , thereby causing a~~n~.~at aon of the med~.um
and the formation of a plasma. This plasma as a
gaseous state, formed when electrons are stripped away
from their atoms in either a gas, liquid or solid.
Once optical breakdown occurs, the plasma that is
formed absorbs or scatters subsequent light in the
~~ 9311~~677 P~CT/~JS9210'722~
12
laser pulse, thereby acting as an effective shield
protecting underlying structures. The quicker the
laser pulses, the faster and :pore easily the plasma is
created.
F'or the present photoablation procedure, laser 50
preferably has the following characteristics:
2. An operating frequency preferably in the
visible and infrared (~R) spectrum; more
preferably, about 1.053 manometers (nm).
2. A repetition rate preferably ranging from
about one to about 1000 Hertz; more prefer;~bly,
about 1000 pulses per second.
3. A pulse width preferably ranging from .about 1
femtosecond to about 1 millisecond; more
preferably, about 60 picosecond.
4. An energy level per pulse preferably ranging
from about i nanojoule to about 50 millijoules;
more preferably, about 30 microjoules.
5. A focused spot a'PS~?ae ~dlameter) preferably
between about ~ micron and about 1.00 microns; more
preferably, about ZO microns.
a A ~~ bone of ef f ect~, pref erably limited t~
between about 1 and about 200 microns with little
c~llateral effect; more preferably, the zone of
effect is limited to about 50 microns.
The procedure described hereinbelow for the laser
photoablation of lens tissue ordinarily requires an
0 initial ocular examination of the prospective patient,
including refractive status, slit lamp biomicroscopy,
and the measurement of axial length of lens 1~ by
standard applanation A~scan ultrasonography. The
accommodative amplitude of lens 1.~ nay be measured by
!W~ 93/O~b77 PG'T/U~92/Q722~
21~~3'~3
13
various techniques. For example, Adler ,(Moses
'°Accommodation" In: Moses Rh, Hart, MA Jr: ads. idler°~
~~ysiolocrv of tie Hve, fit. L~uis, Washington, D. C. ,
T~ront~i The G.~. Mosby Coe , irhapter ~~, ~~~~ s ~9~-.71A--
which is incorporated hereinto by specific reference)
recommends that a convex lens be moved along the
Optical axis in front of the patient ~ s eye, away from
the eye, Until c'1 target Object ~t a convenient dlstanCe
just begins to blur--it is then assumed that
accommodat~can is relaxed. The convex lens is then
reduced (to a concave lens)., or, alternatively, the
target object' is brought closer to the patient's eye
w until the target again starts to blur. The range
between the °'far'° .blur and the '°near'° blur or
maximum
plus (convex lens) to blur and maximum minus (concave
lens) to~ blur is the range s~f accommodation in
diopters.
For the treatment of presbyopia, the amount of
lens thickness to be ablated can be calculated in two
2o ways:
! ~ ed7ased upon ~ord6tatZVe harts of ~~na~ thJ.ckness
'
i and acc~mm~dat~ve amplitude wdth ages
Using the ultrasound data on saggital lens length
soelitl1 age ~5y Raf f arty (~taf f arty, IvT . ~ . "Lens
,~r,
Morphology" Ina Maisel, H., ed. The ~cular Lens.
I~iarcel pekker, II1C. Ne~a York and Basely 185:1~1~,
52~6~~-which is incorporated hereinto by specif is
reference) and the accommodative amplitude at a
Duanes
given age, as shO~an, by way of example, in
.
Table (Horish, Irvin M. "~GCOmmodation", ~lini.Cal
Hef~acti~n, The Professional Press, Inc~, Chicago,
175, 3rd Ed. , VOl.~ 1, p 1~0---which i.s
incorporated hereinto by specific reference) , the
'~6r~ 931ti86'7 PC.'T/LJS92/0?228
2~~~3~~~
amount of requ~.red lens tissue .ablation is
calculated by subtracting the desired
accommodation amplitude from the patient's actual
accommodation amplitude. ~y way of illustration,
with no limitation being thereby intended or
implied, a patient of age 60 has a lens thickness
of ~ . 66 mm and an accommodation amplitude of ~.. 25
Diopters. To increase the patient's accommodative
amplitude to that of a person of age ~0 who has a
~.0 lens thickness of 4.15 znm and an accommodative
amplZtude of ?.5 DZOpters, .51 mm (4.66 mm mi.nu~J'
4.15 mm) of lens tissue from the pat~~ent's lens,.
This would represent an increase of approximately
6.25 Diopters (?.5 Diopters minus 1.25 Diopters)
of accommodative amplitude. Since the maximal
thickness change in the lens during accommodation
is about 0.5 mm, this change should be sufficient
to restore the presbyopic 60 year old patient to
an accommodative state.
2. used on the patient's measured lens
thickness and amplitude of accomm~dation:
The amount of lens tissue to be ablated is
calculated based on the work of ~Goretz and
~iandelman (Koret2, J.F'., Handelman, G.H., 'oI~odel
of the accommodation mechanism in the human eye"
~~.~J1.~n ~e~J. Yol. ~~ ~~~2 a ~~?°~~?°°whlch J.s
incorporated herednto be spe~r~.f .d.c ref stance ) o
two micron change in lens thickness corresponds t~
a 0.02 Diopter change in accommodation. Thus, if
a patient's amplitude of accommodation measures
d.. 25 Diopters and dt ZJ des.a.red t4 l.ncrease that
t~ 5 D.lopters (a change of 3.?5 DlopterS) the
'~C~ 93/08677 P~,"1'/~JS921Q722~
amount of decrease in lens thickness rer~uired
would be approacimately 375 microns.
For the treatn;ent of hyperopia, the amount of lens
5 tissue to be ablated is calculated as described above
fir presbyopia. This will increase the amplitude of
accommodation of the patient°s lens to allow the
hyperope to move the focus of distant objects up °~o his
or her retina 2~e
a0 ~ For the treatment of myopia, the amount of lens
tissue to be ablated can be calculated based on the
refractive status of the eye and the measured lens
thickness as set forth above in paragraph 2.
5 ~ ~~~~~~~
~ For the treatment of presbyopia and hyperopia, a
beam 52 from a HeNe focusing laser 54 (FIG. 3a) is
fbcused, b an associated lens or lens system 56,
. . y
0 through cornea 14 (which is transparent to the focusing
~'~ beam) and iris opening 26, to a region 56 to be
photoablated lb~ Nd:YIGF laser 5th for correction of the
~ specific vision problem under treatment. In this
regard, it is preferred that the more centrally
2f~ located,older c~rt~.cal and,~or nuclear fibers be
ablated since the width of nucleus ~~ (FIG. 2) remains
relatively Constant with age, whereas that of~cortex 38
increases. then, a laser beam 6~ from Nd:YLF laser 50
is focused by an associated focusing lens or lens
:a 3~ ,system 66 through cornea ~.4 (which is transparent to
the laser bean and lrls ~ en~.n 26, Onto rega.on 55
Y.
which is to be photoablated by the Nd: YhF laser beaan.
°Ihe amount of lens tissue to be ablated (i.a.,
decomposed) to achieve the desired vision correction
;: ;,
'WO 93/8677 P~.'T/LJS92/07228
.., ,
16
is determined in the manner described above. The
optical zone (equatorial diameter) should be
approximately ee~ual to the diameter of nucleus 40 and
the axial width (for example, about 51.0 microns). For
treatment of myopia, it is preferred that region 56 be
selected so that nucleus 40 and~or centrally located
older fibers in cortex ~8 are ablated using a smaller
optical zone so as to decrease the curvature of an
anterior (forward) surface 62 of lens 18. Such laser
ablation of lens 18 to correct myopia, presbyopia and
hyperopia may be termed ~°photorefractive phacoplasty°°
or ~°phototherapeutic phacoplasty.°°
For the treatment of cataracts (FZG. 3b), beam 52
from HeNe focusing laser 54 (~F1G. 3) may be directly
focused by lens or lens system 56 (with the beam
passing though cornea 14 and iris opening 26) onto an
area or region 64 of small lenticular opacity. Then
beam 60 from Nd:YLF laser 50 is focused, by lens or
lens system 62 onto area or region F,4 and the laser is
pulsed until the opacity is ablated (as determined, for
example, by visual observation through cornea 12 and
iris opening a6).
Tt is preferred that if opacity area or region 64
is adaacent t~ lens capsule 3.8 (F'I~. 2), aiming beam 52
~5 from HeNe laser 52 is focused more centrally to the
opacity to account for shock wave expansion. Such
treatment (i.e., photoablative removal) of incipient
cataract, which is intended to delay or prevent full
cataract surgery, including removal of lens 18 and the
replacement thereof with an IOh, may be termed
a°phOtotherapeutlC phacOablatlont° or
°°phC?t~°therapeutlc
phaCOectomy. °°
In either of the above°described treatments,
application of photoabiation beam f>0 from Nd:YLF laser
I~VO 93/08b77 FC.°T'/IJS92/07228
:,,:
.;;
21~2~"~3
,7
'~-' S0 produces the formation of gas bubbles at the site of
a~
.
optical breakdown by the focused beam within lens 18
(that is, at regions such as above-described regions 58
and 64). The formed gas bubbles are, however, usually
reabsorbed within lens 18 within 24 to
48 hours and
lens 18 remains optically clear.
dare is taken in the operation of Nd:YLF laser 50
:"
not to rupture lens capsule 3~ by expansion
of laser
shock wave. Moreover, if excessive bubbles are foraned
'~~ 1~ at the ablation site, as detected, for example, by
r.
d
,.: viewing, with a slit lamp (not shown) the ablation
,re
~.,~~.
region through coznea 1~ and iris opening ~6, the laser
ablation procedure is discontinued and additional
er treatment is performed at a later date, for example, in
i:..lpl. .
v~::, 15 one or two weeks .
~
-
,.~ ~ By the method described above, the natural lens in.
~' an eye'.can b~ photoablated by pulsed energy from a
a,
laser--preferably a Nd:YLF laser--in a manner
a~
correcting myopia, presbyopia and hyperopia and in a
o manner remova.ng inCa.p~ent cataracts. Because the
t ~'~'
are
d
-
bl
t
b
d l
e
d
ive proce
ures
aser
a
a
abov
escri
e
-
Y'A~ relatively h~n-invasive (mss compared, for example to
''" laser ph~te~ablati~a of the cornea to correct vision
.,,
problems or the surgical removal of a natural lens in
25 the cage bf cataract) and because lens 1~ is non-
'_~, vascular and contains no nerve supply, no post-ablation
T>~~ .
~ infl~ammati~n or wound-healing problems are anticipated
and the use ~f steroids---commonly used after corneal
laser phetoabl~tion--is not indicated. Moreover,
3~ because of i.ts structural nature, lens 18 is not
expected to revert--with time--to its pre-ablative
\i
shape--as may be the case for laser-ablated carneas.
J
although there are described above methods f or
laser ph~toablation of a natural lens for correcting
dW~ 93/08677 f~"/1J~92/Q722~
~1~~~~~3
18
vision problems for the purpose of illu~tratins~ the
manner in which the present invention can be used to
advantage, it is to be understood that the invention is
not limited thereto. Therefore, any and all
modifications and variations which may occur to those
skilled in the art are to be considered to be included
within the scope and spirit of the claims appended
hereto.
