U.S. patent application number 10/305453 was filed with the patent office on 2004-01-01 for system and method for accurate optical treatment of an eye's fundus.
This patent application is currently assigned to CeramOptec Industries, Inc.. Invention is credited to Neuberger, Wolfgang, Pawlowski, Dirk.
Application Number | 20040002694 10/305453 |
Document ID | / |
Family ID | 24275440 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040002694 |
Kind Code |
A1 |
Pawlowski, Dirk ; et
al. |
January 1, 2004 |
System and method for accurate optical treatment of an eye's
fundus
Abstract
A system and method is provided to accurately treat sites on an
eye's retina employing computer based image generation, processing
and central control means in conjunction with diode laser sources
and optical fibers. The system is designed such that different
photocoagulation and photochemical treatment methods alone or in
combination can be performed and controlled to for simultaneous or
consecutive treatment. The system and method accurately determines
geometry of a treatment zone of a specific eye's fundus and adjust
a treatment beam to irradiate the treatment zone with minimal
coverage of adjacent tissue. Accordingly, also "forbidden zones"
which would be severely damaged by the treatment beam are
determined and their irradiation is prevented. The treatment zone
is accurately determined with digital processing of angiographic
data and slit lamp image data. Such image processing includes
matching or alignment of two distinct images. This information is
integrated with information on the treatment beam characteristics
to better match treatment beam coverage with minimal overlap with
healthy areas of the fundus. Additionally preferred embodiments
also have the ability to automatically track eye movement and
switch the beam source depending on eye movement, adjusting the
beam spot area in real time.
Inventors: |
Pawlowski, Dirk; (Jena,
DE) ; Neuberger, Wolfgang; (Labuan, MY) |
Correspondence
Address: |
BOLESH J. SKUTNIK PhD, JD
515 Shaker Road
East Longmeadow
MA
01028
US
|
Assignee: |
CeramOptec Industries, Inc.
|
Family ID: |
24275440 |
Appl. No.: |
10/305453 |
Filed: |
November 26, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10305453 |
Nov 26, 2002 |
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09569438 |
May 12, 2000 |
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6494878 |
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Current U.S.
Class: |
606/4 |
Current CPC
Class: |
A61F 2009/00846
20130101; A61F 2009/00863 20130101; A61F 9/008 20130101; A61K
41/0042 20130101; A61B 3/135 20130101; A61F 9/009 20130101 |
Class at
Publication: |
606/4 |
International
Class: |
A61B 018/18 |
Claims
What is claimed is:
1. A system for improved, accurate treatment of an eye's fundus
comprising: at least one optical setup for irradiating an eye's
fundus with light emitted by a primary light source; at least one
device to take optical images of said fundus; at least one
secondary light source to generate a reference digital image on an
eye's retina at a predetermined basic position of a treatment beam
imaging optical system; at least one computer based setup for
controlling and for digital image processing to accurately
determine a treatment zone; means for simultaneous generation of a
native digital image of said fundus; a unique marking of said
treatment zone on said digital fundus image, creating a digital
reference image; an adjustment means; and wherein within one
device, through said digital image processing and said adjustment
means, said at least one optical setup for irradiating said fundus
is adjusted to provide optimal irradiation characteristics to
perform an improved, accurate treatment.
2. The system for improved, accurate treatment of an eye's fundus
according to claim 1, wherein said at least one optical setup is
capable of emitting different wavelengths with variable power
densities to be applied in different photocoagulation and
photochemical treatments.
3. The system for improved, accurate treatment of an eye's fundus
according to claim 2, wherein said different photocoagulation and
photochemical treatments are selected from the group consisting of
short-pulse coagulation, long-pulse coagulation, green laser,
transpupillary thermotherapy and photodynamic therapy.
4. The system for improved, accurate treatment of an eye's fundus
according to claim 1, further comprising: means to uniquely mark
"forbidden zones" which are not allowed to be irradiated on said
digital image of said fundus; and means to make a digital reference
image used for adjustment of said treatment optical system to avoid
irradiating said forbidden zones with said at least one primary
light source.
5. The system for improved, accurate treatment of an eye's fundus
according to claim 2, further comprising means to combine said
different treatments.
6. The system for improved, accurate treatment of an eye's fundus
according to claim 2, further comprising means to automatically and
semi-automatically control said at least one treatment beam for
said different photocoagulation and photochemical treatments.
7. The system for improved, accurate treatment of an eye's fundus
according to claim 6, further comprising means to controllably
apply said at least one treatment beam of said different treatments
to a same area, whereby said different photocoagulation and
photochemical treatments can be applied simultaneously or
consecutively within a single treatment.
8. The system for improved, accurate treatment of an eye's fundus
according to claim 6, further comprising means to controllably
apply said at least one treatment beam of said different treatments
to different treatment areas.
9. The system for improved, accurate treatment of an eye's fundus
according to claim 1, further comprising: means for loading,
displaying and processing a digital image of said fundus provided
diagnostically by means of fluorescence angiography; means for
generating a native digital image of said fundus; and means to
align said native digital image by suitable mathematical algorithms
with said loaded previously generated digital image generated by
fluorescence angiography means to obtain a unique correlation
between coordinate systems for these two images.
10. The system for improved, accurate treatment of an eye's fundus
according to claim 9, wherein said means to align is an
automatically operating pattern recognition means.
11. The system for improved, accurate treatment of an eye's fundus
according to claim 9, wherein said means to align said native and
previously generated images is at least two reference points
manually marked in each of said images, and said images are said
native fundus digital image and said loaded previously generated
digital image from said diagnostic fluorescence angiography.
12. The system for improved, accurate treatment of an eye's fundus
according to claim 1, further comprising: at least one variable
aperture; an optical system to image said aperture onto said
treatment zone on said retina; and an additional optical system to
image said treatment beam onto said variable aperture.
13. The system for improved, accurate treatment of an eye's fundus
according to claim 12, wherein said treatment beam has a radiation
intensity profile with a rectangular shape otherwise known as a top
hat shape.
14. The system for improved, accurate treatment of an eye's fundus
according to claim 13, wherein said image generated on said retina
has a polygonal shape which is selected from the group consisting
of substantially circular, substantially oval, substantially
rectangular, and preferably square.
15. The system for improved, accurate treatment of an eye's fundus
according to claim 13, further comprising at least one additional
aperture, having a different shape from said variable apertures,
which can be sequentially applied to create images on said retina
of shapes more complicated than simple polygons.
16. The system for improved, accurate treatment of an eye's fundus
according to claim 15, wherein said variable and additional
apertures are independently variable and can be adjusted to a
desired size by a method selected from the group consisting of
manual, manual with electronic aids, electrochemical, and
completely automatic.
17. The system for improved, accurate treatment of an eye's fundus
according to claim 1, wherein said at least one primary light
source is selected from the group consisting of a laser, a diode
laser, a luminescent diode, and at least one optical fiber whose
opposite end is coupled to at least one laser.
18. The system for improved, accurate treatment of an eye's fundus
according to claim 1, wherein said secondary light source operates
at a wavelength different than that of said primary light source
and said secondary light source is selected from the group
consisting of a laser, a diode laser, and a luminescent diode.
19. The system for improved, accurate treatment of an eye's fundus
according to claim 1, further comprising: at least two variable
orthogonal mirrors; at least one imaging optical system and an
automatic primary beam switch; and scanning means, wherein these
components adjust said treatment beam create a two dimensional
image on said treatment zone on said retina.
20. The system for improved, accurate treatment of an eye's fundus
according to claim 19, wherein said imaging optical system is
variable and preferably replaceable.
21. The system for improved, accurate treatment of an eye's fundus
according to claim 1, wherein said adjustment means further
comprises: a micro-mirror device where each mirror can be addressed
individually; and at least one optical imaging system.
22. The system for improved, accurate treatment of an eye's fundus
according to claim 1, wherein said adjustment means further
comprises: a liquid crystal device where each pixel can be
addressed individually including a polarizer and an analyzer; and
at least one optical imaging system.
23. The system for improved, accurate treatment of an eye's fundus
according to claim 1, further comprising: at least two variable,
linear, orthogonal-arranged position devices; an automatic primary
beam power switch; and whereby scanning an end of an optical fiber
that transfers said treatment beam with said position devices
creates an arbitrary two dimensional region on said retina.
24. The system for improved, accurate treatment of an eye's fundus
according to claim 23, wherein said position devices comprise
piezoelectric elements.
25. The system for improved, accurate treatment of an eye's fundus
according to claim 23, further comprising: an optical system; a
contact lens on a cornea of an eye to be treated to image said two
dimensional region onto said retina; wherein a shape of said two
dimensional region generated on said retina conforms exactly to a
shape of said treatment zone; and wherein said optical system is
variable and preferably replaceable.
26. The system for improved, accurate treatment of an eye's fundus
according to claim 12, wherein said optical system to image said
aperture onto said treatment zone comprises at least one lens.
27. The system for improved, accurate treatment of an eye's fundus
according to claim 12, wherein said optical system to image said
aperture onto said treatment zone comprises an optical module of a
commercial camcorder.
28. The system for improved, accurate treatment of an eye's fundus
according to claim 1, further comprising at least one contact lens
positioned on a cornea of said eye, and wherein said retina can be
observed directly via an eyepiece.
29. An improved, accurate method of treatment of an eye's fundus,
using an optical treatment system, preferably with a slit lamp
assembly, comprising the steps of: a. generating a treatment beam
from a primary light source; b. generating a digital reference
image preferably by means of fluorescence angiography, using a
secondary light source, on an eye's retina at a predetermined
position of said treatment beam's imaging optical system, wherein
said secondary light source preferably operates at a different
wavelength from said primary light source; c. controlling and
processing said digital reference image by at least one computer to
accurately determine a treatment zone; d. simultaneously generating
a native digital image of said fundus; e. uniquely marking said
treatment zone onto a corresponding region of said native digital
image of said fundus; and f. adjusting said treatment beam and said
optical treatment system to have said treatment beam cover said
treatment zone and optimally irradiate said treatment zone.
30. The improved, accurate method of treatment of an eye's fundus
according to claim 29, further comprising the steps of: g. uniquely
marking "forbidden zones" which are not allowed to be irradiated on
said digital reference fundus image; and h. adjusting said
treatment beam and said optical treatment system to have said
treatment beam avoid said forbidden zones.
31. The improved, accurate method of treatment of an eye's fundus
according to claim 29, wherein said method of treatment is a
combination of different photocoagulation and photochemical
treatments; wherein said photocoagulation treatments are chosen
from the group consisting of short-pulse photocoagulation and long
pulse photocoagulation; and wherein said photochemical treatments
are chosen from the group consisting of green laser, transpupillary
thermotherapy, and photodynamic therapy.
32. The improved, accurate method of treatment of an eye's fundus
according to claim 31, wherein said different photocoagulation and
photochemical treatments are controllably applied to selectively
switch between simultaneous and consecutive treatment of a
treatment area within a single treatment.
33. The improved, accurate method of treatment of an eye's fundus
according to claim 31, wherein said different treatments are
controllably applied to different treatment areas.
34. The improved, accurate method of treatment of an eye's fundus
according to claim 29, wherein said adjusting said treatment beam
is accomplished by a method selected from the group consisting of
manual completion by an operator, assistance by an electronic
means, preferably with optical or acoustical signals, and full
automation.
35. The improved, accurate method of treatment of an eye's fundus
according to claim 29, further comprising the steps of: d(1).
aligning said native digital image of said fundus with said image
of said treatment zone by applying suitable mathematical algorithms
to correlate between coordinate systems for these two images,
wherein said aligning is accomplished by one of the following
methods: an automatically operating pattern recognition scheme, and
manually marking at least two reference points in each image;
36. The improved, accurate method of treatment of an eye's fundus
according to claim 29, wherein said step of adjusting said
treatment beam is accomplished by illuminating and imaging at least
one variable aperture having an optical system onto said treatment
zone on said retina and imaging said treatment beam onto said
variable aperture and onto said retina to create pre-selected
polygonal shapes.
37. The improved, accurate method of treatment of an eye's fundus
according to claim 29, wherein said step of adjusting said
treatment beam is accomplished by sequentially illuminating and
imaging at least two apertures having different shapes to generate
said image on said retina in more complicated shapes than simple
polygons.
38. The improved, accurate method of treatment of an eye's fundus
according to claim 37, wherein said apertures are varied
independently of each other and adjusted to a desired size by a
method selected from the group consisting of manual, semi-automatic
and automatic means.
39. The improved, accurate method of treatment of an eye's fundus
according to claim 29, wherein said step of adjusting said
treatment beam is accomplished by scanning with at least two
variable, linear, orthogonal-arranged devices and using an
automatic primary beam power switch to create an arbitrary-shaped
two dimensional region substantially equivalent to said treatment
zone.
40. The improved, accurate method of treatment of an eye's fundus
according to claim 39, wherein said scanning of said treatment beam
over said treatment zone irradiates each point in the treatment
zone for a predetermined period of time.
41. The improved, accurate method of treatment of an eye's fundus
according to claim 39, wherein said step of adjusting said
treatment beam is accomplished by a method selected from the group
consisting of manual adjustment by an operator, assistance by
electronic means, preferably with optical or acoustical signals,
and fully automatic adjustment.
42. The improved, accurate method of treatment of an eye's fundus
according to claim 29, wherein said secondary light source operates
preferably at a green wavelength, and wherein said secondary light
source produces an image containing at least one shape chosen from
the group consisting of a ring and a cruciform.
43. The improved, accurate method of treatment of an eye's fundus
according to claim 36, wherein an image of said treatment beam is
positioned manually on said retina, preferably being positioned
there by at least one secondary target spot and wherein said native
digital image of said fundus is generated in real time, and said
position of said treatment spot area is determined electronically
and transformed into said coordinate system of said diagnostic
fluorescence angiography and displayed thereon.
44. The improved, accurate method of treatment of an eye's fundus
according to claim 43, wherein in real time said position of said
treatment zone is determined and said treatment light source is
appropriately switched on and off; wherein said native image of
said fundus containing said spot of said treatment beam and said
image generated diagnostically by fluorescence angiography means
are digitally processed, superimposed and presented on a display
device; and wherein in real time said position of said treatment
zone is determined and said treatment beam spot is positioned in
real time according to said treatment beam spot position.
45. The improved, accurate method of treatment of an eye's fundus
according to claim 44, wherein in real time said position of said
treatment zone is calculated from a point that is positioned
selected from the group of locations consisting of a retina and a
cornea and not including the treatment zone itself.
46. The improved, accurate method of treatment of an eye's fundus
according to claim 29, further comprising the step of: g. varying
power of said treatment beam generated by said primary light
source, to compensate for optical losses occurring along said
optical path, in order to keep constant power on said retina.
Description
REFERENCE TO RELATED CASE
[0001] This application is a continuation-in-part of co-pending
U.S. patent application Ser. No. 09/569,438 filed on May 12, 2000
by Dirk Pawlowski and Wolfgang Neuberger, inventors, entitled
"SYSTEM AND METHOD FOR ACCURATE OPTICAL TREATMENT OF AN EYE'S
FUNDUS" and Ser. No. 10/208,218 filed on Jul. 30, 2002 by Dirk
Pawlowski and Wolfgang Neuberger, inventors, entitled "METHOD FOR
ACCURATE OPTICAL TREATMENT OF AN EYE'S FUNDUS", and incorporated by
reference herein
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of ophthalmology,
in particular to the field of optical treatment of an eye's fundus
using lasers. More specifically it deals with the application of
computer based image generation, processing and central control
means to accurately treat sites on an eye's retina, particularly
its macula in connection with diode laser sources and optical
fibers. Moreover, the present invention relates to a method and
apparatus for application of different laser based treatment
methods alone or in combination.
[0004] 2. Information Disclosure Statement
[0005] Laser methods are widely accepted in modern ophthalmology
for both treatment and diagnosis such as with laser scanning
ophthalmoscopes. Treatment methods include laser reshaping of the
cornea to correct strong myopic or presbyopic effects, laser
surgery in the eye itself and a variety of retinal treatments.
Retina related methods include conventional short-pulse and
long-pulse photocoagulation laser systems, and more recently,
Photodynamic Therapy (PDT) treatments of the retina. Short-pulse
photocoagulation methods use green, yellow, red and infrared lasers
(wavelengths from 514-810 nm) with high energy doses. The
low-irradiance, long-pulse photocoagulation procedure referred to
as transpupillary thermotherapy, or TTT, was first described for
the use as an adjunct to radiotherapy in the treatment of choroidal
melanomas. Choroidal melanomas as well as retinoblastomas respond
to transpupillary thermotherapy (TTT) as is seen in histologic
studies of TTT-treated choroidal melanomas that show extensive
thrombosis of tumor vessels following treatment. Coagulation laser
treatment is used to re-weld a detached retina to the back inner
surface of the eye. Such detachment could lead to complete
blindness.
[0006] Coagulation methods are also used to treat age related
macular degeneration (AMD). The progression of AMD cannot be
reversed, but it can be stopped to prevent the complete loss of
eyesight. The disease is characterized by a typical blood
agglomeration in the macula, the area of highest vision sensitivity
of the retina.
[0007] Photodynamic therapy (PDT) is a method recently used in
ophthalmology. In this treatment, a PDT drug is introduced into a
patient's bloodstream. The drug is originally harmless and usually
has no therapeutic effects, but it is sensitive to illumination at
a certain wavelength. Long-pulse, low energy radiation is used to
activate such drugs. If light of a suitable wavelength is absorbed
by the drug molecules, they undergo a chemical reaction to another
product, which is responsible for the therapeutic effect. In a
simple case, this effect is the excitation of the drug molecule to
an excited state where it can react with oxygen to form singlet
oxygen, a highly reactive species. The singlet oxygen quickly
reacts with nearby tissue to oxydize it, i.e. cause necrosis.
Alternatively, the splitting of one molecule can create two
radicals, which are chemically very reactive and can destroy body
cells. Because this method is very selective, it prevents negative
side effects of the therapy by restricting necrosis to the infected
area. Typical applications for PDT include tumor treatments,
catheter disinfection and dermatological applications.
[0008] PDT has also recently been applied for the treatment of
age-related macular degeneration. In this treatment, the drug is
given to the patient and after a certain time the macula is
illuminated with a beam spot of light at the critical wavelength,
preferably provided by a laser or a fiber coupled diode laser. The
generated therapeutic substance then destroys blood agglomeration
vessels and the degeneration of the macula is stopped. However,
several disadvantages are associated with the state of the art in
today's PDT methods. First, in many cases the effects seem to be
temporary, with a high rate of recurrence and a resultant high
re-treatment rate. Thus, such treatments are inconvenient and
potentially expensive to the patient. It would be desirable to
improve the method that is addressed in this invention.
[0009] As noted above, laser based methods of fundus treatment are
widely accepted in today's ophthalmology and applied in different
forms. In many of the treatments, focused laser beams are used, and
it is necessary to control the treatment beam precisely in relation
to the treatment area for a more efficient treatment and also to
lower the risk of damaging healthy tissue.
[0010] Means for diagnosis of conditions like AMD include the use
of fundus camera-generated images and fluorescence angiography,
among others. In the latter, a certain fluorescing drug is added to
the patient's blood circuit and then an image of the retina is
taken. The fluorescing drug allows the exact visualization of all
blood vessels on the retina. In the case of AMD for example, the
blood vessels containing the a typical blood agglomerations
responsible for the diseased state can be (and has to be)
visualized by this method because the blood agglomerations do still
circulate. The exact visualization of the treatment sites by
fluorescence angiography is an essential prerequisite for laser eye
treatments such as PDT, TTT, and green laser.
[0011] In WO 01/26591 [E. Reichel et al.] a method and system is
claimed for treating a retinal tissue site using thermal therapy in
combination with PDT or another treatment modality, and
additionally controlling the treatments in response to feedback
received from the retinal tissue site. However, this disclosure
suffers from the fact that it does not describe how to accurately
determine the treatment site, which is especially important for the
application of different treatment beams from different optical
systems to effectively treat the diseased sites.
[0012] In U.S. Pat. No. 5,336,216 [D. A. Dewey] a method for
generating a treatment beam spot on the retina is claimed, which in
particular generates a spot on the retina which has a rectangular
intensity profile, also known as a top-hat profile for all sizes.
However, this method suffers from the fact that knowledge about the
treatment zone is only rudimentary, in that the ability to
specifically determine the size and location of the treatment zone
is limited. Treatment could be significantly enhanced if the
treatment zone is well known and can be specifically targeted so
that side effects like damaging healthy or sensitive tissues
("forbidden areas") can be reduced.
[0013] This striking drawback of state of the art devices and
methods, namely the extreme inaccuracy of the process, can be
attributed to the lack of means for an accurate determination of
the treatment zone and therefore the lack of beam area generating
devices providing the desired accuracy. Because state of the art
calculation of the energy density requires that the value of the
diameter of the treating area is squared, inaccurate determination
of the treating area results that can bear significant risks of
damaging tissue.
[0014] The state of the art illumination means are designed such
that it is impossible to obtain an illumination of the treatment
zone alone. The operator has to calculate from fluorescence
angiographic diagnostics how large the treatment area is, and then
manually adjust the laser beam spot size to be large enough to
completely cover the treatment area. This method is extremely
inaccurate since no information about the specific eye is provided
therein. The spot size on the retina varies with different
patients, but the justification is absolute. This problem is
addressed by the present invention.
[0015] Since typically used slit-lamp generated pictures are only
of medium quality, the treatment zone can be barely noticeable in
the pictures. Hence its size must be determined from fluorescence
angiography, but this image does not have any relation to the
images generated by the slit lamp even though it is from the same
eyeball. Reasons for this discrepancy include the use of different
optics, different viewing angles, etc. In any case, whether the
treatment is determined from the slit lamp picture or from the
angiography, the error made by the calculation of the beam spot
size is significant and typically exceeds 200%.
[0016] For this reason, not only is the treatment zone illuminated,
but healthy zones in the eye are also illuminated. This can lead to
the destruction of important blood vessels resulting in a reduction
of eyesight. The present invention provides a solution to this.
[0017] State of the art methods apply a treatment beam source which
generates a round intensity profile, which is either of a gaussian
or near gaussian shape or of a so-called top hat structure which is
characterized by a very sharp edged rise and fall of the intensity
at the edges and a near constant intensity in the middle. In either
case, the created variable spot size is of a round shape.
Obviously, the shape of the treatment zone is not necessarily
round. In the most simple case, it has an oval or a slit form, but
typically the shape of the area needing treatment is of a more
complicated structure. Since there is already a very large error in
determining treatment areas using state of the art devices and
methods to perform fundus treatments, there has been no need for
generating a better overlap of the treatment zone and the treatment
beam spot area. This is addressed in the present invention, which
can provide variably shaped treatment beam spot areas, now that the
treatment beam is more accurately formed and projected onto the
treatment zone.
[0018] Another general problem in laser based fundus treatment is
movement of the eyeball during treatment. From clinical studies the
optimal illumination times are known, but during treatment it must
be assured that the treatment zone is illuminated for this period.
In the state of the art, operators view the treatment area in real
time by means of a fundus viewing ocular. The device further
provides means for the operator to switch the treatment beam source
on and off and thus control the beam source such that the beam
source is on only if the treatment zone is within a certain region.
This method is a potential source of inaccuracy, because both the
beam and the treatment zone are barely visible during the
treatment. The present invention provides a solution to this and
the several problems identified above.
OBJECTS AND SUMMARY OF THE INVENTION
[0019] It is an object of the present invention to provide a method
and a device for accurately adjusting a laser beam spot size to the
treatment area for each specific eyeball.
[0020] It is another object of the present invention to determine
the exact shape and size of a treatment zone without the need for
an operator-specific method, with less dependence on an operator
for defining a treatment area.
[0021] It is another object of the present invention to determine
the exact shape and size of the treatment zone from digital
processing of a previously generated image generated with one
diagnostic method and a native fundus image generated by the same
or another diagnostic method for live observation.
[0022] It is still another object of the present invention to
provide a method and device to exactly determine "forbidden areas"
as well as treatment areas as to control the treatment beam
appropriately.
[0023] It is yet another object of the invention to provide a
device and method to achieve a significantly better overlap of the
treatment zone and the treatment beam spot area.
[0024] It is a further object of the present invention to provide a
device allowing accurate viewing and means for automatic switching
of the beam source depending on the eye movement as well as a
device capable of adjusting the spot area in real time according to
the eye movement.
[0025] It is a still further object of the present invention to
provide a system and a method to control automatically or
semi-automatically the treatment beam for different
photocoagulation (green laser), TTT treatment and photochemical
(PDT) treatment methods.
[0026] It is another object of the present invention to provide a
device capable of carrying out different photocoagulation and
photochemical treatment methods alone or in combination.
[0027] It is yet another object of the present invention to control
the treatment beams to treat the same or different areas with
different photocoagulation and photochemical methods.
[0028] Briefly stated, the present invention provides a system and
method to accurately treat sites on an eye's retina employing
computer based image generation, processing and central control
means in conjunction with diode laser sources and optical fibers.
The system and method accurately determine geometry of a treatment
zone of a specific eye's fundus and adjust the shape, size and
position of a treatment beam to irradiate the treatment zone with
minimal coverage of adjacent well tissue. The treatment zone is
accurately determined with image processing such as matching or
alignment of two distinct images. In a preferred embodiment, a
previously generated image taken with angiographic data in relation
to a native fundus image generated by a slit lamp. This information
is integrated with information on the treatment beam
characteristics to better match treatment beam coverage with
minimal overlap with healthy areas of the fundus, by preventing
irradiation of "forbidden areas" which would be severely damaged by
the irradiation. The present invention is also capable of carrying
out different photocoagulation and photochemical treatment methods
at different wavelengths, power energies and other treatment
parameters. Additionally, preferred embodiments also have the
ability to automatically track eye movement, switch the beam source
depending on eye movement, and adjust the beam spot area in real
time.
[0029] The above, and other objects, features and advantages of the
present invention will become apparent from the following
description read in conjunction with the accompanying drawings, in
which like reference numbers in different drawings denote like
items.
BRIEF DESCRIPTION OF THE FIGURES
[0030] FIG. 1 illustrates the general setup of a device for
treatment of an eye's fundus.
[0031] FIG. 2 illustrates integration of digital image processing
means into a device for fundus treatment.
[0032] FIG. 3 shows a variable aperture imaging method to obtain a
sharp edged intensity profile of variable beam spot area on a
retina.
[0033] FIG. 4 illustrates implementation of a scanner system with
suitable optical imaging means in order to obtain a sharp edged
intensity profile of arbitrary beam spot area on a retina.
[0034] FIG. 5 illustrates implementation of an optical system
including a two dimensional movable beam source in the device in
order to obtain a sharp edged intensity profile of arbitrary beam
spot area on a retina.
[0035] FIG. 6 contains an alternative device for the displacement
of the laser beam to treat a two dimensional treatment area.
[0036] FIG. 7 illustrates the use of a telescope to vary beam spot
size into the device.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0037] The accuracy of the treatment of the fundus of an eye can be
drastically enhanced by the combination of diagnostic means with a
therapeutic setup. The therapeutic setup consists of a light
source, preferably a fiber coupled diode laser and a suitable
optical system which allows the user to vary the spot size
generated on the retina. The diagnostic device is preferably a slit
lamp with an additional optical setup to allow direct fundus
viewing through an eyepiece and simultaneous generation of a
digital image of the fundus referred to as native fundus image. The
digital image of the fundus is created by a computer based image
processor and an image generation device which is preferably a CCD
camera. The size of the treatment zone can be determined and
electronically processed in the following manner: The treatment
beam spot area is varied by an adjusting optical system provided by
this invention. The reference digital image of the fundus is
generated with a simulation of the treatment beam (aiming beam) on
the retina whereby the spot size of the treatment beam is
predetermined by the optical system by switching the optics to a
basic position. At this basic position the parameters of the spot
size of the treatment or aiming beam are known independently of
further e.g. magnification changing optical means like e.g. eye
pieces. Moreover, from this known spot size the image is calibrated
and the treatment area can be calculated exactly. Moreover, a green
aiming beam emitted by a secondary light source provides a better
and sharper image for the practitioner and means a reduced
irradiation of the patient thereby avoiding undesired side effects.
From these two images it is possible to adjust the treatment beam
spot area to the actual treatment zone size.
[0038] Further, if the treatment zone is not sufficiently clear in
the generated diagnostic native fundus image, it is an object of
the invention to include a digital previously generated image
generated by means of another diagnostic method such as
fluorescence angiography. Because the slit lamp generated image
often is not sufficient to determine the tumor or AMD affected
area, the angiography imaging often is a necessary prerequisite for
successful treatment. Moreover, it is a subject of the present
invention to align the previously generated angiography image,
which is characterized by an extremely high quality, with the
native fundus image obtained by the diagnostic means in the claimed
treatment device and determine the necessary treatment beam spot
size from the treatment zone area that is visible in the previously
generated image obtained by fluorescence angiography.
[0039] In a preferred embodiment the above-mentioned screening,
image processing and controlling means are used to control the
short-pulse photocoagulation treatment. This treatment is
preferably carried out with a green laser (532 nm), but other
wavelengths ranging from 514 to 810 nm are used. This method is
useful for coagulation of damaged vessels or re-welding of the
retina to the eye background. Due to the high power densities of
about 80 W/cm.sup.2 and the resulting damage to tissue, the
treatment beam is not to be used within the macula ("forbidden
area"). Consequently, for this treatment the determination of the
treatment area and the determination of a "forbidden area" is
essential, together with control of the treatment beam.
[0040] In another preferred embodiment, the above mentioned
screening, image processing and controlling means are used in
long-pulse photocoagulation or TTT devices and methods. Preferred
applications of these treatments are tumor therapy (810 nm,
.about.500-800 mW/cm.sup.2) and AMD therapy (810 nm, 7.5
W/cm.sup.2). In all cases the effectiveness as well as the security
of these treatment methods are significantly increased by the
accurate determination of the treatment areas, online image
processing and quality control means provided by the present
invention.
[0041] In yet another preferred embodiment, the above-mentioned
screening, image processing and controlling means are used in
photodynamic therapy (PDT). In this treatment, a photosensitive
drug (photosensitizer) is introduced into the patient's
bloodstream, and after a certain period is activated at the
treatment sites by localized irradiation. The substances are
activated after a period of 15 min to 20 min by long-pulse, low
energy radiation (600 mW/cm.sup.2). The use of an aiming beam
provided by this invention is especially advantageous in PDT to
reduce side effects, since the slit-lamp light normally used
includes a significant range of wavelengths which are able to
activate the photosensitive agent at unwanted sites.
[0042] In a further preferred embodiment, different treatment
methods at different wavelengths, power densities and other
parameters are combined to enhance the effectiveness of the
treatment. The treatment of the same area with different methods
may be advantageous as well as treatments of different areas with
different methods. In all cases it is essential to accurately
determine the treatment areas and control the treatment beams by
means of the present invention. For example, in some cases of AMD,
an effective treatment would be the initial application of TTT to
close feeder vessels by photocoagulation, followed by PDT to
further treat neovascularisation in the same or other areas. This
combination of methods may also be useful in tumor treatment by
first coagulating feeder vessels of the tumor with a green laser
and then destroying the tumor tissue with TTT. The combination of
green Laser and PDT might also be useful for the treatment of
retinal diseases caused by diabetes.
[0043] All treatment methods mentioned above can be either
implemented automatically, require manual settings by the operator,
or be realized in a combination. Several methods to generate a
variable beam spot area on the retina are also subjects of the
invention.
[0044] The device described in the present invention has several
advantages for the practitioner. First, the user is able to safely
determine the treatment area and the "forbidden areas" where
irradiation would be harmful. Second, the user is able to combine
different methods with a single device and accurately control all
methods. The ability to use different treatment methods in a single
device results in cost and space saving over the prior art, which
require a number of devices to deliver different treatments.
[0045] FIG. 1 illustrates a preferred embodiment of the present
invention, including all elements that are necessary to perform
treatments of age related macular degeneration and other diseases
by optical means. For reasons of simplicity, only the basic
elements of patient's eye 1 are included in the figure, which are
retina 2 and lens 3. Optical radiation enters the eye via lens 3
and forms an image on retina 2. For successful laser treatment,
contact lens 4 is placed at the cornea of the patient's eye to
minimize possible eye movement and enable the laser radiation to
enter the eye without damaging the cornea and with enhanced imaging
properties. For reasons of simplicity the complex optical system
present in contact lens 4 is not shown. Contact lens 4 has a
certain refractive power as is well known in state of the art laser
treatment of the retina. Several different kinds of radiation are
imaged on retina 2. One example is laser radiation 5. This
radiation is originated by laser system 14, which is preferably a
diode laser. The present invention bears one or more of these
primary irradiation sources so as to be able to emit irradiation of
one or more different wavelengths for the use in one or more
different treatment methods. Radiation 5 is coupled into optical
fiber 13, which has a well defined core diameter and numerical
aperture. Optical fiber 13 is a preferred element, because it
simplifies the device and helps to shape treatment radiation 5 to
the desired "top-hat" form characterized by very sharp rising and
falling intensity profiles at the edges and a plateau-like near
constant intensity elsewhere. Radiation 5 emitting from the fiber
end is collimated by an optical system and optionally imaged to
obtain a desired beam profile. None of these optics is a necessity;
in fact quite a number of possible systems with an arbitrary number
of lenses or even without any lenses can be used depending on the
targeted problem.
[0046] Beam source 14 has another feature: it contains an optical
system that allows for coupling the radiation from a secondary
light source into optical fiber 13. This secondary light source
preferably has a different wavelength and typically has a much
lower optical power than the treatment source. Due to the retina's
optical characteristics, the treatment beam is sometimes hard to
observe, and this additional light source increases visibility and
thus drastically increases the viewing possibilities. Using viewing
sources at different wavelengths resolves this viewing problem,
because the wavelength can be chosen in order to obtain the maximum
viewing quality. Optional viewing radiation 16 is preferably imaged
via optical system 10 along with treatment beam radiation 5 itself.
In order to better represent the optical system in FIG. 1, the
secondary radiation is illustrated on a different optical path
parallel to the primary radiation, though it can in general also
take the same path depending on the optical setup.
[0047] Both types of radiation pass through beam adjustment device
12. Secondary radiation 16 creates image 11 on the retina, which
does not necessarily coincide with image 15 created by the
treatment radiation itself. Nevertheless, since the radiation
properties are known, it is possible to determine the treatment
image from the secondary image.
[0048] The design of optical system 12 is a subject of the
invention and is now described in detail. Common to all these
embodiments is that adjustments by optical system 12 are not
static, but are variable so as to create variable images on retina
2 that have varying beam spot areas. It is common in laser based
eye treatment methods to allow simultaneous inspection of retina 2.
Therefore, inspection means in the form of a slit-lamp are included
in the device. In its simplest form, a slit lamp consists of light
source 8 with a collimating optical system generating illumination
radiation 7 that has suitable optical characteristics. Mirror 9 is
located at 45 degrees with respect to the optical axis. The purpose
of mirror 9 is to image illumination radiation 7 into the eye. The
illuminated area can be viewed along mirror 9 with back propagating
image radiation 17 passing through the slit of mirror 9 and
entering optical system 18, thereby fulfilling imaging purposes.
Radiation 7 is chosen such that it can pass through dichroitic
mirror 6. Mirror 6 is highly reflective, but not totally
reflective, for treatment radiation 5 and optional secondary
radiation 16. Thus, small portions of both treatment radiation 5
and secondary radiation 16 returning from retina 2 can pass through
the mirror and contribute to the viewing means. Additional filters
19 can be optionally included in the path of viewing radiation 17
in order to enhance the quality or observe only selected kinds of
radiation. Beam splitting means 20 is placed in the general optical
system behind primary optical system 18. A part of radiation 17 is
mirrored into first secondary optical system 23, which creates an
image on the detector area of digital image generation means 24,
preferably a CCD camera. Another set of filters 19 can be applied
in the path. The other part of radiation 17 is propagated through
secondary optics 21 and through ocular 22 for direct viewing by the
operator, preferably a physician.
[0049] As described earlier, the state of the art suffers from
several deficiencies that basically originate from the fact that
the area of the treatment zone cannot be determined accurately.
Thus all treatment beam spot size variation methods are rudimentary
and produce an error up to 600%.
[0050] One significant innovation of the present invention has
already been mentioned above: beam area generation means 10 are of
a more sophisticated nature than is found in the prior art. FIG. 2
shows additional elements that are part of the present invention to
allow highly accurate treatment of the fundus of an eye. A central
processing unit, preferably a PC in a desktop or in an embedded
form is used to both control the incoming data from viewing devices
24 and the variable beam area generating optical system 12. This
unit is programmed to control the adjustment as well as parameters
including wavelength, power density, and treatment duration for one
or for combined treatment methods. One or more display units 27 are
connected to processing unit 25 to display the viewing data,
display external data and perform operations in order to optimize
the treatment procedure. To minimize the error in the above
treatment, the present invention is used in a three step method.
First, the treatment area is determined from images supplied by the
different optical viewing devices which are set in correlation with
each other by the image data processing. Second, based on these
data the beam spot area is adjusted in the same relative way.
Third, the treatment beam is imaged to the retina. This method is a
significant improvement over prior art methods in which the
practitioner determines the treatment area and adjusts the
treatment beam based on fluorescence images generated under
different conditions with a different optical device and which are
not correlated with the optics of the laser treatment device.
[0051] One method for accurately determining the treatment area
consists of the following. A digital image using slit-lamp device 9
and digital image generation means 24 is taken. Another digital
image, the reference image, is taken with the retina irradiated
preferably by secondary light 16 with the optical system 12 being
responsible for setting up the treatment beam area on the retina in
a pre-determined basic position. Alternatively, the treatment beam
light itself can be used, but at significantly lower radiation
power. However, due to reasons of visibility explained above, the
use of a secondary light source is preferred. If PDT is used as
treatment method it is especially advantageous not to use the slit
lamp as image generating means but an aiming beam as provided by
this invention, since the light of the slit lamp contains a
significant part in range of wavelengths which activate the
photosensitizer and lead to undesirable side effects. From this
image generated with light 16, the spot size of treatment beam 5
can be precisely calculated in relative coordinates to the slit
lamp generated native fundus image. Further, a digital image
without treatment radiation 5 or secondary radiation is taken
within a time interval short enough to assure that the eye did not
move. Alternatively, a true real time online image can be taken
using either digital image filtering means or using real filters
and more than one digital image recording device. From this image
the treatment zone as well as the "forbidden zones" may be
determined with sufficient accuracy. If so, the operator marks the
treatment zone with a simple software tool and the computer
calculates the accurate size and coordinates. Applying a simple
method, the operator can then use this data to manually adjust the
beam area spot size with suitable optical system 12, which may be
guided by electronic aids such as acoustical or optical signals. An
even more accurate method is to have central processing unit 25
control optical system 10. The treatment beam parameters are also
provided by central processing unit 25. The operator can now use
manual positioning means 28 to locate the beam spot area center to
a predetermined position within the treatment zone, preferably the
center or one of the edges. As in the prior art, he can stop and
start the treatment beam with a second external control, preferably
a foot-piece, and simultaneously inspect the fundus in order to
decide if the treatment area and the treatment beam are aligned or
if this alignment has been disturbed by eye-movement. A significant
difference and advantage over the state of the art is that the
viewing can also be done via the digital image generated in
real-time and illustrated on display unit 27. Digital image
processing can enhance the image quality, and electronic image
detection means 24 is more specifically sensitive to the applied
wavelengths.
[0052] Another method for accurately determining the treatment area
with the present invention is to align the native fundus image
generated by the slit-lamp means to a diagnostic previously
generated image generated by means of fluorescence angiography.
Slit lamp generated images are generally of medium quality and,
depending on the status of the disease and the specific eyeball,
the treatment zone can hardly be seen or may not be determined with
sufficiently high accuracy. Therefore a digital previously
generated angiography image is loaded onto central processing means
25 and displayed on display device 27. As before, simultaneously or
quasi simultaneously a slit lamp native fundus image is taken with
and without the treatment beam spot and also displayed for the
operator. From a minimum of two characteristic points like blood
vessel crossings which may be marked by the operator himself, the
central processing unit aligns the two images, since they are in
general of different form, because the optics or the eye position
may vary. The operator further marks the treatment zone in the
angiography image, which can be done with high accuracy. These
coordinates are then calculated back to coordinates of the slit
lamp native fundus picture and the system is able to calculate how
optical system 12 responsible for the treatment beam spot
generation must be adjusted in order to achieve high overlap
accuracy. As described above, the adjustment can be performed
manually with possibly electronic aids or fully automatically. In a
preferred embodiment the complete adjustment, including the
positioning of the beam spot to the treatment area, the treatment
process and the treatment control is performed automatically by the
central processing unit on the basis of a real-time viewing of the
retina with the digital image processing means.
[0053] FIG. 3 illustrates a preferred embodiment for optical device
12, which is responsible for the generation of the treatment beam
area. The treatment beam is produced by primary beam source 14 and
is preferably coupled into optical fiber or light guide 13 where it
is shaped to the desired top hat intensity profile. The beam can
then be transported by simple means from primary beam source 14 to
the treatment device, allowing the beam source to be spatially
separated from the patient, which is of particular importance for
laser sources due to safety requirements. From there, primary
radiation 5 illuminates aperture 31. The radiation can illuminate
aperture 31 either directly or by an imaging means, such as a
telescope, to produce a fixed spot on aperture 31. Optimally,
radiation 5 can be collimated in order to minimize the divergence
angle. Aperture 31 cuts a defined section from said beam. This cut
has, apart from diffraction limits, sharp intensity edges, which is
of great advantage to the treatment process in that it assures that
all parts of the treatment zone are irradiated with the same
energy. Aperture 31 is adjustable via mechanical means such as
micrometer screws that are moved by the operator directly or via
electromechanical means 34 such as step motors or piezo actuators.
Means 34 can be controlled directly by the operator with suitable
control devices or by central processing unit 25 that is connected
with means 34 via interface lines 35. More than one aperture may be
included within the setup, illustrated by additional aperture 32 in
FIG. 3. Additional apertures can be controlled in the same manner
as the primary aperture and serve various purposes. One such
purpose is the generation of a two dimensional irradiation surface
on the retina which is of higher complexity than the simple circle
preferably generated by single aperture 31. For example, the
combination of a circular aperture with a slit aperture allows
near-oval irradiation spots or two slit apertures allow rectangular
forms. In a preferred embodiment the whole aperture unit is
exchangeable, allowing the operator to choose a certain combination
in order to adjust the treatment beam image to the treatment area
determined from the diagnostic fluorescence angiography image. As
already mentioned the basic position of the system generating the
reference image is common to all the optical systems used
independently of different magnification characteristics. In the
case of the aperture based solution to the adjustment of beam spot
size to treatment zone size, the basic position of
electromechanical dislocation means 34 is directly related to the
size of apertures 31, 32, and any additional apertures. This
aperture is first illuminated with secondary beam 16 and the
radiation passing the aperture propagates to the eyepiece or is
optionally imaged via optical system 33. The image of the aperture
on the retina is then recorded and digitized. This digital image is
one of the basic images mentioned above to perform the calibration.
Therefore, secondary beam 16 must be coupled into the propagation
path of primary radiation 5. This is done in a unique and well
known way in order to have a well defined system of coordinates to
compute the shape and size of image 15 from secondary beam retina
image 11. In a preferred embodiment, secondary beam 16 is already
coupled to optical fiber 13 together with the treatment beam. The
operator can then use primary beam 5 to chose the exact position of
the treatment zone and start the process. This is performed as
described above utilizing the means illustrated in FIG. 2.
[0054] FIG. 4 illustrates a more advanced system for the generation
of the treatment beam area on the retina. State of the art methods
suffer from the deficiency that they produce round spots since
optical fibers, laser profiles or lamp emitted radiation generally
produce round spots. These spots are then shaped and imaged to the
retina. The new method illustrated in FIG. 3 and described above is
already a significant innovation over the state of the art, since
it allows shapes other than round profiles. Additionally, the
treatment beam is kept at small sizes and thus there is no longer a
requirement for a rectangular top hat intensity profile. However,
the treatment zone usually has a much more complicated form. In the
prior art, the treatment zone could not be determined with
sufficient accuracy, hence there was no need for the generation of
an accurate treatment beam area. By the methods of this invention
the treatment zone becomes well known, hence the mechanisms to
illuminate said treatment zone can be enhanced in the same degree.
FIG. 4 basically consists of the components described above, but
adjusting optical system 12 is embodied as a scanning device. In
its most basic form a scanner contains two movable mirrors 36 and
37 positioned in an orthogonal way. The angle relative to the
optical axis of each mirror is adjustable in one dimension, thus
the beam can be arbitrarily positioned on a two dimensional surface
according to their orthogonal position by independent angle
variation. This surface can further be imaged onto the retina via
contact lens 4 and the eye's lens. Source 14 can be collimated,
optionally be expanded to the desired diameter with suitable
optical system 10 and then be directly imaged by the scanning
means.
[0055] The eye lens and the original beam diameter hitting the eye
lens are responsible for the size of the beam spot on the retina,
on which the beam delivered by the treatment beam spot is dependent
on the beam diameter and divergence angle when it hits the contact
lens and on the contact lens itself. By varying the contact lens
and the beam properties by means of adjustable optical system 10
the beam spot on the retina can be varied accordingly. For use with
a scanner the beam is of relatively low power and small size. If
the scan velocity is chosen to be sufficiently large, each spot on
the treatment zone is impinged by a sufficiently large number of
photons for an optimal treatment process.
[0056] To generate a true image of the treatment zone determined by
use of the methods described above, two ways can be followed. The
first consists of the generation of a rectangular image and
switching the primary beam source on and off sufficiently fast,
hence simply no intensity is emitted if the scanner is positioned
at a point out of the treatment zone and the laser is on if the
scanner is positioned at a point on the treatment zone. Hence even
non connected treatment zones can be mapped accurately.
[0057] The second method is to operate the scanner in an
asynchronous mode with interruption. Mirrors 36 and 37 do not just
map a rectangle, they rather map the concrete form of the treatment
zone. This enhances the scanning efficiency and lowers the
requirements of the switching velocity of primary beam source 14.
However, the requirements of the scanner deflection properties
rise.
[0058] Scanner deflection can be implemented by various methods,
two common methods include the use of galvanometric driven mirrors
and piezo actuator driven mirrors.
[0059] Alternatively, instead of two orthogonal one-dimensional
deflecting mirrors, a single two-dimensional deflecting mirror can
be used. A scanner system can be even of higher complexity. Today,
micro-mirror devices are commercially available, for example by
Texas Instruments, Inc. of Houston, Tex. which consist of a two
dimensional array of micro mirrors. These devices are able to
produce pixel based 2-dimensional image structure which can be used
in display technologies, in micro machining and for applications in
medicine. A device of this type is included as the basic element of
adjusting optical system 12, optionally combined with suitable
optical elements to create optical images which fulfill all the
requirements given by the micro-mirror device and the treatment
zone. The micro-mirror device is directly controlled by central
processing unit 25. The image created directly propagates via the
optics and contact lens 4 to the retina.
[0060] An equivalent effect of the micro mirror method can be
achieved using liquid crystal devices and polarizers, similar to
the use of liquid crystal devices in printing, display and
lithography applications. Optical system 12 would then contain an
optical setup which is a liquid crystal modulation device which
allows generation of an image formed by a sufficiently large number
of pixels that matches the treatment zone. It is obvious that any
image generation means can be included in a treatment setup to
generate the treatment zone illumination beam area.
[0061] The optics further can be positioned externally by the
operator, for example, by using positioning means 28. In
particular, said positioning to treatment zone is enhanced by using
the secondary beam source as an aiming beam and using the digital
image recording and processing means described above.
[0062] The use of a scanner system as described only makes sense if
it is operated with sufficiently fast driving electronics and
controlled by a computer based system. The inclusion of a system of
this type and the connection of all variable elements to the
central processing unit is also a subject of the present
invention.
[0063] FIG. 4 shows another innovative method for the generation of
a variable image on the retina. From the point of the operator and
the patient, this method provides an equivalent interface for the
treatment itself and the result will also be comparable to the
results obtained by using scanner methods. In fact the scanning
facility is maintained, but in this case secondary light source 16
itself, if directly included in the treatment setup, or the
emitting end of fiber 13 if the beam source is external and its
produced radiation is transported to the treatment device by fiber
13, is moved along a special path. This movement can, as with the
scanning method described before, follow a complicated path
directly or follow a rasterized rectangle. Primary light source 14
is switched according to the treatment size image requirements. To
generate the movement of, for example, the fiber end, a
two-dimensional scanning unit can be constructed either
mechanically, electro-mechanically by the application of piezo
actuators or by a combination of these. In FIG. 5, fiber 13 is
connected to mount 36. Mount 36 is fixed on two dimensional
displacement unit 40. Actuators 41, preferably piezo actuators,
cause the appropriate movements and are connected with central
processing unit 25 by connection lines 35. Since aiming beam 16
produced by the fiber is preferably transported by said fiber it
follows the same contour as treatment beam 5 and can thus be still
used for all purposes mentioned above. The optical system images
the plane, in which the fiber end moves to the retina. Optionally,
the optical system can be varied automatically by central control
unit 25 or be exchangeable in order to achieve different imaging
relations.
[0064] FIG. 6 illustrates another element which can be implemented
in the optical path to achieve the desired beam displacement.
Incoming treatment beam 5 passes parallel plate 42 optionally
coated dielectrically in order to minimize losses. This plate is
mounted so that it is movable in relation to one reference point
located on cylinder 47. The plate can now be rotated relative to
this reference point to a certain angle by actuator 49. Actuator 49
can be a simple stepper or, preferably a piezo actuator, which is
in suitable contact with parallel plate 42. In particular it must
allow a certain linear movement of the actuating point. Because of
this angle, incoming beam 5 is displaced by a certain distance
hence outgoing beams 45 and 46 are parallel to the incoming beam,
but displaced by different distances according to the angle at
which the plate is positioned within the beam. If the plate is in
the position marked by feature 43 it creates a smaller
displacement, producing beam 45, than if it is in the position
marked by feature 44, producing displaced beam 46. This
displacement is uniquely given by a mathematical relation between
the displacement and the angle and can hence be controlled
accurately. The two dimensional displacement can be obtained either
by the use of two orthogonal devices each producing a displacement
in one direction or a single plate, which has one fixed reference
point and two orthogonal variable points. For this displacement
unit all optical and electronic features described above can be
used.
[0065] FIG. 7 illustrates another embodiment of the treatment
optics. Primary light source 14 creates treatment radiation 5,
which is preferably coupled into optical fiber 13 and transported
to the treatment device. Radiation 5 is transported together with
secondary radiation 17 which serves as aiming beam and preferably
has a different wavelength. The output 5 and 16 from fiber 13 is
preferably collimated by optical system 10 and then coupled into
optical system 52, which plays the role of adjusting optical system
12 in prior embodiments. System 52 consists of the optical module
of a commercial video camcorder, which is available as a component,
as for example the Sony ELI Series. In their original application
these modules are intended to generate images on a camera chip for
different object distances, which is basically equivalent to the
purpose required for the treatment of the fundus of an eye. The
optical states of module 52 can be varied electronically through
interface 35 and central processing unit (not shown), which is
preferably a PC. The reference image used for the calibration of
the angiography to the native fundus image is recorded at a fixed
position of the video module and with the data obtained from the
image calibration. The correct state is chosen in order to generate
a well defined treatment spot on the treatment zone. The principal
treatment features are equivalent to the other embodiments
described above. This method can in particular be combined with the
aperture method which enhances the performance because it allows
other than round profiles, the aperture creates top hat intensity
structures if desired and operated far from the diffraction limit
and the process can be implemented electronically and thus be
controlled completely by a central processing means.
[0066] Having described preferred embodiments of the invention with
reference to accompanying drawings it is to be understood that the
invention is not limited to those precise embodiments, and that
various changes and modifications may be effected therein by one
skilled in the art without departing from the scope or the spirit
of the invention as defined in the appended claims.
* * * * *