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WO2008127204A1 - Système optique pour trabéculoplastie laser sélective - Google Patents

Système optique pour trabéculoplastie laser sélective Download PDF

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Publication number
WO2008127204A1
WO2008127204A1 PCT/SI2008/000024 SI2008000024W WO2008127204A1 WO 2008127204 A1 WO2008127204 A1 WO 2008127204A1 SI 2008000024 W SI2008000024 W SI 2008000024W WO 2008127204 A1 WO2008127204 A1 WO 2008127204A1
Authority
WO
WIPO (PCT)
Prior art keywords
laser light
laser
optical system
wavelength
light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/SI2008/000024
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English (en)
Inventor
Grisa Mocnik
Gregor Tavcar
Boris Vedlin
Matjaz Zalar
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Optotek doo
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Optotek doo
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Optotek doo filed Critical Optotek doo
Publication of WO2008127204A1 publication Critical patent/WO2008127204A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F9/00—Methods or devices for treatment of the eyes; Devices for putting in contact-lenses; Devices to correct squinting; Apparatus to guide the blind; Protective devices for the eyes, carried on the body or in the hand
    • A61F9/007—Methods or devices for eye surgery
    • A61F9/008—Methods or devices for eye surgery using laser
    • A61F2009/00861—Methods or devices for eye surgery using laser adapted for treatment at a particular location
    • A61F2009/00868—Ciliary muscles or trabecular meshwork

Definitions

  • the present invention relates to the field of medical apparatus for treatment of eye diseases, and more precisely to optical systems designed specifically for performing selective laser trabeculoplasty in therapy of certain types of glaucoma.
  • Glaucoma is a term for a group of eye disorders in which the optic nerve is damaged.
  • the most frequently used classification of glaucoma is based on the pathophysiology of the disease according to which the many forms of glaucoma are grouped into open-angle glaucoma and closed-angle glaucoma. The latter occur as a consequence of anatomical predisposition, inflammation or neovascularization, and their clinical course is generally acute.
  • a risk factor for development of open-angle glaucoma on the other hand is an increased pressure within the eye which builds up most often as a result of decreased outflow of aqueous humor through trabecular meshwork and the canal of Schlemm into the collector channels that join the venous circulation.
  • the resulting increased intraocular pressure can be reduced by applying the selective laser trabeculoplasty which is a minimally invasive surgical method.
  • the selective laser trabeculoplasty procedure the laser light shots are absorbed in the tissue, or more precisely, in the epithelial cells containing melanin in the trabecular meshwork located in the anterior chamber angle of the eye.
  • the duration of laser light shots is much shorter than the thermal relaxation time of the target tissue, hence, the temperature rise is confined solely to the laser light irradiated area and the coagulation effect that could occur in the tissue due to absorbed laser light is prevented.
  • the duration of the laser light shots is typically some nanoseconds, while the wavelength is 532 nm to ensure good absorption of the laser light in the melanin.
  • a typical transverse dimension of the laser beam, specifically of the laser light spot on the trabecular meshwork, is in the order of some tenths of a millimeter, while typical energy of the laser light shot does not exceed 2 mJ.
  • the technical problem which is solved by the optical system according to the present invention is to configure a special optical system for use in a laser device for ophthalmologic surgery which ensures a well defined and uniform distribution of the laser light intensity over the surface of the laser light spot projected onto the target in order to achieve a uniform effect on the radiated tissue.
  • the advanced devices for selective laser trabeculoplasty are typically composed of: - the Nd:YAG Q-switch laser, which includes a compact resonator and generates laser light shots with a wavelength of 1064 nm and a pulse duration of about 5 ns;
  • nonlinear crystal having its geometry optimized for frequency doubling of laser light with a wavelength of 1064 nm, that is for converting laser light with a wavelength of 1064 nm into laser light with a wavelength of 532 nm.
  • An example of such crystal is KTiOPO 4 .
  • a lens system designed for producing a laser light spot of adequate size on the target as well as for ensuring that the laser light beam convergence is small enough so that the beam reaches the eye angle.
  • the energy and the length of the shots produced by the Nd:YAG laser are well defined by the dimensions and optical characteristics of the laser optical elements, consequently, there is very little variation of pulse energy and pulse length from one shot to another.
  • the ratio of resonator length versus beam diameter is relatively small, to wit -10 cm/ ⁇ 1 mm, the distribution of power density over the cross section of the laser light beam is not well defined since this ratio varies from one shot to another.
  • the laser operates namely in a mixture of several transverse modes and the participation of a particular mode in this mixture varies from one laser shot to another.
  • the behavior of the nonlinear crystal is sensitive to power density of the incident laser light; consequently, frequency doubling of such laser shots does not yield a stable outcome.
  • the problem of uniform distribution of energy within sharp edges of the laser light spot is solved by an illumination system described in the patent US6532244.
  • the illumination system includes a multimode diode-laser and two optical fibers. Light from the diode-laser is directed into the first optical fiber, and the outgoing light from the first optical fiber is directed by an optical system into a second optical fiber, having a core diameter greater than the first optical fiber and a numerical aperture greater than the numerical aperture of the optical system. A light beam exiting the second optical fiber has more uniform intensity across the profile than the light beam exiting from the first optical fiber.
  • the present invention includes the following essential parts:
  • planar laser light source having suitable dimension and numerical aperture and emitting light that is uniformly distributed over the planar surface area and over the angle and that has a wavelength that ensures good absorption of light in the melanin;
  • the planar source of laser light in the optical system according to the present invention can be made: a) by using an optical fiber which has adequate dimension and numerical aperture; or b) by using a diaphragm with a circular aperture, having a correspondingly smaller diameter than the light beam projected onto the aperture.
  • Laser light exiting from the planar source can be projected onto a target: a) in the form of overlapping collimated beams when the planar source is a light outgoing surface of optical fiber; or b) as an image of the planar source when the planar source is a light outgoing surface of optical fiber or a circular aperture in a diaphragm.
  • Figure 1 a schematic depiction of the course of the laser beam propagating from the light outgoing surface of the optical fiber through a converging lens.
  • Figure 2 a schematic depiction of the course of the laser beam as well as of individual rays in the laser beam propagating from the light outgoing plane of the optical fiber through the arrangement of lenses of the optical system.
  • Figure 3 a schematic depiction of the transposition of aperture image onto the target by uniformly illuminating the aperture in a diaphragm with a laser beam.
  • Figure 4a a distribution of energy over the laser spot surface before frequency doubling.
  • Figure 4b a distribution of energy over the laser spot surface after frequency doubling by means of one nonlinear crystal.
  • Figure 4c a distribution of energy over the laser spot surface after frequency doubling by means of two nonlinear crystals.
  • the laser beam is conveyed to the optical system through the optical fiber 1.
  • the light outgoing flat surface 2 of the optical fiber 1 is positioned at the left focus of the converging lens 3 situated in the plane G3 1 .
  • a beam waist of the laser beam is created having a homogenous light intensity profile over its cross section and a well defined sharp edge.
  • the light leaving the outgoing surface 2 of the optical fiber 1 has a rather uniform distribution over the cross section as well as over the angle, which is due to numerous reflections of the laser beam in the optical fiber.
  • the edge of the light beam is defined by the outgoing surface 2 and by the numerical aperture of the optical fiber 1.
  • the axes of all beams intersect at the focal point on the other side of the lens where the intensity profiles of individual beams coincide.
  • the key parameters for good coincidence of the profiles are the diameter and the numerical aperture of the optical fiber, since the product of the divergence of individual beam, having a shape of a light cone, and the distance of the beam focus point from the optical axis on one side of the lens equals to the product of the diameter and the angle of incidence of the same beam on the other side of the lens.
  • FIG 2 another embodiment of the optical system according to the present invention is shown schematically.
  • the laser beam is conveyed towards the optical system through the optical fiber 1.
  • the outgoing flat surface 2 of the optical fiber 1 represents a homogenous planar source which is projected through an optical system or a lens system, typically through two converging lenses 3 and 4, as an optical image onto the target 5.
  • the diameter and the numerical aperture of the optical fiber 1 are the key parameters, since in optical imaging the product of the beam's divergence and the distance between beam's focus and optical axis remains unchanged.
  • the smallest angle of beam's convergence is achieved when the symmetry axes of individual rays within a beam are parallel, which means that the geometry of incidence of light onto the target mirrors the geometry of release of light out of the planar light source.
  • Such geometry is achieved when the outgoing surface of the optical fiber is positioned in the focus of the first lens and the optical image of the outgoing surface is created in the focus of the second lens.
  • the laser beam 8 is screened by a diaphragm 9 having an aperture 10 which catches only that portion of a laser beam where the planar intensity profile is most homogenous.
  • a lens system typically with two converging lenses 3 and 4
  • an optical image of the aperture 10 in the diaphragm 9 is created, with suitable magnification or reduction, on the target 5.
  • the laser beam which has typically a wavelength of 532 nm and has a diameter size as needed to ensure the entry into the eye with a very small divergence, creates an optical image of the aperture 10 of the diaphragm 9 exactly in the depth of the target 5.
  • the aperture 10 of the diaphragm 9 must be small enough to catch only the portion of the beam with uniform energy density, and at the same time big enough to forward sufficient energy.
  • the lenses 3 and 4 must be converging lenses, as a real optical image can be created only by converging lenses.
  • the optical system according to the present invention has the following essential parts for generation of laser shots that have stable energy profile and can be absorbed well in melanin: -
  • a pulsed laser light source emitting near infrared light and producing shots of a few nanoseconds length.
  • a type Il of quadrature frequency doubling method proposed by D. Eimerl (D. Eimerl, Quadrature frequency conversion, IEEE J. Quantum Electron. 23, 1361-1371 (1987)), is applied in the optical system according to the present invention.
  • Two nonlinear crystals are used, normally having different lengths.
  • Their main planes i.e. the planes defined by the vector of the laser light beam direction and by the optical axis of the first and of the second crystal, respectively, are perpendicular to one another.
  • phase matching of incoming and outgoing laser light waves is perfect.
  • crystals of different lengths must be applied for different incoming power densities.
  • a very high and constant efficiency of frequency conversion can be achieved by using two nonlinear crystals of different lengths oriented at right angle to each other. Due to right angle positioning of crystals the resulting frequency conversion is called quadrature frequency doubling.
  • the shorter nonlinear crystal performs efficient doubling in regions with high power density, and the longer one in the regions with lower power density.
  • Their arrangement at right angle prevents the light with a 532 nm wavelength that leaves the first crystal from instigating unwanted frequency conversion back to a 1064 nm wavelength in the second crystal, as a 532 nm wavelength light has not the right polarization for such frequency conversion in backward direction.
  • the energy of pulses stays within the range of allowed deviation from nominal energy and the fluctuations of energy density across the intensity profile of the beam in the depth of the target are minimal.
  • the light with a 1064 nm wavelength incoming into the nonlinear crystal in general does not have an even distribution of power density over its cross section, as shown in Figure 4a. If only one nonlinear crystal is used, in the regions with lower energy density frequency doubling is not fully effected, so within the profile of the light with a 532 nm wavelength, captured by the aperture 10 in the diaphragm 9, the regions with insufficient power density occur.
  • the energy density in these regions does not exceed the threshold value required for successful trabeculoplasty, for that reason the region of successful trabeculoplasty is smaller than the laser dot on the target, as illustrated in Figure 4b.
  • a stable energy of a laser shot which typically has a wavelength of 532 nm can be achieved also by using a fiber laser.
  • a fiber laser has a beam quality superior to that of the Nd: YAG laser. Hence, if a fiber laser is used as a source of light with a wavelength of 1064 nm, then the energy density within the beam does not vary from one shot to another, consequently frequency doubling in the nonlinear crystal is constant over time and space.
  • a fiber laser thus ensures a highly homogenous energy density within the sharp edge of the dot on the target, moreover, in all the regions of the dot it provides the energy density level that is above the threshold value needed for efficient trabeculoplasty.

Landscapes

  • Health & Medical Sciences (AREA)
  • Ophthalmology & Optometry (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Optics & Photonics (AREA)
  • Surgery (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Physics & Mathematics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Lasers (AREA)

Abstract

système optique spécial pour trabéculoplastie laser sélective assurant une distribution homogène de densité de puissance et un contour précis de faisceau laser sur la cible par le biais d'une source plane de lumière laser, de dimension appropriée et à ouverture numérique pour l'émission de lumière à distribution uniforme sur la surface transversale et sur l'angle; le système fait appel à un système de lentille acheminant la lumière depuis la source plane vers la profondeur de la cible de sorte que le faisceau lumineux sur la cible ait une densité d'énergie uniforme et que la convergence du faisceau de dépasse pas 3°. Pour l'irradiation du réseau trabéculaire, on utilise une lumière laser à longueur d'onde assurant une bonne absorption de la mélanine, et la longueur d'onde classique est de 532 nm. On produit une telle lumière dans une source laser à travers un cristal non linéaire ou deux cristaux non linéaires. Ladite source peut être soit un laser Nd:YAG à commutation Q soit un laser à fibre.
PCT/SI2008/000024 2007-04-11 2008-04-10 Système optique pour trabéculoplastie laser sélective Ceased WO2008127204A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SIP-200700086 2007-04-11
SI200700086A SI22509A (sl) 2007-04-11 2007-04-11 Optiäśni sistem za selektivno lasersko trabekuloplastiko

Publications (1)

Publication Number Publication Date
WO2008127204A1 true WO2008127204A1 (fr) 2008-10-23

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PCT/SI2008/000024 Ceased WO2008127204A1 (fr) 2007-04-11 2008-04-10 Système optique pour trabéculoplastie laser sélective

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WO (1) WO2008127204A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019028222A1 (fr) * 2017-08-02 2019-02-07 Multi Radiance Medical Système et procédé pour diriger la lumière dans l'œil d'un patient
US11638833B2 (en) 2017-08-02 2023-05-02 Multi Radiance Medical Reducing light polution in photobiomodulation therapy of a patients eye

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SI24527A (sl) 2013-11-11 2015-05-29 Optotek D.O.O. Oftalmološka laserska naprava

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0230094A1 (fr) * 1985-10-18 1987-07-29 Kowa Company, Ltd. Projecteur pour une tache à laser
US5129895A (en) * 1990-05-16 1992-07-14 Sunrise Technologies, Inc. Laser sclerostomy procedure
US5549596A (en) * 1993-07-07 1996-08-27 The General Hospital Corporation Selective laser targeting of pigmented ocular cells
EP1354573A1 (fr) * 2002-04-08 2003-10-22 Lumenis Inc. Dispositif et méthode d'illumination uniforme
US20060224146A1 (en) * 2005-03-30 2006-10-05 Lin J T Method and system for non-invasive treatment of hyperopia, presbyopia and glaucoma

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0230094A1 (fr) * 1985-10-18 1987-07-29 Kowa Company, Ltd. Projecteur pour une tache à laser
US5129895A (en) * 1990-05-16 1992-07-14 Sunrise Technologies, Inc. Laser sclerostomy procedure
US5549596A (en) * 1993-07-07 1996-08-27 The General Hospital Corporation Selective laser targeting of pigmented ocular cells
EP1354573A1 (fr) * 2002-04-08 2003-10-22 Lumenis Inc. Dispositif et méthode d'illumination uniforme
US20060224146A1 (en) * 2005-03-30 2006-10-05 Lin J T Method and system for non-invasive treatment of hyperopia, presbyopia and glaucoma

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
EIMERL D: "QUADRATURE FREQUENCY CONVERSION", INSPEC,, 1 January 1900 (1900-01-01), XP000652798 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019028222A1 (fr) * 2017-08-02 2019-02-07 Multi Radiance Medical Système et procédé pour diriger la lumière dans l'œil d'un patient
US10744341B2 (en) 2017-08-02 2020-08-18 Multi Radiance Medical System and method for directing light into a patients eye
US11638833B2 (en) 2017-08-02 2023-05-02 Multi Radiance Medical Reducing light polution in photobiomodulation therapy of a patients eye
US11724121B2 (en) 2017-08-02 2023-08-15 Medical Quant Usa System and method for directing light into a patients eye

Also Published As

Publication number Publication date
SI22509A (sl) 2008-10-31

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