WO2010060443A1

WO2010060443A1 - System for ophthalmology or dermatology

Info

Publication number: WO2010060443A1
Application number: PCT/EP2008/010032
Authority: WO
Inventors: Klaus Vogler
Original assignee: Wavelight Ag
Priority date: 2008-11-26
Filing date: 2008-11-26
Publication date: 2010-06-03

Abstract

The invention relates to a system for ophthalmology or dermatology, with a laser unit for generating pulsed laser radiation, wherein the pulse length of the laser pulses lies in the femto range, with a hand-held unit for discharging laser radiation generated by the laser unit, and with a flexible optical wave guide by which the laser radiation generated by the laser unit is conveyed to the hand-held unit. The invention further relates to a corresponding hand-held unit for discharging pulsed laser radiation generated by a laser unit, wherein the laser radiation has pulse lengths in the femtosecond range.

Description

System for ophthalmology or dermatology

The invention relates to a system for ophthalmology or dermatology and a hand unit for emitting pulsed laser radiation.

In refractive ophthalmic surgery, the refractive properties of the eye are altered by surgery on the eye of a patient to correct vision defects. In particular, the so-called LASIK method (LASER in situ keratomileusis), in which the patient's cornea is reshaped, is known. According to the conventional LASIK method, a flat corneal incision is made in a first microsurgical operation with a mechanical instrument, usually a microkeratome. The result is a disc called a "flap" that can be unfolded to expose underneath corneal tissue (stroma). In the subsequent part of the LASIK operation, a laser ablates a specific ablation pattern from the stroma. Then the flap is folded back and heals relatively quickly with the remaining stroma. The conventional mechanical microkeratome uses a sharp, fast oscillating blade.

More recently, the microkeratome has been replaced by a laser, in particular a femtosecond laser, which places the above-described flat incision in the cornea. The laser is focused at a level below the surface of the cornea and guided on a path that, like the microkeratome, produces the flap. The extremely short laser pulses used in the femtosecond range have such high powers that, with suitable focusing, it is possible to cut by utilizing the so-called photodisruptive effect, without there being any internal heat effects or the like. In comparison to the conventional mechanical microkeratome, the result is usually a higher accuracy, a better reproducibility of the LASIK sections.

To generate the flap by means of laser, the patient is first positioned under the femtosecond laser. It is, as in the conventional production of a Flaps by microkeratome, a fixation ring placed on the eye, which is usually fixed by suction. Thereafter, a contact glass is introduced into the suction ring, which touches the surface of the cornea and flattening this for the most accurate generation of the corneal cut by exerting a certain pressure. Thereafter, a conventionally cone-shaped contact device is connected to the actual femtosecond laser device. This is usually done so that the part of the laser device which outputs the laser radiation, motor-assisted, enters the cone-shaped contact ^¬ device. The eye of the patient is already fixed and loaded by the suction ring and the contact lens in an unpleasant manner for the patient at this time. Through the contacting process between suction ring and laser device, the burden on the patient is further increased, since the process is usually not completely jerk-free. As a result, at least for a short time, additional pressure is exerted on the patient's eye, which may be physiologically and psychologically disadvantageous for the patient.

It is therefore an object of the present invention to remedy this burden.

For this purpose, the invention provides a system with a laser unit for generating pulsed laser radiation, wherein the pulse length of the laser pulses in the femtosecond range, a hand unit for emitting laser radiation generated by the laser unit, and - a flexible optical waveguide for forwarding the laser radiation generated by the laser unit the hand unit.

Thus, according to the invention, the laser radiation generated by the laser unit is not guided to the site to be treated by means of a rigid free-beam optical connection, but guided to a hand unit by means of a flexible optical waveguide and emitted there. The hand unit can only be connected to the laser unit via the flexible optical waveguide, for example with the suction ring or with its coupling device. The hand unit can be made in a small size and with a low weight, which on the one hand the psychological burden of a much smaller unit on the

Eye is placed, reduced. At the same time, the actual burden is reduced by facilitated handling and associated lower pressure exerted on the eye. In the present case, the term "hand unit" should be understood to mean a unit which, in terms of its dimensions and weight, is designed such that it can be guided by hand by an operator, for example, and placed on an eye. In a preferred embodiment it is provided that the laser unit comprises a fiber laser. A fiber laser provides a high beam quality (typically a beam parameter product <1.3) in a very compact design.

According to a further embodiment, it is provided for the system that the laser unit and the hand unit are interconnected solely by one or more flexible cables, at least one of which comprises the flexible optical waveguide. In the one or more flexible cables, in addition to the flexible waveguide, for example, a power supply, a vacuum supply and one or more data lines may be included.

A further embodiment of the system according to the invention provides that the hand unit can be positioned independently of the laser unit within the scope of the mobility of the cable. If the size of the hand-held unit is comparable to that of a conventional microkeratome or only slightly larger, the production of the flap can be achieved with a comparable load for the patient while at the same time increasing the precision of the cut. The above-described burdens associated with a conventional femtosecond flattening laser are thus reduced.

In this connection, a further embodiment according to the invention provides that the hand unit has a coupling device which enables a mechanical connection to a human eye. The hand unit is placed either in combination with the suction ring directly on the eye or coupled with a previously attached to the eye suction ring.

In a further preferred embodiment of the invention, it is provided that the laser unit comprises a pulse stretching device for the temporal extension of the laser pulses to pulse lengths greater than 1 picosecond. The pulse stretching allows a reduction of the intensity of the laser pulses. Among other things, a lower load for the flexible waveguide is associated with the reduction of the pulse power.

In this context, it is also advantageous if the flexible optical fiber is a photonic transmission fiber with a large mode field. These optical waveguides, which are also called large-mode-area fibers (LMA fibers), have core diameters of 20 μm to more than 40 μm. Due to the distribution of the light output over a larger area and the simultaneous forwarding in a low mode order or in the fundamental mode, LMA fibers allow a transmission of Laser radiation emitted by the laser unit without degrading the beam parameters of the laser unit or destroying the LMA fiber due to excessive intensities.

Furthermore, it may be advantageous in this regard if at least a part of the flexible optical waveguide effects a pulse compression of the pulsed laser radiation generated by the laser unit. This allows the hand unit to be made significantly more compact. The compression of the laser pulses otherwise to be performed in the hand unit can thus be transmitted to the flexible waveguide and corresponding components in the hand unit omitted.

A particularly preferred embodiment in this regard provides that the flexible optical waveguide is a photonic hollow-core fiber. These microstructured optical fibers, also referred to as photonic crystal fibers ("PCF fibers"), typically contain fine, air or gas filled capillary structures in the core or cladding region. These structures are so small that the guided light "sees" different effective material properties of the glass By varying the hole center distances and the diameter of the capillary structures, the optical parameters of the fibers and the properties of the light guide can be controlled Pulskompression the pulsed laser radiation generated by the laser unit can be achieved.

Alternatively, it can be provided in an embodiment according to the invention that the hand unit comprises compression means for temporally compressing the pulses of the laser radiation. Such a compression means may for example comprise an optical grating, preferably a transmission grating.

Furthermore, in one embodiment of the invention, the hand unit may comprise an electro-optical scanner for beam deflection. Such electro-optical crystals for the spatial control of a light beam are usually based on the Pockels or Kerr effect, in which the optical properties, such as the refractive index, are changed by applying an electric field to the medium. In this way, a spatial displacement of the light beam can be realized without moving parts. Also acousto-optic modulators can cause fast and controllable beam deflections by an induced Bragg grating. Alternatively, it may, for example, be an electro-optic hologram formed by recording a volume phase hologram in a liquid crystal monomer medium. produced by external electrical voltages efficient and controllable beam deflections.

According to the invention, a hand unit is also provided for the delivery of pulsed laser radiation generated by a laser unit, with

a fiber input, via which the laser radiation generated by the laser unit enters the hand unit,

- An optics for guiding the laser radiation, and

a compression device for temporal pulse compression of the laser radiation entering via the fiber input, as well as alternatively or additionally to the compression device

- A scanner or an electro-optical crystal for beam deflection of the laser radiation.

Thus, the idea according to the invention - to create a unit for ophthalmology or dermatology which is independently movable from the laser radiation source and which, when used, less stress for the patient - precipitates in one hand unit. The same applies to the manual unit according to the invention for emitting pulsed laser radiation generated by a laser unit, the laser radiation having pulse lengths in the femtosecond range.

One of the principles of the present invention is to provide a compact, substantially fiber-based femtosecond laser source as an easy-to-use laser device for ophthalmic applications. Here, a femtosecond fiber laser is used as the laser source. It has already been shown that pulse energies of approximately 400 nanojoules at 200 kHz are sufficient for a very smooth, easy-to-open flap cut in less than 15 seconds. The omission of large-volume power supplies and complex active cooling units by using a fiber laser allows the creation of a femtosecond LASIK microkeratome of comparable dimensions to a conventional mechanical, blade-based microkeratome. It is further contemplated that the low pulse energies of less than 1 microjoule are readily propagated to pulse lengths of> 1 picosecond transmitted through long mode fiber transmission fibers without degrading the good beam parameters of the femto second fiber source or through the large mode diameter fiber to destroy high intensities. The subsequent pulse compression to <500 femtoseconds can then with miniaturized optical elements in one Handpiece to be made. Possible miniature components are a transmission grating for femtosecond pulse compression and an electro-optical scanner which requires no moving parts. This beam deflection principle, which is based on the use of an electro-optical crystal, allows completely sufficient deflection angles of up to 5 ° in extremely short times of about 1 microsecond. Thus, for a wavelength range from 400 nm to over 2500 nm laser beam deflections are possible, which achieve results with focused radiation, which are comparable to a conventional XY galvanometer scanner. Alternatively, a so-called hollow core photonic fiber can be used which, with suitable dimensioning, can effect not only the transmission but also the compression of the picosecond or femtosecond laser pulse. Thus, the grid compression can be omitted in the handpiece, and this can be realized even more compact. With this invention, a femtosecond microkeratome is provided which, in a similar space-saving manner, is suitable as a refractive surgery device, such as the common blade-based mechanical microkeratome.

The invention will be further explained with reference to the accompanying drawings. They show:

1 shows an embodiment of an ophthalmic laser system,

FIG. 2 shows an alternative laser system according to the invention with a simple focusing hand unit for medical application and FIG

3 shows a further embodiment of a laser system according to the invention with a simple, exchangeable glass tip for the contact treatment of ophthalmic or other tissues.

1 shows an exemplary embodiment of an ophthalmic laser system 10 according to the invention. The system has a laser unit 12 and a hand unit 16, which are connected to one another by a cable 14 having an optical waveguide. Furthermore, an eye 100 to be treated is shown schematically in FIG.

The laser unit 12 is a femtosecond laser unit designed as a tabletop device and comprising a femtosecond fiber laser oscillator 18, an amplifier 20 and a pulse expander 22. The mentioned components of the laser unit can be built borrowed, as summarized in Figure 1, in a single housing or realized by two or more separate, connected via suitable optical waveguide units. The fiber laser oscillator 18 operates in a wavelength range of 1020 nm to 1070 nm. Alternatively, a fiber laser oscillator 5 for the wavelength range of 1500 nm to 1600 nm could be used. After amplifier 20, pulse energies between 10 nanjojoules and> 100 nanjojoules are available, typically 300 nanjojoules. The pulse length is 100 femtoseconds to 800 femtoseconds, typically 300 femtoseconds. The repetition frequency for the pulses is 0.5 MHz to 100 MHz, typically 5 MHz. The pulse expander 22 increases the pulse length to values between 1 picosecond and over 10 picoseconds.

Connected to the laser unit 12 is accommodated in a cable 14 passive transmission fiber, which is designed in the present embodiment as a so-called i5 LMA fiber ("LMA = Large Mode Area" / large mode field). The core diameter of such fibers is typically between 10 and 50 microns, the length of the transmission fiber may be between 0.5 m and 2 m. But there are also shorter or significantly longer versions conceivable. Alternatively, the transmission fiber could also be embodied as active fiber, that is to say that the fiber o itself acts as a gain medium for the laser radiation emitted by the laser unit 12. The transmission fiber is embedded in a cable for ease of handling which may include power, vacuum and / or data lines in addition to the optical waveguide. The cable 14 establishes a connection between the femtosecond laser unit 12 and the handpiece 16 designed as a treatment handpiece. The housing of the hand unit 16 has a handle 38 and a fiber input 24, via which the pulsed laser radiation generated by the femtosecond laser unit 12 enters the handpiece 16. There, the divergent light beam leaving the transmission fiber is collimated by means of a collimator lens 26 along a first optical axis A and directed onto a transmission grating 28. The transmission grating 28 compresses the laser pulses stretched in the femtosecond laser unit 12 by the pulse stretcher 22 to the pulse duration, which is suitable for the ophthalmological procedure, of typically 500 femtoseconds or shorter. The light beam leaving the transmission grating 28 is deflected by a dichroic reflection mirror 30. This serves as a beam splitter: He points to the wavelength of femtosecond pulses at a high reflectivity, while it is rich ^¬ highly transmissive for the visible areas of the spectrum. The light beam is aligned by the reflection mirror 30 on an electro-optical deflector 32. Electro-optic deflector 32, also referred to as a scanner, deflects the incoming beam of light as a function of the voltage applied to the deflector by up to ± 5 ° with a response time of approximately 1 microsecond. In this case, the electro-optical deflector 32 may comprise either an electro-optical crystal, which operates on the Kerr principle. Alternatively, an electro-optic holographic grating can also be used which can be produced by recording a volume phase hologram in a liquid crystal monomer mixture. With this holographic technology, switching times of 50-5000 microseconds can be achieved with an angular accuracy of ± 3 °. In both cases, the electro-optical deflector 32 is transmissive in a wavelength range of 400 nm to 1600 nm.

The deflected by the electro-optical deflector 32 pulsed light beam is focused via an F-theta lens 34 on the working plane 36, which is symbolized by a double arrow. By means of the F-theta objective 34, the laser beam focus is kept in the working plane 36 independently of the angle of incidence in the entire scanning field.

The handpiece 16 has two main optical axes A and B. The aforementioned first optical axis A is defined by the collimating lens 26 in interaction with the fiber input 24, the second is defined by the reflection mirror 30 together with the following components deflector 32 and F-theta. Lens 34 fixed. The F-theta objective 34 is in a preferred embodiment in FIG

Direction of the optical axis B slidably to allow a depth adjustment of the working plane 36 and thus a three-dimensional shape of the flap section.

Further, in the handpiece 16, a CCD camera 40 is housed. This is arranged along the optical axis B on the side of the reflection mirror 30, which faces away from the eye 100 to be treated. Due to the transmissivity of all optical elements along the optical axis B in the visible range, the CCD camera can be used to track the plane production by means of femtosecond laser pulses in real time and if necessary to control it. The housing of the handpiece 16 is provided with a spacer cone 44 which can be coupled with a suction ring 42 attached to the eye 100. The spacer cone 44 further comprises an applanation window 46, the function of which will be explained below. In addition, the human eye 100 to be treated is shown schematically in FIG. The vitreous body 110 and the dermis 120, which adjoins the cornea (cornea) 130 to be treated in the anterior eye region, are sketched. Furthermore, the lens 140 and opposite the lens are schematically indicated the exit of the optic nerve.

To produce a flap cut, the suction ring 42 is first placed on the cornea 130 of the eye 100, aligned and sucked. Subsequently, the handpiece 16 is connected via the spacer cone 44 with the suction ring 42, for example via a vacuum suction (not shown). In this case, the cornea 130 is pressed against the applanation window 46, as a result of which the cornea 130 receives a planar surface approximating the applanation window 46 in the contact region. Optionally, after the coupling, the adjustment of the depth of the cutting plane via an adjustment of the F-theta lens 34 along the optical axis B done. Thereafter, the flap is cut by means of the pulsed laser radiation generated by the femtosecond laser device 12 and conducted via the transmission fiber 14 to the handpiece 16. In this case, the laser beam is deflected by the electro-optical deflector 32 in the working plane 36 in a suitable manner to produce the desired cutting geometry. If appropriate, a three-dimensional cutting guide can also be realized by an interaction of the deflector 32 and the F-theta objective 34.

FIG. 2 shows an alternative embodiment of the present invention in the form of a compact femtosecond laser system 200 with a simple focusing handpiece 216 for medical use in ophthalmology or dermatology. The laser source in the form of a femtosecond laser unit 212 is constructed analogously to the embodiment shown in FIG. 1, ie it also comprises a laser oscillator 218 for generating femtosecond laser pulses, an amplifier 220 and a pulse stretcher 222. In contrast to that used in FIG Transmission fiber is used in the embodiment of Fig. 2, a so-called photonic crystal fiber 214 with a hollow core. This causes inter alia a temporal pulse compression of the pulses generated and stretched by the laser unit 212. This eliminates the need for lattice compression in the handpiece 216. The handpiece 216 becomes even more compact since pulse compression already occurs in the hollow core fiber 214, which also acts as a transmission fiber. Since the hollow core fiber leads the femtosecond pulse into a glass-free, empty space, the fiber is also compressed by pulses in the Femtosecond area not destroyed with high intensity. Accordingly, the handpiece 216 has in its housing only next to a collimator lens 226 a focusing lens 234, which is shown schematically in FIG. 2 by two lenses. The light beam emerging from the focusing lens is directed onto a tissue 202 to be treated. This may be, for example, a skin area or a tissue in the eye.

FIG. 3 shows a further embodiment of the invention in the form of a femtosecond laser system 300 with a simple, exchangeable glass tip for the contact treatment of ophthalmological and other tissue. The embodiment shown in FIG. 3 is similar to that of FIG. 2 in terms of laser source (laser unit 312 with laser oscillator 318, amplifier 320 and pulse stretcher 322) and transmission fiber 314 (photonic crystal fiber). In contrast to the embodiment shown in FIG 3, instead of the handpiece 216 provided with an imaging optical system, a treatment handpiece 316 equipped with a replaceable fiber tip 304. For example, this fiber tip 304 consists of quartz glass - other similar materials such as sapphire are also conceivable Its length is for example between 5 and 10 mm, the tip having a diameter of approximately 100 μm, and this fiber tip 304 acts as a light guiding element for the laser radiation of the laser unit 312 exiting the transmission fiber 314 and to the front end of the fiber tip 30 4 is to be performed. The shape of the tip end of the fiber tip 304 determines the focus diameter of the laser light on the tissue 302q to be treated. For reasons of sterilization, the fiber tip 304 is replaceable. This embodiment of the invention can be used for example for a glaucoma laser treatment, a resection of the trabecular tissue in the eye or a Korneakeratoplastik. In addition, the fiber tip 304 may be equipped with a temperature sensor, which reports any possible inadmissible heating of the treated tissue.

Claims

claims

5. A system for ophthalmology or dermatology, comprising a laser unit (12, 212, 312) for generating pulsed laser radiation, wherein the pulse length of the laser pulses is in the femtosecond range, a hand unit (16, 216, 316) for delivery by the laser unit lo (12, 212, 312) generated laser radiation, and a flexible optical waveguide (14, 214, 314) for relaying the laser radiation generated by the laser unit (12, 212, 312) to the hand unit (16, 216, 316).

i5 2. System according to claim 1, characterized in that the laser unit (12, 212, 312) comprises a fiber laser (18, 218, 318).

3. System according to claim 1 or 2, characterized in that laser unit (12, 212, 312) and hand unit (16, 216, 316) are interconnected solely by one or more flexible 0 cables, of which at least one of the flexible optical fiber ( 14, 214, 314).

4. System according to any one of the preceding claims, characterized in that the hand unit (16, 216, 316) in the context of mobility of the cable inde pendent of the laser unit (12, 212, 312) is positionable.

A system according to any one of the preceding claims, characterized in that the hand unit (16, 216, 316) has a coupling device (44) which mechanically connects to a human eye (100) or suction ring placed on top of the eye (100) (42) allows.

6. System according to any one of the preceding claims, characterized in that the laser unit (12, 212, 312) comprises a pulse extender (22, 222, 322) for the time extension of the laser pulses to pulse lengths greater than 1 picosecond.

7. System according to one of the preceding claims, characterized in that the flexible optical waveguide is a photonic transmission fiber (14) with a large mode field.

8. System according to one of claims 1 to 7, characterized in that at least a portion of the flexible optical waveguide (214, 314) causes a pulse compression of the laser unit (12, 212, 312) generated pulsed laser radiation.

9. System according to claim 9, characterized in that the flexible optical waveguide is a photonic hollow core fiber (214, 314).

10. System according to claim 1 to 7, characterized in that the hand unit (16, 216, 316) comprises compression means (28) for temporally compressing the pulses of the laser radiation.

11. System according to claim 11, characterized in that the compression means comprise an optical grating (28), preferably a transmission grating.

12. System according to any one of the preceding claims, characterized in that the hand unit (16, 216, 316) has an electro-optical scanner (32) for beam deflection

13. Hand unit according to claim 14, characterized in that the hand unit comprises a camera (40).

14. hand unit (16) for emitting by a laser unit (12) generated pulsed laser radiation, with a fiber input (24), via which the laser radiation generated by the laser unit (12) enters the hand unit (16), optical beam guidance means (26, 30, 34), and compression means (28) for temporal pulse compression of the fiber input (24 ) entering laser radiation, as well as alternatively or additionally to the compression means (28) with a scanner (32) for beam deflection of the laser radiation.

15. hand unit (12, 212, 312) for emitting pulsed laser radiation generated by a laser unit (12, 212, lo 312), wherein the laser radiation has pulse lengths in the femtosecond range, with a fiber input (24, 224, 324) via which the laser radiation generated by the laser unit (12, 212, 312) enters the hand unit (16, 216, 316) and i5 - optical beam guiding means (29, 30, 34, 226, 234, 304).