Patent Application
20220202614
The present application claims priority to and the benefit of Switzerland Patent Application 01672/20 filed Dec. 24, 2020, which is incorporated by reference in its entirety herein.
The present disclosure relates to an ophthalmological ultra-violet laser system for eye treatment. In particular, the present disclosure relates to an ophthalmological ultra-violet laser system for surgical treatment an eye using a pulsed laser beam.
Ultra-violet (UV) lasers for eye treatment are used in many different types of eye treatment, for example refractive surgery in which the cornea of the eye is ablated. By using a pulsed laser with an adjustable repetition rate and energy per pulse, it is possible to provide sufficient energy to ablate targeted tissue without causing excess heating in surrounding tissues. A well-known type of laser used for eye treatment is an excimer laser, which uses a combination of a noble gas and a reactive gas under high pressure and electrical stimulation. For eye treatment, excimer lasers using argon as the noble gas and fluoride as the reaction gas are often used, as the laser wavelength produced is 193 nm which has been found suitable for eye treatment. Among the disadvantages of excimer lasers are that they are often large and bulky and that the use of high pressure gasses presents numerous technical challenges.
Nd:YAG is a crystal that is used as a lasing medium for solid state lasers, typically emitting in the infra-red. Other varieties of YAG are known for their lasing properties, including Er:YAG and Yb:YAG, and many other varieties of YAG are in use in cathode ray tubes, LEDs, or temperature sensing devices.
The present disclosure proposes an ophthalmological ultra-violet laser system for eye treatment, which does not have at least some of the disadvantages of the prior art. Particularly, the present disclosure proposes an ophthalmological ultra-violet laser system for eye treatment which is compact and efficient and produces a more biologically suitable wavelength.
According to the present disclosure, advantageous embodiments are achieved by the features of the independent claims. Moreover, further advantageous embodiments emerge from the dependent claims and the description.
An ophthalmological ultra-violet (UV) laser system for eye treatment is proposed. The ophthalmological UV laser system comprises laser source including a Ce:YAG (cerium doped yttrium aluminum garnet) gain medium configured to generate a pulsed primary laser beam, as well as a frequency converter arranged downstream from the laser source comprising one or more non-linear optical crystals configured to multiply the frequency of the primary laser beam to generate a pulsed UV laser beam.
In an embodiment, the laser source is a solid-state laser source including the Ce:YAG gain medium configured to generate the pulsed primary laser beam.
In an embodiment, the laser source is an optical fiber laser source including a Ce:YAG gain medium configured to generate the pulsed primary laser beam.
In an embodiment, the ophthalmological UV laser system further comprises a positioning module arranged downstream of the frequency converter, which frequency converter is configured to position the UV laser beam such that the UV laser beam enters an eye of a patient.
In an embodiment, the positioning module comprises a fiber-optic element configured to guide the UV laser beam directly into the eye.
In an embodiment, the positioning module is configured to position the UV laser beam such that the UV laser beam is focused onto tissue of the eye.
In an embodiment, the frequency converter arranged downstream from the laser source comprises a non-linear optical crystal configured to double the frequency of the primary laser beam.
In an embodiment, the frequency converter arranged downstream from the laser source comprises two non-linear optical crystals configured to triple the frequency of the primary laser beam.
In an embodiment, the Ce:YAG crystal is configured such that the primary laser beam has a wavelength of one or more of: 600 nm to 660 nm, 615 nm to 645 nm, 630 nm to 639 nm, or 614 nm to 618 nm.
In an embodiment, the laser source is configured such that the pulsed UV laser beam has a pulse energy of 0.5 mJ to 2.0 mJ.
In an embodiment, the laser source is configured such that the pulse UV laser beam has a power of 0.5 W to 2 W.
In an embodiment, the laser source is configured such that the pulsed UV laser beam, in particular a pulse energy and a wavelength of the pulsed UV laser beam, generated by the frequency converter results in tissue of a patient being ablated by less than 2 μm, preferably 0.5 μm to 1 μm, per pulse of the UV laser beam.
In an embodiment, the laser source comprises an active Q-switch configured to periodically modulate a Q-factor of the laser source such that the primary laser beam has a pulse repetition rate of one or more of: 10 Hz to 1000 Hz or 250 Hz to 1000 Hz.
In an embodiment, the laser source includes a plurality of blue laser diodes arranged around the Ce:YAG crystal as laser pumps.
In an embodiment, the ophthalmological UV laser system further comprises a beam shaper arranged downstream from the frequency converter comprising one or more optical elements and configured to shape the UV laser beam such that the shaped UV laser beam has a fluence of one or more of: 50 mJ/cm2 to 400 mJ/cm2 or 150 mJ/cm2 to 250 mJ/cm2 on the tissue of the patient.
In an embodiment, the ophthalmological UV laser system further comprises a scanner arranged downstream of the frequency converter configured to direct the UV laser beam onto a plurality of positions on a tissue of a patient according to a pre-determined pattern.
In an embodiment, the ophthalmological UV laser system further comprises a wavelength selector arranged downstream of the frequency converter configured to allow a particular wavelength range of the UV laser beam to pass while redirecting a remainder of the UV laser beam onto a beam dump.
In an embodiment, the ophthalmological UV laser system further comprises a pulse diagnostics module arranged downstream of the frequency converter configured to measure a power of the UV laser beam.
The present disclosure will be explained in more detail, by way of example, with reference to the drawings in which:
In
Depending on the embodiment, the laser source 2 is configured to generate the primary laser beam 20 such that it has a wavelength of one or more of: 600 nm to 660 nm, 615 nm to 645 nm, 630 nm to 639 nm, or 614 nm to 618 nm. The primary laser beam 20 is a pulsed laser beam. The laser source 2 is configured to generate the primary laser beam with a pulse repetition rate of one or more of: 10 Hz to 1000 Hz, or 250 Hz to 1000 Hz. A frequency converter 3 arranged downstream from the laser source 2 increases the frequency of the primary laser beam 20. The frequency converter 3 comprises one or more non-linear optical crystals 31 which multiply the frequency of the primary laser beam 20 by a factor of two or three, depending on the embodiment, to generate a UV laser beam 30, that is, a laser beam 30 with a wavelength in the ultra-violet wavelength range of approximately 100 nm to 400 nm. The UV laser beam 30 has, when the primary laser beam 20 is tripled in frequency, a wavelength of one or more of: 200 nm to 220 nm, 205 nm to 215 nm, or 210 nm to 213 nm. These wavelength ranges have been shown to be particularly advantageous for ablation of collagen tissue. Further, due UV light absorption in humid air which increases at decreasing wavelengths, the wavelength ranges indicated above more efficiently transfer energy through air than, for example, an excimer laser at 193 nm.
The UV laser beam 30 has, when the primary laser beam 20 is doubled in frequency, a range of one or more of: 300 nm to 330 nm, 307 nm to 322 nm, 315 nm to 319 nm, or 307 nm to 309 nm. The UV laser beam 30 is also pulsed and, depending on the embodiment, has the same or a different repetition rate as the primary laser beam 20 which is, depending on the embodiment, 10 Hz to 1000 Hz or 250 Hz to 1000 Hz. The ophthalmological UV laser system 1, in particular the laser source 2 and the frequency converter 3, are configured to generate a UV laser beam 30 of a particular wavelength or wavelength range, depending on the type of eye treatment for which the ophthalmological UV laser system 1 is designed for. The laser source 2 described above is advantageous because it is compact and efficient. It does not occupy much space in an ophthalmological UV laser system 1 in comparison with state of the art systems, in particular because it does not require the use of high temperature and pressure gasses, as is for example required with known excimer lasers. Further, the laser source 2 does not require as much electrical power to run, and also runs more quietly which is a sought-after characteristic.
The ophthalmological UV laser system 1 is particularly flexible in its configuration and, depending on the embodiment, is configured produce one or more of a wide range of wavelengths of the UV laser beam 30, a wide range of pulse repetition rates, pulse durations, and pulse energies. Good results are achieved when the laser source 2 is configured such that the pulsed UV laser beam 30, in particular a pulse energy and a wavelength of the pulsed UV laser beam 30, generated by the frequency converter 3 results in tissue of a patient being ablated by less than 2 μm, preferably 0.5 μm to 1 μm, per pulse of the UV laser beam 30. This results in a treatment of the eye which is both precise because tissue is ablated only on the order of one μm per pulse, and fast, such that a single eye undergoing refractive surgery can usually be treated in less than one minute. Such an ablation depth per pulse is achieved, in an embodiment where the ophthalmological UV laser system 1 is configured such that the pulsed UV laser beam 30 has a pulse energy of 0.5 mJ to 2.0 mJ. This energy range is advantageous as it is used to ablate eye tissue of a patient quickly while also not resulting in excess heat being deposited in the tissue around the ablated tissue. Such an ablation depth per pulse is also achieved in an embodiment where the ophthalmological UV laser system 1, in particular the laser source 2, is configured such that the UV laser beam 30 has a power of 0.5 W to 2 W.
Below, in relation to
In an embodiment, the laser diodes are blue laser diodes 23 arranged on the side of the Ce:YAG gain medium 21 as Ce:YAG absorbs blue light particularly efficiently. Preferably, the blue laser diodes 23 are approximately evenly distributed around the Ce:YAG gain medium 21. A particular homogeneous pumping of the Ce:YAG is achieved with an odd number of blue laser diodes 23, in particular 3, 5, or 7, evenly distributed around the Ce:YAG gain medium 21. The laser source 2 further comprises a pulse generating element 22, configured to generate a primary laser beam 20 which has a pulse repetition rate of one or more of: 10 Hz to 1000 Hz or 250 Hz to 1000 Hz. In an example, the pulse generating element comprises an active Q-switch which is configured to periodically modulate a Q-factor of the solid-state laser source (2), in particular to modulate the Q-factor of the solid-state laser source 2. In another example, the pulse generating element is an acousto-optic modulator (AOM), a saturable absorber, or a Chopper. The laser source additionally has a rear cavity mirror 25 and an out-coupling mirror 26 arranged to form a laser resonator together with the Ce:YAG gain medium 21. In particular, the rear cavity mirror 25 and the out-coupling mirror 26 are arranged in a beam path of the primary laser beam 20, the rear cavity mirror 25 reflecting the entire primary laser beam 20 and the out-coupling mirror 26 reflecting a part of the primary laser beam 20 back into the laser resonator and coupling another part of the primary laser beam 20 out of the laser resonator. A wavelength tuner 24 is arranged in the laser source 20 either between the Ce:YAG gain medium 21 and the rear cavity mirror 25 or between the Ce:YAG gain medium 21 and the out-coupling mirror 26. The wavelength tuner 24 filters primary laser beam 20, allowing only a limited range (band) of wavelengths to pass through. The wavelength tuner 24 is used to configure the laser source 2 to emit one or more of the wavelength ranges described above. In an embodiment, the wavelength tuner 24 includes a bandpass filter, Etalon, and/or a dichroic mirror.
The optical fiber ring resonator 218, 218.1, 218.2 comprises, depending on the embodiment, further modules and/or elements. In an embodiment, the optical fiber ring resonator 218, 218.1, 218.2 comprises one or more polarization controllers 211 arranged as indicated in the Figs, in particular arranged between the optical isolator 215 and the out-coupling element 213, and/or between the out-coupling element 213 and the pump and signal combiner 214. The polarization controllers 211 are configured to control a polarization orientation and/or a shape of the primary laser beam 20. In
The skilled person knows that one or more of the above modules, components, or regions of the laser source 2 described above can be reordered, re-arranged, or omitted without deviating from the scope of the disclosure.
Depending on the embodiment, the primary laser beam 20 travels through free space (i.e. air or a vacuum), and/or through an optical medium, such as an optical fiber, between the modules and/or elements.
The ophthalmological UV laser system 1 comprises a laser system controller (not shown) which is configured to control the ophthalmological UV laser system 1. The laser system controller is configured to ensure the safe and reliable operation of the ophthalmological UV laser system 1. The laser system controller is connected to the laser source 2, as well as to at least some further modules and/or elements of the ophthalmological UV laser system 1. The laser system controller is configured to receive input commands from an operator of the ophthalmological UV laser system 1, to receive status data regarding a current status of the ophthalmological UV laser system 1, including parameters of the primary laser beam 20 and/or the UV laser beam 30, and to send commands to the laser source 2 and one or more other modules and/or elements of the ophthalmological UV laser system 1. In an embodiment, the laser system controller comprises a processor configured to execute program instructions.
In an embodiment, the ophthalmological UV laser system 1 comprises an optical isolator 215 arranged downstream (i.e. in a direction of propagation of the primary laser beam 20) of the laser source 2. Depending on a configuration of the ophthalmological UV laser system 1, the optical isolator 215 is not required. The optical isolator 215 is configured such that the primary laser beam 20, or the UV laser beam 30 generated further downstream, cannot travel upstream through the optical isolator 215. Downstream from the optical isolator 215, an optional laser amplifier 216 is arranged. The laser amplifier 216 comprises a further Ce:YAG gain medium 21 which is pumped from further blue laser diodes 23 (not shown). Further downstream, or also optionally upstream of the laser amplifier 216, a pulse picker 217 is arranged. The pulse picker 217 is configured to pick a single or multiple pulses from the primary laser beam 20, in particular from a pulse train of the primary laser beam 20 generated by the laser source 2. The pulse picker 217 reduces the pulse repetition rate of the primary laser beam 20. The pulse picker 217 includes, in an example, a Pockels cell configured for time-dependent modulation of an intensity of the primary laser beam 20 such that a single or multiple pulses are allowed to pass through the pulse picker 217 while other pulses are prevented from passing through the pulse picker 217. The ophthalmological device 1 is designed such that the pulse generating element 22 of the laser source 2 and/or the pulse picker 217 generate a pulsed primary laser beam 20 with a pulse repetition rate of one or more of: 10 Hz to 1000 Hz or 250 Hz to 1000 Hz.
A frequency converter 3 is arranged downstream from the laser source 2, in particular downstream from the pulse picker 217, and configured to double or triple the frequency of the primary laser beam 20 to generate the UV laser beam 30. The frequency converter 3 comprises one or more non-linear crystals 31. In an embodiment, for generating the UV laser beam 30 by doubling the frequency of the primary laser beam 20, a single non-linear crystal 31 which generates a second-harmonic of incoming light may be used. In another embodiment, for generating the UV laser beam 30 by tripling the frequency of the primary laser beam 20, a first non-linear crystal 31 is used which generates a second-harmonic may be used followed by a second non-linear crystal 31 which generates a sum of the primary laser beam 20 and the second-harmonic to generate the UV laser beam 30 with a tripled frequency of the primary laser beam 20. Examples of such non-linear crystals include lithium triborate (LBO) and beta barium borate (BBO) and are well-known in the art.
A wavelength selector 6 is arranged downstream from the frequency converter 3. The wavelength selector 6 is configured to select a narrow range of wavelengths of the UV laser beam 30 such that only a portion of the UV laser beam 30 corresponding to the narrow range passes onward through the wavelength selector 6, a remaining portion of the UV laser beam 30 being redirected in the wavelength selector 6 onto a beam dump 61 configured to absorb and dissipate the remaining portion of the UV laser beam 30. The wavelength selector 6 includes, depending on the embodiment, a dichroic mirror, and/or a FBG in combination with the optical fiber ring resonator 218 described above.
A pulse diagnostics module 7 is arranged downstream from the frequency converter 3. In an embodiment, the pulse diagnostics module 7 is arranged directly downstream from the wavelength selector 6. The pulse diagnostics module 7 is configured to measure a power of the UV laser beam 30. The pulse diagnostics module 7 ensures the safe operation of the ophthalmological UV laser system 1. The ophthalmological UV laser system 1, in particular the laser system controller, is configured to shut off the UV laser beam 30 if a property of UV laser beam 30 is not within specification, for example by closing a shutter 10 and/or powering down the laser source 2. The shutter 10 is arranged downstream of the frequency converter 3, for example downstream of the diagnostics module 7, as shown in
The beam deflection module 5 is arranged downstream of the frequency converter 3, in particular downstream of the shutter 10 and is configured to direct the UV laser beam 30 onto a plurality of positions in or on the eye according to the pre-determined pattern. The pattern is, in an embodiment, two-dimensional. In an embodiment, the pattern is three-dimensional. The beam deflection module 5 includes, depending on the embodiment, tilting optics and/or scanning optics. For example, a rotating mirror scanner, a polygon scanner, a galvanometer scanner, an acousto-optic scanner, and/or an electro-optic scanner is used depending on the embodiment.
Depending on the embodiment, a beam shaper 4 is arranged downstream from the frequency converter 3. The beam shaper 4 comprises one or more optical elements and is configured to shape the UV laser beam 30 such that the shaped UV laser beam 40 has a fluence of one or more of: 50 mJ/cm2 to 400 mJ/cm2 or 150 mJ/cm2 to 250 mJ/cm2 on the tissue of the patient. The optical elements comprise, for example, a focusing optic, such as an optical lens, and/or mirrors (flat and/or curved). Depending on the embodiment, the beam shaper 4 is configured to produce a Gaussian shaped UV laser beam 40, Supergaussian shaped UV laser beam 40, and/or a tophat shaped UV laser beam 40.
A positioning module 8 is arranged downstream from the frequency converter 3. In an embodiment, the positioning module 8 is configured to position the UV laser beam 30 such that the UV laser beam 30 enters the eye 9 of the patient. Depending on the embodiment, the positioning module comprises a patient interface which fixes a relative position of the eye 9 to the ophthalmological UV laser system or alternatively an eye tracking module that sends position information of the eye to the scan module in order to correct for eye movement 1 such that the UV laser beam 30 is always positioned correctly during treatment.
In an embodiment shown for example in
| Number | Date | Country | Kind |
|---|---|---|---|
| 01672/20 | Dec 2020 | CH | national |
