WO2014125167A1

WO2014125167A1 - System for laser treatment of an eye and method for preparation of the system

Info

Publication number: WO2014125167A1
Application number: PCT/FI2014/050101
Authority: WO
Inventors: Esa Viherkoski
Original assignee: Valon Lasers Oy
Priority date: 2013-02-12
Filing date: 2014-02-11
Publication date: 2014-08-21
Also published as: FI20135123L; EP2956097A1

Abstract

The system of the invention for laser treatment of an eye comprises a laser source (1) that produces a laser beam of an adjustable power. This laser beam is used as an aiming beam when it is adjusted to a first power and as a treatment beam when it is adjusted to a second power. Furthermore, the system comprises means for delivering the beams on a target area of the eye, and a fiber (4) that transports the laser beams to said means. An attenuator (6) can be used to attenuate the aiming beam to a desired power if the first power used is too high to directly be used as an aiming beam. The method of the invention prepares the laser treatment system for laser treatment and comprises the steps of producing a laser beam to be used as an aiming beam, attenuating the laser beam by placing an attenuator (6)in the beam path, and transporting the beam to means for delivering the beam on a target area of the eye through an optical fiber (4).

Description

SYSTEM FOR LASER TREATMENT OF AN EYE AND METHOD FOR PREPARATION OF THE SYSTEM

FIELD OF THE INVENTION

The invention relates to a system for laser treatment of an eye and a method for preparation of a system for laser treatment of an eye.

BACKGROUND

Laser photocoagulation is done to reduce the risk of vision loss caused by diabetic retinopathy. It is most often used to stabilize vision and prevent future vision loss rather than to improve vision loss that has already occurred. However, sometimes focal photocoagulation for macular edema caused by nonproliferative retinopathy can help restore lost vision. Diabetic retinopathy is a disease of the retina, the thin tissue that lines the back of the eye. The condition is a complication of diabetes; it is related to high blood sugar levels, which interfere with oxygen delivery to the cells in the retina. Nerve cells in the retina detect light entering the eye and send signals to the brain, which interprets what the eye sees. Damage to the retina from a lack of oxygen to its nerve cells may not be noticed right away. If the disease gets worse, though, it can cause gradual vision loss. Both eyes are usually affected by the disease.

The early form of the disease, called nonproliferative diabetic retinopathy, develops when diabetes weakens the tiny blood vessels that supply the retina, causing swelling or bleeding in the retina. Changes caused by nonproliferative retinopathy may not affect vision unless fluid and protein from the damaged blood vessels cause swelling in the center of the retina (macula). This condition, called macular edema, can cause severely blurred or distorted central vision. Proliferative diabetic retinopathy is the advanced form of diabetic retinopathy. The main feature of proliferative retinopathy is the growth of fragile new blood vessels on the surface of the retina. These blood vessels may break easily, bleeding into the middle of the eye and clouding vision. They also form scar tissue that can pull on the retina, causing the retina to detach from the wall of the eye (retinal detachment).

People who have diabetes need regular eye exams so that the early stages of diabetic retinopathy can be detected and, in some cases, treated. Blood sugar levels and blood pressure should also be monitored and controlled as much as possible to prevent blood vessel damage.

Laser photocoagulation uses the heat from a laser beam to seal or destroy abnormal, leaking blood vessels in the retina.

One of two approaches may be used when treating diabetic retinopathy. Focal photocoagulation treatment is used to seal specific leaking blood vessels in a small area of the retina, usually near the macula. The ophthalmologist identifies individual blood vessels for treatment and makes a limited number of laser burns to seal them off.

Scatter (pan-retinal) photocoagulation treatment is used to slow the growth of new abnormal blood vessels that have developed over a wide area of the retina. The ophthalmologist may make hundreds of laser burns on the retina to stop the blood vessels from growing. The person may need two or more treatment sessions.

Photocoagulation has been shown to be effective in the treatment of proliferative diabetic retinopathy and advanced forms of nonproliferative diabetic retinopathy associated with macular edema in large, prospective, multi-center, randomized trials performed by The National Eye Institute studies of the surgical treatment of diabetic retinopathy. These studies provide important information that strongly influences the current treatment of diabetic retinopathy. In addition to proliferative and non-proliferative diabetic retinopathy, other treatments and pathologies that may benefit from laser photocoagulation include Choroidal neovascularization, Branch and central retinal vein occlusion, Age-related macular degeneration, Lattice degeneration, Retinal tears and detachments, Iridotomy, Iridectomy, Trabeculoplasty in angle closure and open angle glaucoma.

Retinal photocoagulation is typically performed point-by-point, where each individual dose is positioned and delivered by a physician.

Depending on the disease, various laser types are used. Laser wavelengths used can e.g. be green, yellow, red or infrared. Green (532nm) laser is generally used for treating retinal diseases. ND-YAG (Neodymium-Doped Yttrium Aluminum Garnet; Nd:Y₃AI₅0i2) is a crystal that is used as a lasing medium for solid-state lasers and are used for removing posterior capsule after cataract surgery and for treating Glaucoma cases. The other frequency lasers can e.g. be used in various therapies, like Trans Pupillary Thermotherapy, and Photo Dynamic Therapy. Typically in laser treatment of retina, a red or reddish aiming beam is used together with a green treatment beam. The red aiming beam and the green treatment beam are produced in separate laser sources and combined by optics into same beam path.

A red aiming beam on the retina, however, creates a visibility problem. As the retina is reddish in color, the aiming beam is difficult to distinguish from it and it scatters on the retina making it difficult for a doctor to align the beam to correct location.

US patent 7,766,903 discloses a solution for a patterned laser treatment of the retina. The solution uses an alignment beam from an alignment source to show the target locations for the real treatment beam. The treatment laser beams projected from a treatment source must be accurately aligned since otherwise they will not hit the right place to be treated. By triggering a laser system, doses of laser energy are then automatically provided to at least two locations coincident with the alignment beam spots. A scanner can be used to sequentially move an alignment beam from spot to spot on the retina and to move a treatment laser beam from location to location on the retina.

The solution requires a separate alignment source and does not provide a perfect alignment for aligning the treatment beam with the alignment beam. The object of the invention is to find new ways for aiming the target location making the treatment more accurate and easy to perform for the ophthalmologist.

SUMMARY OF THE INVENTION

The invention is mainly characterised by the main claims and the preferable embodiments are presented in the sub claims.

Thus, the system of the invention for laser treatment of an eye comprises a laser source that produces a laser beam of an adjustable power. This laser beam is used as an aiming beam when it is adjusted to a first power and as a treatment beam when it is adjusted to a second power. Furthermore, the system comprises means for delivering the beams on a target area of the eye, and a fiber that transports the laser beams to said means.

An attenuator can be used to attenuate the aiming beam to a desired power if the first power used is too high to directly be used as an aiming beam.

The method of the invention prepares the laser treatment system for laser treatment and comprising the steps of producing a laser beam to be used as an aiming beam, attenuating the laser beam by placing an attenuator in the beam path, and transporting the beam to means for delivering the beam on a target area of the eye through an optical fiber.

Before the real treatment, the laser light produced with the laser source is used as an aiming beam, the power of which is allowed to be 390 microwatt, i.e. 0,39 milliwatt at the most of medical reasons. Today, there are commercially available low power laser sources that are stable within the designed low power range, whereas the commercially available high power laser sources do not always work reliably within the low power range if they are designed only for the high power. Traditional laser treatment systems use two laser sources, one for the aiming beam and another for the treatment beam.

In the invention, it has, however, found that, it indeed is possible to use a single laser source for producing both the aiming beam and the treatment beam a) by using a laser source constructed to work over the entire power range needed. Then it can be used for emitting an aiming beam with a stable and low power and a treatment beam with a high and stable power, b) by using a high power laser source for treatments that do not require an exact aligning.

Then it can be used for emitting an aiming beam with an approximate low power and a treatment beam with a high and stable power, or c) by using a high power laser source having an attenuator.

Then it can be used for emitting an aiming beam with a high and stable power but by attenuating it to a desired low and a treatment beam with a high and stable power.

In one embodiment of alternative c), the beam attenuator can be arranged to be movable into two functional positions. One of the functional positions is a position, wherein the attenuator is in the laser beam path attenuating the beam with a desired fixed or adjustable factor and the other one being a position, wherein it has been removed out of the laser beam path for the treatment.

In another embodiment, the beam attenuator can consist of two or optionally three different functional parts or places, one of which is a hole providing the function of being translucent with no attenuation another one which is a filter with an attenuating factor, and an optional third part being compact and opaque in which no light can go through. The last mentioned third function can e.g. work as a security mechanism to ensure that any transmittance is prevented. In these preferable embodiments, a higher power can be used also for the aiming beam, such as e.g. 50-100 mW.

The invention can be used for treating different parts of the eye to perform for example panretinal photocoagulation, iridotomy or trabeculoplasty. Thus, even if the invention is in the first hand intended for retina treatment, which is presented in more detail in the detailed description, the invention can also be used for other treatments.

It is an advantage that the laser system of the invention can be used for treatment of the eye, especially the retina, at a single location or multiple locations by using only one laser source. Thus, the present invention provides a system that creates a visual alignment pattern on retina without a separate alignment source since an alignment pattern can be displayed by the laser source by using a beam attenuator.

This also solves the problem of the visibility with red aiming beams on the retina. As retina is reddish in color, a green aiming beam has better contrast and scatters less on the retina providing better visibility of the aiming beam making it easier for the doctor to align the beam to correct location. Better contrast also permits using lower aiming beam power making it safer for the patient. Additionally, only one laser source is required in a system described in this invention.

The laser system of the invention enables fast and effective treatment of retinal diseases. Connected to microscopes, it offers variable functions for transpupillary laser photocoagulation. Aside from standard single shot photocoagulation, varied laser scanning patterns can be produced enabling a faster and high-quality treatment.

In the following, the invention is illustrated more in detail by means of figures showing a preferable embodiment, to which the invention is not restricted.

FIGURES

Figure 1 is a schematic view of a laser treatment system, wherein the invention is implemented Figure 2 is a schematic and more detailed view of the inventive part of the laser system of the invention in the alignment mode

Figure 3 is a schematic and more detailed view of the inventive part of the laser system of the invention in the treatment mode

DETAILED DESCRIPTION

Figure 1 is a schematic view of a laser treatment system, wherein the invention is implemented.

The complete laser treatment system can consist of a trolley with a computer 7, a laser module 9 (with a laser source, a beam attenuator and a fiber coupling module), and a fiber 4, a slit lamp source 9c, a slit lamp mirror 9b, a slit lamp adapter 5, optics 9a to transport the laser beam and slit lamp light, and electronics of the device (not shown). The trolley can of practical reasons be on wheels and be easily movable.

Reference number 10 represents the eye of a patient to be treated. The light from the slit lamp 9c and the laser beam from the laser source 1 (which is inside the module 9 and presented in figures 2 and 3) are combined and reflected on the eye 10 through the slit lamp adapter 5 and the optics 9a and further via the mirror 9b that turns the combined beam 90 degrees against the eye 10.

The computer 7 is preferably a Personal Computer (PC) connected to a monitor with a touch screen and is fixed to the trolley or to a slit lamp table. The computer 7 runs suitable software for the laser treatment and is used through a graphical user interface enabling the person that performs the treatment (such as a physician, ophthalmologist or doctor) to adjust suitable settings for the treatment.

The separate interdependent variables available for setting are the beam size, power, shape and size of the pattern or figure formed on the retina by single spots of laser light, the duration and intensity of the laser pulse, the mutual distance of the spots and the intensity of the aiming beam. The program with which the settings can be adjusted in the system also produces a preview of the spot pattern to visualize the area to be coagulated or treated in the target tissue.

The functions and connections between the relevant parts of the inventive system are described in the following sections describing figures 2 and 3.

Figure 2 presents the laser system of the invention in the aiming (or alignment) mode. The components shown in figure 2 are the laser source 1 (situated within the laser module 9 as presented in figure 1 ) emitting a laser beam 2, a fiber coupling lens 3, the fiber 4 and the slit lamp adapter 5 as well as a beam attenuator 6 situated in figure 2 in the path of the laser beam 2 .

In the invention described in the embodiments of figures 2 and 3, the beam attenuator 6 can be moved into two functional positions. One of them is a position, wherein the attenuator 6 is in the laser beam path attenuating the beam with a desired or adjustable factor and the other one being a position described in figure 3, wherein it has been removed out of the laser beam path for the treatment.

The laser module 9 comprises a laser source 1 that produces a laser beam 2.

The laser wavelengths used can e.g. be green, yellow, red or infrared but the invention is especially signed for green laser light of e.g. 532 nm, which is successfully used for treating retinal diseases. Another good alternative, especially useful for the invention and for treatment of retinal diseases, is a laser light of yellow wavelengths in the range of 560-590 nm. A traditional red wavelength can be used as well. The wavelength chosen partly depends on the area of the eye to be treated and on which wavelength a given available laser source is able to produce.

The laser technology that can be used involves e.g. Diode-Pumped Solid-State (DPSS) lasers, which are solid-state lasers made by pumping a solid gain medium, for example, a ruby, a neodymium-doped YAG (Neodymium-Doped Yttrium Aluminum Garnet; Nd:Y₃AI₅Oi₂) crystal with a laser diode or a neodymium-doped YVO (Neodymium- Doped Yttrium Orthovanadate; Nd:YVO₄ ) crystal with a laser diode. An example of another laser technology that can be used are the Optically Pumped Semiconductor Lasers (OPSL), which use a lll-V semiconductor chip as the gain media, and another laser (often another diode laser) as the pump source. Further examples includes the Vertical-Cavity Surface-Emitting- Laser (VCSEL), which is a type of semiconductor laser diode with laser beam emission perpendicular from the top surface, contrary to conventional edge-emitting semiconductor lasers (also in-plane lasers) which emit from surfaces formed by cleaving the individual chip out of a wafer and the Vertical-External- Cavity Surface-Emitting-Laser (VECSEL) is a small semiconductor laser similar to a vertical-cavity surface-emitting laser (VCSEL) to be used within the green, yellow, red or short Infra Red (IR) range.

Before the real treatment, the laser light produced with the laser source is used as an aiming beam, the power of which is allowed to be 390 microwatt, i.e. 0,39 milliwatt at the most, which is a level that is considered safe for the eye. Said level below 390 μ\Λ is defined in the laser standards. In the embodiment of figure 2 , the power of the production itself of the aiming beam is e.g. within the range of 50-100 mW. This beam can not directly be used as the final aiming beam and is therefore attenuated with a filter with a factor of e.g. 100 or 200 (depending on losses in the optical components used) so that the desired power of the aiming beam could be received. Contrary to an ideal system, there are always losses in a real system. The fiber and the optics are not ideal components and in reality they too attenuate the laser power. Therefore, in practice, the laser source has to be set to slightly higher power to compensate for the losses in the optics and fiber or the fact can be taken into consideration in determining the attenuating factor.

Thus, the aiming beam is aligned and reflected in the form of a spot or a pattern of spots on the patient's retina by placing a beam attenuator 6 into the beam path of the laser beam produced with the laser source 1 for attenuating the beam and in order to show the target locations to be treated. The power of the aiming beam is also partly determined by the size of the spot(s). The bigger spot(s) used, the less power is needed for the aiming beam. The beam attenuator 6 is a filter that in the invention can be realized in different ways.

It can be a Neutral Density (ND) filter, which is an optical filter that reduces or modifies intensity of all (visible) wavelengths or colors of light equally. It can be a colorless (clear) or a grey filter. Other optical filters that can be used selectively transmit light in a particular range of wavelengths, that is, colours, while blocking the remainder. They can usually pass long wavelengths only (longpass), short wavelengths only (shortpass), or a band of wavelengths, blocking both longer and shorter wavelengths (bandpass). The passband may be narrower or wider; the transition or cutoff between maximal and minimal transmission can be sharp or gradual. There are also usable filters with more complex transmission characteristics.

An interference filter or dichroic filter is an optical filter that reflects one or more spectral bands or lines and transmits others, while maintaining a nearly zero coefficient of absorption for all wavelengths of interest. An interference filter may be high-pass, low- pass, bandpass, or band-rejection.

An interference filter consists of multiple thin layers of dielectric material having different refractive indices. There also may be metallic layers. In its broadest meaning, interference filters comprise also etalons that could be implemented as tunable interference filters. Interference filters are wavelength-selective by virtue of the interference effects that take place between the incident and reflected waves at the thin- film boundaries.

A dielectric filter filters only a given wavelength area in a very narrow area. A dielectric filter is of glass coated with a dielectric layer consisting of very thin layers of different materials, such as magnesium fluoride or calcium fluoride. By constructing different combinations of these, a wide variety of filters can be achieved.

The beam attenuator 6 can be a filter that attenuates the laser beam energy by a predefined fixed factor or it can be an adjustable filter. The desired attenuating factor is achieved by selecting type(s), material(s) and/or thickness of the filter or the filter combination to be used as attenuator.

An adjustable filter can for example be a wave plate or a polarizing filter that is used to adjust the beam power (or energy). Polarized laser light can be attenuated using a polarizing filter and the attenuation can be adjusted by rotating the polarizing filter.

Furthermore, the beam attenuator 6 can comprise one or more attenuating elements providing one or more selectable attenuation factor (or value) by varying the positions of the individual elements.

A waveplate or retarder is an optical device that alters the polarization state of a light wave travelling through it. Two common types of waveplates are the half-wave plate, which shifts the polarization direction of linearly polarized light, and the quarter-wave plate, which converts linearly polarized light into circularly polarized light and vice versa.

Waveplates are constructed out of a birefringent material (such as quartz or mica), for which the index of refraction is different for different orientations of light passing through it. The behavior of a waveplate (that is, whether it is a half-wave plate, a quarter-wave plate, etc.) depends on the thickness of the crystal, the wavelength of light, and the variation of the index of refraction. By appropriate choice of the relationship between these parameters, it is possible to introduce a controlled phase shift between the two polarization components of a light wave, thereby altering its polarization. There are therefore endless possibilites in the invention to produce an optimum aiming beam for particular treatments.

There is usually a foot switch (not shown) connected to the laser module 9 with which the turning on and off of the laser source can be controlled. The foot switch or some other switch used by the doctor starts the treatment process but does not directly move the filter itself. Instead, the information of the start goes through a processor that controls the movement of the filter. Mechanically, the filter is moved by e.g. a Direct Current (DC) motor, step motor, a linear solenoid, a rotary solenoid, a piezo motor etc. There is also a sensor identifying the position of the filter in order to ensure a correct position of the filter before starting the process.

An optical fiber 4 transmits the laser beam from the laser source 1 to a slit lamp adapter 5. E.g. a 532 nm laser beam produced by the laser source 1 installed in the module 9 can be transmitted to a Slit Lamp Adapter, SLA, 5 by an optical fiber 4.

As the diameter of the optical fiber 4 can be very small such as e.g. 50 or 100 μιτι, the laser beam has to be focused so that it would enter the optical fiber 4. A fiber coupling lens 3 situated in the laser beam path between the laser source and the fiber focuses the laser beam into the entrance end of the optical fiber 4. The laser beam has to enter the optical fiber in an angle small enough, otherwise the fiber can not take the beam in it. Optical fibers have a numerical aperture defining the maximum angle in which it can take in a beam. The angle depends on the material of the fiber 4 and its refractive index.

The other end of the fiber 4 is connected to a slit lamp adapter 5 being a component, by which the laser beam coming out from the optical fiber 4 is collimated and lead through a laser aperture in the adapter 5 via scanner mirrors and possible other optics to the same optical axle with the light from a slit lamp 9a that also has been lead to the slit lamp 9a adapter 5. The slit lamp 9a is an instrument consisting of a high-intensity light source that can be focused to shine light into the eye through an aperture integrated with the slit lamp for examination of the eye. The size of the slit lamp aperture can be adjusted to produce a rounded light spot or a trace of desired size.

Various types of slit lamps can be used in the system. Several different models of slit lamps exist in the market. They can have different optics and the slit lamp adapter optics has to be adjusted to match the optics of the slit lamp.

The slit lamp adapter 5 can be integrated with compatible microscopes. Foreseen with computer controllable scanners it produces a variety of different predefined spot patterns to suit several treatment applications. The scanners deflect the laser beam delivered from the laser module 9 by an optical fiber. Available Patterns are .e.g. Square, Circle, Line, Sector, Arc, and Spot forms. The pattern is chosen dependency on the form and size of the area to be treated. The slit lamp adapter (SLA) 5 also allows the adjustment of the spot size since the system includes a focusing unit that enables the adjustment of the spot size. Available spot sizes are e.g. 50 μιτι, 100 μιτι, 200 μιτι, 300 μιτι and 400 μιτι. A case envelopes the optics and the scanner electronics. The aiming beam shows the target locations to be treated when the beam attenuator 6 is placed in the beam path as it is in figure 2.

For the treatment itself, the attenuator is moved out of the beam path and a desired high power or full power of the beam is used.

Figure 3 shows the laser system with the beam attenuator (3) moved out of the beam path.

In practice, the moving of the beam attenuator 6 from the treatment can take place e.g. by means of a foot switch as a consequence of which the attenuator 6 is automatically moved away from the beam path 2. When the foot switch is pressed on, the system starts the process of coagulating the selected spot pattern with the treatment laser beam. The laser emission can be interrupted by releasing the foot. On the same time with the start of the coagulation, or earlier, an eye filter should be placed to protect the eyes of the person giving the treatment, i.e. a doctor or an ophthalmologist. The eye filter protecting the eyes of the doctor attenuates the wavelength in question typically by 1 :1000000. To protect the doctor from reflections of the treatment beam, a movable eye filter is used. During alignment, the eye filter is moved out so that the doctor can see the alignment spot or pattern. During treatment, the eye filter is moved in so that the laser light reflecting from the patient's eye to the doctor's eyes is attenuated by the eye filter.

The photocoagulation (or treatment) to be performed entails the delivery of a treatment laser beam to the fundus of the eye with the assistance of a slit lamp or microscope (not shown) and a contact lens (not shown). A certified physician places several hundred laser burns ("spots") in selected areas of the patients' fundus. The burns are used to destroy abnormal blood vessels that are formed in the retina of a diabetic patient. This treatment reduces the risk of severe vision loss for eyes.

The moving of the attenuator away from the beam bath in order to start the treatment takes place very fast, whereafter the laser pulses for the treatment are directed on the area to be treated and were targeted by the aiming beam.

Typically, for diabetic retinopathy, retinal vascular applications, and the treatment of retinal breaks, the retinal laser spot sizes range from 100 to 500 μιτι, the pulse durations from 100 to 200 milliseconds, and the power from 50 - 1500mW, more usually between 100 and 750 mW. The pulse duration is within the range of 10-650 ms, 10-30 ms in a multisport pattern mode. In a single spot mode, when individual spots are treated one-by-one, the longer pulses of more than 30 ms can be used.

The laser is operated via a touch screen and a smart wheel, which gives the physician the freedom to choose a pattern without removing their eyes from the oculars. The smart wheel is a manual control button that allows the user to change figure, figure size, figure position, figure orientation and power during the treatment without having to use the touch screen. The smart wheel is connected to the Universal Serial Bus (USB) port of the computer.

The doctor can see the eye in spite of the eye filter. The eye filter typically filters away only a very narrow wavelength area, in this case the wavelength of 532 nm, and a narrow band (in the order of +- 10nm or even less) around it if the mentioned green filter is used. Thus, the doctor can see everything else but not the green laser light and he can also see where the burns are formed on the retina.

As an alternative to figures 1 and 2, the beam attenuator 6 can be located between the laser source 1 and the fiber 4 or it can be located after the fiber 4, in the slit lamp adapter 5. The slit lamp adapter 5 can contain scanner elements and optics for directing the laser beam to desired locations on the retina in order to create multi-spot patterns.

Claims

A system for laser treatment of an eye, the system comprising:

a) a laser source (1 ) producing a laser beam of an adjustable power, whereby the laser beam is to be used as an aiming beam when adjusted to a first power and as a treatment beam when adjusted to a second power,

b) means for delivering the beams on a target area of the eye,

c) a fiber (4) transporting the laser beam to said means.

The system of claim 1 , further comprising

d) a beam attenuator (6) for attenuating the power of the laser beam of the first power, and

e) a processing element operatively coupled to the beam attenuator (6) to controllably adjust the beam power between an aiming mode and a treatment mode by moving the beam attenuator (6) in to or out of the beam path.

The system of claim 1 , further comprising

f) a beam attenuator (6) with functional places for transmitting the laser beam and for attenuating the laser beam of the first power,

g) a processing element operatively coupled to the beam attenuator (6) to controllably adjust the beam power between an aiming mode and a treatment mode by moving the functional places of the beam attenuator (6) in to or out of the beam path.

The system of claim 3, characterized by the beam attenuator (6) having a third functional place that completely hinders transmitting of the laser beam of a first power.

The system of claim 1 , wherein the laser source (1 ) is a laser source for green, yellow, red or infrared wavelengths.

6. The system of claim 1 , 2, 3, 4, or 5, wherein the laser source (1 ) is a Diode-Pumped Solid-State (DPSS) laser source, a neodymium-doped YAG (Neodymium-Doped Yttrium Aluminum Garnet; Nd:Y₃AI₅0i₂) crystal with a laser diode, a neodymium- doped YVO (Neodymium-Doped Yttrium Orthovanadate; Nd:YV0₄ ) crystal with a laser diode, an Optically Pumped Semiconductor Laser (OPSL) source, a Vertical- Cavity Surface-Emitting-Laser (VCSEL) source, or a Vertical- External-Cavity Surface-Emitting-Laser (VECSEL) source is a small semiconductor laser similar to a vertical-cavity surface-emitting laser (VCSEL).

7. The system of claim 1 , 2, 3, 4, 5, or 6, wherein the beam attenuator (6) is a filter that attenuates the beam power by a fixed factor.

8. The system of claim 7, wherein the beam attenuator (6) is an optical filter, such as a Neutral Density (ND) filter, a longpass filter, a shortpass filter, a bandpass filter, an interference filter, a dielectric filter or some combination of these. 9. The system of claim 1 , 2, 3, 4, 5, or 6, wherein the beam attenuator (6) is an adjustable filter for an adjustable attenuation of the beam power.

10. The system of claim 9, wherein the beam attenuator (6) is a wave plate or a polarizing filter or some combination of these.

1 1 . The system of claim 1 , 2, 3, 4, 5, 6, 7, 8, or 9, wherein the beam attenuator (6) comprises one or more attenuating elements providing one or more selectable attenuation values. 12. The system of claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 1 1 , wherein the beam attenuator (6) comprises two or three different functional places, one of which is a hole providing translucency, another which is a filter providing attenuation, and the optional third place being compact opaqueness.

13. The system of claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , or 12, wherein the beam attenuator (6) is movable to two positions, wherein it is in or out of the beam path, respectively. 14. The system of claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , or 12, wherein the beam attenuator (6) is movable to three positions, each of the positions having some of said functional places in the laser beam path.

15. The system of claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, or 14, wherein the beam attenuator (6) is located between the laser source (1 ) and the fiber (4).

16. The system of claim 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10, 1 1 , 12, 13, or 14,, wherein the beam attenuator (6) is located after the fiber (4) in the means for delivering the beams on a target area of the eye in a desired form.

17. Method of preparing a laser treatment system for laser treatment, comprising the steps of

a) producing a laser beam to be used as an aiming beam,

b) attenuating the laser beam by placing an attenuator (6) in the beam path, c) transporting the beam to means for delivering the beam on a

target area of the eye (10) through an optical fiber (4).

18. Method of claim 17, wherein the beam power is attenuated by a fixed factor by means of an optical filter of a selected material and thickness used as attenuator (6) in order to obtain the desired attenuation value. 19. Method of claim 17, wherein the beam power is attenuated by a fixed factor by means of a combination of optical filter elements of selected materials and thicknesses used as attenuator (6) in order to obtain the desired attenuation value.

Method of claim 19, wherein the attenuation value is adjusted by varying the elements used in the combination filter by moving them in an out of the beam path.

21 . Method of claim 19, wherein the attenuation value is adjusted by using an adjustable filter.

22. Method of claim 17,18, 19, 20, or 21 , wherein the power of the laser beam of a first power is 50-100 mW. 23. Method of claim 17, 18, 19, 20, or 21 , wherein the power of the laser beam of a first power is attenuated by a factor of 100 - 200.

24. Method of claim 17, 18, 19, 20, or 21 , wherein laser beam is reflected on the eye in the form of a spot or a pattern of spot, the pattern having the shape of e.g. a square, a circle, a line, a sector, or an arc.