WO2014174148A1

WO2014174148A1 - System for laser treatment of an eye and method for preparation of the system

Info

Publication number: WO2014174148A1
Application number: PCT/FI2014/050284
Authority: WO
Inventors: Taru RUMMUKAINEN; Markku ERÄLUOTO
Original assignee: Valon Lasers Oy
Priority date: 2013-04-26
Filing date: 2014-04-17
Publication date: 2014-10-30

Abstract

A system for laser treatment of an eye comprises one or more laser sources for producing laser beams of an adjustable power. One laser source produces an alignment (or aiming) laser beam, one laser source produces a treatment laser beam, and delivery means deliver the alignment beam on a target area of the eye in the form of a continuous beam and for delivering the treatment beam on a target area of the eye to locations shown by the alignment beam. The invention is also concerned with a method for preparing a laser treatment system for laser treatment and a method for laser treatment of an eye with the system.

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. If the disease is not noticed in time and the disease gets worse, it can cause gradual vision loss. Both eyes are usually affected by the disease. Early stages of diabetic retinopathy can be detected by regular eye exams especially of people with diabetes.

The early form of the disease, called nonproliferative diabetic retinopathy may not affect vision unless fluid and protein from 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). 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.

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.

Typically in laser treatment of retina, an aiming beam is used together with a treatment beam. The aiming beam shows the location of the retina to be treated by illuminating a given area within which the laser burns are to be directed. The illuminated area usually has a given form formed by separate spots. The aiming beam and the treatment beam are produced in separate laser sources and combined by optics into same beam path.

The separate interdependent variables available for setting in the laser treatment are concerned with e.g. the beam size, power, shape and size of the pattern or figure formed on the retina by the laser light beams, the duration and intensity of the treatment laser pulse, the mutual distance of the spots and the intensity of the aiming beam. These variables need to be selected for the actual treatment in order to ensure a safe and accurate treatment.

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.

US patents 7,766,903 and 8,409,180 disclose such solutions 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 in the form of a pattern of separate spots. 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 the 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. A processor controllably shutters the alignment and treatment beams between the delivered pulses to the target locations.

The solution does not provide a perfect alignment for aligning the treatment beam with the alignment beam due to multiple spot by spot movements.

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 one or more laser sources for producing laser beams of an adjustable power. One laser source produces an alignment (or aiming) laser beam, one laser source produces a treatment laser beam, an delivery means deliver the alignment beam on a target area of the eye in the form of a continuous beam and for delivering the treatment beam on a target area of the eye to locations shown by the alignment beam.

The method of the invention for preparing a laser treatment system for laser treatment, comprises the steps of producing a laser beam to be used as an alignment beam, and delivering the alignment beam on a target area of the eye in the form of a continuous beam.

The method for laser treatment in the system comprises the steps of producing a laser beam to be used as an alignment beam, delivering the alignment beam on a target area of the eye in the form of a continuous beam, producing a laser beam to be used as a treatment beam, and delivering the treatment beam on the target area of the eye shown by the alignment beam in the form of treatment locations.

A continuous alignment (or aiming) beam is used together with the treatment beam. The alignment beam shows the target locations of the retina to be treated by illuminating a given area or line within which or along with which the laser burns are to be directed.

As the alignment beam is not shut off for producing a pattern of separate spots as in prior art, a continuous alignment beam presentation is shown. There are different embodiments for presenting the continuous alignment beam.

In a first embodiment, the continuous alignment beam is shown as an illuminated area of a given pattern forming an outlined square or circle or other pattern with a sharp contour.

In a second embodiment the system has means for changing the energy level of the alignment beam between intended treatment locations from the energy level at the treatment locations by means of which the energy level of the alignment beam is changed son that it is either reduced or increased between the intended treatment (target) locations from the energy level at the intended treatment locations.

In a first variation of the second embodiment of the invention, the energy level of the alignment beam is reduced between the intended treatment (target) locations to enhance the illumination of the overall area to be treated. The intermittent reduction of the energy level between the treatment locations is made possible by the fact that the alignment beam is kept on throughout the alignment and it does not rely on a shutter for turning on or off the alignment beam for showing the exact target locations as the beam is moved between them.

In a second variation of the second embodiment, the energy level could instead be reduced at the target locations, while the locations between the target locations would be illuminated with an increased energy level.

The treatment laser doses are directed by means of said pattern performed with an alignment source. The treatment laser beam may be controlled by turning on or off the laser source, which has a shutter associated therewith. The alignment source is not turned off as the beam is moved from one target location to the next one, since the pattern draws up a continuous line or figure along with or within which the treatment beam is to be directed in pulses. In the first embodiment, wherein the alignment pattern is an outlined pattern of light of an even energy level, the laser doses are delivered to treatment locations inside the alignment frame (or pattern), which treatment locations are not co-located with special locations. There can be a first processor that controls a set of scanning elements that direct the alignment laser beam and the treatment laser beam and a second processor that controls the alignment beam and the laser system.

The second processor has in the second embodiment, the function of lowering the energy level of the alignment beam between the target locations so as to link the target locations shown by the alignment beam to one another and so that a continuous line is formed between the intended treatment (or target) locations. The first processor of the second embodiment operates the scanning element to project a continuous line while the second processor controls the alignment source by switching to a reduced energy level between the target treatment locations and to an increased energy level at the target treatment locations or vice versa. In the second embodiment, wherein the alignment pattern is a pattern with dimmed parts of a lower energy level, the laser doses are delivered to the treatment locations to specially illuminated locations along the alignment pattern and those treatment locations are more accurately on the alignment beam on stronger illuminated locations. In said variation of the second embodiment, the laser doses are delivered to the treatment locations of a lower energy level.

In the outline mode forming the first embodiment, the alignment beam draws a frame around the area where the treatment pulses are to be delivered. This has a great advantage in that the alignment beam does not draw aiming spots in the locations to be treated and the doctor has a clear view of the retina inside the frame. The treatment locations are not covered by aiming beam spots and are therefore clearly visible inside the aiming frame. In some circumstances and because of personal preferences, the outline mode might be the preferred one.

In the second embodiment, an alignment pattern is projected that consists of one or more continuous alignment lines having parts that are illuminated with a reduced energy level as the line extends between treatment locations. The alignment pattern is illuminated at an increased energy level at the treatment locations (compared to the parts between the treatment locations) so that the alignment spots are joined or linked to one another by the lines. Analogously, in said variation, the alignment pattern is illuminated with a decreased energy level at the treatment locations (compared to the parts between the treatment locations) visually working in the same way.

Contrary to the prior art embodiment of having an alignment pattern with separate spots, the invention has the advantage that it does not require a processor that is configured to controllably shutter the alignment beam. The alignment beam is on as it moves from one intended treatment location to another so there is no shuttering of the alignment beam therebetween. It is thanks to the continuous delivery form of the beam that the invention does not need to shutter the alignment beam or projecting a plurality of separate alignment spots that are substantially co-located with the treatment locations. Not even in the second embodiment the invention, there is any need of the first processor to operate the scanning elements to project a plurality of separate alignment spots on the retina and to deliver doses of laser energy to treatment locations which are co-located with the separate alignment spots as in prior art. Instead, the first processor operates the scanning elements to project a continuous line extending between alignment spots to join the alignment spots.

A further advantage with the invention is that the alignment patterns have an additional function in that the patterns do not indicate only the areas to be treated, i.e. where the alignment spots are aligned with the individual treatment locations, because the alignment pattern also illuminates areas that are not to be treated with laser doses thereby providing enhanced illumination of the retina.

In the invention, there might be a shutter inside the laser source for the treatment beam, but not for the alignment beam since the alignment beam power is controlled electrically. The using a mechanical shutter in the way like in prior art might cause many problems.

Problems arise with the shutter in some circumstances if it has to be turned on and off repeatedly as is the case in prior art. The shutter is a mechanical component whereas the laser power is controlled electronically. Mechanical shutters are not as fast, reliable and accurate as electrical switching on/off. If a shutter is used as described in the prior art mentioned in the background section by closing and opening it repeatedly to create short laser pulses, the shutter lifetime might be very short in some situations. Even a very modest number of patients result in a lot of back and forth movements of the shutter in one year alone. The reliability of a mechanical shutter in such use is therefore a problem in use and a mechanical failure of the shutter more than likely happens at some point. The situation becomes much worse if the shutter also controls the power by chopping the beam even faster. Electronic components are very reliable compared to mechanical components and switching the power on and off is not a problem for modern electronics. Another question is the response time of a mechanical shutter compared to electrical control. Electrical control means like those preferably used in the invention can easily react in a very short time - in microseconds or even faster - as opposed to mechanical elements that always include some inertia for moving. A shutter may be fast enough but electronic control is much more accurate with a shorter and controlled pulse duration as a result.

A further disadvantage with having mechanical shutters as in prior art is that the laser beam is constantly on, which consumes a lot of electricity and creates more heat. Lasers typically need to be cooled down to very precise temperatures to operate as designed. The more heat is generated by the laser, the more heat has to be transferred out of the laser. In the invention, the laser beams is actually switched on and off, reducing the duty cycle of the laser. This reduces the heat generation and makes it a lot easier to keep the laser beam at a desired temperature. The laser diode and crystals inside a semiconductor laser need to be temperature controlled typically with an accuracy of +-0.1 degrees centigrade. Any extra heat leads to a more complicated and more efficient cooling system. Also a mechanical shutter creates extra heat because it has to be moved with a solenoid or some kind of a motor. Additionally, in the prior art implementation where a mechanical shutter is used to chop a beam that is always on consumes more power. If the beam is switched on and off electrically, the average power becomes lower because when no laser beam is delivered the power is switched off. Also the movement of the mechanical shutter consumes power and generates heat. In laser systems, heat plays an important role. The crystals inside the laser cavity have to be controlled very accurately, typically within +-0.1 degree of their set value for the laser to operate in the designed operating point. Any additional heat source makes controlling the temperatures more difficult and more energy has to be used for cooling down the system. Also by controlling the alignment beam electrically like in the invention, the alignment beam can be switched completely on and off. The alignment beam is turned off when the device is not used or in rest mode or during treatment but not during aiming. During aiming, the alignment beam it is in the first embodiment kept on all the time at the same level and in the second embodiment is switched between two levels (both on but with different intensity). This allows the use of the alignment beam as an additional illumination between the target locations in a pattern. In other words, drawing the target locations at higher intensity to indicate the spot locations and then use an aiming beam of a lower intensity to illuminate the area between the spots. The level of illumination can be easily adjusted by the user. In the variation, this can be inversed, and a lower intensity alignment beam can be used to mark the target locations to form spots and a higher intensity alignment beam to illuminate the area between the spots. In other words, having an electrical control of the alignment beam gives much more freedom in using different types of alignment beam modes from which the doctor can choose the one to be used. This is not possible by using only a mechanical shutter.

In the invention, two alternative ways of turning the treatment beam on or off, a physical shutter and electrical switching are preferably used. If one fails, the other one ensures that the laser treatment beam is not delivered unintentionally. The alignment beam is only controlled by electrically switching it on/off because the intensity of the alignment beam is low enough not to create any hazard. The additional safety by using a mechanical shutter is only used for the higher power treatment beam. As in our implementation, the alignment beam and the treatment beam are combined into same optical axis after the shutter, the shutter can stay closed in the aiming mode consuming zero power while the alignment beam is switched on and off electrically. This also further improves safety. While the alignment beam is on, the shutter stays closed and in case of a failure in the treatment beam control, where the treatment source would unintentionally produce treatment beam while in aiming mode, the treatment beam would be blocked by the shutter.

In other words, in our invention, the shutter preferably only works as a safety shutter for the treatment beam and the alignment beam can still be shown and switched on and off electrically when not in use or for treatment (during aiming it is on all the time). It is possible to keep the treatment source on and blocking it with the shutter while displaying the alignment beam. In the invention, the alignment beam is never completely switched off at aiming as the beam is moved from one target location to the next one. Instead, it is kept on all the time but in the second embodiment, the power is intermittently changed so that the target locations are shown as spots with higher density and the "lines" between the spots are shown with a lower density (or vice versa). It is also possible to do the same thing with the treatment laser beam so that it is kept on all the time also but at a lower power as it is swept between spots. In such an embodiment, the processor used is not configured to controllably shutter the alignment and treatment beams. The shutters can, if desired be kept half-open between the spots. The invention preferably uses two completely independent processors allowing an improved safety of the device. One processor controls the scanners that are used for directing the alignment and the treatment beam and another processor controls the electrical switching on and off the beams electrically. For example, if one processor stops working, the problem can be identified by the other processor and the laser delivery can be stopped. A potentially dangerous laser beam should not be delivered accidentally. Therefore, the system of the invention has been designed in such a way that one failure does not create a hazardous situation. For this to work, the processors are designed to be completely independent from eachother. The two processors can supervise each other and make sure they are both working properly. This invention can be used in laser treatment systems that use only one laser source for the alignment beam and the treatment beam as well as in in laser treatment systems that use two laser sources.

If only one laser source is used, then before the real treatment, the laser light produced with one laser source is used as an alignment beam, the power of which is allowed to be 390 microwatt, i.e. 0,39 milliwatt at the most of medical reasons. Usually, however, two laser sources, one for the alignment beam and another for the treatment beam, are used. Alternatively, a higher power laser source having an attenuator can be used also for the alignment 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 a continuous laser beam. Thus, the present invention provides a system that creates a visual alignment pattern on retina without having to interrupt and shut the beams spot by spot at the aiming (and not necessarily even at treatment) making the whole treatment much more accurate.

This also solves the problem of the visibility of the retina.

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.

Figures 2a - 2f presents various examples of alignment patterns used in the invention

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 8, a laser module 9 (with a laser source 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 (which is inside the module 9) 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 8 is preferably a Personal Computer (PC) connected to a monitor 7 with a touch screen 1 1 as a graphical user interface and is fixed to the trolley or to a slit lamp table. The computer 8 runs suitable software for the laser treatment and is used through the graphical user interface enabling the person that performs the treatment (such as a physician, ophthalmologist or doctor) to adjust suitable settings for the treatment.

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 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 μππ, the laser beam has to be focused so that it would enter the optical fiber 4. A fiber coupling lens 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 9c that also has been lead to the slit lamp adapter 5. The slit lamp 9c 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 photocoagulation (or other treatment) to be performed by delivering a treatment laser beam to the fundus of the eye takes place with the assistance of the slit lamp 9c or a microscope and a contact lens.

The slit lamp adapter 5 can be integrated with compatible microscopes. Foreseen with computer controllable scanners it produces a variety of different predefined patterns to suit several treatment applications. The scanners deflect the laser beam delivered from the laser module 9 by an optical fiber. The scanner elements and the optics of the slit lamp adapter 5 direct the laser beam to desired locations on the retina in order to create alignment patterns. The scanners are turning mirrors, and usually there are two of them. They are turning mirrors, one of which controls the beam in an x-direction and the other one in the y-direction. A case envelopes the optics and the scanner electronics.

The laser can be operated via said touch screen 1 1 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 1 1 . The smart wheel is connected to the Universal Serial Bus (USB) port of the computer 8.

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 and the laser emission can be interrupted by releasing the foot. The information of the start goes through a first processor, which controls the laser system and the alignment. Another second processor controls a set of scanning elements. The treatment laser doses are directed by means of the pattern performed with an alignment laser source. The treatment laser beam may be controlled by turning on or off the laser source electrically, but it also has a safety shutter associated therewith.

The alignment source is not turned off as the beam is moved from one target location to the next one, since the alignment beam produced by the alignment source draws up a pattern consisting of a continuous line or figure along with or within which the treatment beam is to be directed in pulses.

The safety shutter of the treatment beam is not used to shutter the treatment beam between the target locations. The shutter is opened before the first treatment pulse and individual treatment spots are created by modulating the treatment beam by switching the beam on and off electrically.

At 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 :100000.

To protect the doctor from reflections of the treatment beam, an eye filter that can be movable 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 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.

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 (pulses) on 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 treatment pulses within one pattern are not delivered simultaneously, but sequentially by e.g. 30 ms pulse durations. When the doctor presses the foot switch, the system moves to the first target location in the alignment pattern and delivers a 30 ms laser pulse, moving then to the next location and delivering another 30 ms pulse. This is repeated until all target locations in the pattern are delivered. This all happens with one press of a foot switch. The doctor presses and keeps the foot switch pressed, until the whole pattern is delivered. If the foot switch is lifted during the sequence, the process is interrupted. There is, however, also the option to treat a single target location at a time if the alignment pattern is formed as a pattern of a single target location.

Typically, for diabetic retinopathy, retinal vascular applications, and the treatment of retinal breaks, the retinal laser spot sizes range from 100 to 500 μππ, 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 multidose 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. A base current driven to the treatment laser source enables faster rising times for the laser pulses. Although the current would be set below the laser threshold, the laser could theoretically produce some light if the drive current would change for some reason (such as interference, failure, environmental conditions). Blocking the treatment beam with a shutter ensures that any unwanted treatment beam is blocked. The alignment beam can still operate using the electrical switching on and off because the alignment beam source is not behind the shutter. The laser wavelengths used for the treatment beam 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 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:Y3AI₅0i2) crystal with a laser diode or a neodymium-doped YVO (Neodymium- Doped Yttrium Orthovanadate; Nd:YV0₄ ) 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.

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 laser light, the duration and intensity of the laser pulse, the mutual distance of the dimmed or strengthened parts of the laser beam and the intensity of the aiming (or alignment) beam. The program with which the settings can be adjusted in the system also produces a preview of the alignment pattern to visualize the area to be coagulated or treated in the target tissue.

Figures 2a - 2f present various examples of alignment patterns that can be used in the invention.

The alignment beam is formed by a low-power, usually red, laser diode. The power of the alignment beam 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 μν is defined in the laser standards. In placing the alignment pattern, a contour line or an outline of a figure is drawn of light. The figure is a negative presentation in that the illuminated parts are represented in black colour. The dimmed parts are represented by grey colour.

The pressing on the foot switch starts the treatment beam having a higher power, which typically is green (e.g. of a wavelength of 532 nm) or yellow. At the same time with the start of the treatment beam it follows the alignment pattern. Both beams, e.g. the alignment beam and the treatment beam use the same optical path and the same scanners for the directing of the beam.

The alignment beam and the treatment beam can be but do not need to be produced in separate laser sources and they are combined by optics into same beam path. If the laser light beam to be used as alignment beam is produced with the same laser source as the treatment beam some special technical solutions or considerations are required. Usually, however, separate laser sources are used.

Thus, the alignment beam is aligned and reflected as a continuous beam on the patient's retina in the form of an outlined figure or an outlined figure comprising dimmed or strengthened parts that forms spots of target locations. The power of the alignment beam is partly determined by the size of the dimmed or strengthened parts when dimming or strengthening is used. The bigger spot(s) used, the less power is needed for the alignment beam. Figures 2b, 2d and 2f show patterns of the first embodiment, wherein the alignment patterns is drawn as an outlined figure inside which or at which the treatment pulses are are to be directed.

Figures 2a, 2c and 2e show patterns of the second embodiment, wherein the alignment patterns is drawn as an outlined figure as well but comprising dimmed parts of a reduced energy level.

Figures 2a, 2c and 2e also indicate the path of the light beam.

The second processor has in the second embodiment, the function of lowering the energy level of the alignment beam between intended target locations so as to link the target locations shown by the alignment beam to one another and so that a continuous line is formed between the treatment (or target) locations.

The first processor of the second embodiment operates the scanning element to project a continuous line while the second processor controls the alignment source by switching to a reduced energy level between the treatment locations and to an increased energy level at the treatment locations or vice versa.

Thus, the second processor keeps the alignment beam on during the entire process in both embodiments without either shuttering or turning off the alignment beam.

In the second embodiment, wherein the alignment pattern is a pattern with dimmed parts of a lower energy level, the laser doses are delivered to the treatment locations to specially illuminated locations along the alignment pattern and those treatment locations are more accurately on the alignment beam on stronger illuminated locations.

In the second embodiment, an alignment pattern is projected that consists of one or more continuous alignment lines having parts that are illuminated with a reduced energy level as the line extends between treatment locations. The alignment pattern is illuminated at an increased energy level at the treatment locations so that the alignment spots are joined or linked to one another by the lines. Available Patterns are e.g. a square like in figures 2a and 2b, a circle like in 2c and 2d, an arc or a line, a sector, triangle like in 2e and 2f or any other form. The pattern is chosen dependency on the form and size of the area to be treated. All these shapes can vary in size. In the second embodiment having a reduced (or increased) energy level between intended treatment locations so that they appear as target spots, the distance between the spots can vary and the extent of the energy reduction can be freely selected from an almost invisible level to a more visible one.

In figure 2a, the alignment beam goes through all the spots starting e.g. from the left upper corner and continuing to the right all the way to the right upper corner, continuing then downwards to the middle and then to the left, further downwards and then to the right all the way to the lower right corner. The beam can go through the spots in any order.

The dimmed or alternatively the stronger illuminated parts form areas of e.g. 50 μππ, 100 μππ, 200 μητι, 300 μππ and 400 μππ.

The alignment beam shows the target locations to be treated.

There is no shutter for the alignment beam. The aiming beam is modulated the same way as the treatment beam as controlled by the first processor, which also completely controls the scanners.

The alignment beam is in the invention preferably shut off and on electrically for use and rest modes and for the time of the treatment. During aiming it is on all the time and not shut off. If a shutter is used for chopping the alignment beam instead of said electrical shut off, the treatment source must be switched off while the shutter is chopping the aiming beam. Instead of switching the laser drive current completely off while in aiming mode, the treatment laser can be driven with a current that is just below or at the threshold when it starts producing light.

Claims

1 . A system for laser treatment of an eye comprising one or more laser sources for producing laser beams of an adjustable power, the system comprising:

a) one laser source for producing an alignment laser beam,

b) one laser source for producing a treatment laser beam,

c) delivery means for delivering the alignment beam on a target area of the eye in the form of a continuous beam and for delivering the treatment beam on a target area of the eye to locations shown by the alignment beam, and

d) means for changing the energy level of the alignment beam between intended treatment locations from the energy level at the treatment locations.

2. A system of claim 1 , comprising means for reducing the energy level of the alignment beam between the intended treatment locations from the energy level at the treatment locations.

3. A system of claim 1 , comprising means for reducing the energy level of the alignment beam at the intended treatment locations from the energy level between the treatment locations.

4. System of claim 1 , 2, or 3, the delivery means reflecting the continuous alignment beam in the form of a pattern having the shape of e.g. a square, a circle, a line, a sector, a path of a curved line or an arc.

5. System of claim 4, the means for reducing the energy level dimming parts of the shapes in an extent by leaving spots of desired size to be clearly distinguished from the dimmed parts.

6. System of any combination of claims 1 - 5, wherein the delivery means consists of scanning elements.

7. System of claim 6, wherein the system further comprises a first processor controlling the scanning elements.

8. System of claim of any combination of claims 1 - 7, wherein the system further comprises a second processor controlling the alignment beam and the laser treatment system.

9. The system of any combination of claims 1 - 8, wherein the laser source is a laser source for green, yellow, red or infrared wavelengths.

10. The system of any combination of claims 1 - 9, comprising means for electrically controlling the power of the alignment beam and means for electrically controlling the power of the treatment beam.

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

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

b) delivering the alignment beam on a target area of the eye in the form of a continuous beam, and

c) changing the energy level of the alignment beam between intended treatment locations from the energy level at the treatment locations.

12. Method of claim 1 1 , further characterized by reducing the energy level of the alignment beam between intended treatment locations from the energy level at the treatment locations.

13. Method of claim 12, characterized by reducing the energy level of the alignment beam at intended treatment locations from the energy level between the treatment locations.

14. Method of claim 1 1 , 12, or 13 wherein the power of the laser beam is less than 400 microwatt.

15. Method of claim 1 1 , 12, 13, or 14, wherein laser beam is reflected on the eye in the form of a pattern having the shape of e.g. a square, a circle, a line, a sector, a path of a line with bends or an arc.

16. Method of claim 15 wherein the parts of the shapes are dimmed in an extent by leaving spots of desired size to be clearly distinguished from the dimmed parts to work as intended treatment locations.

17. The method of any combination of claims 1 1 - 16, comprising means for electrically control the power of the alignment beam.

18. Method for laser treatment in a system comprising one or more laser sources for producing laser beams of an adjustable power, comprising the steps of

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

b) delivering the aiming beam on a target area of the eye in the form of a continuous beam,

c) producing a laser beam to be used as a treatment beam,

d) changing the energy level of the alignment beam between intended treatment locations from the energy level at the treatment locations,

e) delivering the treatment beam on the target area of the eye shown by the alignment beam in the form of treatment locations while keeping the alignment beam on.

19. Method of claim 18, further characterized by reducing the energy level of the alignment beam between intended treatment locations from the energy level at the treatment locations.

20. Method of claim 18, characterized by reducing the energy level of the alignment beam at intended treatment locations from the energy level between the treatment locations.

21. Method of claim 18, 19, or 20, wherein the power of the alignment laser beam is less than 400 microwatt.

22. Method of any combinations of claims 18 - 21 , wherein alignment laser beam is reflected on the eye in the form of a pattern having the shape of e.g. a square, a circle, a line, a sector, a path of a line with bends or an arc.

23. Method of claim 22, wherein the parts of the shapes are dimmed in an extent by leaving spots of desired size to be clearly distinguished from the dimmed parts to work as intended treatment locations.

24. Method of any combination of claims 18 - 23, characterized by electrically controlling the power of the alignment beam.

25. Method of any combination of claims 18 - 23, characterized by electrically shutting the treatment beam off between the laser pulses given at the treatment locations during the laser treatment.