WO2010028663A1

WO2010028663A1 - Laser device for ophthalmological surgery

Info

Publication number: WO2010028663A1
Application number: PCT/EP2008/007379
Authority: WO
Inventors: Christof Donitzky; Peter Riedel
Original assignee: Wavelight Ag
Priority date: 2008-09-09
Filing date: 2008-09-09
Publication date: 2010-03-18
Also published as: TW201010685A

Abstract

The invention relates to a laser device for ophthalmological surgery, said device comprising a working laser (110) for generating working laser radiation, a fixing light source (140), a test beam source (130) for sending a test beam (310) towards an eye (200) to be treated, detection means (130) for detecting a return reflex (320) of the test beam reflected from the eye along the radiation direction of the test beam (310), a control computer (150) coupled to the test beam source and the detection means, and a control program for the computer, the control program containing instructions for carrying out a centring test for checking the fixing of the eye on the fixing light source (140), before treating the eye by means of the working laser radiation. The centring test involves sending a test beam (310) from the test beam source (130), subsequently testing whether a return reflex of the test beam can be detected by the detection means (130), and producing a control signal according to the test result by means of the control computer.

Description

Laser device for ophthalmologic surgery

The invention relates to a laser device for ophthalmic surgery.

Surgery of the human eye is familiar with numerous treatment methods in which laser radiation is directed to the eye in order to achieve an indicated treatment purpose as a result of the interaction of the irradiated laser radiation with the eye. An exemplary type of treatment is refractive laser surgery, in which a change in the imaging properties of the "eye" optical system is attempted by means of laser radiation.For the imaging properties of the human eye, primarily the cornea (cornea) is decisive In many cases, the cornea is processed by the targeted introduction of cuts and / or targeted removal of material. A prominent example of refractive laser surgery is LASIK (laser in situ keratomileusis).

Other laser surgical treatments of the eye may involve the lens or other elements of the eye, for example, to help eliminate cataracts or other pathological changes.

As a rule, a precise fixation of the eye is required before a laser treatment can be started. For this purpose, it is known to provide a separate fixation light source which emits a weak fixation light beam and which the patient is to fix. Before starting the treatment, the attending physician checks the correct centering of the eye, i. He checks whether the patient is aiming with his eye as specified, the fixation light source. If the doctor is satisfied, he switches the laser device free, so that the laser treatment can begin. However, the doctor has so far no way to objectively measure the correct centering of the eye and understand. He can only rely on his own subjective

Look at the eye to be treated. So it can easily happen that the patient fixes, without the doctor's notice, instead of the Fixierlichtquelle another, adjacent point.

The object of the invention is to provide a device which allows a reliable assessment of the fixation of the eye to be treated on a Fixierlichtquelle before the treatment of the eye. To achieve this object, a laser device for ophthalmological surgery is provided according to the invention, comprising:

a working laser for the provision of working laser radiation, a fixing light source,

a test beam source for emitting a test beam in the direction of an eye to be treated,

- Detection means for detecting a reflected from the eye along the beam direction of the test beam back reflection of the test beam, - a coupled to the test beam source and the detection means n control computer and

a control program for the computer, wherein the control program contains instructions for performing a centering test for checking the fixation of the eye on the fixation light source before treatment of the laser to be performed by the working laser radiation, wherein the centering test is the emission of a test beam by the test beam source, the subsequent test whether a return reflection of the test beam can be detected by the detection means, and finally includes the generation of a control signal by the control computer as a function of the test result.

The test beam generates a back reflection on the eye to be treated, for example by reflection on the cornea front surface and / or at the interface between the cornea and the anterior chamber of the eye. The detection means are preferably arranged and designed such that they only detect those back-reflections which are reflected by the eye in the same direction as the incident test beam. Because the surface of the human eye is not an exact spherical surface and the center of rotation of the eye is usually different also from the center of curvature of the ocular surface, collinear reflection of the test beam occurs substantially only in a single position of the eye. The patient moves the eye out of this one position, for example, by changing one

Aimed point, this causes a more or less strong angle tilting of the reflected beam with respect to the direction of incidence of the test beam. Only when the test beam strikes the surface of the eye to be treated orthogonally, it is reflected exactly in the same direction and can be detected by the detection means. If the fixation light source is positioned so that the condition for the equiaxed reflection of the test beam is satisfied only if the fixation beam is properly fixed by the patient, this ensures that Detecting a return reflex of sufficient strength the patient's eye is actually properly centered. This gives the physician an objective criterion for checking the correct centering of the eye.

5 Preferably, the detection means work according to an interferometric measuring principle. In particular, it can be provided that the test beam source and the detection means are part of an operating according to the principle of optical short-coherence reflectometry OLCR-Pachymeteranordnung. A pachymeter is generally used for the non-contact measurement of the corneal thickness of the eye. In addition, it may be possible that a distance measurement to a reference point of the laser device is realized. Modern laser systems for eye surgery are often already equipped with an OLCR pachymeter (OLCR: Optical Low Coherence Reflectometry) or another coherence-optical interferometric measuring device with which measurements of the eye can be carried out before, during or after the laser treatment. So far, such pachymeters were of course not used to determine the correct centering of the eye. If the measuring beam emitted by an OLCR pachymeter is used as the test beam and the interferometer of the pachymeter with the connected evaluation means as the detector means, no further apparatus-technical means are required for implementing the

2o invention. This thus represents a particularly cost-effective embodiment of the invention that is easy to integrate in already existing laser devices.

According to an embodiment 25, the control signal generated by the computer can cause an optical or / and acoustic warning output by an output unit if the detection means detects no back-reflection or only a back-reflection of the test beam lying below a predetermined minimum strength. The doctor can be given so before the start of treatment, a message whether the eye is fixed correctly or not.

30

Alternatively or additionally, the control signal can block the laser treatment of the eye if the detection means detects no back-reflection or only a back-reflection of the test beam lying below a predetermined minimum thickness. If, by contrast, a back reflection of the test beam possessing the predetermined minimum strength is detected by the detection means, the control signal can effect a release of the treatment. The centering test can be coupled according to an advantageous development directly with a thickness or distance measurement of the eye. For this purpose, the control program may contain instructions for performing a pachymetric thickness or distance measurement on the basis of the test beam emitted during the centering test and a detected back-reflection of the test beam. Thus, for example, within the scope of a regularly required thickness measurement of the cornea, the centering of the eye can be checked at the same time. It can also be a distance measurement to the apex (vertex) of the cornea. Since the pachymetry is a very sensitive measurement, only measurements are obtained when the eye is well positioned and a back reflex from the corneal surface reaches the pachymeter. As soon as the patient looks to the side, the back reflexes become weaker and, for example, it is no longer possible to measure the thickness. In this respect, the control signal can also be understood as an indication of whether the implementation of pachymetry was successful.

In particular, the back reflex from the front of the cornea is suitable for the reflex detection. This has the advantage that the refractive index jump between the propagation medium air and the cornea is particularly high and the generated back-reflection thus has a particularly high intensity. Alternatively, however, it can also be provided that the back-reflection from the back of the cornea, that is, from the refractive index jump between the cornea and the anterior chamber of the eye, is detected. It is even conceivable to detect both the back reflex from the cornea front and the back reflex from the back of the cornea. This allows a particularly sensitive detection of the angular position of the eye.

In order to make particularly good use of the asphericity of the ocular surface and to increase the sensitivity of the fixation examination, it may be provided that the beam diameter of the test beam is small compared to the extent of the outer surface. Under this condition, the orthogonality between the test beam and the ocular surface, which is necessary for optimum back reflection, is particularly selective, and a centering signal which is easy to detect is produced.

The invention will be explained below with reference to the accompanying drawings. They show: 1 shows a laser device according to the invention, in which the back-reflection from the cornea of the eye is reflected back to a pachymeter in substantially along the beam direction of the test beam;

2 shows a laser device according to the invention in which the eye is not centered and the back-reflection on the cornea caused by the test beam is not reflected along the beam direction of the test beam.

The laser device for ophthalmological surgery shown in FIGS. 1 and 2 comprises as laser radiation source a e.g. working laser 110 suitable for corneal ablation, which emits pulsed laser radiation, an eye tracker 120 which serves to track eye movements during a corneal treatment, a pachymeter 130 which is used to detect the distance between the eye apex and pachymeter and to measure the corneal thickness, for example by means of OLCR (FIG. "Optical Low-Coherence Reflectometry 7 optical short-coherence reflectometry), and a fixing light 140, which is to be fixed by the patient before and during corneal treatment in order to minimize possible eye movements. All said components 110-140 work on a common optical axis X, which is realized by various suitable optical components, such as mirrors, lenses, etc. These optical components are only schematically indicated in FIGS. 1 and 2 as mirrors 160. In addition to the components already known and known per se, the laser device according to the invention has a computer 150 with a control program 160. The control program 160 is designed to control the components 110-140 by means of suitable control signals on control lines 170.

Furthermore, FIGS. 1 and 2 schematically depict a human eye 200. The schematic representation shows the vitreous body 210 and the dermis 220, which adjoins the cornea (cornea) 230 in the anterior eye region. Furthermore, the lens 240, the anterior chamber 250, the iris 260 and the posterior chamber 270 are shown. Opposite the lens is schematically indicated the exit of the optic nerve.

In preparing a laser surgical treatment of the eye 200, it must be ensured that the patient fixes the fixation light 140 correctly. This ensures that the treatment level 300, which after the preparation and the folding back of a cornea flap (Flap) - assuming a LASIK- Treatment - is exposed, is arranged substantially orthogonal to the optical axis X. In order to check this so-called centering, the control program 160 of the computer 150 provides that by means of the pachymeter 130 a test beam 310 is directed along the optical axis X in the direction of the eye 200, in particular on the treatment plane 300. There, the test beam 310 generates a return reflection 320, which is reflected back to the pachymeter 130 in the case of the desired orthogonal alignment of the treatment plane 300 and the optical axis X along the optical axis X. In the figures, the beams 310 and 320 are shown next to each other for reasons of clarity, but can of course also lie directly on top of each other. Only when the orthogonality condition for the angle between the treatment plane 300 and the optical axis X is satisfied within a small tolerance, does the back-reflection 320 fall into the pachymeter 130 so that it can perform pachymetry. This can for example consist in a distance measurement between the pachymeter 130 and the eye 200, in which primarily a back reflection 320 from the front of the cornea 230 is used. An even more angle sensitive approach is to measure the thickness of the cornea 230, taking into account both back and front reflexes of the cornea 230 by the pachymeter 130.

Thus, if it is ensured that the fixation light 140 and the measurement or test beam 310 of the pachymeter 130 are coaxial with one another and the patient fixes the fixation light of the fixation light source 140, a successful measurement of the distance or thickness by the pachymeter 130 can be assumed to that the treatment plane 300 and the optical axis X are oriented orthogonally to one another and there is centering of the eye. If, on the other hand, pachymetry can not be performed by means of the pachymeter 130, it must be assumed that the patient is looking at a false fixation point instead of the fixation light beam of the fixation light source 140.

This situation is shown in FIG. The wrong fixation point 330 chosen by the patient in the present case produces an angular deviation of the back-reflection 320 from the test beam 310 of approximately 5 degrees. By the same angle, the treatment plane 300 is tilted with respect to the optical axis X. It turns out in practice, however, that already angle deviations of 1 to 2 degrees sufficient to make a pachymetry by the pachymeter 130 impossible. Thus, if the control program 160 receives data or signals from the pachymeter 130 that indicate that the pachymetry has not been successfully performed, the control program 160 does not release the working laser 110 via its control line 170. However, in the event of pachymetry being successfully performed by the pachymeter 130, the control program 160 releases the working laser 110 and laser surgical treatment of the eye 200 may begin.

In addition to the embodiment illustrated in FIGS. 1 and 2, in which a pachymeter 130 is used to determine the orthogonality of treatment plane 300 and optical axis X, simplified arrangements are also conceivable in which only one test beam 310 is emitted and the return reflex 320 is received, that is, without the use of interferometric measuring devices. Here, only the intensity of the back reflection 320 would be used for the detection of orthogonality.

Claims

Patentansprϋche

5 1. A laser device for ophthalmic surgery, comprising:

a working laser (110) for providing working laser radiation,

a fixing light source (140),

a test beam source (130) for emitting a test beam (310) towards an eye to be treated (200), lo detection means (130) for detecting a back reflection (320) of the eye reflected along the beam direction of the test beam (310) test beam

a control computer (150) coupled to the test beam source and the detection means n and

a control program for the computer, wherein the control program contains instructions i5 for carrying out a centering test for checking the fixation of the eye on the fixation light source (140) in front of a treatment of the eye to be performed by means of the work laser radiation, wherein the centering test comprises the emission of a test beam (310). by the test beam source (130), the subsequent check as to whether a back reflection of the test beam can be detected by the detection means (130), and

Finally, 20 includes the generation of a control signal by the control computer in dependence on the test result.

2. Laser device according to claim 1, that the detection means (130) operate according to an interferometric measuring principle.

25

3. Laser device according to claim 2, characterized in that the test beam source and the detection means are part of an operating according to the principle of optical short-coherence reflectometry OLCR-Pachymeteranordnung (130).

3o

4. Laser device according to one of the preceding claims, characterized in that the control signal causes an optical and / or audible warning output by an output unit, if detected by the detection means (130) no return reflex or only below a predetermined minimum strength back reflection of the test beam.

35

5. Laser device according to one of the preceding claims, characterized in that the control signal blocking the laser treatment of the eye causes, if by the detection means (130) no back-reflection or only below a predetermined minimum thickness lying back reflection of the test beam is detected, and / or causes a release of the treatment, if a backbone having the predetermined minimum strength of the test beam is detected by the detection means.

6. Laser device according to one of the preceding claims, characterized in that the control program contains instructions for performing a pachymetric thickness or distance measurement on the basis of the test beam emitted during the centering test and a detected back-reflection of the test beam.