WO1987000036A1

WO1987000036A1 - Laser surgery device, in particular for keratotomy of the cornea (i)

Info

Publication number: WO1987000036A1
Application number: PCT/DE1986/000265
Authority: WO
Inventors: Reinhardt Thyzel
Original assignee: Thyzel Reinhardt Meditec
Priority date: 1985-06-29
Filing date: 1986-06-30
Publication date: 1987-01-15
Also published as: DE3523342A1; EP0229789A1; JPS63500495A

Abstract

In a laser surgery device, used particularly to perform the keratotomy of the cornea, the slot (14) of a slot lamp is used as a diaphragm for the surgical light beam. In order to reduce as much as possible the number of reflecting surfaces (9, 10) intended to reflect the surgical light beam in the slot lamp, the latter is not pivotable about an axis, but simply slidable in a rectilinear direction. The excimer-laser beam (1) is directed in the linear displacement direction of the slot lamp by means of a reflecting element fixed at the base of the slot lamp, and is introduced therein and applied by the guiding system for guiding the beam of the slot lamp to the tissue to be operated. In order to maintain constant the distance between the slot lamp and the tissue to be operated, the headrest (4) of the patient is adjustable. Due to this arrangement and to the normal vertical movement of the slot lamp it is possible to displace with greater freedom the image of the slot on the tissue to be operated.

Description

Device for laser surgery and in particular for keratotomy of the cornea (I)

Description

Technical field

The invention relates to a device for laser surgery and in particular for keratotomy of the cornea with a laser according to the preamble of patent claim 1.

State of the art

For example, from the article "Excimer-Laser surgery of the Cornea" by Stephen L. Trokel (American Journal of Ophthalmology, 1983, volume 96, pages 710-715) it is known that in particular argon-fluoride-Excimer-La ≤er with a wavelength of 193 nm suitable for performing operations on the cornea. The aim of such operations is, for example, to correct abnormal corneal curvatures by applying a certain "cutting pattern".

Similar effects can also be achieved with lasers of other wavelengths. With regard to the wavelengths used, reference may be made to the corresponding literature.

In the known devices for keratotomy of the cornea, as described, for example, in the above-mentioned article and required in the formulation of the preamble of claim 1, a mask is used whose UV-light-permeable areas have the shape of the desired "cutting pattern" to have. This mask becomes tight arranged in front of the eye to be operated on and irradiated with UV laser light.

As a result of this structure, the known devices have a number of disadvantages according to the preamble of patent claim 1:

A specially made mask is required for each desired pattern. Since the individual eyes to be operated differ with regard to their shape, their curvature, etc., even with a "topologically" identical pattern, it is practically necessary to make a mask for each operation.

In addition, the arrangement of the mask directly in front of the eye to be operated on hinders control of the success of the treatment during the operation.

By using the mask arranged close to the eye to be operated on, it is also not possible to integrate the known device for keratotomy into normally used eye examination devices, such as slit lamp devices etc.

The invention is based on the basic idea of integrating a device for laser surgery and in particular for keratotomy of the cornea into a slit lamp device in such a way that the normal slit provided in the slit lamp can be used as an aperture for the laser beam.

Devices have already been proposed in which a surgical laser is combined with a split-lens device.

With these proposals, the laser beam is either through the slit lamp housing - but without using the slit of the slit lamp to limit the beam - or through the arm that carries the slit lamp microscope. In these known proposals, the laser light is first deflected coaxially to the axis of rotation of the slit lamp or the slit lamp microscope passing through the eye to be operated on, then mirrored out of the axis of rotation into the support arm of the slit lamp or slit lamp microscope and then reversed parallel to the axis of rotation ¬ steers, so that it goes through the slit lamp or the vertical part of the support arm of the slit lamp microscope. Only after a new reflection is the light directed into the eye to be operated on in a horizontal plane.

With the known proposals, it is therefore necessary to deflect the light of the surgical laser at least four times by means of mirrors, prisms, etc. For the argon lasers used exclusively in the prior art, the light of which lies in the visible range, or neodymium-YAG lasers, which emit light in the near infrared, these multiple reflections play no role, since mirrors with a high level are used for light in this wavelength range Efficiency are available.

However, in the UV wavelength range, for example for wavelengths of 193 nm, there are no mirror elements with a high degree of reflection available.

Presentation of the invention

The object of the invention is therefore to specify a device for laser surgery and in particular the keratomy of the cornea with a laser and in particular with a UV laser, in which the slit of a slit lamp can be used as a diaphragm - something which has not yet been considered has been drawn - and where the number of Reflections of the UV laser beam is as low as possible.

A solution to this problem according to the invention is specified with its developments in the claims.

The invention is based on the principle of separating the movement of the slit lamp from the movement of the slit lamp microscope, which can be pivoted in a known manner about a vertical axis which, for example, can pass through the eye to be operated in the basic position of the device. In contrast to the known slit lamp devices, the slit lamp itself cannot be pivoted about this vertical axis, but can only be displaced in the horizontal direction perpendicular to the axis of the eye to be operated. It is thus possible to introduce the laser beam directly into the beam path thereof by means of a deflection device, for example a prism, which is firmly connected to the base of the slit lamp, without the laser beam first having to be guided over the pivot axis. As a result, two of the four prisms or mirrors required in the known devices can be saved, since only the deflection device, which reflects the laser beam initially guided in the direction of the displacement of the slit lamp into the beam path of the slit lamp, and the deflection device is required directs the laser beam emerging from the slit lamp onto the eye to be operated. In order nevertheless to obtain all degrees of freedom with regard to the movement of the operating device and the observation unit, the chin rest for the patient's head can be displaced in the direction of the axis of the eye to be operated on, so that the distance between the slit lamp which can be displaced in the lateral direction and the to be operated on can be kept constant. Here, chin support is understood to mean any device that is suitable for fixing the patient's head. The chin rest can therefore also have, for example, an additional forehead rest at any time. The terms horizontally and vertically likewise relate to a device which is designed for the operation of a seated patient. For devices that are intended for the operation of a lying patient, the terms horizontal and vertical are to be defined accordingly, ie refer to a "body coordinate system". The horizontal plane is therefore understood to mean any plane which contains the straight line connecting the patient's two eyes and the axis of the eyes in the normal position.

In the case of running on a lying ^"operating table patients optionally be used instead of a chin support a headrest.

By separating the movement of the slit lamp and the slit lamp microscope and moving the slit lamp in only one direction perpendicular to the axis of the examined eye with simultaneous movement of the chin rest as the third axis, it is possible to reduce the number of deflecting elements to two and thus to halve their number compared to the beam guidance, as is known for devices of another type.

Developments of the invention are specified in the subclaims.

According to claim 2, the slit lamp is attached to a telescopic arm. This not only allows the slit lamp to be attached and moved comparatively easily, but also completely encapsulates the laser beam before entering the slit lamp.

In principle, the movement of the headrest or chinrest can be coupled in any way with the movement of the slit lamp and, if appropriate, the rotation of the mirror element, which directs the illumination and the operating light beam onto the eye to be operated on. For example, a mechanical coupling can be used for this.

A particularly simple design is obtained according to claim 3, however, if the slit lamp can be moved by hand or by motor in a manner known per se by the operator, while the chin rest, i.e. the fixing element for the patient's head is moved by a motor. The coordination between the individual displacements and, if necessary, the rotation of the deflecting element for the illuminating and operating light beam is carried out by an electronic control which ensures that the length of the light path between the eye to be operated and the slit lamp remains constant regardless of the lateral deflection of the slit lamp .

Since the eye surface as the image plane is not a flat surface, but an extremely curved surface, which typically has a 45 ° inclination to the operating light beam, problems can arise with regard to the depth of field of the slit image imaged with UV light. Such problems lead to a "figure frayed at the edges". This can be avoided if, according to claim 4, the slit of the slit lamp is arranged between two collecting optical elements which form a telecentric arrangement. Surprisingly, because of the coherence of the UV laser light in connection with the telecentric arrangement, there is a large depth of field in the range of several millimeters, so that the gap shown with UV light shows a constant contour sharpness over several millimeters. However, the slit lamp image illuminated with visible and coherent light still shows the known shallow depth of field of an incoherent image.

It is therefore possible, under certain circumstances, to provide a further laser, for example a helium-neon laser, which operates in the visible range and serves exclusively as a target beam.

The mechanical slit of the slit lamp can of course be rotated mechanically in a manner known per se in order, for example, to carry out radial keratotomy cuts. However, since the gap then has to be areally illuminated with UV laser light, the gap cuts out only a small part of the available laser light.

However, the design according to the invention, in which the number of prisms or mirror elements is halved, permits a further advantageous variant in which the gap image on the cornea is optically, for example, by means of a Dove prism, an Oxley prism or, for example, a further developed Oxley prism, as described in the simultaneously filed application "Device for laser surgery and in particular for keratotomy of the cornea (III)" are rotated.

This optical rotation of the slit image as claimed in claim 5 has the advantage that the beam cross section of excimer lasers, which is elongated from the outset, does not have to be expanded square, but can be left elongated and only has to be fully concentrated on the slit. This can be done by a simple telecentric beam expansion and, if necessary, by a Beam expansion with cylindrical lenses.

With a device having the features of claims 1, 4 and 5, optimum utilization of the power present in the beam cross section of an excimer laser is obtained, so that the operating times are significantly reduced.

Brief description of the drawing

The invention is described below by way of example with reference to the drawing, in which:

1a shows a schematic cross section through a device according to the invention,

1b shows a schematic longitudinal section through a device according to the invention, and

2 shows a cross section through a further embodiment of the invention.

Way of carrying out the invention

1a and 1b show a cross section and a longitudinal section through a device according to the invention. The device, shown only schematically, has an excimer laser 1, a slit lamp 2, a slit lamp microscope 3 and a chin rest 4 for the patient's head. The slit lamp 2 is held on a telescopic arm 5 in the direction of an arrow labeled x. The chin rest 4 can be moved by a motor in the direction of an arrow labeled y. The slit lamp microscope 3 can be pivoted in a manner known per se about a vertical axis 6 which, in the basic position of the chin rest 4, passes through the eye to be operated on.

The beam 7 of the excimer laser 1 is widened and expanded by a widening optics 8, which is only shown schematically passed through the telescopic arm 5, on which the slit lamp 2 is guided and attached.

A prism 9 deflects the beam 7 by 90 °, so that the laser beam 7 runs in the beam path of the slit lamp 2. The optics and the gap of the slit lamp 2 is only shown schematically and is designated by the reference numeral 10. The laser beam 7, which is limited by the gap of the slit lamp 2, is then directed by the prism 11 onto the eye to be operated on.

The invention is described in more detail below with reference to FIG. 2.

Fig. 2 shows a cross section through a slit lamp 2 designed according to the invention, which is held on the telescopic arm 5 in the direction of arrow x slidably. The laser beam 7 of the laser 1 (not shown in FIG. 2) strikes a mirror 9 and is deflected by it by 90 °, i.e. deflected in the direction of arrow z. Then the laser beam 7 passes through a lens 13 with a positive effect, the slit 14 of the slit lamp 2 and a further lens 15 with a positive effect. A rotating prism 12, for example a Dove-r prism or an Oxle prism, is arranged after the lens 15. The prism 12 is able to rotate the image of the gap 14 on the cornea to be operated, so that radial and "tangential" cuts as well as all cuts lying between these two layers can be carried out.

As already described in connection with FIG. 1, the prism 11 has the task of directing the beam of the slit lamp 2 onto the eye to be operated on. In addition, a lighting device 16 known per se is provided in the slit lamp 2, which illuminates the slit 14 with a visible one Illuminated light. The lighting device, which is constructed in a known manner and has a lamp, a condenser, etc., is generally referred to by reference numeral 16. In the embodiment shown, the mirror 9 is a quartz glass plate provided with a coating, which is partially transparent, so that both the laser beam 7 and the light from the lighting device 16 are introduced into the beam path of the slit lamp. The lenses 13, 15 are UV achroates, which can consist, for example, of CaF ₂ and Si0 ₂ and which form a telecentric arrangement, ie the “distance” between the two lenses 13 and 15 is equal to the sum of their focal lengths. In the exemplary embodiment shown in FIG. 2, the focal length of the lens 13 is approximately 200 mm, while the focal length of the lens 14 is between 50 and 100 mm, preferably approximately 60 mm. However, it is expressly pointed out that the focal length values of the lenses 13 and 14 forming a tele-centric arrangement depend on the respective conditions; the only decisive factor is that the two lenses or lens groups form a telecentric arrangement.

The exemplary embodiment shown in FIG. 2 has a number of advantages:

By moving the slit lamp 2 in the direction of the arrow x, the displacement of the chin rest 4 in the direction of the arrow y, and the height drive of the gap, which enables a displacement in the direction of the arrow z, one has all degrees of freedom in the adjustment of the individual elements. Nevertheless, only two mirrors, namely mirrors 9 and 11, are required, which direct the UV laser beam 7 onto the eye to be operated on.

By using the existing in a slit lamp Column 14 14 as a mask for the UV laser light, the construction effort is significantly reduced, since the gap present in each slit lamp has all the adjustment options required for operations on the cornea.

By using an optical rotating device 12, it is possible to change the gap only in its length and width without rotating it in the splitting plane. The slit image on the cornea is rotated exclusively by means of the optical rotating device (12). The gap can thus be illuminated in such a way that virtually all of the UV laser light can be used for surgical purposes.

Above all, the arrangement of the gap between two lenses, which form a telecentric arrangement, has the following surprising advantage:

The UV slit image, i.e. the image of the gap on the cornea, which is caused by UV laser light, has a much greater depth of field than the visible gap image. The depth of field of the UV slit image is several millimeters, so that a high contour sharpness of the slit image is maintained despite the inclination of the cornea. The high depth of field is a consequence of illuminating the gap with coherent laser light. In contrast, the illumination with incoherent visible light by means of the illumination device 16 results in the normal slit image with a shallow depth of field and, accordingly, a lower contour sharpness on the cornea.

The invention has been described above by way of example using an exemplary embodiment. Within the general idea of the invention, the number of mirror elements A large number of modifications are possible to reduce the elements required for guiding the laser beam onto the eye to be operated and to use the slit of a slit lamp as a mask for the operation.

For example, all the mirror elements used can be quartz glass prisms, which have the advantage of a higher degree of reflection than mirror layers. It is also possible, in order to achieve a high contour sharpness of the slit image even in the visible region, to additionally use a target beam laser, for example a helium-neon laser. The device that a motorized adjustment of the chin rest and possibly a rotation of the prism 11 according to the lateral deflection of the slit lamp 2, i.e. the displacement of the slit lamp 2 in the direction of arrow x can be an electronic control or a mechanical coupling. However, electronic control is preferred, since electronic control makes it easy to adjust the chin rest by motor.

Furthermore, instead of the excimer laser described, another laser, for example an HF laser with a wavelength in the infrared range, can also be used.

The simplicity has been assumed above from a device in which the patient sits. The ideas according to the invention can of course also be used in a device in which the patient lies.

Claims

Patent claims

1. Device for laser surgery and in particular for keratotomy of the cornea, with a laser, in particular a UV laser (1), the beam (7) of which can be imaged on the tissue to be operated on, and an aperture (14) arranged in its beam path which delimits the illuminated area of the tissue, characterized in that the device has a slit lamp (2) which can be displaced perpendicularly (x) to the axis of the eye and parallel to the connecting line of the two eyes and a headrest (4) which can be displaced in the direction of the axis of the eye (y) , and that the beam (7) of the laser (1) is initially guided in the direction (x) of the linear displacement of the slit lamp (2), and into the beam path of the slit lamp (9) by means of a mirror device (9) that is firmly connected to the base of the slit lamp (9). 2) is reflected, the gap (14) also serves as an aperture for the surgical light beam.

2. Device according to claim 1, characterized in that the slit lamp is held on a telescopic arm (5) linearly displaceable.

3. Apparatus according to claim 1 or 2, characterized in that an electronic control with linear displacement of the slit lamp (1) moves the headrest (4) motorized such that the distance between the slit lamp and the eye to be operated remains constant, and the mirror device (9 ) on the eye to be operated on.

4. Device according to one of claims 1 to 3, characterized in that the gap (14) of the Spaltleuch¬ te (1) between two collecting optical elements (13, 15) is arranged, which form a telecentric arrangement.

5. Device according to one of claims 1 to 4, characterized in that an optical rotary element (12) is arranged to rotate the gap image between the gap (14) and the tissue to be operated, which rotates the beam about the optical axis.

6. The device according to claim 4, characterized in that the rotary element (12) between the gap (14) and the second collecting optical element (15) is arranged.

7. Device according to one of claims 1 to 6, characterized in that the headrest + tze is a chin rest in a seated patient.

8. Device according to one of claims 1 to 7, characterized in that the laser is an excimer laser.

9. The device according to claim 8, characterized in that tempered prisms made of quartz glass are used as mirror elements for beam deflection.