Abstract:
The invention relates to a contact glass for ophthalmic surgery. Said glass comprises a lens body that is held in a frame and a front lens surface that is designed to be placed against the eye. According to the invention, the front lens surface is concave and follows a surface curvature (K) and an annular gap is formed at the edge of the front lens surface between the lens body and the frame, said gap being used to apply a negative pressure in order to fix the contact glass to the eye. The frame is designed to follow the contour of an imaginary continuation of the surface curvature (K), or at least does not project beyond the latter.

Description:
FIELD OF THE INVENTION 
     The invention relates to a contact glass for ophthalmic surgery, which glass comprises a anterior lens surface provided for placement onto the eye and means for fixing the contact glass to the eye by vacuum. 
     Such contact glass is shown in WO 2005/048895 A1, which otherwise deals with fixing the contact glass to a laser treatment device. 
     BACKGROUND OF THE INVENTION 
     Contact glasses in ophthalmic surgery are examples of adapters which mechanically couple the laser processing device to an object. Such coupling is required because the precision with which the laser beam is positioned in the object usually determines the precision achieved in processing. Only exact three-dimensional positioning of the laser beam in the processing volume, for example in the cornea of the eye, allows high-precision processing. Therefore, fixation of the object to be processed is effected via an adapter ensuring a precisely defined position of the object, for example of the eye, relative to the laser processing device. The adapter, which is usually referred to as contact glass, is thus part of the beam path. If the exact external shape of the object to be processed is not known, the adapter at least also functions to give the object, if possible, a certain shape which is pre-defined when applying a laser beam. 
     Since the anterior surface of the human eye&#39;s cornea varies from patient to patient, an adapter in the form of a contact glass is regularly provided in laser-assisted ophthalmic surgery. US 2001/0021844 A1 describes a corresponding contact glass which not only fixes the eye, but also deforms the anterior surface of the cornea. The US publication proposes to apply a vacuum between the cornea and the contact glass provided as a lens body, by which vacuum the eye&#39;s cornea is drawn towards the contact glass. With the lens body and the eye&#39;s cornea fixed by vacuum in this manner, the eye&#39;s cornea automatically assumes the shape of the lens body&#39;s anterior surface (anterior surface with respect to the patient). However, this type of fixing is rather inconvenient for the patient, in particular when using the barb-shaped projections provided at the bottom surface of the lens body mount according to one embodiment of US 2001/0021844 A1, said projections being intended to achieve improved fixing of the contact glass to the eye. 
     SUMMARY OF THE INVENTION 
     Therefore, it is an object of the invention to further embody a contact glass of the above-mentioned type such that secure fixing of the lens body to the eye and reliable deformation of the cornea are effected as gently as possible for the patient. 
     According to the invention, this object is achieved by a contact glass of the type mentioned above, wherein the anterior lens surface is annularly surrounded by an annular gap, which does not protrude with respect to an imaginary extension of the anterior lens surface, or by a multiplicity of suction orifices, through which gap/orifices a vacuum acts on the eye. 
     Thus, the eye&#39;s cornea is placed in contact with the anterior surface of the lens, or held against it, by mechanical pressure, said mechanical pressure resulting from suction of the eye&#39;s cornea effected in a ring-shaped region surrounding the anterior surface of the lens. The ring-shaped region comprises suction orifices which apply the vacuum. This approach has essential advantages. First, the vacuum can be applied to the eye&#39;s cornea as gently as possible. Moreover, according to an embodiment it is excluded that the eye&#39;s cornea is sucked in a ring shape into an annular gap. This also prevents undesired occlusion of the suction channel. On the other hand, the patient side of the contact glass can be substantially smooth; the eye is pressed against a smooth surface provided with suction orifices. This prevents sharp edges acting on the eye, and the complicated production method required in the prior art in order to avoid sharp edges at a suction ring is now eliminated. Thus, the invention provides a contact glass for ophthalmic surgery, which contact glass comprises a lens body, which is received in a mount and has a concave anterior lens surface designed to be placed on the eye, there being formed, at the periphery of the anterior lens surface between the lens body and the mount, an annular gap or ring-shaped region which, together with the contacted eye, acts as a suction channel via which the vacuum for fixing the contact glass to the eye can be applied, and the mount does not protrude with respect to an imaginary extension of the anterior lens surface. Together with the contacted eye, the annular gap or ring-shaped region forms a mostly air-tight chamber, allowing a force to be applied for fixing the contact glass to the eye&#39;s cornea by a vacuum. 
     The object is achieved, for example, by a contact glass of the above-mentioned type, wherein the mount is formed such that the suction channel between the annular gap and the eye is not yet closed when the eye is in full-surface contact with the anterior lens surface. 
     In contrast to the approach described in US 2001/0021844 A1, the eye&#39;s cornea is, thus, not sucked directly onto the anterior lens surface by a vacuum, but contacts the anterior lens surface due to mechanical pressure. Since the mount is provided such that the suction channel between the annular gap and the eye still remains open (i.e. the eye&#39;s cornea does not yet cover the annular gap) when the eye is in full contact with the anterior lens surface, exact mutual aligning of the contact glass and the eye can be effected. Only if the contact glass is pushed further towards the eye does the eye&#39;s cornea cover the annular gap, so that the suction channel between the annular gap and the eye is closed and the fixation by vacuum becomes active. Thus, the vacuum applied in the annular gap only serves to fix the eye, but does not directly cause the eye&#39;s cornea to deform. This makes the entire process of contacting and fixing easier to control. 
     The vacuum applied through the suction channel only serves to fix the eye&#39;s cornea, but does not directly cause the eye&#39;s cornea to deform, because no vacuum acts between the anterior surface of the lens and the eye&#39;s cornea. Thus, the contact glass according to the invention is particularly suitable for patients with corneal damage, anomalies or even cuts from previous ophthalmic operations that never healed in the region of the cornea to be placed in contact with the anterior surface of the lens. Since there is no vacuum acting in this region of the eye&#39;s cornea, a damaging effect can now be excluded when fixing the contact glass. 
     Thus, on the patient&#39;s side, the transition between the anterior lens surface and the mount is smooth (except for the annular gap); beyond the annular gap, the mount does not constitute a discontinuity. 
     The mount has a geometric design such that the eye&#39;s cornea, in a state where the eye is already in full-surface contact with the anterior lens surface, does not yet contact the edge of the mount which limits the annular gap and, as a consequence, does not yet close the annular gap to the suction channel. This may be achieved, for example, in that the axially foremost contour of the mount does not protrude, or even recedes, with respect to a curved surface which the eye&#39;s cornea has when the eye fully contacts the anterior lens surface. The shape of the curved surface depends substantially on the state which the eye has when it fully contacts the anterior lens surface. 
     A simple design also allows to refer the curved surface, with respect to which the axially foremost contour of the mount does not protrude or even recedes, to the curvature of the anterior lens surface, so that the axially foremost contour of the mount will then not protrude or will even recede with respect to the imaginary extension of the anterior lens surface. 
     The contact glass according to the invention allows the natural shape of the cornea to be maintained with the contact glass placed thereon, which is particularly convenient for the patient. The eye is placed in contact with the contact glass at a suitable radius of curvature with minimal deformations. 
     Particularly simple manufacture is achieved if the annular gap is formed by one or more frustoconical surfaces or conical surfaces, respectively, on the mount and/or on the lens body. Moreover, a further embodiment is easily realized by such conical surfaces as a rule, wherein the annular gap tapers away from the eye and, in particular, tapers off at an acute angle of less than or equal to ninety degrees at the end facing away from the eye. 
     Such design of the annular gap is further advantageous, because it effectively prevents parts of the eye&#39;s cornea from being sucked into the upper region of the suction channel and thereby partially clogging it. As a consequence, introduction of the vacuum into the annular gap is uncritical then, because the entire annular gap is always effective as a suction channel and, in particular, the vacuum connector cannot be occluded by the eye&#39;s cornea. 
     The contact glass according to the invention enables particularly easy placement of the contact glass onto the eye&#39;s cornea, in particular if the curved surface of the anterior lens surface has a slightly flatter curvature than the eye&#39;s cornea. When approaching the contact glass, only the central region of the eye&#39;s cornea, i.e. the corneal vertex, touches the anterior lens surface. As placement progresses, the eye&#39;s cornea gradually contacts the full anterior lens surface, with the suction channel still not being closed in this condition either and the patient still being able to move his eye freely in spite of partial deformation. In this condition, easy alignment of the contact glass with the eye is possible. Once the desired adjustment position is achieved, the distance between the contact glass and the patient&#39;s eye is reduced somewhat further, causing the annular gap to be closed by the cornea of the eye and causing the eye to be vacuum-fixed relative to the contact glass. 
     The curved surface imposed upon the eye as the desired shape by the anterior lens surface can be selected in an application-dependent manner. In particular, aspherically curved surfaces are also possible which allow optical imaging errors to be minimized when introducing treatment laser radiation. The anterior lens surface may also be spherical, with a radius of from 5-30 mm. A radius of slightly less than that of the human cornea, i.e. between 15 and 25 mm, for example, is particularly preferred. This sphericity is possible without a problem due to the design according to the invention, because contrary to the prior art in the form of US 2001/0021844 A1, there is no danger of the eye&#39;s cornea occluding the vacuum suction channel such that the contact glass is fixed only incompletely to the eye. 
     The suction orifices surrounding the anterior surface of the lens in a ring shape are preferably provided as part of a suction channel. Further, the suction orifices are favorably provided such that, when the eye fully contacts the anterior surface of the lens, they are not yet covered by the eye&#39;s cornea so that suction is not yet effected as a result. In this condition, precise positioning of the contact glass relative to the eye is possible. It is only when the contact glass is pressed further onto the eye that the eye&#39;s cornea also covers the suction orifices, whereby the vacuum fixation becomes effective. 
     This design of the contact glass may be achieved, for example, by the annular region in which the suction orifices located being angled relative to the optical axis and/or having a concave curvature, e.g. one which is slightly smaller than the curvature of the eye&#39;s cornea. Of course, the anterior surface of the lens may also be concave. 
     A convenient and particularly easy-to-produce structure of the contact glass consists in that the anterior surface of the lens is formed on a lens body held in a mount, with the suction orifices being provided in the mount. The just mentioned two-step mounting, wherein the vacuum mounting is effective only when the contact glass, in its adjusted condition, is pressed further onto the eye, can then be achieved simply if the axially forward contour of the mount does not protrude with respect to a curvature which the eye&#39;s cornea has when the eye is in full contact with the anterior surface of the lens, or if said contour even recedes relative to said curvature. That part of the mount which comprises the suction orifices will conveniently be seamlessly contiguous with the anterior surface of the lens. 
     Particularly easy production is achieved if the suction channel is formed between the mount and the lens body and individual channels extend from the suction channel through the wall of the mount and into the suction orifices. The suction channel may then be, for example, an annular gap between the mount and the lens body, which gap is covered by a wall of the mount on the patient&#39;s side, said wall extending from an exteriorly located edge of the mount to the edge of the anterior surface of the lens. Breakthroughs in this wall form individual channels and, thus, form the suction orifices. 
     The number of suction orifices is not fixed to a specific figure but will have to be selected according to the conditions of manufacture. The shape of the suction orifices may also be selected according to conditions of manufacture; in particular, they may be round, oval or rectangular. In order to prevent injuries of the eye&#39;s cornea, care should be taken, of course, to remove burrs during manufacture. 
     The curved surface imposed upon the eye as the desired shape by the anterior lens surface can be selected in an application-dependent manner. In particular, aspherically curved surfaces are also possible which allow optical imaging errors to be minimized when introducing treatment laser radiation. 
     The contact glass according to the invention allows the natural shape of the cornea to be maintained with the contact glass placed thereon, which is particularly convenient for patients. With a suitable curvature of the anterior lens surface, the eye is placed in contact with the contact glass with minimal deformations. The anterior lens surface may be spherically curved in this case, having a radius of curvature of 5-30 mm; a radius which is slightly greater than that of the human eye is preferred and therefore lies in the range from 15-25 mm. 
     The annularly arranged suction orifices effectively prevent parts of the eye&#39;s cornea being sucked into the upper part of the suction channel and thus partially occluding the latter. As a consequence, introduction of the vacuum into the suction channel is uncritical, because the entire suction channel is effective at all times and, in particular, the vacuum connector cannot be occluded by the eye&#39;s cornea. 
     The contact glass according to the invention enables particularly easy placement of the contact glass onto the eye&#39;s cornea, in particular if the curved surface of the anterior lens surface has a slightly flatter curvature than the eye&#39;s cornea. When approaching the contact glass, only the central region of the eye&#39;s cornea, i.e. the corneal vertex, touches the anterior lens surface. As placement progresses, the eye&#39;s cornea gradually contacts the full anterior lens surface, with the suction orifices still not being covered in this condition either and the patient still being able to move his eye freely in spite of partial deformation. In this condition, easy alignment of the contact glass with the eye is possible. Once the desired adjustment position is achieved, the distance between the contact glass and the patient&#39;s eye is reduced somewhat further, causing the annular gap to be closed by the cornea of the eye and causing the eye to be vacuum-fixed relative to the contact glass. 
     It has turned out that suction of the conjunctiva (sclera) to the vacuum fixing means should be avoided during vacuum fixing of an ophthalmic contact glass, because otherwise insufficient fixing of the eye&#39;s cornea on which surgery is to be performed may occur. Thus, said vacuum fixation preferably acts exclusively on the cornea and not on the sclera of the eye. 
     Regardless of how the contact glass is designed in other respects and in particular regardless of the design of the means for vacuum fixation, it is convenient to provide a contact glass for ophthalmic surgery comprising an anterior lens surface designed to be placed on the eye and means for vacuum fixture of the contact glass to the eye, and which is further characterized in that a coding element encoding a geometric or optical parameter of the contact glass is provided on the contact glass. The geometric or optical parameter is conveniently the diameter of the anterior lens surface. The coding element is favorably attached to the contact glass in a manner allowing a user, i.e. an eye surgeon, to recognize the desired geometric or optical parameter, e.g. the desired diameter of the anterior lens surface, from the outside. A suitable coding element is a bar code, a number or letter code or even a geometric or color code, for example. A contact glass bearing a color mark is particularly preferred, the color mark being assigned to the diameter of the anterior lens surface or to another geometric or optical parameter of the contact glass. If the contact glass is produced in two parts, i.e. from a lens body comprising the anterior lens surface as well as a mount holding the lens body, it will be favorable to arrange the coding element on the mount. In the case of a color code, the mount itself can be colored, for example. 
     Of course, a variant is also possible including an information carrier and a device for wireless reading and/or modification of the information stored thereon. The transmission of information may be effected by electromagnetic signals (e.g. in the radio frequency range between 100 kHz and 1 GHz, or as described in WO 2005039462 A1). 
     The device for wireless reading and/or modification of the stored information, which device communicates with the contact glass, may comprise a transmitter and a receiver. By its signal, the transmitter can transmit energy to the information memory, which information the latter uses in turn to emit information stored by it in the form of a response signal. 
     It is possible to modify the information stored in the information memory by means of a signal from the transmitter. (When transmitting information again from the accessory part to the product, the modified information will then be transmitted.) The information memory and the mount may constitute a mechanical unit, and it is possible to sterilize the accessory part together with the integrated information memory. 
     In order to allow a user to select a contact glass having the desired parameters, the code is advantageously provided as an optically perceivable code, allowing a surgeon to select the desired contact glass in a quick and unerring manner. 
     Use of the above-described coding element is particularly advantageous, of course, in a contact glass of the type described hereinbefore or hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in more detail below, by way of example and with reference to the Figures, wherein: 
         FIG. 1  is a schematic representation of a laser processing device for ophthalmic surgery; 
         FIG. 2  is a schematic view of a patient&#39;s cornea; 
         FIGS. 3 and 4  depict a contact glass for the laser processing device of  FIG. 1 , with  FIG. 3  being a top view and  FIG. 4  being a sectional view; 
         FIGS. 5 to 8  are schematic sectional views of contact glasses similar to that of FIG.  3 / 4 ; 
         FIG. 9  is a sectional view of a further variant of a contact glass for the laser processing device of  FIG. 1 ; 
         FIG. 10  is a plan view of the contact glass of  FIG. 9  from below (with respect to  FIG. 3 ) and 
         FIG. 11  is a representation similar to  FIG. 10  depicting a further construction of a contact glass. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a treatment device for an ophthalmic method similar to those described in EP 1159986 A1 and U.S. Pat. No. 5,549,632. The treatment device  1  of  FIG. 1  serves to perform correction of an eyesight defect on a patient&#39;s eye  2  according to the known femtosecond LASIK method. For this purpose, the treatment device  1  has a laser  3  which emits pulsed laser radiation. The pulse duration is within the femtosecond range, for example, and the laser radiation acts by means of non-linear optical effects in the cornea, as described above. The treatment beam  4  emitted by the laser  3  along an optical axis A 1  is incident on a beam splitter  5  which transmits the treatment beam  4  to a scanning unit  6 . The scanning unit  6  comprises two scanning mirrors  7  and  8  which are rotatable about mutually orthogonal axes such that the scanning unit  6  two-dimensionally deflects the treatment beam  4 . Adjustable projection optics  9  focus the treatment beam  4  onto or into the eye  2 . The projection optics  9  comprise two lenses  10  and  11 . The treatment device  1  is a laser processing device. 
     Arranged following the lens  11  is a contact glass  12  which is securely connected to the lens  11 , and thus to the beam path of the treatment device  1 , via a holder H. The contact glass  12 , which will be explained in more detail below, contacts the cornea of the eye  2 . The optical combination of the treatment device  1  with the contact glass  12  fixed thereto causes the treatment beam  4  to be focused in a focus  13  located within the cornea of the eye  2 . 
     Like the laser  3  and the projection optics  9 , the scanning unit  6  is controlled by a control device  14  via control lines (not specifically designated). The control device  14  determines the position of the focus  13  both transverse to the optical axis A 1  (by the scanning mirrors  7  and  8 ) and in the direction of the optical axis A 1  (by the projection optics  9 ). 
     The control device  14  further reads out a detector  15  which reads out radiation scattered back from the cornea and passing through the beam splitter  5  as return radiation  16 . The detector  15  allows very precise control of the operation of the laser  3 . 
     The contact glass  12  ensures that the cornea of the eye  2  obtains a desired specified shape. Due to the cornea  17  contacting the contact glass  12 , the eye is located in a predetermined position with respect to the contact glass  12  and thus to the treatment device  1  connected thereto. 
     This is schematically illustrated in  FIG. 2  which shows a sectional view of the eye&#39;s cornea  17 . In order to achieve exact positioning of the focus  13  in the eye&#39;s cornea  17 , the curvature of the eye&#39;s cornea  17  has to be considered. The cornea  17  has an actual shape  18  which differs from patient to patient. The adapter  12  contacts the eye&#39;s cornea  17  such that it deforms the latter towards a desired shape  19 . The exact profile of the desired shape  19  depends on the curvature of the anterior lens surface of the contact glass that faces towards the eye  2 . Known geometric and optical conditions for introducing and focusing the treatment beam  4  into the cornea  17  are given by the adapter  12 . Since the cornea  17  contacts the contact glass  12 , which is in turn stationary with respect to the beam path of the treatment device  1  due to the holder H, exact three-dimensional positioning of the focus  13  is achieved by controlling the scanning unit  6  as well as the adjustable projection optics  9 . 
       FIGS. 3 and 4  show an embodiment of the contact glass  12  in detail;  FIG. 4  is a sectional view,  FIG. 3  is a front view of the contact glass  12  (bottom view in  FIG. 4 ), i.e. within view of the patient. The contact glass  12  has a two-part design and consists of a lens body  22 , which is secured in a mount  37 , e.g. glued in at a gluing location  43 . The lens body consists of glass or a medically approved plastic material, e.g. PMMA or polycarbonate. These substances are also suitable for the mount, which may be additionally made of polyurethane or silicone rubber. By pressing the contact glass  12  onto the eye&#39;s cornea  17 , the anterior lens surface  29  of the lens body  22  held in the mount  37  imparts the desired shape  19  to the eye&#39;s cornea  17 . 
     In order to provide the vacuum, the mount  37  comprises a port  38 , which includes a Luer lock connection  39  as well as a vacuum supply line  40  extending inside the port. The supply line  40  terminates laterally of the lens body  22  above an attachment ring  41  of the mount  37 . An annular gap  41  is formed between an inner ring surface  46  of the attachment ring  41  and the lens rim  47 , which is frustoconical in this embodiment, said annular gap  41  being in communication with the supply line  40  and acting as a suction channel by which a vacuum can be applied in a ring shape on the eye&#39;s cornea. Thus, the contact glass  12  is fixed to the eye by a vacuum at the Luer lock connection  39  such that the cornea contacts the anterior lens surface  29  by mechanical pressure, thus achieving the desired shape  19 . 
     The attachment ring  41  protrudes from the anterior lens surface  29  relative to the optical axis A 1 . 
     When placing the contact glass on the eye&#39;s cornea, contact is established first between the anterior lens surface  29  and the corneal vertex. As the application of the eye&#39;s cornea to the anterior lens surface  29  progresses, contact with the eye&#39;s cornea is established in an increasingly large surface region of the anterior lens surface. When the eye&#39;s cornea fully contacts the anterior lens surface  29 , no contact is established yet between the axially foremost contour line of the attachment ring  41  and the eye&#39;s cornea, due to the increasing curvature in the peripheral region of the eye&#39;s cornea, so that the suction channel provided by the annular gap  44  is not yet closed by the eye&#39;s cornea. Accordingly, it is still possible in this condition to adjust the eye, which is in contact with the anterior lens surface  29 , such that the optical axis A 1  is located exactly as desired, e.g. coincides with the axis of vision. Only upon pressing the contact glass and the eye closer together does the eye&#39;s cornea also contact the axially foremost contour line  45  of the attachment ring  41 , whereby the suction channel at the annular gap  44  is closed at the suction orifices  45  and the contact glass  12  is fixed to the eye. 
     The mount  37  is accordingly designed such, with respect to the attachment ring  41 , that the axially foremost contour line  45  of the attachment ring  41  does not protrude relative to that of a curved surface defined by the curvature of the eye when the eye&#39;s cornea is in full contact with the anterior lens surface  29 . In one embodiment, the attachment ring  41  is located exactly in the imaginary extension of the curved surface. For simplification, the curvature of the anterior lens surface  29  can also be used as a reference. 
     Tapering off from the eye, the shape of the annular gap  44  reliably prevents parts of the cornea being sucked into the region of the supply line  40  and thereby at least partially clogging or covering it. Clogging of the suction channel  44  is also avoided, so that ring-shaped application of the vacuum is ensured. 
       FIGS. 5 to 8  schematically show different embodiments of the geometry of the lens body  22  and mount  37 . Any elements already present in the construction of FIGS.  3 / 4  are designated with the same reference symbols, so that reference is made here also to the description pertaining to  FIGS. 3 and 4 . 
     The contact glass  12  again comprises the lens body  22  which is held in the mount  37 . The lens body  22  is limited by an entrance surface  23  and the anterior lens surface  29 . The shape of a piano-concave lens is preferred, with the curvature of the concave anterior lens surface  29  particularly preferably corresponding to the human cornea or having a somewhat flatter curvature. However, other shapes are also possible. In particular, the anterior lens surface  29  may also be aspherical so as to minimize optical imaging errors. 
     The mount  37  encloses the lens body  22  on part of its circumference, thus forming a connecting surface between the lens body  22  and the mount element  37  substantially along a cylindrical shell. The annular gap  44  serving as a suction channel is formed between the rim of the lens body  22  and the attachment ring  41  of the mount  37  and the rim  47  of the anterior lens surface  29  of the lens body  22 . 
     Now, in order to provide the annular gap, as shown in  FIGS. 5 to 8 , either the internal ring surface  46  of the attachment ring  41  and/or the lens rim  47  may be conical, i.e. may extend obliquely with respect to the optical axis A 1 . In the embodiment of  FIG. 5 , the lens rim  47  is conical and the internal ring surface  46  is cylindrical. Further, it is clearly evident that the attachment ring  41  does not protrude, but rather recedes somewhat, with respect to the already mentioned curved surface K, which is predetermined by the curvature of the contacted cornea of the eye. The construction of  FIG. 5  has the advantage that a simple, substantially tubular mount  37  can be used. Further, the diameter of the anterior lens surface  29  is smaller than that of the entrance surface  23 . 
     The opposite case is shown in  FIG. 6 , wherein the lens rim  47  is cylindrical, while the internal ring surface  46  is conical, with the cone now opening towards the curved surface K. Also, the attachment ring  41  extends exactly as far as the curved surface K here. 
     In the construction according to  FIG. 7 , both the lens body  22  at the lens rim  47  (tapering towards the eye) and the internal ring surface  46  (expanding towards the eye) are conical. Further, the axially foremost contour line of the attachment ring  41  recedes with respect to the curved surface K. This has the advantage that full adjustment of the eye with respect to the contact glass  12  is possible and the suction channel is closed by the contact of the eye&#39;s cornea only upon applying additional mechanical pressure. 
     Finally,  FIG. 8  shows a construction similar to that of  FIG. 7 . However, both the internal ring surface  46  and the lens rim  47  conically taper towards the eye. In this case, it is advantageous if the contact surface of the contact glass  12  on the eye has a smaller diameter, while the entrance surface  23  has a large diameter. 
       FIG. 9  shows a detail of a further variant of the contact glass  12  in a sectional view. This is a modification of the contact glass of  FIGS. 3 and 4 ; therefore, like elements are identified by like reference symbols. The contact glass  12  has a two-part design and consists of the lens body  22 , which is secured in a mount  37 , e.g. by gluing. The lens body  22 , which may be made of glass, for example, has the planar entrance surface  23 , at which the treatment radiation from the laser treatment device  1  is supplied, and the anterior lens surface  29 , which is located opposite, on the patient&#39;s side, and is adapted to the curvature of the human cornea. By pressing the contact glass  12  onto the eye&#39;s cornea  17 , the anterior lens surface  29  of the lens body  22  held in the mount  37  imparts the desired shape  19  to the eye&#39;s cornea  17 . The lens body  22  consists of glass or of medically approved plastics, such as PMMA or polycarbonate. These materials are also suitable for the mount, which may be additionally made of polyurethane or silicone rubber. 
     In order to provide the vacuum, the mount  37  comprises the port  38  which is provided with the connecting port  39 , with a vacuum tube fitted thereon, as well as the vacuum supply line  40  extending inside the port  38 . The supply line  40  terminates laterally of the lens body  22  above the attachment ring  41  of the mount  37 . 
     With its surface located on the patient&#39;s side (viewed from below in the illustration of  FIG. 3 ), the attachment ring  41  continues the curvature of the anterior lens surface  29  such that the axially outermost contour of the attachment ring  41  is located, in the form of the lower edge  42 , in an extension of the curvature of the anterior lens surface  29 . The suction surface  43  is formed between said edge  42  and the outer edge of the anterior lens surface  29 . 
     The suction surface  43  covers the annular suction channel  44 , which is formed by a gap between the mount  37  and the lens body  22  in this embodiment. In principle, however, it would also be possible for the suction channel to be located completely within the material of the mount  37 . In the embodiment shown in  FIG. 9 , the suction surface  37  is thus formed by a wall extending from the outermost edge  42  of the attachment ring  41  to the edge of the anterior lens surface  29 . In the suction surface  43 , i.e. within said wall, suction orifices  45  are formed, which constitute the patient-side ends of individual channels  46  whose other ends terminate in the suction channel  44 . 
     Thus, through the vacuum supply line  40 , a vacuum applied to the vacuum connection  39  reaches the vacuum channel  44 , where it acts on the eye&#39;s cornea by means of the suction orifices  45  surrounding the anterior lens surface  29  in a ring-shaped manner. 
     Since the suction surface  43  preferably continues the curvature of the anterior lens surface  29  in a smooth manner (with a continuation of a spherically curved surface being possible, but also an aspherical curvature or a curvature with a radius of curvature which differs from that of the anterior lens surface  29  and is either greater or smaller), there is a largely smooth transition from the anterior lens surface  29  to the suction surface  43  on the whole. In any case, the transition has no sharp edges, but consists, at the most, of an annular boundary at which the curvature or inclination changes. 
       FIG. 10  shows the contact glass  12  of  FIG. 9  in a view from the patient&#39;s side, i.e. from below in  FIG. 9 . As is clearly visible, the suction orifices  45  are oval here and surround the anterior lens surface  29  externally of a boundary  147  between the mount  37  and the lens body  22  in the region of the annular suction surface  43 . 
       FIG. 11  shows a modified design, wherein the suction orifices  45  have a different geometric shape, namely the shape of half-ovals providing an arcade-shaped structure of the suction orifices  45 . The vacuum connection is also differently designed here, namely as a Luer lock connection. 
     The diameter of the annular suction surface  43  and thus also of the anterior lens surface  29  is preferably selected in a patient-dependent manner. Thus, different contact glasses  12  having different diameters of the anterior lens surface  29  and thus different diameters of the annular suction surface  43  are kept in store for one single treatment device, so that the suction orifices  45  are definitely in place on the cornea of the patient receiving treatment, thus ensuring optimal suction. This avoids suction of the conjunctiva in the region of the suction surface  43 . In order to make it easier for the user to distinguish between different contact glasses  12 , e.g. contact glasses having different diameters of the anterior lens surface  29  (and thus of the suction surface  43 ) or having different radiuses of curvature, a code is optionally provided in the region of the mount  37 . It is particularly advantageous here to dye the entire mount. 
     Alternatively, the mount is provided with an RFID chip and the device  1  is provided with a corresponding transmitter/receiver unit. The range of the transmitter/receiver unit is confined to a narrow space (e.g. 10 cm). When the contact glass is placed in the mount, the device  1  verifies, evaluates and, if necessary, modifies the stored information. Such modification is advantageous in disposable contact glasses, because it allows avoidance of repeated use. 
     Specifically, the RFID chip may be integrally cast. The RFID chip may be sterilized individually or in connection with the entire contact glass. A glass sterilization using ethylene dioxide (ETO) is preferable. The treatment device  1  is equipped with an RFID transmitter/receiver and reads the stored information (e.g. of an ID or use code). Multiple use is prevented either in that the same code of use is accepted only once by the respective device  1 , i.e. only one single laser therapy is activated by this ID code (as described also in US 2006/0129140), or the device  1  modifies the information in the chip such that a second or n th  use is ruled out even with other devices. 
     Of course, this principle may be employed for any combinations of an accessory part and a medical device. 
     For easier observation of the patient&#39;s eye when using the contact glass  12 , it is possible to irradiate light from a light source through the mount  37  to the site of treatment. This is described, for example, in DE 10353264 A1. The suction surface  43  being interrupted merely in the region of the suction orifices  45  considerably facilitates coupling-in of the radiation and it is no longer required to use the optical means described in DE 10353264 A1, which are provided in order to compensate for the optical effect of an annularly opened suction channel. 
     When placing the contact glass on the eye&#39;s cornea, contact is established first between the anterior lens surface  29  and the corneal vertex. As the application of the eye&#39;s cornea to the anterior lens surface  29  progresses, contact with the eye&#39;s cornea is established in an increasingly large surface region of the anterior lens surface. When the eye&#39;s cornea fully contacts the anterior lens surface  29 , no contact is established yet between the axially foremost contour line of the attachment ring  41  and the eye&#39;s cornea, due to the increasing curvature in the peripheral region of the eye&#39;s cornea, so that the suction orifices  45  are not yet covered by the eye&#39;s cornea. Accordingly, it is still possible in this condition to adjust the eye, which is in contact with the anterior lens surface  29 , such that the optical axis A 1  is located exactly as desired, e.g. coincides with the axis of vision. Only upon pressing the contact glass and the eye closer together does the eye&#39;s cornea also contact the axially foremost contour line  42  of the attachment ring  41 , whereby the suction channel  44  is closed at the suction orifices  45  and the contact glass  12  is fixed to the eye. 
     For example, the mount  37  is designed such, with respect to the attachment ring  41 , that the axially foremost contour line of the periphery  42  of the attachment ring  41  does not protrude relative to that of a curved surface defined by the curvature of the eye when the eye&#39;s cornea is in full contact with the anterior lens surface  29 . In one embodiment, the periphery  42  is located exactly in the imaginary extension of the curved surface. For simplification, the curvature of the anterior lens surface  29  can also be referred to. 
     Of course, the geometric designs described herein can also be advantageously used individually or in other combinations not explicitly shown or described.