Patent Publication Number: US-10322031-B2

Title: Ophthalmological device

Description:
RELATED APPLICATIONS 
     The present application is a continuation of U.S. application Ser. No. 15/415,353, filed Jan. 25, 2017, entitled “Ophthalmological Device,” which is a continuation of U.S. application Ser. No. 14/006,017, filed Nov. 26, 2013, now U.S. Pat. No. 9,554,943, issued Jan. 31, 2017, entitled “Ophthalmological Device,” which is a National Phase entry of PCT Application No. PCT/EP2012/050035, filed Jan. 3, 2012, which claims priority to DE Application No. 102011006085.5, filed Mar. 25, 2011, and U.S. Provisional Patent Application No. 61/467,712, filed Mar. 25, 2011, which applications are incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an ophthalmic instrument for the use of laser radiation on and in the eye, especially for the examination and/or surgical laser treatment of the cornea and the lens of the eye. 
     BACKGROUND 
     Ophthalmic instruments are used, for example, to correct an ametropia of the human eye by means of a surgical laser operation on the cornea. A method of particular importance is known as “LASIK” (laser in-situ keratomileusis), in which, by application of a pulsed laser beam, material is ablated from inside the cornea rather than from its surface. For this purpose, a flap is formed on the outer corneal surface, the thickness of this flap being substantially smaller than the thickness of the cornea. For the ablation treatment proper, the flap is folded back, whereupon a pulsed laser beam is used to ablate material from the exposed area to correct the ametropia. Thereafter, the flap is closed again onto the treated surface. 
     To form the flap at a precisely defined depth of the cornea and as gently and precisely as possible, it has been suggested to use femtosecond laser pulses, i.e. laser pulses having pulse widths smaller than 10 −12  s. By application of such pulses it is possible to create localized optical ruptures in the cornea, known as photodisruptions, the size of which is limited to a few micrometers. By positioning a dense array of many such disruptions in exactly defined places, the flap can be made to measure very precisely. For the precise forming of the flap it is essential that the focus of the pulsed laser beam is exactly positioned not only laterally but also, and mainly so, in the depth of the cornea, i.e. in the propagation direction of the laser beam. 
     In this connection, DE 10 2005 013 949 A1 describes a scanning device for, and a method of, focusing a beam of rays into a given volume. This scanning device is especially suitable for use in instruments intended for surgical laser treatment of the cornea with laser radiation pulsed in the femtosecond range. The device allows the laser light to be focused on any target points within the cornea. 
     DE 10 2008 027 358 A1 describes a laser system that can be used in ophthalmic instruments for the analysis and treatment of the lens of the eye. Other than laser systems in comparable instruments, it has the advantage that the detection of the laser light backscattered in the lens of the eye is possible with greater accuracy, so that a refractive surgical therapy of the lens of the eye can be performed with higher precision. For this therapy, laser radiation pulsed in the femtosecond range is focused on selected target points within the lens of the eye. 
     The state of prior art described above regarding the medical examination and surgical laser treatment of the cornea (situated at the periphery of the eye) on the one hand and the lens (situated within the eye) on the other has the disadvantage that the ophthalmic instruments available satisfy the requirements of one of these special applications only; i.e., they differ with regard to their imaging properties, in particular: to their aperture, focal spot size, focus position in the eye, correction of the aperture aberration or correction of field aberrations to such an extent that they are exclusively suitable either for the examination and treatment of the cornea or for the examination and treatment of the lens of the eye. 
     This means that an oculist needs to procure two instruments, which is inefficient (a) with regard to acquisition cost and (b) because several single-purpose instruments are seldom used to capacity. In addition, separate instruments involve extra time for getting adjusted at least to the same eye of a patient being examined. 
     SUMMARY OF THE INVENTION 
     Departing from this, the invention is based on the problem of creating an ophthalmic instrument that can be used for the examination and surgical laser treatment of both the cornea and the lens of the eye. 
     According to the invention, this problem is solved by an ophthalmic instrument of the kind described above, which comprises:
         a femtosecond laser as a source of laser radiation,   an objective from which laser radiation emerges that is focused in the direction of the patient&#39;s eye,   optical assemblies   which are arranged upstream of the objective, and   which are, in operative connection with the objective, intended for varying the focus position in the coordinate direction X, Y and Z, selectively either within the region of the cornea or within the region of the lens of the eye,   with the objective itself being movable relative to the eye or at least having one lens group whose position is movable relative to the eye,   the variation of the objective or lens group position being intended to shift the focus position from the region of the cornea to the region of the lens of the eye and vice versa.       

     The distances are varied by shifting the respective lens groups of the objective along their optical axis. Besides the focus position, the variation of the distances also influences the correction of the imaging aberrations. Variation of the focus in depth causes changes, e.g., in spherical aberration, unless this is compensated by the lens movements. 
     Favorably, the lens groups of the objective can be displaced between two limit positions that define two different specified distances along the optical axis. One of these limit positions is assigned to the focus positioned in the region of the cornea, the other to the focus positioned in the region of the lens of the eye. In the sense of the invention, positioning the focus “in the region of the cornea” means that the focus can be directed at any target points on or in the cornea, while positioning the focus “in the region of the lens of the eye” means that the focus can be directed at any target points on or in the lens of the eye. For the purpose of shifting from one limit position to the other, the movable lens groups are preferably coupled with electromechanical drive units, which are connected to a control unit. 
     In principle, the shifting of lens groups of the objective corresponds to switching between two operating modes, with the instrument being available for the examination and treatment of the lens of the eye in one operating mode, and for the examination and treatment of the cornea in the other operating mode, which, in principle, solves the problem of the invention. 
     In an embodiment, an optical element of negative refractive power that can be moved in the direction of radiation is arranged upstream of the objective, that movement being used to vary the focus position in the coordinate direction Z, but only either within the region of the cornea or within the region of the lens of the eye. The moving of this element varies the divergence of the beam. Depending on the currently set divergence angle, the objective focuses the beam on various positions in Z direction—either within the region of the cornea or within the region of the lens of the eye. 
     The movable optical element may be configured, e.g., as a lens, a reflective or a diffractive optical element. Preferably, it is a lens. To permit its controlled movement along the optical axis, the lens moves in a straight-line guide that is aligned in parallel with the beam path. 
     Also arranged upstream of the objective, there is a device for deflecting the laser radiation in the X and Y coordinate directions, this lateral deflection also being possible only within either the region of the cornea or the region of the lens of the eye. 
     In principle, the deflecting device may be designed in a manner that is known per se. For example, it may merely consist of a mirror that is tiltable about two different, preferably orthogonal, axes. Preferably, though, it comprises two mirrors arranged at a distance from each other and oscillating relative to each other. This advantageous design permits the mirrors to be seated and adjusted and, thus, the focus to be positioned laterally, with very high precision, though by simple means. 
     Between the two mirrors, an optical pupil element may be arranged that images the first mirror onto the second one, which results in a defined pupil position. In a precisely working optical system, a defined, permanent position of the pupil is a prerequisite for good correction. 
     Between the deflecting device and the objective, a beamsplitter may be arranged, by which part of the observation light coming from the cornea or the lens of the eye is coupled out for observation or imaging purposes. 
     During the examination or treatment of the eye it is preferable to apply onto the cornea a contact glass with a concave contact surface in order to suppress eye movement. Moreover, the contact glass reduces the eye&#39;s refractive power and makes focus correction easier. 
     In an example embodiment of the invention, a collecting lens is arranged downstream of the movable lens of negative refractive power, so that both elements together form a beam expander assembly, which expands the diameter of a parallel beam incident to the lens by a specified amount. Thus, if a parallel beam having a diameter d 1  enters the beam expander, the emerging parallel beam will have an exit diameter d 2 &gt;d 1 . 
     The exit diameter has an influence on the aperture angle on the side of the patient&#39;s eye. This given, it is within the scope of the invention to provide structures for varying the aperture angle on the side of the patient&#39;s eye, e.g., several exchangeable negative lenses of varied divergence angles. 
     Exchanging the negative lenses for getting varied aperture angles on the side of the patient&#39;s eye can be done in connection with shifting the focus position from the region of the cornea to the region of the lens of the eye and vice versa, or else according to the size of the eye to be examined or treated, that size being defined preferably by the depth of the eye&#39;s anterior chamber. Such lens assemblies can be exchanged automatically or manually. 
     The instrument according to the invention can be used to advantage for fast and easy adjustment of the focus position in three dimensions within the region required, i.e. that of the cornea or that of the lens of the eye. There is no need any more to change from one instrument to another as in prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Subject matter hereof may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying figures. Below, the invention will be explained in greater detail with reference to exemplary embodiments. In the accompanying drawings: 
         FIG. 1  is a schematic diagram of an ophthalmic instrument for the application of laser radiation according to prior art; 
         FIG. 2  depicts a variation of the arrangement shown in  FIG. 1 , featuring a beamsplitter for deflecting the observation beam towards a viewing tube with an eyepiece, or towards a camera, 
         FIG. 3  is a schematic diagram of the invented instrument for surgical laser examination and treatment of the eye in a first preferred embodiment; 
         FIG. 4  depicts a variation of the embodiment shown in  FIG. 3 , featuring a beamsplitter for deflecting the observation beam towards a viewing tube with an eyepiece, or towards a camera; 
         FIG. 5  is a schematic diagram of the invented instrument for surgical laser examination and treatment of the eye in a second preferred embodiment. 
     
    
    
     While various embodiments are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the claimed inventions to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter as defined by the claims. 
     DETAILED DESCRIPTION 
       FIG. 1  shows an instrument for the treatment of a human eye  1  according to prior art. This instrument comprises a radiation source  2 , which emits a beam  3  of laser radiation pulsed in the femtosecond range, and a scanning device  4 , with which the beam  3  can be focused on selected positions within the region of the cornea. On the cornea there is a contact glass  5  having a concave contact surface, which suppresses movements of the eye  1  during examination or treatment. 
     The radiation source  2  is designed to emit, e.g., laser radiation in a wavelength range around 1040 nm with a pulse width of about 200 fs. 
     On its end facing the beam  3  emerging from the radiation source  2 , the scanning device  4  features an optical entrance system  6 . Next to this in the radiation direction, there is a deflecting device  7 , which deflects the beam  3  emerging from the optical entrance system  6  laterally, i.e. in X and Y directions (across the Z direction of the incident beam  3 ) according to given control signals. Next to the deflecting device  7  in the beam path there is an objective  8 , which focuses the beam  3  in the region of the cornea. 
     The deflecting device  7  is provided with two deflecting mirrors  9  and  9 ′, which are mounted in bearings so as to be tiltable about axes not shown in  FIG. 1 . To simplify the diagram, the mirrors  9  and  9 ′ in  FIG. 1  are aligned in parallel; actually, however, the tilting axes are orthogonal to each other and to the optical axis of the optical entrance system  6 , so that tilting the first mirror  9  deflects the beam  3  in Y direction, and tilting the second mirror  9 ′ deflects it in the X direction orthogonal to the Y direction. The mirrors  9  and  9 ′ are driven by actuators  10  and  10 ′, respectively, which are connected to a control device via signal paths (indicated by arrows). According to the desired focus position in lateral direction, the control device sends control signals to the actuators  10  and  10 ′, which then cause the mirrors  9  and  9 ′ to tilt. 
     The optical entrance system  6  features a lens  11  of negative refractive power that is movable relative to the deflecting device  7 , and a collecting lens  12 . The lens  11  is connected with a straight-line guide  13 , thanks to which it can be moved to vary the optically effective distance from the deflecting device  7 . The movement of lens  11  in parallel to its optical axis can be effected, e.g., by means of a linear drive  14 , which is also connected with the control device (which is not shown). According to the desired focus position in Z direction, the control device generates control signals sent to the linear drive  14 . 
     The lens  11  and the collecting lens  12  are so designed that the optical entrance system  6  acts as a beam expander, which expands the diameter of the beam  3 . Thus, if a parallel beam  3  with a diameter d 1  enters the optical entrance system  6 , a parallel beam  3  with a diameter d 2 &gt;d 1  will emerge from it. 
     The objective  8  is shown as a fixed lens  15 ; it focuses the beam  3  emerging from the optical entrance system  6  on a position in the region of the cornea, the position being defined by the lens  11  and the deflecting device  7 . 
     The position of the focus F in the depth of the region of the cornea is defined by moving the  11  along its optical axis. The lateral position of the focus F is set by means of the deflecting device  7 . 
       FIG. 2  shows a variation of the arrangement shown in  FIG. 1 , with a beamsplitter  16  arranged in the beam path between the deflecting device  7  and the objective  8 . By means of the beamsplitter  16 , part of the light coming from the cornea and shaped by the objective  8  into an observation beam  17  is coupled out and deflected towards a viewing tube (not shown) with an eyepiece, or towards a camera (not shown either), so that the cornea can be observed during examination or treatment. 
     Further details of this state of prior art can be found in DE 10 2005 013 949 A1. Deviating from prior art, the problem of the invention is solved in such a way that the objective  8  consists of several lens groups and is designed to allow itself or at least one lens group to be moved relative to the eye, so that the distance variation effects a shifting of the focus position from the region of the cornea to the region of the lens of the eye and vice versa. 
       FIG. 3  is a diagram of the invented instrument in a first preferred embodiment. Here, the objective  8  consists of two lens groups  15 . 1  and  15 . 2 , which are shown as single lenses for the sake of clarity. The lens group  15 . 2  is in a fixed position along the beam path, whereas the lens group  15 . 1  is arranged to as to be movable along the optical axis and, for this purpose, is coupled via with a straight-line guide with, e.g., a linear drive  22 , which, triggered by a control device (not shown), effects the movement. 
     The distance through which the lens group  15 . 1  is moved, while principally depending on the control signal, is preferably defined by two limit positions. In  FIG. 3 , a first limit position is indicated by the lens group  15 . 1  drawn in solid lines, whereas the second limit position is drawn in broken lines. 
     This invariable moving distance defined by the limit positions corresponds to the shifting of the focus position from the region of the cornea to the region of the lens of the eye and vice versa. As a result, the arrangement according to the invention can be used for the examination and treatment of both the cornea and the lens of the eye. As patients&#39; eyes naturally differ in size, one embodiment of the invention provides for the moving distance to be variable according to the eye  1 . In this case there is only one fixed stop for cornea work, and a continuously variable limit for eye lens work. 
     If the lens group  15 . 1  is in the first limit position, the focus position can be varied in Z direction by means of lens  11  and in X and Y direction by means of deflecting device  7  in such a way that this allows targeting of all desired targets within the region of the lens of the eye but not beyond this region. Analogously this also applies to the second limit position and, thus, to the possibility of targeting all desired targets within the region of the cornea. 
     The movement of lens group  15 . 1  between the two limit positions, or the release of instructions for such movement, corresponds to the switching of the invented instrument between two operating modes, with the instrument being usable for the examination and treatment of the lens of the eye in one operating mode, and for the examination and treatment of the cornea in the other. 
     In an extended embodiment, an optional facility is provided to vary the beam diameter  3 ′ in order to adapt the aperture angle α on the side of the eye  1  to the operating mode employed. If the ratio of the amounts of the refractive powers of lens  11  and the collecting lens  12  is decreased, the diameter of the parallel beam  3 ′ emerging from the collecting lens  12  will decrease, too, and, as a result, so will the aperture angle α on the side of the eye  1 . A smaller aperture angle α is advantageous for focus positioning on or in the lens of the eye, as in front (upstream) of the lens of the eye there is the pupil as a restricting aperture for the convergent beam  3  entering the lens of the eye, which improves the optical correction. 
     As shown in  FIG. 3 , a change of the ratio of the refractive powers in the optical system  6 , and, thus, of the diameter of the beam  3 ′ is effected by exchanging several—here, for example, two—lenses  11  and  11 ′ with differing refractive powers against one another. Either, one may exchange merely lenses  11  and  11 ′ against one another, or the assembly consisting of radiation source  2 , lens  11 , lens holder  13  and linear drive  14  against an assembly consisting of radiation source  2 ′, lens  11 ′, lens holder  13 ′ and linear drive  14 ′. 
     Optionally, lens  11  and collecting lens  12  may be exchanged together as a pair to achieve the same effect. 
     The change of the divergence angle may, in a first version, be positively coupled with switching between the operating modes, i.e., be effected automatically, or, in alternative second version, as a function of the size of the eye to be examined or treated. As a measure of the eye&#39;s size one may use, e.g., the depth of the eye&#39;s anterior chamber, which is separately ascertained prior to the start of an examination. In the first place, it is the movement of lens  15 . 1  that is derived from the measurement of the eye. The adaptation of the diameter of the beam  3 ′ via the ratio of refractive indices within the optical system  6  may be effected automatically in connection with switching between the operating modes. 
       FIG. 4  shows a variation of the arrangement shown in  FIG. 3 , with a beamsplitter  16  arranged between the deflecting device  7  and the objective  8 . By application of the beamsplitter  16 , part of the light coming from the eye and shaped by the objective  8  into an observation beam  17  is coupled out and deflected towards a viewing tube (not shown) with an eyepiece, or towards a camera (not shown either), so that the eye detail being examined or treated can be observed. 
       FIG. 5  shows another preferred embodiment of the invention. In  FIG. 5 , components like those in the preceding examples have like reference numbers. 
     Here, arranged between mirrors  9  and  9 ′ in the beam path is an optical pupil system  18 . It comprises two collecting lenses  19  and  19 ′, which project the beam  3  deflected by mirror  9  onto mirror  9 ′, with an intermediate real image being produced in the air between the collecting lenses  19  and  19 ′. In this way, a fixed position of the pupil results, which makes an optically favorable design of the objective  8  possible. Moreover, due to each of the mirrors  9  and  9 ′ being imaged in the other, mirror  9 ′ can be kept small. The mirrors  9  and  9 ′ may be, e.g., of elliptical shape. 
     In this embodiment of the invention, the objective  8  is a multiple assembly, comprising an entrance group of lenses  20 , a tube lens  21 , and the lens groups  15 . 1  and  15 . 2 . 
     The beam  3  laterally deflected by the deflecting device  7  enters the entrance group of lenses  20 , which focuses it to form an intermediate real image. The tube lens  21  projects the intermediate image to infinity. A beamsplitter  16  deflects the beam  3  to the lens groups  15 . 1  and  15 . 2 . 
     Changing the focus position in the coordinate directions X, Y and Z is effected as described in the preceding embodiment example. The same applies to the switching between the two operating modes by moving the lens group  15 . 1  between two limit positions, with the instrument being configured for the examination and treatment of the lens of the eye in one mode, and for the examination and treatment of the cornea in the other. 
     Advantageously, all optical components are designed in such a way that the intermediate real images are situated in air, so that high-intensity laser radiation cannot cause any optical breakdown in optical components. 
     In all embodiments of the invention, the radiation source  2 , the optical entrance system  6  and the objective  8  are designed for the beam  3  to have a diameter of less than 5 micrometers at the focus. Preferably, the objective  8  has an aperture greater than 0.35. 
     Various embodiments of systems, devices, and methods have been described herein. These embodiments are given only by way of example and are not intended to limit the scope of the claimed inventions. It should be appreciated, moreover, that the various features of the embodiments that have been described may be combined in various ways to produce numerous additional embodiments. Moreover, while various materials, dimensions, shapes, configurations and locations, etc. have been described for use with disclosed embodiments, others besides those disclosed may be utilized without exceeding the scope of the claimed inventions. 
     Persons of ordinary skill in the relevant arts will recognize that the subject matter hereof may comprise fewer features than illustrated in any individual embodiment described above. The embodiments described herein are not meant to be an exhaustive presentation of the ways in which the various features of the subject matter hereof may be combined. Accordingly, the embodiments are not mutually exclusive combinations of features; rather, the various embodiments can comprise a combination of different individual features selected from different individual embodiments, as understood by persons of ordinary skill in the art. Moreover, elements described with respect to one embodiment can be implemented in other embodiments even when not described in such embodiments unless otherwise noted. 
     Although a dependent claim may refer in the claims to a specific combination with one or more other claims, other embodiments can also include a combination of the dependent claim with the subject matter of each other dependent claim or a combination of one or more features with other dependent or independent claims. Such combinations are proposed herein unless it is stated that a specific combination is not intended. 
     Any incorporation by reference of documents above is limited such that no subject matter is incorporated that is contrary to the explicit disclosure herein. Any incorporation by reference of documents above is further limited such that no claims included in the documents are incorporated by reference herein. Any incorporation by reference of documents above is yet further limited such that any definitions provided in the documents are not incorporated by reference herein unless expressly included herein. 
     For purposes of interpreting the claims, it is expressly intended that the provisions of 35 U.S.C. § 112(f) are not to be invoked unless the specific terms “means for” or “step for” are recited in a claim. 
     LIST OF REFERENCE NUMBERS 
     
         
         
           
               1  eye 
               2  radiation source 
               3  beam 
               4  scanning device 
               5  contact glass 
               6  optical entrance system 
               7  deflecting device 
               8  objective 
               9 ,  9 ′ mirrors 
               10 ,  10 ′ actuators 
               11  first lens 
               12  collecting lens 
               13  lens holder 
               14  linear drive 
               15 . 1 ,  15 . 2  lens groups 
               16  beamsplitter 
               17  observation beam 
               18  optical pupil system 
               19 ,  19 ′ collecting lenses 
               20  entrance group of lenses 
               21  tube lens 
               22  linear drive