FR2595243A1 - Knife for surgery of the anterior segment of the eye - Google Patents

Abstract

The present invention relates to a knife for surgery of the anterior segment of the eye, in particular of the cornea. This knife 1 includes on the one hand a longitudinal handle 2 having a first transverse end 4 and on the other hand a blade 5 carried by the handle 2 and forming a longitudinal projection from the handle 2, at the said first transverse end of the latter; in order to improve the quality of the incisions and to make them easier to produce, the blade 5 has a shape of revolution around a transverse axis 6 while the handle 2 is hollow and internally comprises means for guiding the blade 5 in rotation around the said transverse axis 6, with respect to the handle 2, as well as a system for kinematic connection between the blade 5 and means 16, 17, 18 for driving the blade 5 in rotation around the said axis 6 which is transverse with respect to the handle 2.

Description

 The present invention relates to a knife: for surgery of the anterior segment of the eye, and in particular for surgery of the cornea.

 More specifically, it relates to a knife comprising for this purpose on the one hand a longitudinal handle having a first transverse end and on the other hand a blade carried by the handle and forming a longitudinal projection outside the handle, at said first transverse end of that -this.

 Traditionally, the blade is carried integrally, possibly adjustable longitudinally, by the handle and has a transverse cutting edge zone to facilitate its penetration into the cornea by a longitudinal movement of the knife, and a longitudinal cutting zone to allow the realization of an incision of desired length by consecutive transverse displacement of the knife.

 It appears in use that it is difficult to overcome the resistance of the cornea with such knives, whatever the quality of the edge of the blade may be; both during penetration of the blade into the cornea by a longitudinal movement of the knife and during the continuation of the incision by a transverse movement of the latter, the cornea offers resistance such that it tends to slip under the knife, taking advantage of the deformability of the eye, so that it is difficult to give the incision a regular depth and of predetermined value.

 The object of the present invention is to propose a knife for surgery of the anterior segment of the eye, in particular of the cornea, which makes it possible to obtain without difficulty an incision of predetermined and regular depth.

For this purpose, the knife according to the invention, comprising in a manner known per se on the one hand a longitudinal handle having a first transverse end and on the other hand a blade carried by the handle and forming a longitudinal projection outside the handle, said first transverse end thereof, is characterized in that the blade has a shape of revolution around a transverse axis and in that the handle is hollow and has internally
means for guiding the blade in rotation about said transverse axis, relative to the handle,
- A kinematic link chain between the blade and means for driving the blade in rotation about said transverse axis.

 The blade advantageously has a circular peripheral edge, smooth, of revolution around said transverse axis.

 In a knife with a rotary blade of the type recommended by the present invention, the quality of the cutting edge of the blade and the force applied to it, via the handle, by the surgeon are no longer the only elements used for overcoming the resistance of the cornea to these elements is added the peripheral speed of rotation of the blade, which introduces between the cutting edge thereof and the cornea a relative speed of displacement which can be much higher than that which results from the movement of the surgeon's hand, thereby considerably facilitating cutting.

 This advantage is all the more noticeable since the blade, for a determined diameter for example of the order of 3 mm, rotates faster and it is possible to provide for a speed of rotation of the blade of the order of 1000 to 5000 t / min. using as a drive means a driving turbine, integrated or external to the handle and connected, respectively directly or by a hose, to a longitudinal drive shaft which is housed inside the handle and guided in rotation around a longitudinal axis, with respect to this, by suitable guide means and is moreover kinematically linked to the blade by means of transmission of movement with angle transmission, inside the handle; other drive means, for example electric, external to the handle or integrated in whole or in part thereof can however also be chosen.

 According to a preferred embodiment of the knife according to the invention, the depth of penetration of the blade into the cornea can be precisely adjusted by providing the handle, at said first transverse end and around the blade, with a transverse face d 'support on the eye, said transverse axis being set back relative to this support face and the blade partially forming a longitudinal projection relative to this support face; advantageously, the handle then comprises micrometric means for adjusting the value of said longitudinal projection of the blade relative to the bearing face; for this purpose, the handle may have at least in the immediate vicinity of said first transverse end a sheath mounted with relative longitudinal sliding, which sheath carries integrally at said first transverse end a transverse plate having a transverse face defining said bearing face as well as means for the longitudinal passage of the blade t the aforementioned micrometric means are then provided for adjusting the relative longitudinal position of the sheath and the handle.

 To facilitate guiding the blade as and when the incision is made, as well as to allow permanent control, the handle and the possible sheath are notched near said first transverse end to allow vision of the blade by the surgeon.

A knife thus designed can be used for any form of incision; by giving the blade the shape of a flat disc, for example with a diameter of the order of 3 mm, it is possible to make rectilinear incisions, for example in radial surgery, such as curved incisions of relatively large radius; it is also possible to make incisions of relatively small radius by giving the blade the shape of a cup, which makes it possible to produce a knife which is particularly suitable for the surgical treatment of cataracts or the trepanation of the eye; Advantageously, provision is made for an assembly allowing easy interchangeability of the blade, to allow the surgeon to easily equip, at will, the same knife with blades of different shape for making different types of incision.
Other characteristics and advantages of the invention will emerge from the description below, relating to a non-limiting mode of implementation, as well as from the appended drawings which form an integral part of this description.

 - Figure 1 shows an overall perspective view of a knife according to the invention.

 - Figure 2 shows a view of this knife in section through a plane including the transverse axis of rotation of the blade as well as the longitudinal axis of rotation of the motor shaft.

 - Figure 3 shows, in a sectional view similar to that of Figure 2, a variant shape of the blade.

 - Figure 4 shows, in a sectional view through a plane including the longitudinal axis and perpendicular to the transverse axis, identified in IV-IV in Figure 2, part of the means for guiding the blade in rotation around of the transverse axis with respect to the handle and means for guiding the drive shaft to rotation about the longitudinal axis with respect to the handle.

 - Figure 5 shows a view of these means in section through a plane marked in V-V in Figure 4 and coinciding with the section plane of Figure 2.

 FIG. 6 shows a view of these means in section through transverse planes marked in VI-VI in FIG. 5.

 FIG. 7 shows a view of the plate defining the transverse face for bearing on the eye and of the sheath carrying this plate, in section through the plane marked in IV-IV in FIG. 2.

 FIG. 8 shows an end view of this plate and of this sheath, in a longitudinal direction identified in VIII in FIG. 7.

 - Figure 9 shows a view of the plate and the sheath in section through a plane including the longitudinal axis and marked in IX-IX in Figure 8, this plane being angularly offset by an angle a, for example from order of 150, compared to the plan identified in IV-IV in Figure 2.

 - Figure 10 illustrates the use of the knife, when provided with a blade in the form of a flat disc, for making a radial incision on an eye shown in diagrammatic section through a plane including the optical axis.

 Reference will firstly be made to the window views of FIGS. 1 and 2, where the knife has been designated by 1, comprising in particular a longitudinal handle 2 having a shape and dimensions similar respectively to the shape and dimensions of a pen for easy handling; more precisely, the handle 2 has, along a longitudinal axis 3, dimensions much greater than those which it presents transversely with respect to this axis; for example, it has along the axis 3 a length of the order of 15 to 20 cm while it presents transversely to the axis 3, over most of its length from a first transverse end 4, an outer cylindrical shape of revolution around the axis 3 with a diameter of the order of 4 to 5 mm; naturally, these figures are given by way of nonlimiting example although they are currently considered as an optimum.

 At its first transverse end 4, the handle 2 carries a blade 5 which forms a longitudinal projection out of the handle 2 and, in accordance with the present invention, has a shape of revolution around a transverse axis 6, and more precisely perpendicular to the axis 3 in the example illustrated s in particular, the blade 5 may have the shape of a flat disc, having a mean plane perpendicular to the axis 6 and coinciding with the cutting plane identified in IV-IV in the figure 2 in an embodiment illustrated in Figures 1 and 2; the blade may however have another shape and for example illustrated in FIG. 3 is a blade 5 ′ which can replace the blade 5 and which in turn has the shape of a cup of revolution around an axis 6 'intended to replace axis 6; in one case as in the other, the blade has a circular peripheral cutting edge, respectively 7, 7 ', smooth, of revolution around the transverse axis, respectively 6, 6'; the cutting edge 7 is located along the mean plane of the blade 5 while the cutting edge 7 ′ is situated along an approximately frustoconical medium ring of revolution around the axis 6 ′; in one case as in the other, the maximum diameter of the cutting edge 7, 7 ′, or external peripheral diameter of the blade 5 or 5 ′, is of the order of 3 mm but this figure is only a non-limiting example although currently considered an optimum.

 By way of nonlimiting example of material which can constitute the blade 5 or 5 ′, mention may be made of synthetic sapphire but other materials can also be used.

 Along its axis, respectively 6, 6 ', the blade 5, 5' is traversed right through by a hole, respectively 8, 8 'allowing the coaxial passage of a coaxial shaft, respectively 9, 9' on which the blade 5, 5 ′ is wedged 8 against a relative rotation as well as against a relative translation by any appropriate means, the realization of which is within the domain of the normal aptitudes of a person skilled in the art t the shaft 9 or 9 'is housed inside the handle 2, which is hollow, and it is guided in rotation around the axis 6 or 6' relative to the handle 2 by coaxial bearings 10, 11, for example plain bearings, which are disposed respectively on either side of the blade and retained in the handle 2, as will be described later.

Inside the handle 2, movement transmission means ensuring an angle gear at 900, constituted in the example illustrated by a gear train with angle gear 12 which is carried by the handle 2 and will be described below, kinematically connect the shaft 9 or 9 'to a straight, longitudinal drive shaft 13, of axis 3; this tree mrr
teur 13 is guided in rotation about the axis 3 relative to the handle 2 by guide means 14, for example with plain bearings, housed in the handle and which will be described later, and runs longitudinally around the handle 2 of the train of gears 12 up to a second transverse end 15 of the handle 2, open longitudinally opposite to the first transverse end 4 t the drive shaft 13 forms a longitudinal projection out of the handle 2 at this second transverse end 15 thereof and carried removable connection means, known in themselves for example in the field of dentistry and therefore not shown, to connect in a mutual tra # lnemant relationship to a transmission hose of dry movement matted at 16, furthermore connected to a rotary shaft 17 for output of drive means 18; these means 18 are for example constituted by a turbine fitted with a supply compressor or by an electric motor with adjustable speed and by on-off control and speed adjustment means provided on the handle 2 or independent of that -this and then actuable for example at the foot, as is also known in the field of dentistry; thus, when in service, the drive means 18 provide, via a kinematic link chain constituted by the output shaft 17, the transmission hose 16, the drive shaft 13, the gear train to angular gear 12 and the shaft 9 or 9 ', the drive of the blade 5 or 5' to rotation about its axis 6 or 6 'relative to the handle 2.

 Alternatively, the drive means can be integrated in whole or in part into the handle 2; for example, there is shown diagrammatically in 18 ′, in FIG. 2, drive means carrying a driving turbine or an electric micro-motor integrated into a longitudinal extension 2 ′ of the handle 2, at the end 15 thereof ; this turbine or this micr # motor directly drives the motor shaft 13 and is preferably connected, respectively, by a flexible tube to a compressor for supplying power independent of the handle or by flexible conductors to a source of electricity supply also independent the handle; the extension 2 ′ of the handle 2 then advantageously carries the on-off control and speed adjustment means of the drive means, although these control and adjustment means can also be arranged otherwise, for example for a foot actuation; other arrangements could however be chosen as to the nature, the position, the catrtaede of the drive means without departing from the scope of the present invention.

 A currently preferred concrete structure of the knife 1 will now be described with reference to FIGS. 1 to 9.

 As can be seen more particularly in FIG. 2, the handle 2 is formed from two coaxial longitudinal sub-assemblies 19 and 20, mounted with relative longitudinal sliding without the possibility of relative rotation, with the sole aim of authorizing the adjustment of their position relative longitudinal because these two sub-assemblies are fixed relative to each other when the knife 1 is in service; the sub-assembly 19 is housed for the most part inside the sub-assembly 20, so that it will be called "internal sub-assembly" while the sub-assembly 20 will be said "external sub-assembly".

 The two subsets 19 and 20 have respective general forms of revolution around the longitudinal axis 3 so that, in their detailed description which follows and in the absence of an explicit contraindication, the concept of form of revolution will be understood by reference to this axis 3 as well as the concepts of longitudinality and transversality; from itfre, a longitudinal direction 24 of reference is defined, going from the second transverse end 15 of the handle 2 towards the first transverse end 4 thereof, which direction 24 will serve as a reference to the concepts of upstream and downstream used by the following.

 The interior sub-assembly 19 is formed of an integral assembly of several pieces, one of which, assigned the reference 21, extends over the major part of the length of the handle 2 from the second transverse end 15 of this. .

The part 21 has the general shape of a sleeve of revolution around the axis 3, towards which the part 21 is delimited by an inner peripheral face 22 longitudinal, cylindrical of revolution; at the second end
15 of the handle 2, the face 22 is connected to a flat transverse face 23, annular of revolution and facing upstream; this face 23 connects the face 22 to an external peripheral face
25 longitudinal, cylindrical of revolution and rotated in the direction of a radial distance from the axis 3, with a dianotre greater than that of the face 22; downstream, the face 25 is connected by a planar transverse face 26, annular of revolution and turned downstream, to an outer peripheral face 27 longitudinal, cylindrical of revolution and turned in the direction of a radial distance from at axis 3, with an intermediate diameter between the respective diameters of the faces 22 and 25 t traversed in the direction 24 from the annular face 26, the annular face 27 successively presents, near the face 26 but spaced apart longitudinal, relative to the latter, a transverse groove 28, annular of revolution, accommodating a compressible O-ring 29 for example of rubber forming when it is relaxed a projection relative to the face 27 in the direction of a radial distance by relative to the axis 3, then, spaced from the groove 28, a helical thread in relief 30; downstream, the face 27 is connected by a flat transverse face 31, annular of revolution and turned downstream, to an outer peripheral face 32 longitudinal cylindrical of revolution and turned in the direction of a distance from the axis 3, this face 32 having an intermediate diameter between the respective diameters of the faces 27 and 22; downstream, the face 32 is connected by a flat transverse face 33, annular of revolution and turned downstream, to an outer peripheral face 34 longitudinal, cylindrical of revolution, turned in the direction of a radial distance by relative to axis 3 and having an intermediate diameter between the respective diameters of the faces 32 and 22; downstream, the face 34 is itself connected by a flat transverse face 35, annular of revolution and turned downstream, to the inner peripheral face 22 of the part 21 in the immediate vicinity of its connection with the face 35 , this inner peripheral face 22 has a thread 36 by which is assembled in a solid but removable manner, to part 21, a second part 37 of the internal sub-assembly 19.

 To cooperate with the internal thread 36 of the part 21, the part 37 has a longitudinal external peripheral face 38, of a generally cylindrical shape of revolution, turned in the direction of a radial distance relative to the axis 3, with a diameter corresponding substantially to that of the inner peripheral face 22 of the part 21; this face 38 carries an external thread 39 complementary to the internal thread 36; of longitudinal dimension less than that of the internal thread 36, the threaded face 38 is connected respectively upstream and downstream to planar transverse faces, respectively 39 and 40, annular of revolution and turned upstream; the face 39 connects the face 38, in the direction of a radial approximation with respect to the axis 3, to a longitudinal inner peripheral face 41, of generally cylindrical shape of revolution with a diameter smaller than that of the face 38 and provided of a thread 42, while the face 40 connects the face 38 to an outer peripheral face 43 of longitudinal cylindrical revolution, turned in the direction of a radial distance from the axis 3, and having a diameter identical to that of the face 34 of the first part 21; therefore, when the thread 39 of the face 38 is fully screwed into the thread 36, the faces 35 and 40 then being in mutual contact as illustrated in FIG. 2, the face 43 exactly extends the face 34 towards the 'downstream ; downstream, the face 43 is connected by a planar transverse face 44, annular of revolution and turned upstream, to an outer peripheral face 45 longitudinal cylindrical of revolution and turned in the direction of a radial distance from the axis 3, which face 45 has a diameter identical to the diameter of the face 32 of the part 21; downstream, the face 45 is connected to a transverse, flat, annular face of revolution and turned downstream, which face 46 connects the face 45, in the direction of a radial approximation with respect to the axis 3, with a frustoconical face 47 of revolution, turned towards axis 3 and converging upstream until it is connected to the tapped face 41 via a 48-transverse, annular revolution chamber.

 By its tapped face 41 and its frustoconical face 47, the second part 37 of the interior sub-assembly 19 carries in a solid but removable manner a body 49 formed from the assembly of two identical parts 50, 51 joined nutually along a plane 169 containing b both the longitudinal axis 3 and the transverse axis 6 (plane marked in VV in Figure 4), for reasons of ease of assembly and disassembly, and in particular to allow the blade change.

 The body 49 is more particularly visible in FIGS. 4 to 6.

 Considered as a whole, that is to say when the two parts 50 and 51 are thus assembled, the body 49 is notably delimited in the direction of a radial distance from the axis 3 by a longitudinal face 52 of general cylindrical shape of revolution with a diameter corresponding to that of the face 41, this face 52 being provided with a thread 53 complementary to the tapping 42 of the face 41, and by a frustoconical face 54 of revolution, with a conicity identical to that from the face 47 of the part 37, the face 54 diverging downstream from the face 52 to which it is connected by means of a transverse groove 55, annular of revolution; thus, the body 49 is assembled to the second part 37 of the interior sub-assembly 19 by screwing the threaded face 52 into the threaded face 41 until the face 54 comes into intimate contact with the face 47; downstream, the frustoconical face 54 is connected to an outer peripheral peripheral face 56 which is longitudinal, cylindrical in revolution, turned in the direction of a radial distance from axis 3, with a diameter substantially identical to that of the face 45 of the part 32 and that of the face 32 of the part 21; upstream, the threaded face 52 is connected to a flat transverse face 57, annular of revolution and turned upstream, which face 57 connects itself, in the direction of a radial approximation relative to the axis 3, to a longitudinal inner peripheral face 58, cylindrical of revolution and facing the axis 3, with a diameter less than that of the face 52; from the face 57, this face 58 extends longitudinally substantially up to the level of the mutual connection of the faces 54 and 56, level at which it is connected downstream to a flat transverse face 59, annular of revolution and turned towards downstream; this face 59 connects, in the direction of a radial distance with respect to the axis 3, the face 58 to an inner peripheral face 60 longitudinal cylindrical of revolution and turned towards the axis 3, with an intermediate diameter between the diameters respective of the faces 56 and 58 and greater than the maximum diameter of the cutting edge 7 or 7 'of a blade 5 or 5'; the faces 56 and 60 are connected to each other in particular by two flat faces 61 and 62, oblique with respect to the plane 169 and arranged symmetrically with respect to this plane, respectively on the part 50 and on the part 51 t the two faces 61 and 62 converge mutually downstream without cutting the plane 169 and are connected downstream to two planar faces 63 and 64 coplanar, perpendicular to the axis 3, each of which is symmetrical with respect to the plane 169 then that they are symmetrical to each other with respect to a plane 170 including the longitudinal axis 3 but perpendicular to the axis 6 (plane identified in IV-IV in Figure 2); these two faces 63 and 64, each of which has the shape of a flat transverse face sector, annular of revolution, also connects the face 56 to the face 60, in the direction of a radial approximation with respect to the axis 3, downstream of axis 6 but at a longitudinal distance from this axis less than the maximum radius of the cutting edge 7 or 7 'of a blade 5 or 5' so that this cutting edge can form a longitudinal projection, towards downstream, with respect to the common geometric plane of the faces 63 and 64 as appears from the examination of FIG. 5.

Except for the faces 61 and 62 specifically specific to the part 50 and to the part 51 respectively, each of the previously described faces of the body 49 is defined for half by the part 50 and for half by the part 51, which are joined by planar faces respective 65, 66 merging with the plane 169 and mutually connecting the respective parts of the faces 52, 54, 56, 57, 58, 59, 60, 63, 64 specific to the parts 50 and 51 respectively; the screwing of the threaded face 52 into the threaded face 41 and a resulting wedge effect between the faces 47 and 54 ensure the assembly of the two parts 50 and 51, this assembly being able to be further strengthened by mutual keying; for this purpose, each of the parts 50 and 51 has along two axes 67, 68 perpendicular to the plane 169, in positions symmetrical to each other with respect to the plane 170, respectively on either side of the face 58 , two bores such as 69 and 70 (part 50), 71 and 72 (part 51) and each pair of bores thus aligned, respectively of one and the other of parts 50 and 51, receives a respective rectilinear key 73 (bores 69 and 71 with the same alignment 67),
74 (bores 70 and 72 of the same alignment 68).

 It will be noted that the oblique faces 61 and 62 of the body 49 define, for an observer, two notches 75, 76 allowing a vision towards the axis 3 as well as towards the axis 6 inside the body 49; the obliquity of the faces 61 and 62 is low enough for the notches 75 and 76 to extend upstream at a distance from the axis 6 as greater as possible than the maximum radius of the cutting edge 7 or 7 'of a blade 5 or 5 '(of the order of 2 times this radius in the example illustrated, this figure however being only a non-limiting indication).

 Between the faces 61 and 62, along the axis 6, each of the parts 50 and 51 is hollowed out for half in its face 65 or 66 respectively, of two cylindrical bores 77 and 78 of revolution around the axis 6, with the same diameter, to receive and retain the plain bearing 10 and the plain bearing 11 respectively, in order to guide the shaft 9 or 9 'in rotation about the axis 6 or 6' relative to the body 49, c ' that is to say with respect to handle 2; similarly, around a second transverse axis 79 parallel to axis 6 and perpendicular to axis 3 and located upstream of axis 6 are arranged, half in room 50 and half in room 51, identical bore gods 80 and 81, cylindrical of revolution around the axis 79 and adapted to receive and immobilize with respect to the body 49 two plain bearings, respectively 83 and 84 suitable for guiding rotation around the axis 79, relative to the body 49 and to the handle 2, for a coaxial shaft 85; in addition, along the same transverse axis 86 parallel to axis 6 and perpendicular to axis 3, offset with respect to axis 79, upstream, by a longitudinal distance equal to the longitudinal distance, the axis 79 is offset upstream relative to axis 6, are arranged half in part 50 and half in part 51 two identical coaxial bores 87 and 88, cylindrical of revolution around axis 86 and clean to be immobilized with respect to the body 49 two smooth bearings, respectively 89 and 90 providing guidance, for rotation about the axis 86 with respect to the body 49 and to the handle 2, for a shaft 82.

Advantageously, as illustrated, the two parts 50 and 51 have in the face 60 two flats 91 and 92, parallel to the plane 170 and svmétrictues of each other relative to this plane, to serve as a stop, in the direction of a radial joint relative to axis 3, for the various bearings 10, 11, 83, 84, 89, 90 additionally, each of these bearings, all identical in the example illustrated, present in abutment against the flat respective 91 or 92 a respective annular flange 93, 94, 95, 96, 97, 98, of revolution around the respective axis and projecting radially in the direction of a distance from it in addition, each of the shafts 9, 85, 82 presents in an integral manner, for example due to the presence of an insert on it, two annular shoulders of revolution around the respective axis 6, 79, 86, these shoulders designated by the references 99 and 100 for tree 9, 101 and 102 for tree 85, 103 and 104 for concerning tree 82, being turned in the direction of a distance
ment relative to the plane 170 and mutually spaced apart by a distance substantially identical to the distance separating perpendicular to this plane the respective flanges of the two bearings respectively associated; thus, two bearings associated with the same shaft not only ensure the guiding of this shaft for rotation about the respective axis relative to the body 49 and to the handle 2, but also an immobilization of this shaft against a translation along this axis relative to the body 49 or to the handle 2.

 Each of the shafts 9 or 9 ′, 85.82 carries in solidarity, in addition to the blade 5 or 5 ′ with regard to the shaft 9 or 9 ′, a respective straight pinion 105, 106, 107, the pinion 106 being in permanent engagement with the pinions 105 and 107 t in addition, the shaft 82 carries integrally a bevel pinion 108 in permanent engagement with a second bevel pinion 109 as for it of axis 3, so that the pinions 109 , 108, 107, 106, 105 together define the gear train 12 with bevel gear at 900; the bevel gear 109 is carried integrally by a downstream end of the longitudinal drive shaft 13 which passes longitudinally through the body 49 via the face 58 thereof, being guided in rotation about the axis 3 relative to the body 49 and the handle 2 while being immobilized against a relative translation along the axis 3 by the guide means 14.

 To this end, the guide means 14 comprise two smooth bearings juxtaposed longitudinally, on the basis of a downstream smooth bearing 110 and an upstream smooth bearing 111, and each of these bearings 10, 110 and 111, of a similar type. to that of the bearings 10, 11, 83, 84, 89, 90 is on the one hand engaged in the face 58 of the body 49 and on the other hand in longitudinal abutment against this body respectively by an annular flange 112, of revolution around the axis 3 and projecting in the direction of a radial distance relative to the latter to bear upstream against the face 59 of the body 49 with regard to the bearing 10, 110, and an annular flange 113 of revolution around the axis 3 and projecting in the direction of a radial distance with respect to the latter in order to bear downstream against the face 57 of the body 49 as regards the bearing 111; in addition, the drive shaft 13 has in its passage in the body 49, that is to say in the plain bearings 110 and 111, a section 114 delimited in the direction of a radial distance from the axis 3 by a cylindrical outer peripheral face 115 of revolution about this axis with a diameter less than that of the face 58 and compatible with the bearings 110 and 111 while the pinion 109 has a greater diameter, so that it constitutes for the section 114, which carries it integrally, a shoulder capable of pressing upstream against the flange 112 itself pressing upstream against the face 59; upstream, the section 114 of the drive shaft 13 has a longitudinal projecting area beyond the flange 113 of the plain bearing 111 and it carries, in this projecting area, a thread 116 in relief relative to its face 115, and by which it is removably secured with a nut 117 having downstream 11 a flat annular face 118 perpendicular to the axis 3; this face 118 constitutes a shoulder which leans downstream on the flange 113 which itself bears downstream on the face 57, which immobilizes the section 114 of the motor shaft 13, that is to say more generally of the assembly of this drive shaft 13, against a longitudinal translation relative to the body 49 and to the handle 2.

 The threading projection of the section 114 of the motor shaft 13 extends longitudinally upstream beyond the nut 117 and a second section 119 of the motor shaft 13, having for this purpose downstream and along the axis 3 a bagne hole 120 provided with a thread 121 complementary to the thread 116, is immobilized relative to the section 14 by screwing the thread 121 on the thread 116 and effect of nut - lock nut with the nut 117 t the section 119 is also full and delimited, in the direction of a radial distance with respect to the axis 3, by a cylindrical face 122 of revolution around this axis with a diameter less than that of the inner peripheral face 22 of the first part 21 ; of the granny, in the direction of a radial distance relative to the axis 3, the nut 117 is delimited by an outer peripheral face 223 of cylindrical casing of revolution around the axis 3 with a diameter less than that of the inner peripheral face 22 of the part 21; it will be noted that, as soon as the body 49 is screwed into the second part 37 of the interior sub-assembly 19, the faces 57 and 39 are substantially coplanar so that no contact is to be feared between the nut 117 and the second part 37 of the interior sub-assembly 19.

 Upstream, the section 119 of the motor shaft 13 continues beyond the second transverse end 15 of the handle 2 to connect, as indicated above, to the flexible 16 for transmitting movement or to the means of 'in traction 18' - at least partially integrated into the extension 2 'of the handle 2, which extension 2' is carried integrally by the upstream face 23 of the part 21 of the interior sub-assembly 19.

 It is understood that the internal sub-assembly 19 constitutes the basic sub-assembly of the handle 2 of the knife 1, of which it brings together most of the essential constituent elements, which it connects to the external sub-assembly 20.

 The external sub-assembly 20 will now be described with reference to FIGS. 2, and 7 to 9.

 Like the interior sub-assembly 19, the exterior sub-assembly 20 is formed from an integral assembly of several parts, referenced respectively 123, 124, 125, 126.

 The part 123 has the general shape of a sheath resting, with the possibility of relative lonaitudinal sliding, on the external peripheral faces 32, 45 and 56 of the parts 21, 37, 50, 51 of the internal sub-assembly 19.

 To this end, the sheath 123 has an inner peripheral face 127 longitudinal, cylindrical of revolution and facing the axis 3; the face 127 has a diameter as close as possible to the common diameter of the faces 32, 45, 56 although greater than this, to ensure guiding with relative longitudinal sliding by preventing any relative transverse movement between the sheath-shaped part 123 and the interior sub-assembly 19; for this purpose, in addition, the face 127 has a longitudinal dimension greater than the longitudinal distance separating the faces 33 and 44 of the interior sub-assembly 19; upstream, the face 127 is connected to a flat transverse face 128, annular of revolution and facing upstream; this face 128 connects the face 127, in the direction of a radial distance relative to the axis 3, to an outer peripheral face 129 longitudinal cylindrical of revolution and turned in the direction of a radial distance relative to the axis 3, the face 129 having a diameter approximately identical to that of the face 27 of the first part 21 of the interior sub-assembly 19; downstream, the outer peripheral face 129 connects the face 128 to a flat transverse face 130, annular of revolution and facing downstream, and this face 130 itself connects the face 129, in the direction of approximation radial opposite axis 3, to an external peripheral face 131 longi tudinal, cylindrical of revolution and turned in the direction of a radial distance with respect to axis 3, with a diameter intermediate between the respective diameters from face 129, or from face 27 of the first part 21 of the sub-assembly 19, and from face 127 downstream, the outer peripheral face 123 is connected to the inner peripheral face 127 by two flat faces 132 and 133, having the same obliquity with respect to the plane 169 while being arranged symmetrically with respect to this plane without cutting the latter and converging downstream, and by two transverse planar and coplanar faces 134 and 135 perpendicular to axis 3 and facing downstream ; the two faces 134 and 135 are symmetrical to each other with respect to the plane 170 and each of them is symmetrical with respect to the plane 169.

It will be noted that the presence of the oblique faces 132 and 133, whose obliquity is advantageously identical to that of the faces 61 and 62 of the body 49, emerges. in the piece 123 in the form of a sheath two notches - 136 and 137 fully comparable to the notches 75 and 76 of the body 49 and capable of being superimposed on the latter to allow a vi
blade extension 5 or 5 'through the shaped part
sheath 123 and through the body 49.

For this purpose, the sheath-shaped part
123 has between its face 128 and its faces 134 and 135 a longitudinal dimension less than the dimension
longitudinal that the inner sub-assembly 19 has between the face 31 of the first part 21 of the inner sub-assembly 19 and the faces 63 and 64 of the body 49 of this sub-assembly; thus, the sheath-shaped part 123 can in particular be placed, on the interior sub-assembly 19, in a position in which the faces 134 and 135 are coplanar with the faces 63 and 64 and in which the notches 136 and 137 are respectively superposed on the notches 75 and 76, for example with coplanarity of face 132 with face 61 and coplanarity of face 133 with face
62, while it remains between the face 128 of the part
123 and the face 31 of the part 21 a longitudinal space 138, as illustrated in FIG. 2 where the sub-assemblies 19 and 20 are precisely illustrated in this relative position.

The sheath-shaped part 123 carries a favon integral with the parts 124 and 125 by its face 127,
on which the parts 124 and 125 are for example glued or welded.

 Each of the parts 124 and 125 is in the form of a straight, longitudinal rod, that is to say parallel to the axis 3, with a cross section which is approximately rectangular in the example illustrated but could be different ; the two parts 124 and 125 are placed symmetrically to each other with respect to the longitudinal axis 3, along the same longitudinal plane 139 including the axis 3 (plane marked in IX-IX in Figure 8) and offset angularly with respect to the plane 170 of an angle a greater than 0 but less than 900, and for example of the order of 150, so that the parts 124 and 125 form a projection downstream facing the notches 136 and 137 relative to the sheath 123; radially with reference to axis 3, each piece 124, 125 has a transverse dimension greater than the dimension radially separating the faces 56 and 60 of the body 149; upstream, the parts 124 and 125 extend over a longitudinal distance just sufficient to ensure the -solidariation with the face 127; downstream, the parts 124 and 125 extend # to a level corresponding to that of the faces 134 and 135, level at which the parts 124 and 125 have respective end faces 140, 141 facing downstream; these two faces 140 and 141 are planar, perpendicular to the axis 3, and coplaid to the faces 134 and 135 of the part 123.

 In the parts 50 and 51 of the body 49, the parts 124 and 125 are received in respective longitudinal grooves 142 and 143, that is to say rectilinear and parallel to the axis 3, located along the same mean longitudinal plane 139 that the parts 124 and 125 and opening radially, with reference to the axis 3, in the faces 56 and 60 of the body 49 as well as longitudinally in the face 54 and, respectively, in the faces 61 and 62 thereof; the grooves 142 and 143 have a constant cross section, closely complementary to the constant cross section of the parts 124 and 125 so that these parts can slide in the grooves 142 and 143, respectively, and thus ensure guiding of the external subassembly 20 to the longitudinal sliding with respect to the interior sub-assembly 19 without the possibility of relative rotation about the axis 3.

In addition, the parts 124 and 125 serve to connect the part 126 to the part 123 in a solid manner for this purpose, the parts 124 and 125 have in their faces 140 and 141 respective notches 144 and 145 open downstream as well as in the direction of a radial approximation vis-a-is of the axis 3, and in the notches 144 and 145 is embedded, and secured by any suitable means and for example by welding or gluing, the part 126 being in the form of a plate in the form of a transverse washer, presenting respectively upstream and downstream two faces 146 and 147 of generally planar shape, perpendicular to axis 3, connected to each other by a longitudinal edge face 148, cylindrical of revolution,
and turned in the direction of a radial distance with respect to the axis 3, with a diameter less than that of the face 60 of the body 49 while being as close as possible to the latter; because of this, the room
126, whose face 147 is coplanar with the faces
134, 135, 140, 141, Must be housed inside the body 49 when the external sub-assembly 20 occupies with respect to the internal sub-assembly 19 the position illustrated in FIG. 2, in which there is co-planarity between the sides 63 and 64 on the one hand, the faces
134, 135, 140, 141 and 147 on the other hand.

 To this end, in addition, the piece in the form of a wafer 126 is pierced longitudinally right through a slot 149 having a shape and dimensions suitable for allowing its passage through the blade 5 or 5 ′, in particular in this position, so that the peripheral cutting edge 7 or 7 'of this blade forms a longitudinal projection, downstream, relative to the face 147 of the piece in the form of a wafer 126; for this purpose, too, the longitudinal distance between the faces 146 and 147 is chosen so that contact is not established between the shaft 9 and the face 146, which further presents for this purpose, on both sides and d 'Other of the slot 149, millings 150 adapted to allow partial penetration, without mutual contact, of the pinion 105 in the plate 126.

 In general, the slot 129 has a shape and dimensions suitable for closely matching the blade 5 or 5 '; for example, there is illustrated in FIGS. 2 and 7 to 9 a shape of this slot adapted to the case of a blade 5 in the form of a flat disc and, in this case, the slot 149 has a rectangular cross section, syrti # tri- e relative to the two planes 169 and 170, with a dimension in the second of these planes much greater than the dimension in the first of these planes, which corresponds substantially to the maximum thickness of the blade 5 measured along the transverse axis 6 , increased by a value just sufficient to avoid any contact between the blade 5 and the plate-shaped part 126; for the use of a blade of the type illustrated in 5 ′, in the form of a cup, provision would be made for the use of an external sub-assembly 20 having a piece in the form of a wafer such as 126, the slot of which is like 149, retaining the orientation illustrated in Figures 2 and 7 to 9, would also have parallel to the transverse axis 6 a dimension greater than that of the slot 149, and adapted to the overall dimensions of the blade 5 'parallel to its axis 6 '.

 By marrying the blade 5 or 5 ′ as well as possible, in particular on either side thereof parallel to the axis 6 or 6 ′, the piece in the form of a wafer 126 offers, by its face 147, a transverse face of longitudinal support alr the eye, face with respect to which the longitudinal projection formed by the cutting edge 7 or 7 'of the blade 5 or 5' can be adjusted, from a maximum value corresponding to the coplanarity between the faces 63 and 64 and the faces 134, 135, 140, 141, 147, by adjusting the relative longitudinal position of the external sub-assembly 20 and the internal sub-assembly 19.

 To this end, in the space 138 intermediate between the face 128 of the sheath-shaped part 123 and the face 31 of the first part 21 of the interior sub-assembly 19, a longitudinal stack of transverse Belleville washers 151 is prestressed in the position. relative of the two sub-assemblies 19 and 20 illustrated in FIG. 2, to elastically urge the external sub-assembly 20 relative to the internal sub-assembly 19 in the direction of a longitudinal offset downstream of the faces 134, 135, 140, 141 147 with respect to the faces 63 and 64, that is to say in the direction of a reduction in the value of the longitudinal projection formed by the peripheral cutting edge 7 or 7 'of the blade 5 or 5' by relative to the surface 147 for bearing on the eye.

 Opposed to such a stress is a micrometric stop piece 152 thus making it possible to fix the longitudinal position of the faces 134, 135, 140, 141, 147 relative to the faces 63 and 64, that is to say to fix so choose the value of the projection of the peripheral cutting edge 7 or 7 'of the blade 5 or 5' relative to the face 147 bearing on the eye.

The micrometric abutment piece 152 has a general shape of revolution around the axis 3, towards which it is delimited in particular by an inner peripheral face 153 which is longitudinal, cylindrical of revolution with a diameter greater than the respective diameters of the face 27 of the first part 21 of the interior sub-assembly 19 and of the external peripheral face 129 of the sheath-shaped part 123 but nevertheless close to these two diameters; the face 153 has in an upstream section a tapping 154 complementary to the helical thread in relief 30 of the face 27 and engaged with this thread 30 so that the longitudinal position of the micrometric stop piece 152 can be adjusted relative to to the first part 21 of the interior sub-assembly 19 by a relative rotation about the axis 3; upstream, the rauded section ta of the face 153 is connected to an inner peripheral face 155 of the part 152, longitudinal, cylindrical of revolution and facing the axis 3, with a diameter intermediate between the respective diameters of the faces 27 and 25 of the first part 21 of the interior sub-assembly 19; the face 155 is smooth and suitable for being applied against the O-ring 129 by means of compression of the latter so as to constitute a brake against a relative rotation of the part 152 and the part 21; downstream, the inner peripheral face 153, smooth facing the stack of Belleville washers 151 as well as facing the outer peripheral face 129 of the sheath-shaped part 123 so as to allow relative rotation around axis 3, is connected to a flat transverse face 156, annular of revolution and facing upstream; in particular when the two sub-assemblies 19 and 20 occupy the relative position illustrated in FIG. 2 and described above, the face 156 is in flat contact, with the possibility of relative rotation around the longitudinal axis 3, with the face 130 of the sheath-shaped piece 123 to constitute the abovementioned abutment t in the direction of a radial approximation with respect to the axis 3, the face 156 connects the face 153 to another inner peripheral face 157 longitudinal cylindrical of revolution and turned towards axis 3, with a diameter intermediate between the respective diameters of the faces 129 and 131 of the sheath-shaped part 123, however being as close as possible to the diameter of the face 131 to ensure mutual contact with possibility relative rotation about axis 3; longitudinally, the face 157 has negligible dimensions compared to the dimensions of the face 131 of the part 123 in particular between the face 130 of this and the notches 136 and 137; downstream, the face 157 is connected to a flat transverse face 158, annular of revolution and turned downstream, and this face 158 is connected itself, in the direction of a radial distance from the axis 3, to a face 159 frustoconical of revolution and converging downstream while also facing downstream; the face 159 connects the face 158, in the direction of a radial distance relative to the axis 3 and upstream, to an outer peripheral face 160 longitudinal, cylindrical of revolution and turned in the direction of a radial distance relative to axis 3; this face 160 has a diameter identical to that of the face 25 of the first part 21 of the interior sub-assembly 19 and it is connected to the face 155, in the direction of a radial approximation relative to the axis 3, by a planar transverse face 161, annular of revolution and facing upstream, which face 161 is applied flat against the face 26 of the first part 21 when the sub-assemblies 19 and 20 occupy their relative position illustrated in FIG. 2 and described above; thus this position in which the faces 134, 135, 140, 141, 147 are coplanar with the faces 63 and 64 constitutes, due to the cooperation of the external sub-assembly 20 with the internal sub-assembly 19 by means of the piece of micrometric stop 152 and longitudinal stack of washers
Belleville 151, which could moreover be replaced by other similar means of elastic stress, an upstream limit position of the external sub-assembly 20 relative to the internal sub-assembly 19 it is easy to understand that by turning the micrometric stop piece 152 with respect to the part 21 of the internal sub-assembly 19 so that the face 161 moves longitudinally from the face 26 by a movement downstream, it is possible to allow a longitudinal movement of the external sub-assembly 20 relative to the sub -internal assembly 19 downstream under the action of the Belleville washers 151, to bring the faces 134, 135, 140, 141, 147 into a position offset downstream by a determined value relative to the faces 63 and 64 , corresponding to a determined projection of the peripheral cutting edge 7 or 7 ′ of the blade 5 or 5 ′ with respect to the face 147 bearing on the eye, the value of this projection being lower than the value corresponding to the position illustrated in figure 2 ; when a desired value is reached, the part 152 is no longer urged to rotate relative to the part 21, and the O-ring 29 ensures relative immobilization; naturally, the continuation of such a relative movement of the two sub-assemblies 19 and 20 and a reverse relative movement can then be brought about at will by an appropriate rotation of the part 152 with respect to the part 21.

 By thus adjusting the value of the longitudinal projection formed by the cutting edge 7 or 7 'of the blade 5 or 5' relative to the face 147 bearing on the eye, an incision depth of the cornea is adjusted, as it appears from FIG. 10 where a diagrammatic illustration has been made of the making of a radial incision, on the cornea 162 of an eye 163, by means of a blade in the form of a flat disc of the type illustrated in 5 t we know that is meant by radial incision an incision made in a plane including the optical axis 164 of the eye (plane of FIG. 10) outside the cane 165 of vision, in order to cause a predetermined deformation of the cornea 162 and thus correct curvature defects thereof.

 For this purpose, a number of radiating incisions, their depth p and the respective angular positions ss and y, relative to the optical axis 164, of their zones respectively the farthest and closest to it are predetermined.

 After having determined these various parameters, a surgeon having a knife according to the invention can adjust, by rotation of the micrometric stop piece 152 relative to the piece 21 of the interior sub-assembly 19, the longitudinal projection formed by the cutting edge. 7 of the blade 5 relative to the face 147 bearing on the eye at a value corresponding to p; advantageously, this operation is facilitated by a direct graduation of the face 160 of the part 152 and of the face 25 of the part 21 of the internal sub-assembly 19 in value of the longitudinal projection of the edge of the blade relative to the face 147 bearing on the eye, according to the relative angular position of the part 152 and the part 21; after having made this adjustment, the surgeon starts the means 18 or 18 ′ for driving the blade 5 in rotation about its axis 6 then, by making the plane 170 coincide with the incision plane (plane of the figure 10) and holding the knife 1 by the face 123 of the external sub-assembly 20, approach in the direction 24 the blade 5 of the cornea 162, in an area corresponding to one 166 of the ends of the incision to be made, taking care to orient the axis 3 substantially perpendicular to this zone of the cornea; as soon as the cutting edge 7 of the rotating blade 5 comes into contact with the cornea, it initiates the incision and the movement of the knife 1 is continued in the direction 24 relative to the cornea 162 until the face 147 is applied tangentially against the cornea; the corresponding position of the axes 3 and 6, of the blade 5 and of the bearing face 147 is illustrated in dotted lines in FIG. 10; then, keeping a coincidence of the plane 170 with the incision plane, a perpendicularity of the axis 6 with respect to this incision plane, a tangential nature of the face bearing on the eye 147 with respect to the cornea 162, and a perpendicularity of the axis 3 with respect thereto, the surgeon moves the entire knife 1 towards the second end 167 of the incision to be made, and this incision 168 is made progressively by action of the cutting edge of the blade on the cornea not only due to the existence of a relative translational movement of the assembly of the knife 1 and the cornea, but also, and above all, due to the rotation of the blade 5 on itself around axis 6; when the second end 167 of the incision 168 is reached, which corresponds for the axes 3 and 6, the blade 5 and the bearing face 147 to a second position illustrated in dotted lines in FIG. 10, in dotted lines in FIG. 10, the surgeon moves the knife 1 in the opposite direction to the direction 24 relative to the cornea 162, in order to extract the blade 5 therefrom; the speed of rotation of the latter can be continuously controlled and adjusted throughout the duration of the incision, which the surgeon can also observe permanently via the notches 75, 76, 136, 137; when the blade 5 is completely disengaged from the cornea, the drive means 18 or 18 ′ can be stopped, which limits the wear of the moving parts.

 Naturally, curved incisions can also be made, either by means of the flat blade 5 if their radius of curvature is sufficiently large, or by means of a cup-shaped knife 5 'in the case of smaller radii, with a large ease of control of the proper progress of the incision due to the presence of the notches 75, 76, 136, 137 and intervention on this progress due to the maneuverability of the knife and the possibility of acting on the speed of rotation of the blade.

 A person skilled in the art will readily understand that the embodiment of a knife according to the invention which has just been described constitutes only a nonlimiting example and that, without departing from the scope of the invention, it will be possible to bring to it numerous variants relating for example to the mode of guiding and driving the blade in rotation and a mode of adjusting the projection which it forms outside the handle.

Claims (18)

 1. Knife for surgery of the anterior segment of the eye, in particular of the cornea, comprising on the one hand a longitudinal handle (2) having a first transverse end (4) and on the other hand a blade (5, 5 ' ) carried by the handle (2) and forming a longitudinal projection out of the handle (2), at said first transverse end (4) thereof,  characterized in that the blade (5, 5 ') has a shape of revolution around a transverse axis (6, 6') and in that the handle (2) is hollow and has internally  - Means (10, 11) for guiding the blade (5, 5 ′) to rotation about said transverse axis  (6, 6 '), relative to the handle (2),  - a chain (12, 13) of kinematic connection between the blade (5, 5 ') and means (16, 17, 18, 18') for driving the blade (5, 5 ') to the rotation of said axis transverse (6, 6 ') relative to the handle (2).  2. Knife according to claim 1, characterized in that the handle (2) has, at said first transverse end (4) and around the blade (5, 5 '), a transverse face (147) bearing on the 'eye, in that said transverse axis (6, 6') is set back relative to said bearing face (147) and in that the blade (5, 5 ') partially forms a longitudinal projection relative to said bearing face (147).  3. Knife according to claim 2, characterized in that the handle (2) comprises micrometric means (152) for adjusting the value of said longitudinal projection of the blade (5, 5 ') relative to the bearing face (147).  4. Knife according to claim 1, charac terized in that the handle (2) has at least in the immediate vicinity of said first transverse end (4) a sheath (123) mounted with relative longitudinal sliding, in that said sheath (123 ) carries integrally at said first transverse end (4) a transverse plate (126) having a transverse face (147) defining a bearing face on the eye, said plate (126) having means (149) for passage longitudinal of the blade (5, 5 '), in that said transverse axis (6, 6') is set back with respect to said bearing face (147), in that the blade (5, 5 ') partially forms a longitudinal projection relative to said bearing face (147), and in that micrometric means are provided for adjusting the relative longitudinal position of the sleeve (123) and of the handle (2), to adjust the value of said longitudinal projection.  5. Knife according to claim 4, characterized in that the sheath (123) and the handle (2) are notched near said first transverse end (4), to allow a vision of the blade (5, 5 ') by an operator.  6. Knife according to any one of claims 1 to 4, characterized in that the handle (2) is notched near said first transverse end (14>, to allow a vision of the blade (5, 5 ') by an operator.  7. Knife according to any one of claims 1 to 6, characterized in that the chain (12, 13) of kinematic connection comprises a longitudinal drive shaft (13) housed inside the handle (2), means ( 14) for guiding said drive shaft (13) in rotation about a longitudinal axis (3), with respect to the handle (2), and means (12) for transmitting movement with angle transmission between said drive shaft (13) and the blade (5, 5 '), inside the handle (2).  8. Knife according to claim 7, ca acterized in that the means (12) for transmitting movement comprise a gear train with bevel gear (12).  9. Knife according to any one of claims 7 and 8, characterized in that the longitudinal handle (2) has a second transverse end (15) open longitudinally opposite said first transverse end (4), and in that that said drive shaft (13) forms a longitudinal projection out of the handle (2) at said second transverse end (15) thereof for connection with the drive means (16, 17, 18, 18 ' ).  10. Knife according to any one of claims 1 to 9, characterized in that the drive means (16, 17, 18, 18 ') comprise a driving turbine.  11. Knife according to any one of claims 1 to 9, characterized in that the drive means (16, 17, 18, 18 ') comprise an electric motor.  12. Knife according to any one of claims 1 to 11, characterized in that the drive means (16, 17, 18) are external to the handle (2).  13. Knife according to any one of claims 1 to 11, characterized in that the drive means (18 ') are at least partially integrated into the handle (2).  14. Knife according to any one of claims 1 to 13, characterized in that the blade (5, 5 ') has a peripheral cutting edge (7, 7') circular, smooth, of revolution around said transverse axis (6, 6 ').  15. Knife according to any one of claims 1 to 14, characterized in that the blade (5) has the shape of a flat disc.  16. Knife according to any one of claims 1 to 14, characterized in that the blade (5 ') has the shape of a cup.  17. Knife according to any one of claims 1 to 16, characterized in that the blade (5, 5 ') has a periphery (7, 7') with a diameter of the order of 3  18. Knife according to any one of claims 1 to 17, characterized in that the blade (5, 5 ') is made of synthetic sapphire.