Blade assembly

ES 2 286 751 T3

DESCRIPTION

Blade assembly.

Field of the invention

The present invention relates to a blade assembly for a microkeratome for performing a LASIK operation.

Background of the invention

LASIK (laser-assisted in situ keratomileusis) is a procedure commonly used to treat myopia (short-sightedness), hyperopia, (farsightedness), and astigmatism through the use of excimer laser. LASIK is an operation that is performed in the excimer laser room. The entire procedure is carried out under topical anesthesia (anesthetic drops) and the total duration is almost never more than 10 minutes. A suction ring approximately 20 mm in diameter is placed over the sclera (the white part of the eye) to hold the eye firmly. When performing LASIK, the surgeon first uses a microkeratome, currently with a special oscillating steel blade, to make a partial cut through the front surface of the cornea. This creates a flap of transparent tissue in the front center of the eye. Therefore, the automated microkeratome passes through the cornea to create a thin flap. This part of the operation usually takes only a few seconds. The suction ring is then removed from the eye, and the flap is raised again to allow enough space for the use of the laser. The excimer laser is then applied, which has previously been specifically programmed for correcting the desired amount of visual effect. A rapid and continuous emission of laser pulses removes very small precise amounts of corneal tissue. Depending on the type of refractive error, this part of the surgery takes between 30 and 60 seconds. The cornea is then irrigated with saline, and the flap is folded back to its original position. Within a few minutes, the flap attaches itself to the rest of the cornea and the LASIK procedure is done. In a couple of days, the cornea will be crystalline and a barely noticeable scar will be visible.

US Patent No. 5,133,726 describes a microkeratome. It comprises a support with a suction ring for attachment to the sclera of a patient's eye. A suction source is connected to the suction ring. A sliding element is mounted on the bracket so that it can be moved in a linear guide. The slider has a flat front surface that includes a transparent plate for contacting the cornea of ​​the patient's eye and that can slide over the cornea in a direction parallel to the front surface. Attached to the sliding element is a flexible shaft that is driven by the motor. The end of the shaft has a threaded area that engages a pinion. The pinion drives, through transmission gears, a driving gear that engages a grid on the bracket to move the sliding element. At the end end of the shaft an eccentric is formed which engages a slot in a slide mounted so that it can be moved over the slide member. A steel cutting blade with a cutting edge that is parallel to the front surface is mounted on the slide. In operation, when the motor is started, it simultaneously oscillates the blade parallel to the cutting edge and moves the sliding element on the support. With a microkeratome, it takes a lot of practice for the surgeon to position and fix the provided abutment surface to stop the motor at the right time, that is, at the right place. The abutment surface is to ensure that the desired width of the remaining joint is obtained that joins the cut flap of tissue with the remaining cornea. Oscillation speed and frequency are fixed and have a fixed ratio determined by the gear.

Summary of the invention

The problem to be solved by the present invention is to provide an improved microkeratome. This problem is solved by the combination of the features described in the appended claims.

Brief description of the drawings

A preferred embodiment of the invention is described herein below with reference to the drawings, in which:

Figures 1 and 2 show perspective views of the microkeratome, Figures 3 to 5 show longitudinal sections, Figure 6 is a perspective view of the support with the gripping unit, Figure 7 is a perspective view of the parts of the element slide, Figures 8a to 8c show the parts of the slide, Figures 9 and 10 show a tonometer in an assembled and disassembled position, Figures 11 and 12 schematically illustrate a control unit, Figure 13 is a cross section along the upper surface of part of the holder, and Figures 14 to 16 show a mounting unit for a diamond blade.

The microkeratome comprises a support 1 with a suction ring 11 for attachment to the sclera 12 of the eye 13 of a patient (see Figure 10). The suction ring 11 has two spherical surfaces 14, 15 (figure 5) and an annular recess 16 between them. A ring-shaped insert 17 is removably mounted in the recess 16. Insert 17 has radially extending notches 18 with contact surfaces 19 that are rounded on all sides to contact the eye and that lie in the same sphere as surfaces 14, 15. Between adjacent notches 18, insert 17 has through holes 20 that communicate with recess 16 behind insert 17. This recess 16 is connected to a channel 22 which, at the rear end of the support, communicates with a connector 23 to connect to a suction pump. The channel 22 is covered by a cover plate 24. Removable insert 17 has the advantage that recess 16 and insert 17 can be easily cleaned and sterilized after use. The insert 17 is made of metal and is slotted at one point on its circumference, so that it can be easily removed by tweezers (see slot 25 in Figure 2).

The support 1 has two rectilinear guide rails 27 (Figure 10) that are symmetrical to the longitudinal median plane 28 extending through the axis 29 of the ring 11. The rails 27 are oriented opposite the median plane 28. The longitudinal extent of

ES 2 286 751 T3 the rails 27 is perpendicular to the axis 29. This particular and unusual arrangement of the rails 27 has the advantage that the sliding element 2 described below, which has guide grooves 30 guided in the rails 27, in the line in which the movable sliding element 2 meets the support 1, does not come into contact with or obstruct or squeeze the tissue of the eye. Therefore, eye injury and pressure changes during cutting can be avoided. A rear raised portion 31 of the bracket has a top surface 32 that is perpendicular to axis 29. Portion 31 has a rectilinear groove 33 that extends perpendicular to and through median plane 28. At one end, groove 33 merges with a longitudinally extending groove 34 that is open toward the forward end (Figures 6 and 13).

The guide grooves 30 of the slider 2 are best seen in figure 7 which shows the parts of the slider 2, a slider 3 with a cutting blade 4 having a cutting edge 5, part of a motor unit 6 mountable in separable shape into the sliding element 2, a mounting aid element 7 and a handle 8 for the slide 3. The sliding element 2 has two lateral arms 38 on which is mounted a transverse plate 39 with a flat contact surface 40 to come into contact with the cornea of ​​the eye 13. The surface 40 is perpendicular to the axis 29 and therefore parallel to guide rails 27 and grooves 30. In a parking position shown in Figure 5, the front end face 41 of plate 39 is slightly behind opening 42 of ring 11. This allows free access to the eye in the parking position, for example, for the purposes described below. Plate 39 may be transparent, for example glass, and may have markings to read the diameter of the area of ​​contact of plate 39 with eye 13 for the purposes described more specifically in US Patent Application No. 5,997,559. by Frank Ziemer, filed August 5, 1998.

The sliding element 2 has a transverse prismatic opening 44 (Figures 1 and 7a) in which the thermoplastic and prismatic slide 3 is guided. Opening 44 extends perpendicular to axis 29 and rails 27 and is open to both sides. In a portion 45 of the opening 44 with rectangular cross section, the slider 3 is guided. An elastic arm 46 integrally formed on the slider 3 has connecting pins 47 formed therein. Blade 4 (Figure 8c) has corresponding holes 48 corresponding to pins 47. Blade 4 is attached to slide 3 by thermoplastic deformation of the free ends of pins 47.

The blade 4 is elastically preloaded by the arm 46 against two sliding surfaces 53, 54 (figure 7a) that are perpendicular to each other and form part of the opening 44. The surface 53 is coplanar with a lower surface of a slot 55 through which extends the blade 4. The cutting edge 5 extends to about 0.16 mm below the plane of the contact surfaces 40. The preloading of the blade 4 by the arm 46 has the advantage that the play of the slide 3 in the opening 44 and of the blade 4 in the slot 55 have no influence on the precise guiding of the blade 4 in operation. Therefore, the spacing between the cutting edge 5 and the plane of the surface 40 remains accurate within a few pm.

Prismatic mounting aid 7 and handle 8 each have the same cross-section as a forward portion 56 of aperture 44. Each has prismatic or cylindrical extensions 57 that engage draggingly to slide 3 and / or to the arm 46. The assembly aid 7 is tapered at the front end to facilitate insertion into the part 56 of the openings 44. The handle 8 has, separate from the slide 3, a step 58. The slide 3 has a transverse slot 59 that extends perpendicular to the opening 44. A conical countersink 60 extends from the upper surface of the slide 3, its axis coinciding with the central axis of the slot 59.

The sliding element 2 further comprises two prismatic extensions 63 having centering holes 64 and threaded holes 65 in their end surfaces. Two counteracting ring-shaped locking elements 66, 67 surround the extensions 63 and are separated by two springs 68. On a wall opposite a gripping surface 69, each element has a locking bar 70 which, at the mounted position of the motor unit 6, engages grooves 72 in a cylindrical extension 71 of the motor unit 6. The elements 66, 67 are secured in the sliding element 2 by a cover unit 74 which is centered with pins 75 in the holes 64 and screwed into the extensions 63 by means of the screws 76. The unit 74 has a central cylindrical opening 77 in the that extension 71 is centered.

The motor unit 6 (figure 1,3,5) comprises a housing 81 in which a first motor and a second motor 83 are mounted. The axis of the motor 82 is perpendicular to the rails 27 and the contact surface 40. Its output shaft 84 drives a disk 85 carrying an eccentric pin 86. The pin 86 carries a shoe 87 that is square in a silver view and engages in the grooves 33, 34. The motor shaft is tilted rearward for better access and view of the suction ring 11. The output shaft 88 of the motor 83 has an additional eccentric pin 89 which engages in the slot 59 and thus drives the slide 3. The motor unit 6 is covered by a cover 90 which is fixed to the unit 6 by screws 91 and has on both sides two guide rails 92 for suspension on a platform (not shown).

The gripping unit 9 is shown in figures 2 and 6 is made of metal. The unit 9 has two opposite side side walls 95 and a rear wall 96, the lower ends of the walls 95, 96 are welded or assembled to the upper surface 32 of the raised part 31 of the support 1. The gripping unit 9 surrounds to the motor unit 6 on at least part of its lateral sides and on its rear side. The surgeon holds the microkeratome in its grasping unit during the operation. This gripping unit 9, through the support 1, is fixed with respect to the suction ring 11, while the motor unit 6, together with the sliding element 2, moves towards the suction ring 11. The larger parts of the microkeratome, in particular the holder 1, the grip unit 9 and the housing 81 are made of titanium to save weight.

As shown particularly in figure 6, the support 1 has along the sides of the periphery of the suction ring 11 and along the part

ES 2 286 751 T3 rear of the guide rails 27, a vertical narrow flange 98. The flange prevents the sliding element 2 from coming into contact with the eyelid. Therefore, the surgeon always has one free hand during the operation.

Fig. 4 and the upper part of Fig. 3 further show a cable connection unit 101 which can alternatively be coupled to either the motor unit 6 or the gripper unit 9. In the unit 101 a female socket 102 is fixed into which a male socket 103 is inserted. To the male plug 103 are connected a plurality of connection sockets 104 of a cable 105 connecting the unit 101 with a control unit. A two-arm lever 106 is pivotally supported on unit 101. The forward arm of lever 106 has a hook 107, which in the position shown in Figure 3, engages a projection 108 of unit housing 81 6 motor and coupled with it the unit 101 to the unit 6. The rear end of the other arm of the lever 106 has a cylindrical extension 109. At the top of the rear wall 96 of the gripper unit 9 an impeller 110 is mounted. The impeller 110 is attached to two cylindrical pins 111 which can slide into corresponding through holes 112 in the wall 96. The pins 111 have at the front end a wedge surface 115 that merges into a cylindrical recess 116.

Lever 106 is urged into its position shown in Figure 3 by two laterally spaced pins 117 that are upwardly preloaded by springs 118. Figure 4 shows a cross section parallel to the longitudinal section of Figure 3 but containing the axis of one of the pins 117.

When the bracket 1 is inserted into the slider 2 for the position shown in Figure 3, the pusher 110 is pushed inward. Wedge surface 115 urges extension 109 upward so that lever 106 pivots counterclockwise against the force of springs 118. In the fully pushed position, extension 109 rests in recess 116 of the pins 111 (shown in dashed lines in Figure 4). The lower ends of the two pins 117 in that position engage in corresponding holes 119 in the rear wall 96. The hook 107 is out of adjustment with the projection 108 and the unit 101 is now coupled to the grip unit 9 and with it to the bracket 1. This has the advantage that the cable 105 does not move when the sliding element 2 with the motor unit 6 moves forward. During cutting, the cable does not transmit any force to the mobile unit.

Portions of the pins 122 of the socket 102 are connected (not shown) to one end 123 of a flexible, band-shaped electrical cable 124. The end 123 is clamped on a cylindrical drum 125 which is fixed to the connection unit 101. In the park position shown in Figure 3, cable 124 surrounds drum 125 in a loose loop. Its other end is fixed to the motor unit 6 and its various connection sockets are connected to the motors 82, 83 and to an angle detector 126 that is coupled to the output shaft 84 of the motor 82 as a feedback of the position of the element 2. slide on bracket 1.

An electronic circuit board 129 comprising a Hall effect detector 130 is mounted in unit 101 above lever 106. Extension 109 contains a permanent magnet 131 that cooperates with Hall effect detector 130. The plate 129 is connected through the connection sockets 132 to one of the pins 122.

Figures 9 and 10 show a tonometer 136 for use with the microkeratome of the present invention. Tonometer 136 comprises a titanium housing 137 with a cylindrical bore 138 which, in the assembled position shown in Figure 10, is coaxial to shaft 29. At the upper and lower end of bore 138, two thermoplastic slip rings 139 of low friction are inserted in corresponding grooves. Two cylindrical sleeves 140 are slidably guided by rings 139. Sleeves 140 are pressed on or attached to a transparent, sapphire, cylindrical body 141 having a flat lower end surface 142 perpendicular to axis 29 and a spherical upper surface 143 . The bottom surface 142 is imprinted or engraved with transverse lines 144 of which one, in the mounted position, is parallel to the guide rails 27 and the other is perpendicular to it. Lines 144 cross axis 29. The bottom surface further has a circular mark 145. A pin 146 screwed into the housing 137 engages a longitudinal groove 147 in one of the sleeves 140 and ensures a precise angular position of the transverse lines 144.

The upper face of the suction ring 11 has two diametrically opposed vertical stiffeners 151 (not shown in Figures 1 to 6) with flat upper surfaces 152 containing spherical or cylindrical recesses 153. Each brace 151 further comprises a hole 154 parallel to rails 27. Housing 137 has corresponding contact surfaces 155 for contacting surfaces 152 and pins 156 for insertion into holes 154. Housing 137 further has two inserts 157 with spring loaded balls 158 that snap fit into recesses 153 when tonometer 136 is mounted on suction ring 11.

The microkeratome further comprises a control unit 162 (figure 11) with a touch screen 163, a female plug 164 to be plugged into a male plug at the end of the cable 105, a connector 165 to connect the unit 162 with the connector 23 by means of a vacuum hose (not shown), and a female socket 166 for connecting a cable to two foot switches (not shown). Control unit 162 contains a vacuum pump, a vacuum container, a vacuum switch, a vacuum sensor, and a programmable microprocessor.

Before starting an operation, the motor unit 6 with the cover 90 and the connection unit 101 are suspended on the rails 92 on a platform. These units do not need to be sterilized because they do not come into contact with the patient or the surgeon's hands. However, they can be gas sterilized. The holder 1 with the gripper unit 9, the sliding element 2 and the tonometer 136 are sterilized in an autoclave. The slide 3 with the blade 4, the assembly aid element 7 and the handle 8 are contained in a sterile pouch or box. The patient's eye 13 is marked by a conventional marking known as a LASIK marker with transverse lines crossing the axis of the eye and with a small circle around this axis. The surgeon enters his name into the control unit 162,

ES 2 286 751 T3 whereupon your last set of parameters used appears on the touch screen. Enter the patient's name and change the parameters if necessary. When you touch one of the fields with the parameter name, a new keyboard appears allowing the corresponding input. A numeric keyboard is displayed for numeric parameters and an alphanumeric keyboard for names. The cables and the flexible tube are connected to the control unit 162.

To mount the microkeratome, first the slide 3 is inserted into the sliding element 2 until it abuts the step 58 of the handle 8 on the sliding element 2. In this position, the slot is centered on the axis of the opening 77. The slider 2 is then pushed towards the extension 71. The bars 70 automatically snap into the grooves 72. The pin 89 enters the conical recess and automatically centers slot 59 on pin 89. The assembly aid element 7 and the handle 8 are removed. Now, the support 1 is inserted with its rails 27 into the grooves 30 of the sliding element 2 from behind. Shoe 87 enters groove 34 best seen in Figure 13, showing a cross section along upper surface 32 of raised bracket 31

1. The shaft 169 of the disk 85 and the output shaft 84 of the motor 82 are circled. This axis 169 is parallel to the median plane 28 but is offset to one side. The rotational position of the shoe 87 with respect to the axis 169 is shown in solid lines in Figure 13. The bracket 1 is pushed forward until the shoe 87 abuts the rear face 170 of the groove 33.

Now the impeller 110 is pushed so that the unit 101 disengages from the motor unit 6 and engages the gripper unit 9. The signal from the sensor 130 initiates a rotation of the output shaft 84 of approximately 10 °, so that the shoe 87 enters the groove 33 and reaches the position shown in the broken lines in Figure 13. The sliding element 2 is now in its parking position shown in Figures 3 and 4. The microkeratome is still suspended with its 92 rails on its platform and is ready to begin operation.

The tonometer 136 can now be attached to the suction ring 11 and the surgeon grasps the microkeratome and places the suction ring 11 over the patient's eye 13 so that the transverse lines 144 are exactly aligned with the transverse lines marked on the eye of the patient. patient. Now the vacuum is switched on with the right foot switch, so that the suction ring adheres to the eye 13 and is immobilized relative to the eye. Eye pressure is checked. The gravitational force of the shaft 141 and the sleeves 140 creates a certain visible contact area that must not be greater than the area marked with the circle 145.

If this is the case, the tonometer 136 is removed and the slider 2 is moved to its initial position by depressing the right foot switch. The shoe 87 is then in the position shown in the double dashed lines in Figure 13 and the plate 39 has moved forward, so that the end face 41 is somewhat ahead of the axis 29. The cutting edge 5 is at a specified distance h away from axis 29, for example 6mm.

Some surgeons are so experienced that they do not need a tonometer, but instead find the eye pressure with a finger. In this case, the transverse lines 170 on the suction ring are used to center the suction ring on eye 13. Plate 39 is transparent and has a set of marks 171 with increasing radii on its upper and lower surface around the axis. 29 in the initial position of the sliding element 2. The surgeon reads the diameter of the contact surface of the plate 39 with the eye 13 with the help of these marks 171 and enters the value on the touch screen 163. It checks if all the parameters are correct and confirms them by pressing the right footswitch. Pressing that switch again initiates cutting and the microkeratome now operates in the manner described in the aforementioned US Patent Application No. 5,997,559. The control unit 163 varies the angular speed of the disk 85, so that the linear speed of the sliding element 2 is constant and corresponds to the set value. The total angle of rotation is calculated from the distance h, the diameter of the flap, and the width of the joint.

When the cut is finished, the slider 2 returns to the park position and the vacuum is switched off with the right foot switch. Disassembly of the microkeratome for cleaning and sterilization is done in the reverse order of assembly. The slide 3 and the blade 4 are discarded.

A test program can be run before use by touching screen 163 in the "test" field. An insert is then displayed on the touch screen, instead of the fields "database", "help" and "service" and the program is executed, which checks the various functions and the vacuum by pressing the tube at a certain stage. empty, with the foot switches. This test only lasts a few seconds.

An overwhelming majority of surgeons use 4 steel blades on microkeratomes. These blades are quite expensive, since they are used only once. Another possibility is the use of diamond blades which are cheaper in the long run and have several advantages, in particular a much sharper cutting edge that results in a cleaner cut. The rpm of the motor 83 may be set lower or it may not even be necessary to vibrate the blade 4, thus reducing the vibrations. A diamond blade can be used indefinitely if handled properly.

However, the cutting edge of a diamond blade is extremely vulnerable. The blade must be removed from the side after use for cleaning and sterilization.

Figures 14 to 16 show a bracket and mounting unit 176 for such a diamond blade. The blade 177 and the slide 178 are actually designed for the microkeratome according to US Patent No. 5997559 (without the elastic arm 46 of the slide 31 and therefore with a different shape than the opening 44) but it is intended to later use a slide comparable to that shown in figure 7 and 8. In this case, elastic arm 46 would have to include a cylindrical body to fit the female thread, and extension 57 may need a press fit for arm 46 (Figures 7 and 8).

Blade 177 is comprised of a narrow diamond blade 179 assembled under high vacuum to a blade 180 of steel of the same thickness. The blade 180 is screwed into the slide 178 prismá5

ES 2 286 751 T3 tics by means of screws 181. The slot 182 and the wedge-shaped countersink 183 correspond to the slot 59 and the countersink 60 of Figure 8. On one of its front surfaces, the slide 178 has two holes 184 and in the center, a female thread 185.

Unit 176 has a sleeve-shaped bracket 188 with a cup-shaped end 189 and a deep hole 190. A shaft 191 can be slid in bore 190 and secured against rotation by a pin 192 engaged in a longitudinal groove 193. A spring loaded ball 194 engages one of two axially spaced circumferential grooves 195 of shaft 191 to fix its two longitudinal positions. The shaft 191 has a deep stepped longitudinal bore 196, and at its forward end, two pins 197 engage the bores 184.

A pin 199 with a gripping end 200 can slide and rotate in bore 196. The axial position of pin 199 is maintained by a spring-driven ball 201 that engages in one of two splines 202. The forward end of pin 199 has a male thread 203 which corresponds to thread 185. Two pins 204, 205 of different diameters project from the flat end face 206 parallel to the axis of pin 199. These pins correspond to corresponding holes in the sliding element. Before use, a cover with corresponding holes 208, 209 is slid over these pins 204, 205.

After use of the microkeratome, unit 176 is attached to the microkeratome slider via two pins 204, 205. Pin 199 is removed and shaft 191 is moved to its forward position. The pin 199 is then moved forward and rotated, so that the screw 203 is screwed into the thread 185. The motor unit is now removed from the slider and the shaft 191 is removed. The slider 178 with the blade 177 is cleaned, for example, in an ultrasonic bath, and sterilized, and the end 189 is covered by the cover 207. For the assembly of the slider 178, the unit 176 is coupled back to the microkeratome slider and shaft 191 and pin 199 move to their forward position. In this position, the slot 182 is centered in the middle of the slider, so that the motor unit can be mounted as described above.

The double dashed lines in Figure 16 indicate the slider 213 corresponding to the slider 30 of US Patent No. 5997559, but adapted for coupling the unit 176. For this purpose, one side of the slider 213 has two holes 214, 215 to accommodate pins 204, 205.

With this mounting unit 176 it is ensured that the blade 177, and in particular the diamond blade 179, is handled with extreme care when the slide 178 is mounted and removed and when it is cleaned. There is no risk of touching the cutting edge 5 with an object or a finger.