4220-1.doc Intraocular lens insertion device Field of Invention This invention relates to replacement of natural tenses in human eyes with artificial tenses. 5 Background Human eye tenses degenerate for various reasons, one of which is age. Degeneration of the lens, including the formation of cataracts, can result in degeneration of vision until the eye is effectively blind. Effective sight can be restored by replacing the natural lens with an artificial lens. 10 Flexible artificial tenses can be used and these may be inserted into the patient's eye using a manually operated insertion device. The flexible lens is located in a cartridge and manually pushed into the eye using a plunger. The insertion device is typically an elongate cylindrical tubular body having a plunger mounted within the tubular body for movement along the tubular 15 body. The plunger may have a simple sliding action, whereby force applied to the exposed end of the plunger causes it to slide into the tubular body, thereby pushing the lens from the cartridge into the eye. Alternatively the plunger has a screw thread that engages a complementary thread on the tubular body. Rotation of the plunger causes inwards movement and, again, 20 expulsion of the lens into the patient's eye. The problem with current systems is that movement of the plunger is carried out manually. In the case of the simple slide type device, the surgeon holds the device in a similar manner to a syringe and uses a thumb to push the plunger inwards. In the case of the screw type device, the tubular body is held 4220-1.doc -2 with one hand whilst the other turns the plunger. The act of ejecting the tens from the device occurs whilst the end of the device is located within the tens region of the eye and the device needs to be positioned accurately and with minimal movement to avoid or minimise 5 unnecessary damage to the eye. Both methods of manipulation of the plunger result in some loss of control of the device, which can lead to unnecessary damage. For example, the surgeon or patient may jerk and drive the tens into the back of the eye. Summary of the Invention 10 In an attempt to overcome at least some of the disadvantages of the existing systems the present invention provides a tens insertion device having an elongate body with a plunger mounted on or within that moves axially relative to the body and a drive mechanism for moving the plunger axially relative to the elongate body. 15 Preferably the drive mechanism includes an electric motor but other dive motors, such as hydraulic or pneumatic motors may be used. The plunger may be mounted for simple sliding motion relative to the elongate body or may be mounted via screw threads, whereby rotation of the plunger results in axial motion. 20 The electric motor may be connected directly of indirectly to a threaded plunger, whereby rotation of the motor causes rotation of the plunger relative to the tubular body, thereby causing relative motion of the plunger in the tubular body. Where the plunger is a slideable type, the drive mechanism may include 4220-1.doc -3 means to transfer the rotary motion of the motor to a linear motion, such as by way of two threaded components. Alternatively a linear motor may be used. Preferably the drive mechanism has switch means whereby the direction 5 and/or speed of plunger motion may be controlled. The switch means may be foot operated or may be hand operated. The drive mechanism may be mounted directly on or incorporated into the device as a whole, connected to the plunger or may be located remotely from the device. 10 Where the drive mechanism is located remotely from the device, the drive mechanism is preferably connected to the plunger by at least one flexible cable or shaft. The invention also includes a drive mechanism for retrofit to existing lens insertion devices having an elongate body with a plunger mounted on or within 15 that moves axially relative to the body, the drive mechanism including a motor and connecting means for connection to the plunger, whereby activation of the motor causes axial movement of the plunger relative to the body. The invention shall be better understood from the description of the following 20 non-limiting example shown in representations and of other embodiments. Brief Description of the Drawings Figure 1 is a plan view of a conventional intraocular lens insertion device. Figure 2 is a detailed view of the insertion end of the device of figure 1.
4220-1.doc -4 Figure 3 is a plan view of the device of figure 1 and the drive components of a first example of the invention in a disassembled state. Figure 4 is a plan view of the drive components of figure 3 in an assembled state. 5 Figure 5 is a plan view of foot peddles of the first example of the invention. Detailed Description of Preferred and other Embodiments Referring to the drawings there is shown a conventional screw type intraocular lens insertion device 10. The device 10 includes an elongate tubular body 12 and a plunger 14. The plunger 14 has a threaded portion 16 that engages an 10 internal thread 18 at the outer end 19 of the tubular body 12. A knurled knob 20 allows the surgeon to rotate the plunger 14 relative to the tubular body 12. The other end 22 of the tubular body 12 is adapted to hold a disposable lens cartridge 24. The cartridge 24 is hollow and has a passageway 26 that is relatively large at its inner end 28 and decreases to a narrow circular cross 15 section at its outer end 30. A flexible lens may be introduced into the passageway 26 from the inner end 28. The inner end portion 32 of the plunger 14 decreases in size so that its free end 34 may pass into the passageway 26 and push a flexible lens along the passageway 26 and out the outer end 30. 20 The above is known and the exact arrangement of the cartridge and plunger is not critical to the invention. Nor is the exact method of engagement of the plunger 14 with the tubular body 12. Referring figure 3 there is shown a drive mechanism, generally indicated by numeral 50, for the intraocular lens insertion device 10. The drive mechanism 4220-1.doc -5 50 includes an electric motor 52, first connector 54 and a second, flexible, connector 56. The drive motor 52 has an output shaft 58 that engages in a passageway 60 in the first connector 54. This connection is preferably a quick release 5 mechanism that allows the motor 52 and connector 54 to be easily and rapidly connected or disconnected by pushing or putting axially. The connection is similar to that found in dental equipment and may be easily sterilised. However, the invention does not require a quick release mechanism or the specific mechanism described. 10 The connector 54 changes the axis of rotation and has an output shaft 62 that rotates about an axis angled to the output shaft 58 of the motor 52. This is at about 70 degrees to the axis of the motor 52. This angle is not critical and is dependant on the nature of the connector 54. The angle may be changed as needed. The connector 54 may be configured to allow the angle to be varied. 15 The output shaft 62 is preferably releasable from the connector 54 but may be permanently affixed if desired. The free end 64 of the output shaft 62 engages one end 68 of flexible coupling 56. The coupling 56 has an opening 72 at its other end 70 that is an interference push fit onto the knob 20 of the plunger 14. Obviously the size of 20 the opening 72 depends on the size of the knob 20. In the example shown the flexible coupling 56 includes a flexible tube-like member. The output shaft 62 has a disc like end that engages the inner surface of the tube. This provides a small amount of radial freedom of movement between the output shaft 62 and the flexible coupling 56. This is not critical and the output shaft 62 may 25 engage the tube 66 with no radial freedom of movement. The output shaft 62 may also be permanently affixed to the flexible coupling 56. The flexible 4220-1.doc -6 coupling is preferably formed of a suitable plastics polymer that may be sterilised for reuse. The flexible coupling 56 also allows for some movement and variation in alignment between the axis of the insertion device 10 and the output shaft 62. 5 Whilst a flexible coupling is preferred, a rigid coupling may be provided. The motor 52 is controlled by electric cabling 80 that connects to foot peddle control 82. By pressing on either of the foot peddles 84, 86 the motor 52 may be caused to rotate in either direction, thereby causing rotation of the plunger 14 and consequently inwards or outwards motion. The foot peddles 10 84, 86 are preferably proportional controls, so that the speed of the motor depends on the amount by which the peddles are depressed. In this example, in use, the motor 52 is rests on or is attached or mounted to the forearm of the surgeon that will be holding the insertion device 10. The insertion device 10 is held in a similar manner to a pen, hence the need for 15 the coupling 54 that changes the axis of rotation. The insertion device 10 is loaded with a lens in the conventional manner and the tip 30 of the cartridge inserted via an incision into the patient's eye until it lies in the lens region of the eye. The surgeon presses on the "down" peddle 84 with a foot and the plunger 14 is caused to rotate. The surgeon is holding 20 the tubular body 12 in their hand so the plunger 14 moves inwards relative to the tubular body 12. The surgeon's other hand is not required to be involved in manipulation of the plunger 14 and may be used to stabilise the surgeon, the patient's eye or for other actions. 25 The surgeon may stabilize their operating hand and, because the drive 4220-1.doc -7 mechanism 50 only provides a rotational force, the drive mechanism 50 does not introduce sideways or axial forces, which may result in unintended movement of the tip 30. The motor 52 continues its rotation until the plunger 14 has expelled the tens 5 from the tip 30 into the patent's eye. After insertion of the tens the motor 52 may be reversed by pushing on the up peddle 86, thereby retracting the plunger 14. If the plunger 14 needs to be slowed, stopped or reversed during the insertion stage it is merely a matter of appropriate foot control and no gross movement is required by either of the surgeon's hands. 10 Whilst the example shown in the drawings has the motor 52 close to the insertion device it will be appreciated that the motor 52 may be located remotely from the device 10 and provided with a flexible drive shaft that connects to the plunger 14. Thus, for example, the motor and foot peddles could be incorporated into a single floor mounted unit. 15 Whilst foot controls are shown in the example, the controls may be incorporated into or on the insertion device, such that the surgeon may control the motor via pushing on appropriate buttons with one or more fingers. The motor itself may be mounted on or in the insertion device itself rather 20 than remotely, whereby the plunger is effectively driven directly by the motor. However, with conventional insertion devices, it has been found that the motor needs to provide a significant amount of low speed torque. This requirement results in a relatively large motor. Mounting a large motor on the tubular body 12, particularly near its outer end 19, results in significantly 25 reduced control of the insertion device 10, which is undesirable. Notwithstanding the foregoing, it is within the scope of the invention to 4220-1.doc -8 include a motor directly mounted on or incorporated into the insertion device. However, the advantage of the example shown is that the system may be dismantled easily and all of the components, except the motor, subject to a conventional sterilising regime without any special procedures required. 5 Whilst the example described is for use with a screw type insertion device, it may be easily modified for use with syringe type insertion devices. Rather than providing a rotary drive to the plunger the drive mechanism 50 needs to provide a linear push-pull motion. This may be achieved by having a first threaded member driven by the motor, such as the motor output shaft, that 10 engages a second threaded member that is prevented from rotating but which may move axially. Thus rotary motion is converted to linear motion. This may be transferred via a flexible drive shaft or cable located within an outer sheath. The inner cable connects to the plunger and the sheath engages the tubular body. Motion of the cable relative to the sheath will cause motion of 15 the plunger relative to the tubular body. The drive means for a simple sliding type plunger insertion device may be a linear motor rather than a rotary motor. A linear motor has a stator that moves linearly rather than in a rotary manner. Thus such a motor may be connected directly top the device or incorporated in the device. As an 20 example the plunger itself could be the stator of such a linear motor, with the windings incorporated into the elongate body. It will be apparent to those skilled in the art that many obvious modifications and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention.