Actuator for device for delivery of ophthalmic lenses

The actuator comprises a barrel and a plunger received within the barrel. A clutch mechanism is operable between the plunger and the barrel. The clutch mechanism includes a driven member and a fixed member having respective castellations. The driven member carries pins which engage a three-start thread on the plunger. The castellations are urged into engagement by three annular springs. In the engaged condition of the clutch, the plunger is advanced by rotation relative to the barrel. An axial load on the plunger disengages the clutch mechanism, allowing the plunger to be advanced axially while rotating the driven member. Two-handed or one-handed operation according to a user's choice is therefore possible. The actuator can be used in combination with a lens delivery device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from United Kingdom Application 1206480.4 filed 12 Apr. 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the delivery of ophthalmic lenses.

2. Description of the Prior Art

Intraocular lenses are implanted into the eye through very small incisions in the eye, usually in the cornea, the lenses being rolled into a spiral or cylindrical shape prior to delivery.

Delivery can be carried out using a delivery device which is controlled manually by a surgeon, employing either a one-handed or a two-handed technique.

In many delivery devices substantial manual force can be required to progress the lens through the device. This can lead to difficulties for the surgeon as the procedure requires a great deal of control at the final stage of lens delivery, this often being as a result of the lens delivery device having a tapered cavity through which a rolled lens is progressed linearly prior to delivery into the eye, the degree of rolling of the lens being increased by the tapering of the cavity.

The lack of control at the final stage of delivery is an issue particularly associated with one-handed delivery techniques. These techniques usually involve delivery of a lens by depression of a plunger by the surgeon to progress the lens through the device and into the eye. This offers the advantage of freeing the surgeon's other hand for other actions.

An alternative is the two-handed technique of lens delivery. This usually involves delivery of a lens by rotation of a threaded plunger by the surgeon to produce linear motion in order to progress the lens through the device and into the eye. This technique offers the advantage of greater control of the delivery but with the disadvantage restricting the surgeon's freedom to perform other tasks using his other hand.

WO 2011/126144 A1 (Hoya Corporation) discloses an ocular implant insertion apparatus configured for screw-type and push-type operation. The apparatus has a body and a plunger, one of which has a helical slot and a longitudinal groove which intersects the slot. The other of the body and plunger has a protrusion which fits within the groove or the slot. The apparatus is switched between the two types of operation by visual alignment by the user of appropriate parts of the apparatus.

US 2009/0112223 A1 (Downer et al) discloses a lens delivery system handpiece having a threaded plunger rod with a ball lock ring. Locking the ring causes the plunger to be advanced by turning a thumbscrew or knob. Unlocking the ring allows the plunger to be advanced by pushing on the thumbscrew or knob in a manner similar to a syringe.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an actuator for a device for delivery of ophthalmic lenses, the actuator comprising a barrel, a plunger receivable within the barrel and movable between a first, withdrawn position and a second, more advanced position, and a coupling means operable between the plunger and the barrel and operable selectively in a first condition to allow the plunger to move axially relative to the barrel from the first to the second position and in a second condition in which rotation of the plunger relative to the barrel produces axial movement of the plunger from the first position to the second position, the coupling means being responsive to an axial load on the plunger to change from the second to the first condition and from the first to the second condition on release of the load.

With such an actuator, the surgeon or other user can select between longitudinal or rotary plunger movement simply by adjusting the longitudinal manual load on the plunger. This allows the user a choice between employing a one-handed technique, when the coupling means is in its first condition, and a two-handed technique, when the coupling means is in its second condition, of lens delivery, or a combination of the two, during any particular lens insertion procedure.

Further, the user may maintain one-handed operation, even when resistance to plunger movement is encountered, simply by applying an axial load to the plunger, as can conveniently be done whilst holding the actuator in one hand.

The plunger may include means for coupling the linear movement of the plunger to a delivery device, the coupling means preferably being arranged to remove any rotational element of the motion of the plunger to produce a solely linear output.

Generally-speaking, the actuator preferably produces a linear output which may or may not also have a rotational component.

Advantageously, the first and the second conditions are attainable over the same portion of the axial movement of the plunger relative to the barrel.

Conveniently, the coupling means comprise a screw-threaded portion of the plunger.

Advantageously, the coupling means comprise a clutch mechanism operable between the plunger and the barrel, the plunger conveniently extending extends coaxially of the clutch mechanism.

Preferably, the clutch mechanism comprises relatively-movable first and second interengageable elements, one of which is fixed relative to the barrel and the other of which is moveable relative thereto, and resilient biasing means urging the clutch elements into engagement with each other.

The clutch elements may have respective sets of castellations which engage with each other in the engaged condition.

Conveniently, the plunger passes coaxially through the first and second clutch elements and has a screw-threaded portion which is engageable with one of the elements, whereby the plunger can move by rotation thereof from its first to its second position when the first and second elements are engaged.

Preferably, the plunger can move from its first to its second position by axial movement thereof when the first and second clutch elements are disengaged.

Advantageously, an axial load on the plunger produces relative movement of the clutch elements and thereby changes the coupling means from its second to its first condition.

When a screw thread is provided, the clutch element which is in engagement with the screw thread has one or more protruding pins or other follower elements engaging with the thread.

Preferably, the thread is a multi-start thread, for example a two- or three-start thread. The use of a multi-start thread can provide a large degree of advancement of the plunger per rotation in the second condition of the coupling means.

A multi-start thread also facilitates coupling of the protruding elements with the thread with the minimum amount of rotation of the plunger being required to achieve this.

Preferably, the plunger has a first, forward portion which does not engage with the coupling means and a second, rearward portion, preferably a threaded portion, which engages with the coupling means, whereby the plunger can move axially relative to the barrel over a first portion of its stroke without operation of the coupling means.

Advantageously, the groove(s) of the threaded portion are flared at the transition between the first and second portions.

Alternatively however it is possible for the threaded portion to be in engagement with coupling means throughout the stroke of movement of the plunger. Flaring of the entry points of the thread(s) is then not needed.

Preferably, the resilient biasing means of the clutch mechanism are operable between the movable clutch element and an annular carrier member through which the plunger extends.

The resilient biasing means conveniently comprise a plurality of resilient annular elements lying in planes lying parallel to the axis of the plunger.

In another arrangement, the resilient biasing means comprise a plurality of resilient elements extending axially between the carrier member and the movable clutch element which are conveniently formed integrally.

Actuators according to the invention can be supplied as separate parts for fitment to delivery devices of a wide range of types. Alternatively, delivery devices can incorporate an actuator according to the invention as a part of the delivery device.

Actuators according to the invention are preferably linear actuators, or actuators producing a combined linear and rotational output movement.

DETAILED DESCRIPTION

FIG. 1of the drawings shows an actuator indicated generally at10fitted to a delivery device12of known type. The delivery device is fitted at its forward end with a lens cartridge14, also of known type, which contains a rolled or folded lens located in a tapering cavity. The lens is delivered to a patient's eye through an opening in the tip of the cartridge14.

FIG. 2shows the assembly ofFIG. 1with the actuator disassembled from the delivery device12and the lens cartridge14dismounted from the delivery device. It will also be seen fromFIG. 2that the actuator10comprises a barrel16which fits inside a sleeve18of the delivery device12, the barrel16and sleeve18being secured together by a bayonet connection consisting of a slot20in the sleeve18and a pin (not visible in the drawings) on the barrel16.

FIGS. 2 and 3of the drawings also show that the actuator10comprises a plunger22which is slidable in the barrel16. The plunger22(shown in more detail inFIG. 3) comprises a stem24which terminates at its rearward end in a cylindrical head26. The stem24terminates at its forward end in a bush28which is a sliding fit in the interior bore of the barrel16. The bush28is made from a suitable plastics material such as a polyetherketone (PEEK) and is freely rotatable on the stem24and carries a pin30which is received in a longitudinal slot32in the barrel16to constrain the bush against rotational movement relative to the barrel. A delivery needle34is mounted at its rearward end on the bush28, the needle being shaped to be received in the lens cartridge14in order to make contact with a folded or rolled lens and to deliver the lens from the cartridge into a patient's eye as the needle is moved forwards as a result of forward movement of the plunger22in the barrel16.

The stem24of the plunger22has a plain forward portion36and a threaded rearward portion38which has a three-start thread formed by three helical grooves40of U-shaped transverse section. For reasons which will become evident hereinafter, the grooves40widen at their open, forward ends into flared portions42which terminate in respective circumferential openings44which extend over arcs of about 100 degrees between rounded ends of the inter-groove ridges46which extend over arcs of about 20 degrees, as will be evident fromFIG. 5of the drawings.

The barrel16terminates at its rearward end in a cylindrical cup50, just forwardly of which a pair of outwardly-extending ears52protrude one to each side. The ears52allow the actuator to be held in one hand by a user with the user's first and second fingers behind the ears and the user's thumb resting on the head26of the plunger22.

The cup50receives a clutch mechanism54which is operative to provide coupling between the plunger22and the barrel16of the actuator10. The clutch mechanism54is arranged coaxially around the plunger22, as can be best seen inFIG. 4of the drawings which also shows the rearward end of the barrel16and a portion of the plunger22.

The clutch mechanism54includes a PTFE friction-reducing washer56, an annular support member58, an annular driven member60and an end cap62which is a press-fit in the rearward end of the cup50and is secured against rotation relative thereto. The stem24of the plunger22extends coaxially through the washer56, support member58, driven member60and end cap62.

The annular support member58is formed with three circumferential turrets64, each extending over an arc of approximately 90 degrees. Three arcuate gaps66each extending over arcs of about 30 degrees lie between the turrets64. Each turret64has in it a recess68of elongate transverse section. A resilient biasing member70, such as a clutch spring, is seated in each recess68, each resilient biasing member70consisting of a rectangular-section ring of resilient plastics material. The resilient biasing members70are circular in plan when in a relaxed condition but can be resiliently deformed to be oval in plan. Springs of this type have been found to be particularly simple to form and their rates readily determined and controlled.

The resilient biasing members70act on a forward annular face72of the driven member60and therefore act to bias the support58and the driven member60apart in the axial direction.

The driven member60is formed on its forward face72with three equidistantly-spaced turrets74, each extending over an arc of approximately 30 degrees, as will be seen most clearly inFIG. 6of the drawings. The turrets74of the driven member are received in the gaps66between the turrets64of the support member58. As can be seen fromFIG. 6, each turret74has a radial bore76having an internal circumferential ridge78. Each bore76receives a respective drive pin80which has a circumferential groove82which is a snap-fit over the corresponding ridge78in the respective bore76. Each pin80has a hemispherical inner end84which projects radially inwardly from the driven member60.

The driven member60is formed on its rearward annular face with a series of castellations86which engage a series of corresponding castellations88formed on the forward face of the end cap62. The resilient biasing members70therefore bias the series of castellations86,88into engagement with each other and lock the driven member60and end cap62together against relative rotational movement. The axial length of the cup50is chosen such that the resilient biasing members70are slightly deformed from their circular shapes in this condition of the clutch mechanism, thus providing a small preloading force.

The hemispherical end portions84of the pins80which protrude radially inwardly are positioned so as to be received in a respective one of the grooves40formed by the threads of the threaded portion38of the plunger24, entry of the pins into the grooves being facilitated by the flared end portions42of the grooves40.

The support member58, resilient biasing members70and pins80are formed from a suitable engineering plastics material such as a polyetherketone (PEEK). The driven member60is formed from a polyetherimide such as that sold under the name ULTEM®. Except as specifically mentioned otherwise, the actuator is made from a suitable titanium alloy. Stainless steel could be used instead.

The clutch mechanism operates as follows. In the disengaged condition of the mechanism already referred to, the driven member60is urged by the resilient biasing members70rearwardly relative to the end cap62. The castellations86,88are thereby brought into engagement and the driven member60and the support member58are locked against rotation relative to the end cap62. In this condition of the clutch, the forward, plain portion36of the plunger24can pass unimpeded through the clutch mechanism and the plunger24can be advanced correspondingly axially of the barrel16.

If the plunger24is advanced through the barrel to an extent that its threaded portion38passes into the clutch mechanism, the pins80engage in respective grooves40of the threaded portion38. Whilst the clutch mechanism remains engaged, the plunger22can be advanced further through the barrel16if it is rotated to allow the pins80to pass helically along the grooves40of the thread. This is achieved in the absence of any significant axial load on the plunger22.

If however a significant axial load is placed on the plunger22, the pins80, rather than passing helically along the grooves40, engage with the walls of the grooves with the result that the load on the plunger22is transferred to the driven member60which is shifted axially against the bias of the resilient biasing members70such that the castellations86,88disengage to allow the driven member60to rotate relative to the end cap62. The plunger22can now be advanced forwardly relative to the barrel16for so long as the axial load is maintained.

FIG. 7shows a modified clutch mechanism, the parts of which corresponding to parts of the mechanism54are indicated by reference numerals increased by “100” compared with the reference numerals used for the parts of the mechanism54.

The modified clutch mechanism154comprises a support member158and a driven member160which are formed integrally as a plastics moulding and which are joined by integral resilient biasing members170, such as resilient twisted straps, corresponding to the resilient biasing members70. The driven member160has three circumferentially-spaced turrets174which support drive pins180in a manner corresponding exactly to that described hereinbefore for the clutch mechanism54. The rearward face of the driven member160is formed with castellations186which engage with castellations188on the forward face of the end cap162.

The modified clutch mechanism operates in a very similar manner to the mechanism54, except that the resilient loading is provided by the resilient biasing members170and not the resilient biasing members70.

The use of the actuators shown inFIGS. 1 to 6andFIG. 7in connection with a delivery device for the insertion of a rolled ophthalmic lens into the human eye will now be described.

An actuator having a clutch mechanism54as shown inFIG. 4or a clutch mechanism154as shown inFIG. 7is assembled to a delivery device12as shown inFIGS. 1 and 2, the delivery device being fitted with a lens cartridge14as also shown inFIGS. 1 and 2. Advancement of the plunger22of the actuator10through the barrel16of the actuator causes the delivery needle34to pass into the lens cartridge14with the result that the rolled ophthalmic lens contained in the cartridge14is delivered outwardly through the aperture in the tip of the cartridge14.

During the first portion of the stroke of movement of the plunger22, the plain, unthreaded forward portion36of the stem24of the plunger22passes through the clutch mechanism54or154without contact, allowing the delivery needle34to be advanced rapidly and with little resistance, as is desirable during the initial phase of lens delivery before the tip of the needle34contacts the rolled lens in the cartridge14. During this initial phase, the surgeon may hold the delivery device and actuator with his first and second fingers behind the ears52and his thumb on the head26.

In the next phase of the delivery process, the threaded portion38of the plunger stem24engages with the clutch mechanism54or154as described above. The surgeon now has the option as he wishes either to continue the forward movement of the plunger in the actuator barrel in a one-handed operation which results in an axial loading on the plunger22with the effect that the clutch mechanism54or154disengages and the plunger can continued to be moved forwardly through the delivery device. Alternatively, if he wishes, the surgeon can continue to hold the barrel16of the actuator in one hand and then, by twisting the head26of the plunger22advance the needle to deliver the lens from the cartridge14. In this case, in the absence of substantial axial loading on the plunger, the clutch54or154remains engaged and the twisting movement of the plunger stem24results in further forward movement of the plunger with the pins80or180of the clutch mechanism54or154engaged in the grooves40of the threaded portion of the plunger stem. This allows the surgeon, according to his choice, to control the second stage of the insertion operation in a two-handed operation involving a rotary motion of the plunger22relative to the barrel16. The particularly advantageous feature of allowing the surgeon at his choice to employ a one-handed or a two-handed technique of lens delivery is therefore provided by the actuator of the present invention.