GB2247174A

GB2247174A - Surgical knife with retractable blade for cataract surgery

Info

Publication number: GB2247174A
Application number: GB9023202A
Authority: GB
Inventors: Ahmed Salih Mahmud
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-08-14
Filing date: 1990-10-25
Publication date: 1992-02-26
Anticipated expiration: 2010-10-25
Also published as: GB2247174B; GB9023202D0; GB9017784D0

Abstract

A surgical knife for use in cataract surgery has a handle portion that supports a cutter portion provided with a blade that can be moved selectively by fluid pressure from a retracted position to a cutting position for making a cut in a lens capsule. The handle portion may be provided with a fluid pump to create pressure in a housing in the cutter portion and thereby cause movement of the blade. The fluid pump may be arranged also to create a suction effect in the vicinity of the blade. <IMAGE>

Description

Surgical Knife This invention relates to a surgical knife and in particular to a surgical knife for use in eye surgery to treat a cataract condition by extra-capsular extraction.

The procedures involved in extra-capsular cataract extraction surgery require that an incision is made in the cornea in the region of the limbal line so as to facilitate access to the existing lens which is then carefully cut from the ciliary region and removed.

The step of cutting the anterior capsule is difficult to perform because there is very little space. During hitherto known surgical procedures manoeuvering of a knife in such a small space together with the inevitable fine tremor of the surgeon's hand has meant that great care must be exercised to ensure that the knife does not cause damage to the endothelium of the corneal cells or other complications such as damage to the zonular region. Because of the space limitations it is very difficult to achieve a smooth and regular curved cut line to allow subsequent accurate and stable location of an intraocular implant. Added to that, with existing procedures several pieces of equipment are needed in the anterior chamber which again contributes to the risk of complications.

The present invention seeks to provide an improved surgical knife and procedure for removing a lens capsule in which the aforedescribed difficulties are mitigated or overcome.

In accordance with one of its aspects the present invention provides for use in cataract surgery a surgical knife comprising a handle portion and a cutter portion, the cutter portion being supported by the handle portion and comprising a housing which provides support for blade means, said blade means being movable relative to the housing whereby it may be moved selectively from a retracted position to a cutting position for making a cut in a lens capsule.

The invention envisages that the housing of the cutter portion preferably is of a substantially tubular form and more preferably is curved along its length. The cutter portion may be annular in which case the housing may be of a toroidal shape.

Preferably biasing means is provided and arranged normally to bias the blade means to said retracted position. The biasing may be provided by resilient material which may form part of the housing or be associated therewith.

Additionally or alternatively the knife may comprise fluid pressure biasing means. Thus a fluid tight seal may be provided between the blade means and housing whereby an inherent potential vacuum may be maintained in a chamber within the housing so that in a balanced situation with external atmospheric pressure the blade will normally lie retracted to give atmospheric or near atmospheric pressure in the chamber.

Particularly but not necessarily only in an arrangement having fluid pressure biasing, means may be provided selectively to apply or create a fluid pressure within the housing chamber and thereby cause the blade means to move to said cutting position.

The cutter portion preferably is of a rigid or substantially rigid form and where the housing is of a kind which defines a fluid chamber preferably at least a substantial part of the structure defining said chamber is formed of a substantially inextensible material. Suitable materials for forming the housing, especially when in the form of a tubular fluid chamber, include plastics such as The blade means may comprise a single blade or a plurality of individual blades. If the cutter housing is curved along its length the blade means may comprise an elongate blade which is correspondingly curved along its length or a plurality of rectilinear blades disposed to lie in a curved path corresponding to the curvature of the cutter housing.

The handle portion may incorporate control means for control of the blade means to move it from a retracted to a cutting position. Where the cutter portion is of a kind which has a fluid chamber, the handle portion may incorporate a variable volume fluid chamber interconnected with said fluid chamber of the cutter portion such that change of said volume causes a change of fluid pressure and movement of the blade means. The fluid chamber(s) in the handle and cutter portions may be filled with an incompressible fluid or, more preferably, a compressible fluid such as air.

The handle portion may incorporate a flexible or movable wall which defines a part of said variable volume chamber and is biased e.g. by spring means (which may be provided by resilient material forming part of the chamber) normally to tend to maximise the volume of the chamber.

Movement of said wall against the biasing effect will thus tend to increase the pressure in the chamber thereby to cause movement of the blade means to a cutting position.

The cutter portion additionally may comprise a fluid flow passage having one or a plurality of outlet passages through which fluid such as a saline solution may be supplied. The handle portion may comprise a supply passage and a supply reservoir or a port for connection to a supply for flow of fluid to the fluid passage in the cutter portion. The fluid passage in the cutter portion may extend alongside the cutter housing; where the latter is annular in form the fluid passage may also be annular and preferably lies radially inwards of the housing. The handle portion may incorporate a movable control member and valve arranged to be operable as a pump means whereby fluid such as a saline solution may be supplied in a readily controlled manner to the vicinity of the cutter portion.

The knife may also comprise a passage for enabling a suction effect to be created in the vicinity of the cutter portion. The passage may extend through the handle portion and the aforementioned pump means, where provided, may be arranged to be operable also to pump fluid or waste material in a direction away from the vicinity of said cutter portion.

The housing of the cutter portion and any other structure forming part of the cutter portion preferably is contoured to provide a surface which conforms substantially to the outer surface of a lens capsule.

The invention envisages that the surgical knife may be manufactured in a range of sizes and that in particular the cutter portion may be in a range of sizes and shapes so as to allow selection of an appropriately sized and shaped knife having regard to the size and shape of the lens capsule to be removed. The invention envisages that the knife may be of a disposable type such that it may be constructed of materials which are not necessarily suitable for subjecting to repeated sterilisation as would be required of a re-usable knife.

In accordance with another of its aspects the present invention provides a method for removing a lens capsule comprising making an incision in the cornea in the region of the limbal line, introducing through said incision the cutter portion of a knife of a kind in accordance with the present invention and with the blade means in a retracted position, arranging the cutter portion to lie over the lens capsule and then advancing the blade means to a cutting position.

Gentle pressure may be maintained to hold the cutter portion on the lens capsule to cause cutting as the blade means advances and or the cutter portion may be gently moved, e.g. with a small to and fro rotational movement, to effect a cutting action.

Other aspects of a method in accordance with the present invention are described below in relation to use of a knife in accordance with an embodiment of the invention.

A surgical knife in accordance with one embodiment of the present invention and for use as a capsulectomy knife will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a general view of a knife in accordance with one embodiment of the present invention; Figure 2 is a schematic view of the fluid passages in parts of the knife of Figure 1; Figure 3 is a view similar to that of Figure (3) of a part of a knife in accordance with a modified embodiment; Figure 4 shows part of Figure 2 in more detail; Figure 5 is a section on the line 5-5 of Figure 4 with the blade (shown part in perspective) retracted; Figure 6 is a view similar to that of Figure 5 but with the knife operational to make a cut; Figure 7 is a perspective view including the section view of Figure 5;; Figure 8 is a perspective view including the section view of Figure 6, and Figure 9 is a perspective view, part removed, of the cutter portion of the knife when operational to make a cut.

A capsulectomy knife 10 comprises a handle portion 11 one end of which supports a relatively smaller cutter portion 12.

The handle portion 11 comprises a pump unit 13 and internal fluid passages, described in more detail below, which are arranged to communicate with the cutter portion.

The cutter portion 12 comprises a tubular blade housing ring 14 having at one side an annular surface 15 (see Figure 5) of substantially part-spherical shape and intended to conform substantially to the curvature of the lens surface 60. Typically said surface 15 may have a radius of curvature of 10 mm. The housing 14 typically will have a mean diameter in the range 6 to 8 mm as viewed in plan in Figure 2 and be selected according to the size of the capsulectomy. The housing typically will have a width of 2 mm as viewed in plan and a height (see Figure 5) of approximately 1.5 mm, these cross-sectional dimensions being selected without necessarily having regard to the mean diameter of the housing.

The annular surface 15 of the housing has an annular opening 16 through which a circular ring blade 17 may be caused to move from a retracted to a cutting position, as shown in Figures 5 and 6 respectively.

The ring blade 17 is of a T shape in cross-section (see Figure 5) and has a head portion 18 from which a limb portion 19 extends. The limb portion extends for approximately 0.5 mm from the head portion and has a sharpened edge 20 at its distal end. The head portion 18 stiffens and gives strength to the otherwise weak limb portion and also provides seal surfaces 21 by which the blade is sealingly secured to the housing.

The annular opening 16 is defined by a pair of groove wall members 22 each of flexible elastomeric material and each secured in fluid tight manner to a respective one of the blade seal surfaces 21. The wall members are arranged to be flexible in a manner which allows them to be compressed in a direction perpendicular to the plane of the blade head portion 18. Thus it will be appreciated that when the chamber 23 defined within the housing ring 14 is subject to a fluid pressure greater than that externally of the ring, the wall members 22 will tend to collapse and the blade will move from the retracted position shown in Figure 5 to the cutting position shown in Figure 6.Retraction will tend inherently to occur if the fluid pressure is removed from the chamber 23 because of the tendency of the resilient wall members 22 to restore to their initial configuration as shown by Figure 5, but this restoration may be further assisted by applying to within the chamber 23 a pressure less than that externally of the ring.

Instead of the ring blade 17 there may be provided a curved blade of C-shape i.e. not annular, and in this case ends of the blade must also be sealingly secured to the housing so that the housing may be selectively pressurised.

The cutter portion 12 additionally comprises an annular fluid flow passage 25 to serve as a jet ring through which saline solution may flow and issue onto a lens through a series of jet holes 26 proximate the housing surface 15. The jet ring lies inwards of the cutter housing, supported thereby, and typically has a diameter of 1 mm as viewed in Figure 5.

The cutter portion 12 also comprises an end portion 30 of a suction pipe 31 operable to remove saline solution which has been supplied via the jet ring and or to apply suction to an incised segment.

The handle portion 11 will now be described in more detail. It incorporates three passages 40, 41, 42 which communicate respectively with the tubular blade housing ring 14, the jet ring 25 and the suction pipe end 31.

The passage 40 is an air supply passage which extends to an air pump section 43 of the pump unit 13. The air pump has a compressible body 44, a distal end face 45 of the body being substantially rigid and shaped to act as a thumb rest. When the end face 45 is moved to compress the body 44 the volume of air contained within the pump, the passage 40 and chamber 23 of the housing ring becomes pressurised thereby to tend to cause the blade 17 to move from a retracted to a cutting position. The resiliency of the body 44 and or internal spring means (not shown) within the pump body may be relied upon to normally bias the air pump to a maximum volume condition and thereby normally hold the blade 17 in a retracted position.

The other two passages 41, 42 extend to a saline/suction pump section 50 of the pump unit 13. Each passage 41, 42 is separated from the chamber 51 of the pump section 50 by a one way valve 52, 53. The valve 52 in the passage 41 is arranged to allow flow only in a direction from the pump chamber 51 whilst the valve 53 in the passage 42 allows flow only in a direction into the chamber 51. The pump section 50 is constructed in a substantially similar manner to the air pump section 43 but is a little longer and has an end rest 54 for a forefinger. The passage 41 may incorporate a side port 55 (see Figure 3) for attachment of a saline bag.

The handle portion 11 has a casing 56 (see Figure 1) which contains and or defines in part the passages 40, 41, 42 and extends between pump unit 13 and the cutter portion 12 of the knife. The casing tapers in crosssectional dimensions from the pump unit 13 to the cutter portion 14. A first part 56a is straight but a second, distal part 56b is curved to a bent configuration so that the cutter portion lies at a ergonomically convenient orientation relative to the pump unit and first part 56a of the casing. The cutter portion is interconnected with said second, distal part 56b of the casing by a third part 56c of a straight shape.

Typically the handle portion will have a length in the range of 7 to 10 cm.

An example of a method of using the aforedescribed capsulectomy knife in an extra-capsular cataract extraction procedure will now be described.

Initially a curved incision is made in the cornea in the region of the limbal line and of a size sufficient to allow entry of the knife cutter portion 12 to the anterior chamber. The pupil is then fully dilated.

The knife is checked to ensure that the blade 17 lies in a fully retracted position, the incision is gently lifted with forceps, healonid is optionally injected into the anterior chamber if the surgeon so chooses in order to protect the endothelium of the corneal cells and the cutter portion of the knife is slid gently through the incision into the anterior chamber. The cutter portion is then rested gently, centrally on the anterior surface of the lens capsule.

The air pump 43 is pressed gently to advance the blade 17 to a cutting position whilst the handle portion 11 is controlled to ensure that a gentle pressure is maintained on the lens capsule. The knife is then rotated slightly clockwise and anti-clockwise to promote a cutting action by the blade 17 whilst simultaneously gentle finger pressure is maintained on the saline pump 50 to produce a flow of saline from the jet ring 25.

The flow of saline assists in lifting the incised segment (see Figures 8 and 9).

When finger pressure is removed from the saline pump 50 a suction effect will be produced and the incised part 61 of the capsule will be drawn into or held against the end portion 30 of the suction pipe 31.

After completion of the cutting procedure thumb pressure is removed from the air pump to ensure that the blade 17 moves to its retracted position. The cutter portion can then be removed through the incision, the saline pump preferably being operated at this stage so that the saline flow tends to lift the cornea and assist in avoiding contact with the knife during withdrawal.

Claims

1. A surgical knife for use in cataract surgery comprising a handle portion and a cutter portion, the cutter portion being supported by the handle portion and comprising a housing having a housing chamber and which housing provides support for blade means, said blade means being movable relative to the housing by fluid pressure means operable selectively to change the fluid pressure within the housing chamber whereby the blade means may be moved selectively from a retracted position to a cutting position for making a cut in a lens capsule.

2. A surgical knife according to Claim 1 wherein biasing means is provided and arranged normally to bias the blade means to said retracted position.

3. A surgical knife according to Claim 2 wherein the biasing means comprises resilient material.

4. A surgical knife according to Claim 2 or Claim 3 wherein biasing means comprises fluid pressure biasing means.

5. A surgical knife according to any one of the preceding claims wherein a fluid tight seal is provided between the blade means and the housing.

6. A surgical knife according to any one of the preceding claims wherein the blade means comprises a single blade.

7, A surgical knife according to any one of Claims 1 to 5 wherein the blade means comprises a plurality of individual blades.

8 A surgical knife according to anyone of the preceding claims wherein the cutter portions is of a substantially tubular form.

9. A surgical knife according to any one of the preceding claims wherein the cutter portion is of a curved and elongate form.

10. A surgical knife according to Claim 9 wherein the blade means lies in a curved path corresponding to the curvature of the cutter housing.

11. A surgical knife according to any one of the preceding claims wherein the handle portion incorporates control means for control of the blade means to move it from a retracted to a cutting position.

12. A surgical knife according to Claim 11 wherein the handle portion incorporates a variable volume fluid chamber which is interconnected with said housing chamber whereby variation of the volume of the said fluid chamber may cause movement of the blade means.

13. A surgical knife according to Claim 12 wherein the handle portion incorporates a wall biased normally to tend to maximise the volume of the fluid chamber.

14. A surgical knife according to any one of the preceding claims wherein the cutter portion comprises a fluid flow passage having at least one outlet passage through which fluid such as a saline solution may be supplied.

15. A surgical knife according to Claim 14 wherein the handle portion comprises a supply passage and a supply for flow of fluid to said fluid flow passage.

16. A surgical knife according to Claim 15 wherein the handle portion incorporates a movable control member and valve arranged to be operable as pump means to supply fluid to the fluid flow passage of the cutter portion.

17. A surgical knife according to any one one of the preceding claims and comprising a passage for enabling a suction effect to be created in the vicinity of the cutter portion.

18. A surgical knife according to Claim 17 when dependant on Claim 16 wherein said pump means is operable also to pump fluid in a direction away from the vicinity of said cutter portion.

19. A surgical knife according to any one of the preceding claims wherein the cutter portion is contoured to provide a surface which conforms substantially to the outer surface of a lens capsule.

20. A surgical knife constructed and arranged substantially as hereinbefore described with reference to the accompanying drawings.