CAPSULORHEXIS APPARATUS AND METHOD

Abstract

Apparatus (100) for use with a motion source that generates reciprocating linear motion. The apparatus includes a cutting ring (120) comprising a sharp cutting edge shaped and sized to engage an anterior lens capsule of the eye (20) and a longitudinal-motion member (150) coupled to the cutting ring, and that is configured to be coupled to the motion source, such that the motion source imparts reciprocating linear motion to the longitudinal motion member. The apparatus additionally includes a motion-conversion mechanism coupled to the longitudinal-motion member and to the cutting ring and configured to convert the reciprocating linear motion of the longitudinal-motion member into back-and-forth rotational motion of the cutting ring to create a circular aperture in the anterior capsule of the eye by the cutting ring. Other applications are also described.

Claims

1. Apparatus for use with a motion source that generates reciprocating linear motion, the apparatus comprising: a cutting ring comprising a sharp cutting edge shaped and sized to engage an anterior lens capsule of the eye; a longitudinal-motion member coupled to the cutting ring, and that is configured to be coupled to the motion source, such that the motion source imparts reciprocating linear motion to the longitudinal motion member; and a motion-conversion mechanism coupled to the longitudinal-motion member and to the cutting ring and configured to convert the reciprocating linear motion of the longitudinal-motion member into back-and-forth rotational motion of the cutting ring to create a circular aperture in the anterior capsule of the eye by the cutting ring.

2. The apparatus according to claim 1, wherein the cutting ring comprises a first cutting ring and wherein the apparatus further comprises at least a second cutting ring, and wherein the motion-conversion mechanism is coupled to the longitudinal-motion member and to the first and second cutting rings and configured to convert the reciprocating linear motion of the longitudinal-motion member into back-and-forth rotational motion of the first and second cutting rings, the back-and-forth rotational motion of the first cutting ring being in an opposite direction of the back-and-forth rotational motion of the second cutting ring.

3. The apparatus according to claim 1, wherein the apparatus is configured for use with motion source that generates reciprocating axial linear motion, and the motion-conversion mechanism is configured to convert the reciprocating axial linear motion of the longitudinal-motion member into back-and-forth rotational motion of the cutting ring.

4. The apparatus according to claim 1, wherein the apparatus is configured for use with motion source that generates reciprocating transverse linear motion, and the motion-conversion mechanism is configured to convert the reciprocating transverse linear motion of the longitudinal-motion member into back-and-forth rotational motion of the cutting ring.

5-7. (canceled)

8. The apparatus according to claim 1, wherein the sharp cutting edge is shaped to define a serrated cutting edge.

9. The apparatus according to claim 1, wherein the motion source includes an ultrasonic motion source.

10. The apparatus according to claim 9, wherein the ultrasonic motion source includes a phacoemulsification probe and wherein the longitudinal-motion member comprises a shaft that is configured to be coupled to the phacoemulsification probe.

11. The apparatus according to claim 1, wherein the motion-conversion mechanism comprises a shaft engaging the longitudinal-motion member and the cutting ring such that the reciprocating linear motion imparted to the longitudinal-motion member produces (a) relative motion of the shaft with respect to the ring, and (b) rotation of the ring with respect to a longitudinal axis of the longitudinal motion member.

12. The apparatus according to claim 11, wherein the cutting ring comprises a first cutting ring and wherein the apparatus further comprises at least a second cutting ring, and wherein the apparatus further comprises a first cantilever engaging the longitudinal-motion member and the first cutting ring, and a second cantilever engaging the longitudinal-motion member and the second cutting ring.

13. The apparatus according to claim 1, wherein the apparatus is configured to restrain linear motion of the cutting ring.

14. The apparatus according to claim 13, wherein the longitudinal-motion member comprises an outer shaft that is fixedly coupled to the cutting ring at a first location on the cutting ring, and an inner shaft that is able to undergo reciprocating linear motion with respect to the cutting ring and that is coupled to the cutting ring at a second location on the cutting ring, such that the reciprocating linear motion that is imparted to the longitudinal-motion member produces back-and-forth rotational motion of the ring with respect to the longitudinal motion member.

15. The apparatus according to claim 13, wherein the longitudinal-motion member comprises an inner shaft that is fixedly coupled to the cutting ring at a first location on the cutting ring, and an outer shaft that is able to undergo reciprocating linear motion with respect to the cutting ring and that is coupled to the cutting ring at a second location on the cutting ring, such that the reciprocating linear motion that is imparted to the longitudinal-motion member produces back-and-forth rotational motion of the ring with respect to the longitudinal motion member.

16. A method for creating a circular aperture in the anterior capsule of an eye of a subject, comprising: creating a corneal incision in the eye of the subject; inserting a cutting ring through the incision; positioning a sharp cutting edge of the cutting ring over the anterior capsule of the eye; activating a motion source to produce reciprocating linear motion; using a motion-conversion mechanism, generating back-and-forth rotational motion in the cutting ring by converting the reciprocating linear motion into back-and-forth rotational motion; and creating a circular aperture in the anterior capsule of the eye using the back-and-forth rotational motion of the cutting ring.

17. The method according to claim 16, wherein inserting the cutting ring through the incision comprises radially compressing the cutting ring to facilitate insertion of the cutting ring through the incision.

18. The method according to claim 16, wherein the reciprocating linear motion includes reciprocating axial linear motion, and wherein converting comprises converting the reciprocating axial linear motion into back-and-forth rotational motion.

19. The method according to claim 16, wherein the reciprocating linear motion includes reciprocating transverse linear motion, and wherein converting comprises converting the reciprocating transverse linear motion into back-and-forth rotational motion.

20. Apparatus for use with a phacoemulsification probe that includes a source of ultrasonic motion that generates ultrasonic motion, the apparatus comprising: a cutting ring comprising a sharp cutting edge shaped and sized to engage an anterior capsule of the eye; a shaft coupled to the cutting ring and configured to be coupled to the phacoemulsification probe such as to impart the ultrasonic motion to the cutting ring, to thereby cause the ring to cut an aperture in the anterior capsule of the eye.

21. The apparatus according to claim 20, wherein the shaft has a proximal portion and a distal portion, and wherein the proximal portion of the shaft is configured to be removably couplable to the phacoemulsification probe and the cutting ring is disposed on the distal portion of the shaft.

22. The apparatus according to claim 20, wherein the ultrasonic motion includes a reciprocating linear motion and wherein the apparatus further comprises a motion-conversion mechanism coupled to the shaft and to the cutting ring and configured to convert the reciprocating linear motion into back-and-forth rotational motion of the cutting ring to create the aperture in the anterior capsule of the eye.

23. The apparatus according to claim 22, wherein the shaft comprises an outer shaft and wherein the motion-conversion mechanism comprises a an inner shaft disposed within the outer shaft and engaging the cutting ring such that reciprocating linear motion to the inner shaft produces (a) relative motion of the inner shaft with respect to the cutting ring, and (b) rotation of the cutting ring with respect to a longitudinal axis of the outer shaft.

24. A method comprising: creating a corneal incision in the eye of the subject; inserting a cutting ring through the incision, the cutting ring being disposed on a shaft, the shaft being coupled to a phacoemulsification probe that includes an ultrasonic motion source; positioning a sharp cutting edge of the cutting ring over the anterior capsule of the eye; using the ultrasonic motion source of the phacoemulsification probe, imparting motion through the shaft to the cutting ring; and thereby cutting an aperture in the anterior capsule of the eye using the cutting ring.

25. The method according to claim 24, further comprising removing the lens of the eye at least partially using the phacoemulsification probe.

26. The method according to claim 24, wherein inserting the cutting ring through the incision comprises radially compressing the cutting ring to facilitate insertion of the cutting ring through the incision.

27. The method according to claim 24, wherein the phacoemulsification probe is configured to undergo reciprocating linear motion and wherein the method further comprises converting the reciprocating linear motion of the phacoemulsification probe into back-and-forth rotational motion of the cutting ring, and wherein cutting the aperture comprises using the back-and-forth rotational motion of the cutting ring to cut the aperture.

28. The method according to claim 27, wherein the phacoemulsification probe is configured undergo reciprocating axial linear motion, and wherein converting comprises converting the reciprocating axial linear motion of the phacoemulsification probe into back-and-forth rotational motion of the cutting ring.

29. The method according to claim 27, wherein the phacoemulsification probe is configured to move in a reciprocating transverse linear motion pattern, and wherein converting comprises converting the reciprocating transverse linear motion of the phacoemulsification probe into back-and-forth rotational motion of the cutting ring.

30-38. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0082] FIG. 1 is a schematic illustration of apparatus for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with some applications of the present invention;

[0083] FIG. 2 is a schematic illustration of apparatus for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with another application of the present invention;

[0084] FIG. 3 is a schematic illustration of a portion of a cutting ring of the apparatus for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with another application of the present invention;

[0085] FIGS. 4A, 4B and 4C, which are schematic illustrations of a double-blade cutting ring of the apparatus for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with some applications of the present invention;

[0086] FIGS. 5A and 5B are schematic illustrations of apparatus for performing capsulorhexis used with a phacoemulsification probe motion source during cataract surgery in an eye of a subject, in accordance some applications of the present invention;

[0087] FIGS. 6A and 6B are schematic illustration of apparatus for performing capsulorhexis in an expanded state (6A), and in a compressed state (6B), in accordance some applications of the present invention; and

[0088] FIG. 7 is a schematic illustration of apparatus for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with additional applications of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0089] Reference is made to FIG. 1, which is a schematic illustration of apparatus 100 for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with some applications of the present invention. Apparatus 100 typically comprises a cutting ring 120 and a longitudinal-motion member 150.

[0090] For some applications, cutting ring 120 has a sharp cutting edge 122 shaped and sized to engage the anterior lens capsule of the eye to create a circular aperture of a predetermined diameter in the anterior lens capsule of the eye. Cutting ring 120 typically comprises a resilient yet flexible metal alloy, e.g. nitinol. Cutting ring 120 is typically shaped to define sharp cutting edge 122, a blunt edge 124 and a circumferential surface having an inner surface 128 and an outer surface 126. For some applications, cutting ring 120 has a nominal diameter of 4-9 mm, e.g., 4.2-8.2 mm, and a wall thickness of 0.05-0.25 mm.

[0091] For some applications, longitudinal-motion member 150 has a proximal end 154 and a distal end 156. It is noted that in this context, in the specification and in the claims, “proximal” means closer to the user of the apparatus, and “distal” means farther from the user. The proximal and distal ends of the apparatus are indicated in FIG. 1. Longitudinal-motion member 150 is configured to engage cutting ring 120 by being positioned through openings 132 and 134 in cutting ring 120. Distal end 156 of longitudinal-motion member 150 typically terminates at, or protrudes from, opening 134.

[0092] Apparatus 100 is for use with a motion source that generates reciprocating linear motion (the motion source is not shown in FIG. 1). Longitudinal-motion member 150 is configured to be coupled the motion source, such that the motion source imparts reciprocating linear motion to longitudinal-motion member 150. Typically, proximal end 154 connects to the motion source such that the linear motion generated by the motion source is imparted to longitudinal-motion member 150. For some applications, the motion source comprises an ultrasonic motion source, e.g., a phacoemulsification probe, and proximal end 154 of longitudinal-motion member 150 couples to the ultrasonic motion source, e.g., the phacoemulsification probe.

[0093] For some applications, the reciprocating linear motion generated by the motion source is a reciprocating axial linear motion (i.e., a back-and-forth motion along longitudinal axis A1 of the longitudinal-motion member) as indicated by arrow A4 in FIG. 1. This reciprocating axial linear motion is imparted to longitudinal-motion member 150 to cause at least a portion of the longitudinal-motion member to move in the same reciprocating axial linear motion. For some such applications, apparatus 100 comprises a motion-conversion mechanism coupled to longitudinal-motion member 150 and to cutting ring 120 and which converts the reciprocating linear motion of longitudinal-motion member 150 into rotational motion of cutting ring 120, to create the circular aperture in the anterior capsule of the eye.

[0094] For some applications, longitudinal-motion member 150 has an outer shaft 158 and an inner shaft 152 that facilitate motion conversion from the linear motion of longitudinal-motion member 150 to the rotational motion of cutting ring 120. For some applications, outer shaft 158 of longitudinal-motion member 150 is configured to be coupled to the motion source. Inner shaft 152 typically engages outer shaft 158 and cutting ring 120 such that the reciprocating linear motion imparted to longitudinal-motion member 150 produces (a) relative motion of inner shaft 152 with respect to outer shaft 158 and with respect to cutting ring 120, and (b) rotation of cutting ring 120 with respect to a longitudinal axis A1 of longitudinal-motion member 150. Alternatively (not shown), inner shaft 152 of longitudinal-motion member 150 is configured to be coupled to the motion source. For such application, outer shaft 158 typically engages inner shaft 152 and cutting ring 120 such that the reciprocating linear motion imparted to longitudinal-motion member 150 produces (a) relative motion of outer shaft 158 with respect to inner shaft 152 and with respect to cutting ring 120, and (b) rotation of cutting ring 120 with respect to a longitudinal axis A1 of longitudinal-motion member 150.

[0095] Referring to the application shown in FIG. 1, inner shaft 152 extends through a portion of outer shaft 158, passes out of shaft 158 through lateral opening 138, and into slit 136 in the circumferential surface of cutting ring 120 to form a type of a cantilever, extending from longitudinal-motion member 150 to slit 136 (indicated by arrow A8). The reciprocating linear motion imparted to longitudinal-motion member 150 by the motion source produces relative motion of inner shaft 152 with respect to slit 136 of cutting ring 120, and this relative motion causes rotation of cutting ring 120 with respect to longitudinal-motion member 150, thereby converting the linear motion produced by the motion source into rotational motion of the cutting ring. For some applications, inner shaft engages the cutting ring indirectly. For example, a separate cantilever (not shown) may extend from the inner shaft to the cutting ring, rather than the inner shaft itself extending to the cutting ring.

[0096] Typically, relative motion of inner shaft 152 with respect to slit 136 (inner shaft moving sideways in the slit) causes back-and-forth rotational motion of cutting ring 120 in the directions indicated by double-headed arrow A6. Thereby, when placed on the anterior lens capsule of the eye, cutting ring 120 cuts a circular aperture in the lens capsule through high-speed back-and-forth rotational motion of the ring as indicated by arrow A6. Typically, the motion source (e.g., the ultrasonic motion source) generates high-speed vibrational motion such that the reciprocating linear motion imparted to longitudinal-motion member 150 is converted into high-speed rotational back-and-forth motion of cutting ring 120 (arrow A6). This high-speed rotational back-and-forth motion of cutting ring 120 typically prevents the lens capsule from adhering to the cutting ring during motion of the cutting ring, thereby resulting in a clean and clear cut of the anterior lens capsule.

[0097] It is noted that slit 136 is shown by way of illustration and not limitation. For some applications, the circumferential surface of cutting ring 120 is shaped to define a curved groove instead of slit 136. For some such applications, inner shaft 152 passes out of outer shaft 158 through lateral opening 138 and into the curved groove. A distal end of inner shaft 152 is typically disposed within the curved groove, and is configured such that reciprocating linear motion of longitudinal-motion member 150 produces relative motion of inner shaft 152 with respect to the curved groove causing rotation of the cutting ring with respect to longitudinal axis A1 of longitudinal-motion member 150.

[0098] Typically, not only is apparatus 100 configured to convert linear motion into rotational motion, but apparatus 100 is additionally configured to inhibit axial linear motion of cutting ring 120. For some applications, a portion of longitudinal-motion member 150 is fixedly coupled to cutting ring 120 such that axial linear motion of cutting ring 120 is restrained. For example, as shown in FIG. 1, outer shaft 158 is fixedly coupled to cutting ring 120 at a first location 160 on the cutting ring. In this example, location 160 is an edge of opening 132 in cutting ring 120, opening 132 being shaped and sized to allow rotational motion of the ring with respect to the longitudinal-motion member 150. Inner shaft 152 undergoes reciprocating linear motion with respect to the cutting ring and engages the cutting ring at a second location (e.g., slit 136) on the cutting ring, such that the reciprocating linear motion that is imparted to longitudinal-motion member 150 produces rotational motion of the ring with respect to the longitudinal motion member.

[0099] As described hereinabove, for some applications, the functions of inner shaft 152 and outer shaft 158 of longitudinal-motion member 150 are reversed, Mutatis mutandis.

[0100] Reference is now made to FIG. 2, which is a schematic illustration of apparatus 200 for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with another application of the present invention. Apparatus 200 typically comprises a cutting ring 220 and a longitudinal-motion member 250, comprising an inner shaft 252 and an outer shaft 258. Longitudinal-motion member 250 has a proximal end 254 and a distal end 256 and is coupled to cutting ring 220 by being positioned through opening 232 and by attaching to location 234 at the distal end of the cutting ring. Distal end 256 of longitudinal-motion member 250 typically terminates at location 234 (however, in some applications, distal end 256 protrudes from an opening at location 234). It is noted that, apparatus 200 is generally similar to apparatus 100 except where indicated otherwise.

[0101] In accordance with some applications of the present invention, apparatus 200 is for use with a motion source that generates reciprocating transverse linear motion as indicated by arrow A9 in FIG. 2 (the motion source is not shown in FIG. 2). This reciprocating transverse linear motion is imparted to longitudinal-motion member 250 (e.g., to inner shaft 252) to cause distal end 256 of the longitudinal-motion member to move in the same reciprocating transverse linear motion (indicated by arrow A9). The reciprocating transverse linear motion of longitudinal-motion member 250 is converted into rotational motion of cutting ring 220, such that when placed on an anterior lens capsule of the eye, cutting ring 220 rotates back-and-forth at a high speed to cut the circular aperture in the lens capsule due to the back-and-forth rotational motion pattern.

[0102] Typically, a portion of longitudinal-motion member 250 is fixedly coupled to cutting ring 220 such that only motion of cutting ring 220 in the direction indicated by arrow A6, is possible. For example, as shown in FIG. 2, outer shaft 258 is fixedly coupled to cutting ring 220 at a first location 260 on the cutting ring. In this example, location 260 is an edge of opening 232 in cutting ring 220, opening 232 being shaped and sized to allow rotational motion of the ring with respect to the longitudinal-motion member 250. Inner shaft 252 undergoes reciprocating linear motion with respect to the cutting ring and is coupled to the cutting ring at a second location 234on the cutting ring, such that the reciprocating transverse linear motion that is imparted to distal end 256 of longitudinal-motion member 250 produces rotational motion of cutting ring 220 with respect to longitudinal-motion member 250. For some applications, the functions of the inner and outer shafts are reversed, Mutatis mutandis.

[0103] For some applications, the motion source that generates the transverse linear motion is an ultrasonic motion source, e.g., a phacoemulsification probe, and proximal end 254 of longitudinal-motion member 250 is coupled to the phacoemulsification probe.

[0104] Reference is now made to FIG. 3, which is a schematic illustration of a portion of cutting ring 120, in accordance with some applications of the present invention. As shown, for some applications, sharp cutting edge 122 of cutting ring 120 is shaped to define a serrated cutting edge for facilitating improved cutting of the anterior lens capsule and for preventing adhering of the lens capsule to the cutting ring during the rotational motion of the ring. It is noted that any suitable serrated pattern may be used. It is further noted that cutting ring 120 is shown in FIG. 3 by way of illustration and not limitation, and that sharp cutting edge 122 of cutting ring 220 (shown in FIG. 2) may also be shaped to define a serrated sharp cutting edge.

[0105] Reference is now made to FIGS. 4A, 4B and 4C, which are schematic illustrations of a double-blade cutting ring 320, for use with apparatus 100 or 200 in accordance with some applications of the present invention. Cutting ring 320 typically comprises first and second concentric cutting rings 322 and 324 each having a sharp cutting edge. In FIGS. 4A-C, double cutting ring 320 is shown being used in apparatus 100 by way of illustration and not limitation. It is noted that the cutting ring of apparatus 200 may also comprise two or more concentric cutting rings.

[0106] First and second concentric rings 322 and 324 typically rotate back and forth in opposite directions thereby facilitating smooth and well-defined cutting of the circular aperture in the anterior lens capsule typically while preventing adherence of the lens capsule to the cutting rings.

[0107] For example, as shown in FIGS. 4A and 4B, first and second cantilevers 352 and 354 extend from inner shaft 152, to a respective concentric cutting ring (cantilever 352 being coupled to cutting ring 322 and cantilever 354 being coupled to cutting ring 324). As shown, cantilevers 352 and 354 are typically oriented in opposite directions from each other. Reciprocating linear motion imparted to longitudinal motion member 150 is converted by cantilevers 352 and 354 into rotational motion of rings 322 and 324 as described hereinabove with reference to FIG. 1 (motion of cantilever 352 with respect to cutting ring 322 causes rotation of cutting ring 322 and relative motion of cantilever 354 with respect to cutting ring 324 causes rotation of cutting ring 324). The reciprocating axial linear motion of longitudinal motion member 150 is indicated by arrows A4a and A4b.

[0108] As shown in FIG. 4A, when longitudinal motion member 150 vibrates in the direction indicated by arrow A4a, first cutting ring 322 rotates in the direction indicated by arrow A6c, and second cutting ring 324 rotates in the direction indicated by arrow A6a. When longitudinal motion member 150 vibrates in the direction indicated by arrow A4b (FIG. 4B), first cutting ring 322 rotates in the direction indicated by arrow A6d, and second cutting ring 324 rotates in the direction indicated by arrow A6b. Thus, rotational back-and-forth motion of the first and second cutting rings in opposing directions is generated, in response to longitudinal motion member 150 moving in the reciprocating axial linear motion. Such motion (typically occurring at a high speed as described hereinabove) reduces the likelihood of the anterior lens capsule adhering to the cutting rings and facilitates clean and defined cutting of the lens capsule.

[0109] Typically, cutting edges of first and second cutting rings 322 and 324 are sharpened on opposite edges from each other such that when assembled together, the cutting edges of concentric rings 322 and 324 are closely positioned with respect to each other (as shown in FIG. 4C) further facilitating cutting a clean and well-defined circular aperture in the anterior lens capsule.

[0110] Reference is now made to FIGS. 5A and 5B, which are schematic illustrations of apparatus 100 being used with a phacoemulsification probe 300 motion source during cataract surgery in an eye 20, in accordance some applications of the present invention.

[0111] Typically, subsequently to creating a corneal incision in eye 20, apparatus 100 is advanced towards the anterior lens capsule 70, as shown FIG. 5A. Cutting ring 120 is inserted through the incision such that the sharp cutting edge of cutting ring 120 is positioned over anterior lens capsule 70, as shown in FIG. 5B. As shown, longitudinal-motion member 150 is coupled to phacoemulsification probe 300 such that when the probe is activated, vibratory motion of phacoemulsification probe 300 is imparted to the longitudinal motion member. As described hereinabove with reference to FIGS. 1 and 2, phacoemulsification probe 300 may generate reciprocal axial linear motion in the direction indicated by arrow A4 in FIG. 1, or reciprocal transverse linear motion in the direction indicated by arrow A9 in FIG. 2. As further described hereinabove with reference to FIGS. 1 and 2, apparatus 100 and 200 convert the linear motion into back and forth rotational motion of cutting ring 120 (or 220), as indicated by arrow A6. Rotational motion of the sharp cutting edge of cutting ring 120, when in contact with anterior lens capsule 70, produces, in a controlled manner, an accurate circular aperture of a predetermined diameter in anterior lens capsule 70. The cut piece of lens capsule is typically removed and discarded, leaving lens 75 exposed.

[0112] Subsequently to performing the capsulorhexis by cutting the aperture in anterior lens capsule 70, apparatus 100 is removed from eye 20. As mentioned in the Background section, typically following capsulorhexis, the lens of the eye is removed by phacoemulsification. In accordance with some applications of the present invention, the same phacoemulsification probe 300 that is used for capsulorhexis is also used to subsequently emulsify and remove the lens.

[0113] It is noted that although FIGS. 5A-B show apparatus 100 in use with phacoemulsification probe 300, it is to be understood that apparatus 200 is similarly used with phacoemulsification probe 300, Mutatis mutandis.

[0114] Reference is now made to FIGS. 6A and 6B which are schematic illustration of apparatus 100 or 200 for performing capsulorhexis. Apparatus 100 and 200 are shown in an expanded state (6A), and in a compressed state (6B), in accordance some applications of the present invention. As described hereinabove, with reference to FIG. 1, cutting ring 120 (or 220) is typically a flexible cutting ring. When introduced into the eye through the corneal incision, cutting ring 120 (or 220) is typically radially compressed as shown in FIG. 6B in order to facilitate insertion of the ring through the relatively small incision. Once in the eye, cutting ring 120 (or 220) is expanded, and/or undergoes self-expansion, into the operative state as shown in FIG. 6A.

[0115] Reference is now made to FIG. 7, which is a schematic illustration of apparatus 400 for performing capsulorhexis during cataract surgery in an eye of a subject, in accordance with additional applications of the present invention. For some applications, the apparatus includes an elongate shaft 402, which is coupled, at its proximal end, to a source of motion (not shown) that is configured to generate rotational motion (as indicated by arrow A7). For some applications, the motion source generates rotational motion in a single direction (i.e., clockwise, or counterclockwise (as shown)). Alternatively the motion source is configured to generate rotational motion in both directions, e.g., by alternating between directions.

[0116] At the distal end of the elongate shaft, the shaft is curved such as to define an offset axial portion 404 that is offset relative to the proximal end of the shaft. (That is to say that the offset axial portion is radially offset with respect to proximal end of the shaft. However, the offset axial portion is typically parallel to the proximal end of the shaft, as shown.) The offset axial portion of the elongate shaft is coupled to a cutting ring 420 of the apparatus, e.g., by being inserted into an opening 422 of the cutting ring, and/or in some other manner (e.g., by being welded to the ring). (Cutting ring 420 is typically generally similar to cutting rings 120 and 220 described hereinabove. For example the dimensions and configuration of the edges of cutting ring 420 are typically generally similar to those of cutting rings 120 and 220 described hereinabove.) Due to the offset of offset axial portion 404, as the elongate shaft rotates it causes offset axial portion 404 to move from side-to-side in an alternating manner. In turn, this causes the portion of the cutting ring to which offset axial portion 404 is coupled (e.g., opening 422) to move from side-to-side in an alternating manner. For example, referring to FIG. 7, opening 422 of the cutting ring is moved in the direction of arrow A11, and then in the direction of arrow A12, in an alternating manner. In turn, this generates back-and-forth rotational motion of the cutting ring, as described in further detail hereinbelow.

[0117] For some applications, the cutting ring is stabilized such that it remains centered about a central axis 424. For example, a plurality of struts 426 may extend radially from the central axis to the cutting ring to stabilize the cutting ring such that it remains centered about central axis 424. Typically, as a result of the cutting ring being maintained such as to be centered about central axis 424, the side-to-side motion of portion 404 is converted to back and forth rotational motion of cutting ring 420, as indicated by arrow A13. Typically, cutting ring 420 is configured to be radially compressed (e.g., as shown in FIG. 6B) in order to facilitate insertion of the ring through the relatively small incision. Further typically, struts 426 are configured to be foldable and to become folded when the cutting ring is radially compressed. Once they are disposed within the eye the cutting ring and the struts are configured automatically assume their expanded states (which are shown in FIGS. 7A-B). For example, the cutting ring and the struts may be made of a shape memory alloy (such as nitinol) that is shape set to the configuration of the cutting ring and the struts that is shown in the FIGS. 7A-B.

[0118] It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.