WO2005014093A1

WO2005014093A1 - Cannula

Info

Publication number: WO2005014093A1
Application number: PCT/GB2004/003400
Authority: WO
Inventors: Abdel Taguri
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-05
Filing date: 2004-08-05
Publication date: 2005-02-17
Anticipated expiration: 2006-02-05
Also published as: GB0318309D0; GB2404592A; GB0417512D0

Abstract

A cannula (1) is disclosed. It comprises a resilient flexible sleeve (4) having a distal end for insertion into the tissue surrounding the eyeball of a patient during ocular surgery and through which local anaesthetic may be administered into said tissue and, a needle (7) that extends through the sleeve and has a tip that protrudes from the distal end of the sleeve to make an initial incision in the tissue to facilitate insertion of the sleeve into the tissue through the incision. The needle is removable from the sleeve once an incision has been made and the sleeve has been inserted into the tissue through the incision.

Description

Caπnula

Description

The present invention relates to a cannula and more specifically to a cannula that may be used to facilitate the safe and effective administration of local anaesthetic to a patient during eye surgery.

The majority of eye surgery procedures are nowadays performed under local anaesthetic where the anaesthetic agent is injected into the tissues surrounding the eyeball. Such injections are commonly known as "sub-tenon" injections. Traditionally, a sharp needle has been used for the injection. However, the use of a sharp needle often results in a haemorrhage occurring around the eyeball or even perforation of the eyeball, during the procedure. In an attempt to overcome or alleviate this problem, it is now more commonly known to use a blunt needle for injecting local anaesthetic beneath the sheaths surrounding the eyeball. While this technique may reduce the risk of eye perforation and major haemorrhages, a small cut in the outer coat of the eye has to be made to introduce the blunt needle into the desired space. The cut usually results in a superficial haemorrhage and so needs to be performed by a trained eye surgeon to avoid damage to adjacent delicate eye structures. In addition, the cut, which is routinely made using scissors, is usually much larger than the needle size resulting in a loss of substantive amount of the anaesthetic agent to the outer ocular surface.

The present invention seeks to provide a cannula for safer and easier injection of local anaesthetic into any of the desired tissue spaces around and behind the eyeball. It is also envisaged that the cannula may be retained in position around the eyeball during the procedure allowing for anaesthetic top up during prolonged procedures.

According to the invention, there is provided a cannula comprising a resilient flexible sleeve having a distal end for insertion into the tissue surrounding the eyeball of a patient during ocular surgery and through which local anaesthetic may be administered into said tissue and, a needle that extends through the sleeve and has a tip that protrudes from the distal end of the sleeve to make an initial incision in the tissue to facilitate insertion of the sleeve into the tissue through the incision, the needle being removable from the sleeve once an incision has been made and the distal end of the sleeve has been inserted into the tissue through the incision.

In a preferred embodiment, a portion of the length of the sleeve close to its distal end is arcuate in shape when the sleeve is in an unstressed state.

Preferably, a portion of the length of the needle close to its distal end is arcuate in shape in an unstressed state.

The sleeve preferably includes a mid-portion that exhibits increased flexibility relative to the remainder of the sleeve.

The sleeve may be corrugated to form the mid-portion.

In a particularly preferred embodiment, the sleeve has an outer diameter of approximately 1mm and is preferably formed from plastic tubing.

According to another aspect of the invention, there is provided a method of inserting a cannula into the tissue surrounding the eyeball of a patient during ocular surgery to enable the administration of local anaesthetic into said tissue, the method including the step of making an incision with the tip of a needle protruding from the distal end of a resilient flexible sleeve, inserting the distal end of the sleeve into the incision, and removing the needle from the sleeve once the distal end of the sleeve has been inserted.

The method preferably includes the step of positioning the distal end of the sleeve within the incision after removal of the needle. An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 illustrates a side-elevation of a cannula according to an embodiment of the present invention; FIGURE 2 illustrates a side-elevation of the inner part of the cannula shown in Figure 1;

FIGURE 3 illustrates a side-elevation of the outer part of the cannula shown in Figure 1;

FIGURE 4 shows how the cannula of the present invention may be inserted into the tissue surrounding the eye; and

FIGURE 5 shows removal of the inner part of the cannula and insertion of the outer part into the desired location in the tissue surrounding the eye.

Referring now to the drawings, there is shown in Figure 1, a cannula 1 comprising inner and outer parts 2,3. The outer part 3 includes a resilient flexible sleeve 4 formed from plastics material and which, in a preferred embodiment, has a longitudinally extending mid-section 5 that exhibits increased flexibility relative to the remainder of the sleeve 4. The mid-section 5 may be formed from an integrally formed corrugated section of the sleeve, as shown in the drawings. The sleeve 4 widens at its proximal end that remains outside the patient to receive a head portion 6 of the inner part 2 therein and to facilitate the administration of anaesthetic agent into the sleeve 4. The distal end of the sleeve 4, which is inserted into the tissue surrounding the eyeball, is blunt.

The inner part 2 includes a needle 7 that is slideably received in the sleeve 4 of the outer part 3. The needle is made from metal, such as steel and the tip 8 of the needle protrudes from the distal end of the sleeve 4 by approximately 1mm and is sharpened. The head portion 6 of the outer part 3 may be grasped by the surgeon and facilitates the manipulation and control of the needle within the sleeve 4. Preferably, the needle does not protrude from the end of the sleeve 4 by any more than 1mm.

The flexible sleeve 4 is slightly arcuate or curved in shape close to its distal end in its unstressed state so that it may be guided in an arcuate path into the tissue around the eye, as shown in Figures 4 and 5, and so that the tip remains substantially the same distance from the eyeball when it has been inserted. The needle 7 may also be slightly arcuate or curved towards its distal end in an unstressed state so that it conforms to the curvature of the sleeve 4.

When the cannula is used, the superficial tissue surrounding the eyeball is punctured with the sharp tip of the needle 7 protruding approximately 1mm from the end of the sleeve 4, as shown in Figure 4 and the blunt end of the sleeve 4 is inserted through the incision into the tissue to a depth of approximately 2-3mm. Once the sleeve 4 has been inserted into the tissue by about 2-3mm, the needle 7 is removed, as shown in Figure 5, to prevent further damage to the ocular cavity and the sleeve 4 is then positioned within the tissue to facilitate the administration of anaesthetic fluid therethrough. As the needle 7 only ever protrudes 1mm from the sleeve 4, the risk of ocular perforation or injury to a major blood vessel is substantially reduced. The sleeve 4 is sufficiently flexible and compliant so that it conforms to the shape of the curvature of the rigid needle 7 as the needle is withdrawn from the sleeve 4.

Removal of the needle 7 is facilitated by the flexibility of the mid-section 5 of the sleeve 4, which possesses increased flexibility relative to the remainder of the sleeve 4. Once the needle 7 has been removed, the blunt end of the sleeve 4 can then be safely positioned in the correct location witiiin the tissue for the administration of anaesthetic fluid without causing any additional trauma to the patient.

In a preferred embodiment, the sleeve 4 may be 1mm in diameter and can be of various lengths to reach different depths or destinations around the periphery of the eyeball For example, the length of the sleeve 4 may be 25mm or 16mm. The needle 7 is 1mm longer than the outer sleeve 4 and may have a diameter of 0.8 mm.

Once inserted, the sleeve 4 may be retained in position with its distal end inserted into the tissue space for the administration of further anaesthetic agent during prolonged procedures. Many modifications and variations of the invention falling witiiin the terms of the following claims will be apparent to those skilled in the art and the foregoing description should be regarded as a description of the preferred embodiments only.

Claims

1. A cannula comprising a resilient flexible sleeve having a distal end for insertion into the tissue surrounding the eyeball of a patient during ocular surgery and through which local anaesthetic may be administered into said tissue and, a needle that extends through the sleeve and has a tip that protrudes from the distal end of the sleeve to make an initial incision in the tissue to facilitate insertion of the sleeve into the tissue through the incision, the needle being removable from the sleeve once an incision has been made and the distal end of the sleeve has been inserted into the tissue through the incision.

2. A cannula according to claim 1, wherein a portion of the length of the sleeve close to its distal end is arcuate in shape in an unstressed state.

3. A cannula according to claim 1 or claim 2, wherein a portion of the length of the needle close to its distal end is arcuate in shape.

4. A cannula according to any preceding claim, wherein the sleeve includes a mid- portion that exhibits increased flexibility relative to the remainder of the sleeve.

5. A cannula according to claim 3 or claim 4, wherein the sleeve is integrally corrugated to form the mid-portion.

6. A cannula according to any preceding claim, wherein the sleeve has an outer diameter of approximately 1mm.

7. A cannula according to any preceding claim, wherein the needle has a diameter of approximately 0.8 mm.

8. A cannula according to any preceding claim, wherein the sleeve is formed from plastic tubing.

9. A cannula according to any preceding claim, wherein the needle is rigid.

10. A cannula according to any preceding claim, wherein the tip of the needle protrudes from the sleeve by approximately 1mm.

11. A method of inserting a cannula into the tissue surrounding the eyeball of a patient during ocular surgery to enable the administration of local anaesthetic into said tissue, the method including the step of making an incision with the tip of a needle protruding from the distal end of a resilient flexible sleeve, inserting the distal end of the sleeve into the incision, and removing the needle from the sleeve once the distal end of the sleeve has been inserted.

12. A method according to claim 11, including the step of positioning the distal end of the sleeve within the incision after removal of the needle.