Phacoemulsification cannula with improved purchase

1. A phacoemulsification cannula for use in ophthalmic surgery comprising:

a hub for engagement with an ophthalmic surgical instrument;

an elongated needle having a proximal end attached to the hub and a distal end;

wherein the needle has an aspiration lumen with a first diameter spanning a majority of a length of the needle from the proximal end towards the distal end;

wherein the needle has a venturi lumen formed from the distal end to the aspiration lumen, wherein the venturi lumen includes a first venturi section having a maximum diameter, and a second venturi section having a minimum diameter, and a third venturi section ending at a place connecting the aspiration lumen to the venturi lumen; and

wherein the venturi lumen includes structure forming smoothly varying transitions between each of the first, second, and third venturi sections.

2. The cannula of claim 1 , wherein the venturi lumen has a generally hour-glass shape.

3. The cannula of claim 1 , wherein the venturi lumen includes structure creating a double-venturi.

4. The cannula of claim 1 , wherein the minimum diameter of the second venturi section is approximately equal to the first diameter.

5. The cannula of claim 1 , wherein the third venturi section has a largest diameter greater than the minimum diameter and equal to or less than the maximum diameter.

6. The cannula of claim 5 , wherein the largest diameter of the third venturi section is equal to or greater than the first diameter.