Retinal surgery

1. A system comprising:

an injection and extraction system adapted to inject a retina manipulation fluid into an eye through a first channel and extract fluid from the eye through a second channel, the first channel extending distally beyond the second channel to form an annular opening between the first channel and the second channel;

a fluid extraction system adapted to apply negative pressure to the injection and extraction system to facilitate fluid extraction;

a computer system adapted to adjust the negative pressure applied by the fluid extraction system, and

an infusion system adapted to inject infusion fluid to maintain the shape of the eye undergoing retinal surgery.

2. The system of claim 1 , wherein the computer system is adapted to adjust the negative pressure based on intraocular pressure in the eye.

3. The system of claim 1 , wherein the computer system is further adapted to control injection of the retina manipulation fluid through the injection and extraction system.

4. The system of claim 3 , further comprising a fluid pressure system, the fluid pressure system controllable by the computer system to apply positive pressure to inject the retina manipulation fluid.

5. The system of claim 1 , wherein the first channel is adapted to inject a fluid having a higher specific gravity than fluids for which the second channel is adapted to extract.

6. The system of claim 1 , wherein the first channel is inside the second channel.

7. The system of claim 6 , wherein the second channel serves as a cannula for introducing medical instruments into the eye.

8. The system of claim 1 , wherein the injection and extraction system comprises a body through which the first channel passes and to which the second channel engages.

9. The system of claim 8 , wherein the body comprises a cavity into which fluid extracted through the second channel enters.

10. A method, comprising:

injecting a retina manipulation fluid into an eye through a first channel of an injection and extraction system that extends distally beyond a second channel to form an annular opening between the first channel and the second channel, the retinal manipulation fluid having a higher specific gravity than other fluids within the eye;

applying negative pressure to the injection and extraction system to facilitate extraction of fluid from the eye through the annular opening;

adjusting, via a computer system, the applied negative pressure; and

extracting the other fluids from the eye.

11. The method of claim 10 , wherein adjusting the negative pressure is based on intraocular pressure in the eye.

12. The method of claim 11 , further comprising injecting fluid to maintain the shape of the eye.

13. The method of claim 11 , further comprising measuring the intraocular pressure.

14. The method of claim 10 , further comprising controlling injection of the retina manipulation fluid through the injection and extraction system via the computer system.

15. The method of claim 11 , wherein the computer system controls a fluid pressure system to apply positive pressure to inject the retina manipulation fluid.

16. The method of claim 10 , wherein:

the extracted fluid is extracted around the first channel.

17. The method of claim 16 , wherein the second channel serves as a cannula for introducing medical instruments into the eye.

18. The method of claim 16 , wherein the retina manipulation fluid, while in the first channel, passes through a first internal cavity of the injection and extraction system.

19. The method of claim 18 , wherein the extracted fluid enters a second internal cavity of the injection and extraction system after passing through the second channel.