Methods and apparatus for intraocular brachytherapy

1. A method of positioning a first cannula having a distal end for the intraocular delivery of a therapeutic treatment to a target tissue within an eye having a lens so that the distal end of the cannula is in contact with the target tissue comprising:

introducing a second cannula into the eye through an access site on the eye, the second cannula having a light source that projects a beam of light toward the target tissue;

introducing the first cannula into the eye through a second access site on the eye so that the distal end of the first cannula is between the second cannula and the target tissue within the beam of the light projected toward the target tissue by the second cannula so that a shadow is cast by the distal end of the first cannula that falls on the target tissue, the shadow being observable through the lens of the eye; and

advancing the distal end of the first cannula toward the target tissue until the shadow cast by the distal end of the first cannula coincides with the distal end of the first cannula as viewed through the lens, thus indicating contact of the distal end of the first cannula with the target tissue.

2. A device for local intraocular delivery of a therapeutic treatment to a target tissue comprising:

a cannula sized for intraocular insertion into an eye and having a proximal end and a distal end;

a therapeutic treatment source adapted to be located in the distal end of the cannula, the source intended to be spaced a predetermined distance from the target tissue for the delivery of the therapeutic treatment; and

at least one source of light adapted to project two visible beams of light out of the cannula, the beams of light forming an intersection such that when the intersection is coincident with the target tissue, the treatment source is spaced the predetermined distance from the target tissue.

3. The device of claim 2 wherein the source of light is a light pipe.

4. The device of claim 2 wherein the source of light is a laser.

5. A device for local intraocular delivery of radiation to a target tissue comprising:

a probe sized for insertion into an eye and having a proximal end and a distal end;

a radiation-emitting source having a predetermined length adapted to be located in the distal end of the probe, the radiation-emitting source having a proximal end and a distal end; and

a filter associated with the distal end of the probe that blocks a greater amount of radiation at the distal end of the radiation-emitting source than at the proximal end of the radiation-emitting source so that a generally-symmetrical dose profile is delivered to the target tissue by the radiation emitting source when the distal end of the probe is orientated at an angle with respect to a plane defined generally by the target tissue.

6. The method of claim 1 wherein the target tissue comprises a retina.

7. The method of claim 1 wherein the light source of the second cannula is a light pipe.

8. The device of claim 2 wherein the cannula comprises two ports through which the two visible beams of light are projected out from the cannula.

9. The device of claim 8 wherein the two ports are located on the distal end of the cannula.

10. The device of claim 8 wherein one of the ports is located at the distal end of the cannula and the other of the ports is located proximally of the distal end of the cannula.

11. The device of claim 5 wherein the filter is made of a material having a higher density than that of the probe.

12. The device of claim 11 wherein the filter is made of a platinum iridium alloy.

13. A device for local intraocular delivery of a therapeutic treatment to a target tissue comprising:

a cannula sized for intraocular insertion into an eye and having a proximal end and a distal end;

a therapeutic treatment source adapted to be located in the distal end of the cannula, the source intended to be spaced a predetermined distance from the target tissue for the delivery of the therapeutic treatment; and

the cannula further comprising two ports and at least one source of light adapted to project a visible beam of light out of each of the ports of the cannula, the beams of light forming an intersection such that when the intersection is coincident with the target tissue, the treatment source is spaced the predetermined distance from the target tissue.

14. The device of claim 13 wherein the two ports are located on the distal end of the cannula.

15. The device of claim 13 wherein one of the ports is located at the distal end of the cannula and the other of the ports is located proximally of the distal end of the cannula.