An apparatus and method for safely cannulating a blood vessels, including but not limited retinal blood vessels, is described. In one embodiment, the apparatus can consist of a micropipette/microcannula, micromanipulator and positioner mounted to a base, which is attached to a wrist rest commonly used in eye surgery. The micropipette/microcannula is connected to tubing such that a medication may be injected through the micropipette/microcannula into the blood vessel or conversely, a small quantity of material may be removed from a blood vessel. Alternatively, a catheter, wire or stent may be placed through the micropipette/microcannula to treat or diagnose an area remote from the insertion site. The ability to cannulate a retinal blood vessel should be efficacious in the treatment of vein and artery occlusion, ocular tumors and other retinal, vascular and optic nerve disorders that would benefit from diagnosis and/or treatment. In another embodiment, a self-sealing needle is provided which allows the perforation of a blood vessel or other structure and the minimization of hemorrhaging when the needle is withdrawn from the blood vessel/structure. Another embodiment discloses an ocular implant needle.