Retractable Injection Port

Abstract

A cannula, for delivering a bolus of a pharmaceutically active agent to the posterior chamber of the eye, having an orifice disposed at the distal tip. The cannula is slidably disposed within a hypodermic needle. The sliding action of the cannula within the needle provides a means for trimming a formed bolus of a pharmaceutically active agent from the orifice of the cannula. In addition, the double wall formed by the cannula within the needle provides insulation from the cooler temperatures within the eye to allow for the delivery of phase transition substances.

1 . A retractable injection port comprising:
 a hypodermic needle having a sharpened distal tip; and   a cannula, slidably disposed within the needle, the cannula having an orifice disposed at a distal end, the orifice fluidly coupled to a mechanism for delivering a substance;   wherein the needle and the cannula provide insulation to the substance contained therein.   
     
     
         2 . The port of  claim 1  wherein the orifice is disposed in a side wall of said cannula. 
     
     
         3 . The port of  claim 1  wherein the distal end of the cannula is rounded. 
     
     
         4 . The port of  claim 1  wherein the distal end of the cannula is flat. 
     
     
         5 . The port of  claim 1  wherein the mechanism is a syringe having a heated dispensing chamber. 
     
     
         6 . The port of  claim 1  wherein the substance comprises a phase transition compound. 
     
     
         7 . The port of  claim 1  wherein sliding said needle over said orifice trims a bolus of said substance. 
     
     
         8 . A retractable injection port comprising:
 a cannula having an orifice disposed at a distal tip; and   a hypodermic needle slidably disposed within the cannula.   
     
     
         9 . A retractable injection port comprising:
 a hypodermic needle having a sharpened distal tip; and   a cannula, slidably disposed within the needle, the cannula having an orifice disposed at a distal end, the orifice fluidly coupled to a syringe having a heated dispensing chamber;   wherein the needle and the cannula provide insulation to a heated phase transition compound.   
     
     
         10 . The port of  claim 9  wherein the orifice is disposed in a side wall of said cannula. 
     
     
         11 . The port of  claim 9  wherein the distal end of the cannula is rounded. 
     
     
         12 . The port of  claim 9  wherein the distal end of the cannula is flat. 
     
     
         13 . A method for delivering a substance into an eye comprising the steps of:
 providing a retractable injection port having a cannula slidably disposed within a hypodermic needle, said needle disposed at a distal end of a heated syringe;   piercing the sclera of said eye with said hypodermic needle;   partially withdrawing said needle to expose said cannula;   expressing substance into said eye through an orifice disposed at a distal tip of said cannula;   trimming said substance from said cannula by withdrawing said cannula into said needle.   
     
     
         14 . The method of  claim 13  wherein said orifice is disposed in a side wall of said cannula. 
     
     
         15 . The method of  claim 13  wherein said orifice is disposed in a distal tip of said cannula. 
     
     
         16 . The method of  claim 13  wherein said substance comprises a heated phase transition compound. 
     
     
         17 . The method of  claim 16  wherein said phase transition compound is insulated by said needle and said cannula.