Pulse extraction of ocular medical devices

Abstract

A method of extracting residual materials from a polymeric, ophthalmic biomedical device, such as a contact lens, by using a mixture comprised of a primary solvent, such as carbon dioxide, and a polar co-solvent, such as isopropanol: By exposing the device to the co-solvent, the device expands. By pulsing or varying the concentration of the polar co-solvent in the mixture, the lens dimensions vary accordingly. When the lens is extracted while retained in a mold, the changes in lens dimensions causes the lens to be released from the mold.

1 . A method of extracting a polymeric, ophthalmic biomedical device comprising: 
 (a) subjecting said device to a primary solvent;    (b) subjecting said device to a mixture of a co-solvent and the primary solvent for a predetermined period of time; and    (c) subjecting said device to the primary solvent for a predetermined time such that said device is in a dry state,    wherein said ocular medical device goes through at least one cycle of expansion and shrinkage.    
     
     
         2 . The method of  claim 1 , wherein said primary solvent is selected from the group consisting of liquid carbon dioxide, hexane and heptane.  
     
     
         3 . The method of  claim 1 , wherein said primary solvent comprises liquid carbon dioxide.  
     
     
         4 . The method of  claim 1 , wherein said co-solvent is selected from the group consisting of alcohols, glycols, ethers, ketones, alkanes and aromatic solvents.  
     
     
         5 . The method of  claim 1 , wherein said co-solvent is isopropyl alcohol.  
     
     
         6 . The process of  claim 1 , further comprising, surface treating the dry device obtained from step (c).  
     
     
         7 . The method of  claim 1 , wherein said ocular medical device is a contact lens.  
     
     
         8 . The method of  claim 1 , wherein said ocular medical device is an intraocular lens or ophthalmic implant.  
     
     
         9 . A method of extracting a polymeric, ophthalmic biomedical device contained within a chamber, said method comprising: 
 (a) subjecting said device to a supercritical fluid for a first predetermined time in said chamber;    (b) introducing isopropyl alcohol into said chamber to obtain a first mixture including a first predetermined level of isopropyl alcohol and subjecting said device to said first mixture for a second predetermined period of time;    (c) reducing the amount of isopropyl alcohol within said chamber to a second, lowered predetermined level and subjecting said device to the mixture for a third predetermined period of time; and    (d) subjecting said device to supercritical fluid for a fourth predetermined time such that said lens is in a dry state,    wherein said device goes through at least one cycle of expansion and shrinkage.    
     
     
         10 . The method of  claim 9 , wherein said supercritical fluid is selected from the group consisting of supercritical carbon dioxide, supercritical nitrous oxide, supercritical methane, supercritical ethane, supercritical propane, supercritical butane, supercritical ethylene, supercritical fluoroform, and supercritical chloroform.  
     
     
         11 . The method of  claim 9 , wherein said first predetermined level contains at least 20% isopropyl alcohol and said second predetermined level contains 2 to 10% isopropyl alcohol.  
     
     
         12 . The method of  claim 9 , wherein said device is placed in a chamber and said extraction steps occur under pressures in the range of 69 to 276 bar and at temperatures in the range of 31° C. to 95° C.  
     
     
         13 . The method of  claim 9 , wherein the supercritical fluid is carbon dioxide.  
     
     
         14 . The method of  claim 9 , wherein steps (b) and (c) are repeated such that said device undergoes at least two cycles of expansion and shrinkage.  
     
     
         15 . The method of  claim 9 , wherein said device is a contact lens.  
     
     
         16 . A method of extracting a contact lens retained in the mold in which it was cast, comprising: 
 subjecting the lens to alternating concentrations of a supercritical fluid and a co-solvent, such that said contact lens goes through at least one cycle of expansion and shrinkage and whereby the contact lens is released from the mold.    
     
     
         17 . The method of  claim 16 , wherein the lens is subjected to alternating concentrations of carbon dioxide and isopropyl alcohol.  
     
     
         18 . A process of making a contact lens comprising: 
 (a) casting said lens in a two-part mold assembly;    (b) removing a first mold portion such that said lens is retained in a second mold portion;    (c) extracting said lens with mixture of a supercritical fluid and a co-solvent and releasing said lens from said second mold portion;    (d) subjecting said lens to the supercritical fluid, whereby a dry lens is obtained;    (e) surface treating said dry lens such that at least one lens said surface is rendered hydrophilic; and    (f) hydrating and packaging said lens.    
     
     
         19 . A method of extracting an ocular medical device comprising, sequentially: 
 (a) subjecting said device to a supercritical primary solvent, or a first mixture of a supercritical primary solvent and a co-solvent, in a chamber;    (b) subjecting said device to a second mixture of the supercritical primary solvent and a co-solvent in the chamber, wherein the concentration of the co-solvent is higher than the first mixture;    (c) reducing the level of the co-solvent in the chamber;    (d) repeating steps (a) through (c); and    (e) subjecting said device to the supercritical primary solvent to dry the device.    
     
     
         20 . The process of  claim 19 , wherein in step (c), substantially all of the co-solvent is removed from the chamber.  
     
     
         21 . The process of  claim 19 , wherein the device is a silicone hydrogel contact lens.  
     
     
         22 . The process of  claim 19 , wherein after step (c), substantially all of the primary solvent and co-solvent are removed from the chamber.