Abstract:
The present invention includes a method of intraocular delivery by needless injection of a medicament through the sclera of an eye and into a back of the eye as well as instruments for such delivery.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a national stage application under 35 U.S.C. § 371 of PCT application PCT/US2005/038703, filed Oct. 26, 2005, which claims the benefit of U.S. Provisional Application Ser. No. 60/623,533 filed Oct. 29, 2004 which is incorporated by reference in its entirety herein. 
     
    
       [0002]    The present invention generally relates to method of ophthalmic administration. More specifically, the present invention relates methods of intrascleral injection of therapeutic or diagnostic materials. 
         [0003]    Delivering therapeutic or diagnostic agents to the posterior segment of the eye, especially to the retina, macula, etc., is difficult. Topical instillation of a medicament to the front of the eye such as by eye drops, generally does not provide sufficient amounts of the agent to the posterior portion of the eye. This is due in part to poor diffusion through the various layers as well as the natural clearing processes encountered. 
         [0004]    Accordingly, introducing effective amounts of a medicament to, for example, the retina via topical instillation is generally not possible given the distance and tissue between the sclera and the retina. Another potential shortcoming with topical instillation is that the composition tends to be quickly removed from the eye by tears and other natural clearing processes. The resulting short duration of contact can further limit the likelihood of an appreciable amount of the agent reaching the posterior segment. 
         [0005]    Systemic delivery of an agent to the posterior segment of the eye such as by oral administration, is limited by the blood-retinal barrier. The barrier limits the size and amount of agents that can reach the choroid and retina. Moreover, because the medicament is systemically delivered, the dosage is limited so as not to provide a toxic dose of the agent to other parts of the body. 
         [0006]    Inserts which release the agent over time onto or into the eye may be utilized to deliver a medicament to the posterior segment of the eye. The medicament that is released from the insert can diffuse through the sclera and into the eye. However, little if any of the medicament reaches the posterior segment of the eye for much the same reasons as topical instillation. 
         [0007]    Implants are devices similar to inserts but they are surgically placed within the eye. Accordingly, implants bring the risk of infection and other problems due to the invasive procedure required. 
         [0008]    Intraocular delivery instruments in accordance with the prior invention provide for intrascleral system of medicament. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention includes a method of intraocular delivery by needless injection of a medicament through the sclera of an eye and into a back of the eye as well as instruments for such delivery. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The advantages and features of the present invention will be better understood by the following description when considered in conjunction of the accompanying drawings, in which: 
           [0011]      FIG. 1  is a perspective view of the needleless injector in accordance with the present invention generally showing a housing and injection head and a vial along with a trigger; 
           [0012]      FIG. 2  is a side view and partial cross section of the mechanism disposed within the housing shown in  FIG. 1  which generally includes: an injection head, a vial, a bolt, a cocking stud, a valve tube a mainspring, a hammer, a sear, a valve seat, a trigger, a cup seal, a rear spring and a gas cartridge; 
           [0013]      FIG. 3  is a cross sectional view of the injector shown in  FIG. 2  with the bolt shown in a cocked position ready for injection of medicament through an injection head; 
           [0014]      FIG. 4  is a view similar to that shown in  FIG. 3  with the bolt shown in an uncocked position after dispensing of medicament through the injection head; 
           [0015]      FIG. 5  is a front perspective view of another embodiment in accordance with the present invention generally showing a frame, barrel, vial, a cylinder for supporting a plurality of cartridge and a trigger mechanism; 
           [0016]      FIG. 6  is a rear perspective view of the injection; 
           [0017]      FIG. 7  is a cross-sectional view of the injector shown in  FIG. 5  showing a port near the barrel distal end, a bolt disposed within a barrel bore along with a hammer and spring mechanism, a bolt being shown in a second position before firing of a cartridge and ejection of medicament through the injection head; 
           [0018]      FIG. 8  is a cross-sectional view similar to that shown in  FIG. 7  illustrating depression of the trigger and movement of a gas cartridge aligned with the hammer and bore for driving the bolt forward as with hereinafter described in greater detail; 
           [0019]      FIG. 9  is a view taken along the line  9 - 9  of  FIG. 7 ; 
           [0020]      FIG. 10  is a perspective view of yet another embodiment of a needleless spring injector in accordance with the present invention generally showing a tubular casing having a bottom half shell and a top half shell; 
           [0021]      FIG. 11  is a perspective view similar to that shown in  FIG. 10  there showing the top half shell in an open position during cocking of a spring shown disposed within the tubular casing; 
           [0022]      FIG. 12  is a cross sectional view of the needleless spring injector shown in  FIGS. 10-11  illustrating a spring in a cocked position, a plunger ratchet, push rod, syringe and trigger; 
           [0023]      FIG. 13  is a cross sectional view similar to that shown in  FIG. 12  illustrating movement of the ratchet one step causing forward motion of the plunger by the spring and ejection of medicament to the injection head; 
           [0024]      FIGS. 14-18  illustrate the cocking mechanism of the present invention effected through hinged opening of the top half shell of the injector. 
           [0025]      FIG. 19  is a perspective view of a further embodiment of a needleless push-release injector in accordance with the present invention generally showing a housing, cocking ring; 
           [0026]      FIG. 20  is a perspective view of the present invention illustrating internal components including a vial, check valve, piston, spring, along with the cocking ring and injection head as shown in  FIG. 19 ; 
           [0027]      FIG. 21  is a cross-sectional view of the injector shown in  FIGS. 19-20 , more particularly illustrating components of the present invention in which the spring is held in the compressed state by a sear prior to release for injection of medicament through an injection head into the patients skin, not shown in  FIG. 21 ; 
           [0028]      FIG. 22  is a cross-sectional view similar to that shown in  FIG. 21  illustrating release of the piston upon pressure being applied to the injection head by the skin of a user; 
           [0029]      FIG. 23  is a perspective view of the injection head cylinder piston and cocking ring illustrated; 
           [0030]      FIG. 24  is a perspective view of still another embodiment in accordance with the present invention generally showing a housing, a vial for containment of a medicament, an injection head, a cocking grip and a trigger; 
           [0031]      FIG. 25  is a cross sectional view of the injector shown in  FIG. 24  more specifically showing a chamber disposed within the housing, a piston slidably disposed within the housing with a piston head fitted within the chamber, and having a stem with a spring disposed therearound along with a sear for holding the piston in a second position with the spring compressed; 
           [0032]      FIG. 26  is a cross sectional view similar to  FIG. 25  showing release of the piston with the spring forcing the piston head through the chamber in order to force medicament through the injection head; 
           [0033]      FIG. 27  is a cross sectional view similar to  FIGS. 25 and 26  showing cocking of the spring and withdrawal of medicament from the vial into the chamber for subsequent injection; 
           [0034]      FIG. 28  is a perspective view of a twist-set embodiment injector in accordance with the present invention generally showing a housing, an injection head, a rotatable grip and a trigger; 
           [0035]      FIG. 29  is a plan view of the injector shown in  FIG. 28  partially broken away to illustrate a vial for containment of a medicament, a piston, a one-way valve, a mainspring, and a check valve; 
           [0036]      FIG. 30  is a cross sectional view of the injector shown in  FIGS. 28 and 29  more specifically showing a chamber disposed within the housing, a piston slidably disposed within the housing with a piston head fitted within the chamber, and having a stem with a spring disposed therearound along with a sear for holding the piston in a second position with the spring compressed; 
           [0037]      FIG. 31  is a cross sectional view similar to  FIG. 30  showing release of the piston with the spring forcing the piston head through the chamber in order to force medicament through the injection head; 
           [0038]      FIG. 32  is a cross sectional view similar to  FIGS. 30 and 31  showing cocking of the spring and withdrawal of medicament from the vial into the chamber for subsequent injection by rotation of the grip; 
           [0039]      FIG. 33  is a perspective view of an inline needleless injector in accordance with the present invention generally showing a casing, an injection head disposed at a casing distal end, and a gas line; 
           [0040]      FIG. 34  is a view of the embodiment of  FIG. 33  in accordance with the present invention in partial cross section generally showing a hollow casing having a chamber disposed therein along with a piston, gas manifold, drug manifold, vial, duckbill valve, and cocking stud; 
           [0041]      FIG. 35  is a cross section of the embodiment shown in  FIGS. 33-34  of the generally showing a chamber piston biased by a spring; 
           [0042]      FIG. 36  is a cross sectional view corresponding to the embodiment shown in  FIG. 35  however utilizing application of gas pressure for driving a piston forward for forcing medicament through the injection head; 
           [0043]      FIG. 37  is a perspective view of a needleless solenoid driven injector in accordance with the present invention generally showing a housing, an injection head, and an attached power cord; 
           [0044]      FIG. 38  is a cross sectional view of the injector shown in  FIG. 37  illustrating a cylinder, a piston disposed therein along with a solenoid driven plunger operated by a trigger, check valves for controlling flow of medicament through a manifold and dip tube for withdrawal of medicament from a vial disposed within the housing; and 
           [0045]      FIGS. 39-40  are cross sectional views illustrating operation of the needleless solenoid driven injector in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0046]    With reference to  FIGS. 1-4 , an intraocular delivery instrument  10  for practice of the method of the present invention generally includes a barrel  12  having a proximal end  14  and a distal end  16  and a bore  20  therethrough. An injection head  24  is disposed at the barrel distal end  16  which is in fluid communication with the bore  20  for the injection of a medicament therethrough. 
         [0047]    A vial  28  is provided for containing a medicament, with the vial  28  being in fluid communication with the bore  20  through a port  32  near the barrel distal end  16 . Preferably, the vial  28  is removably attached to the barrel  12 . 
         [0048]    A gas cartridge  36  is disposed at the barrel proximal end  14 . A bolt  38  is provided and disposed in the bore  20  for reciprocal movement therein from a first position closing the port  32  ( FIG. 4 ) to a second position ( FIG. 3 ) opening the port  32  for release of medicament into the bore  20 . The bolt  38  is sized and fitted to provide sufficient seal between the bolt  38  and the bore  20  in order to draw medicament from the vial  28  into the bore  20  upon movement of the bolt  38  from the first position to the second position and to force medicament through the injection head  24  upon movement of the bolt  38  from the second to the first position as will be hereinafter described in greater detail. 
         [0049]    A cocking stud  40  is provided for enabling manual movement of the bolt  38  from the first to the second position. In this cocking movement, medicament is drawn into the bore  20  between the bolt  38  and the injection head  24  through the port  32 . 
         [0050]    A hammer  44  is provided and disposed for reciprocal movement within the bore  20  between the bolt  38  and the barrel proximal end  12 . A mainspring  46  is disposed between the bolt  38  and the hammer  44  for forcing the hammer  44  toward the barrel distal end  16 . 
         [0051]    A sear  50  is provided for releasably holding the bolt  38  in the second position with the mainspring  46  compressed between the bolt  38  and the hammer  44  and a trigger  52  is disposed in an operative relationship with the sear  50  for releasing the spring  46  in order to drive the hammer  44  toward the barrel distal end  16 . 
         [0052]    A valve tube  54  is provided and disposed within the bore  20  with a distal end  56  thereof attached to the bolt  38  and a proximal end  58  attached to the gas cartridge  36 . The valve tube  54  extends through the hammer  44  and mainspring  46 . 
         [0053]    A cup seal  62  includes a valve seat  64  for controlling gas flow from the cartridge  36  into the valve tube  54 . In that regard, a rear spring  66  is provided for releasably sealing the cup seal  62  against the valve seat  64 , the cup seal  62  being open momentarily by impact of the hammer  44  after release by the sear  50  in order to allow gas to flow through the valve tube  54  to force the bolt  38  to the first position which ejects medicament through the injection head  24 . The rear spring  66  thereafter closes the cup seal  62  against the valve seat  64  after the momentary opening. 
         [0054]    In operation, when the bolt  38  is not cocked a forward portion  68  blocks entry of medicament into the bore  20  extending through the barrel  12 . In order to cock the bolt  38 , the cocking stud  40  is moved rearwardly pushing against the mainspring  46  in order that the bolt  38  butts up against the hammer  44 . This motion opens the port  32  between the vial  28  and the bore  20  and draws medication into the bore  20  between the injection head  24  and the bolt  38 . The sear  50  catches the bolt  38  as the bolt  38  is pushed against the hammer  44  and this binds the bolt  38  and the hammer  44  together so they move as one unit. 
         [0055]    For injecting a medicament, the trigger  52  is pushed in order to release the sear  50  which releases the hammer  44  from the bolt  38  and the mainspring  48  propels the hammer  44  rearwardly in order to push momentarily onto the valve tube  54  which propels the valve tube  54  backward with sufficient force to overcome the rear spring  66 . At that point, gas pressure is released from the gas cartridge  36  through the tube  54  which causes the bolt  38  to rapidly move forward and eject medicament disposed between a front of the bolt  38  and the injection head  24  through the injection head  24 . 
         [0056]    With reference to  FIGS. 5-8  another embodiment of an intraocular delivery instrument  72  in accordance with the present invention generally includes a barrel  76  having a proximal end  78  and a distal end  80  and a bore  82  therethrough with an ejection head  86  disposed at the barrel distal end  80  in fluid communication with the bore  82 . 
         [0057]    A vial  90  is provided for containing a medicament with the vial  90  being in fluid communication with the bore  82  through a port  92  near the barrel distal end  80 . Preferably, the vial  90  is removably attached to the barrel  76 . 
         [0058]    A frame  94  is provided for supporting the barrel  76  and a cylinder  98  mounted for rotation at the barrel proximal end  78  with the cylinder  98  having a plurality of chambers  100  therein for receiving gas cartridges  102 . 
         [0059]    A bolt  106  is disposed in the bore  82  for reciprocating movement from a first position closing the port ( FIG. 8 ) to a second position opening the port ( FIG. 7 ) for release of medicament into the bore  82 . The bolt  106  is fitted within the bore  82  in order to draw medicament from the vial  90  into the bore  82  upon movement of the bolt  106  from the first position to the second position and to force medicament through the injection head  86  upon movement of the bolt  106  from the second to the first position. 
         [0060]    A spring  110  is disposed adjacent to the bolt  106  for driving the bolt  106  from the first to the second position and a hammer  112  is disposed between the bolt  106  and the cylinder  98  which includes a firing pin  114  for puncturing a gas cartridge  102  aligned with the hammer  112  and bore  82  by rotation of the cylinder  98 . 
         [0061]    A trigger  118  is pivotally attached to the frame  94  for forcing the aligned gas cartridge  102  into the hammer  112  for puncture of the aligned gas cartridge  102  in order to drive the bolt  106  from the second position to the first position and thereby force medicament in the bore  82  through the injector head  86 . After release of pressure the spring  110  forces the bolt  106  from the first position to the second position thus drawing additional medicament into the bore  82  from the vial  90  for repeated injection. 
         [0062]    It should be appreciated that the cylinder  98  may be manually rotated to align the bore  82  and hammer  112  or a pawl and ratchet arrangement (not shown) may be provided in order to rotate the cylinder  98  prior to a movement of a gas cartridge  102  into engagement of the hammer  112  for release of pressure therein. 
         [0063]    Yet another embodiment  124  in accordance with the present invention generally includes a tubular casing  126  having a bottom half shell  130  extending from a rear end  132  thereof. A top half shell  132  is hingeably  134  attached to the casing rear end  132  for covering the bottom half shell  130 . 
         [0064]    A nose cap  138  is removably attached to a front end  142  of the tubular casing  126  and a injection head  144  is disposed in an end of the nose cap  138 . 
         [0065]    A syringe  148  is releasably disposed within the tubular casing  126  and is in fluid communication with the injection head  144 . Slidably disposed within the tubular casing  126  is a plunger  150  which engages one end  154  of the syringe  148  for injecting medicament therefrom through the injection head  144 . A push rod  158  is provided between the bottom shell  130  and top half shell  132  for slidably moving the plunger  150 . A spring  162 , disposed about a rear portion  164  of the push rod  158  is provided for driving the push rod  158 . 
         [0066]    A ratchet  168  is disposed on a forward portion  170  of the push rod  158  and a manually operated trigger  172 , pivotally mounted within the tubular casing  126 , and including a button  174  extending outwardly from the tubular casing  126  is provided in order to enable manual depression thereof and a sear  176  is also provided for releasably engaging the ratchet  168 . 
         [0067]    A cocking mechanism  180  engages the push rod  158  and the top half shell  132  compresses the spring  162  upon hinge  134  opening of the top half shell  132  from the bottom half shell  130 . 
         [0068]    The spring  162  is retained in a compressed state by engagement of the sear  176  with the ratchet  168  and the depression of the button  174  releases the sear  176  from the ratchet  168  enabling expansion of the spring  162  to drive the push-rod  158  and the plunger  150  in a forward direction in a metered manner to effect the ejection of the medicament from the syringe  148  through the injection head  144 . 
         [0069]      FIGS. 14-16  illustrate the depression of the button  174  initiating a single step forward movement of the ratchet  168  and push rod  158  for single dose ejection of a medicament. 
         [0070]      FIGS. 17 and 18  show a cocking mechanism  180  for engaging the push rod ratchet  168  and compressing the spring  162  on hinged opening of the top half shell  132  from the bottom half shell  130 . The spring  162  is retained in a compressed state by engagement of the sear  176  with the ratchet  168 . 
         [0071]    With reference to  FIGS. 19-23  there is shown a needleless push-release injector  184  in accordance with the present invention generally showing a housing  186  along with a cocking ring  188 , a cylinder  190 , injection head  192 , a vial  194 , piston  196 , valve  198 , and a spring  200 . With reference to  FIGS. 21 and 22 , the housing  186  includes a distal end  204  and a proximal end  206  with a bore  210  therein. The cocking ring  188  extends from the housing distal end  204  and includes a rear portion  214  disposed within the housing bore  210 . 
         [0072]    The cylinder  190  is slidably disposed within the cocking ring  188  and includes a front end  218  and a rear end  220  with a chamber  224  disposed proximate the front end  218 . The vial  194  for containing a medicament is replaceably disposed in the housing  186  and is in fluid communication with the chamber  224  through a dip tube  228  and check valve  198 . 
         [0073]    The injection head  192  is disposed at the cylinder front end  218  and in fluid communication with the chamber  224 . The injection head  192  may be of any suitable design. 
         [0074]    The piston  196  is slidably disposed within the cocking ring  188  and includes a front head  232  slidably disposed within the cylinder  224  and a rear head  234  slidably disposed within the housing bore  210 . 
         [0075]    The front head  232  is fitted to the cylinder  190  in order to draw medicament from the vial  194  into the chamber  224  through the one-way valve  198  upon movement of the piston  196  from a first position shown in  FIG. 22  to a second position shown in FIG.  21 . Movement of the piston  196  from the first position to the second position forces medicament from the chamber  224  through the injection head  192 . 
         [0076]    The main spring  200  is disposed between the housing proximal end  206  the piston rear head  234  and a sear  218  is provided for releasably holding of the piston  196  in the second position with the main spring  200  compressed. The sear  238  includes a sear spring  240  and a tapered end  242  which provides releasable engagement with the piston rear head  234 . 
         [0077]    In use, the injector head  192  is pressed against skin (not shown) which causes rearward motion of the cylinder  190  and the cylinder rear end causes compression of the sear spring  240  which releases the piston rear head  234  and piston  196 , thus causing the spring  200  to force the piston front head  232  into the chamber  224  forcing medicament through the injection head  192 , as indicated by the arrow  246 . 
         [0078]    To re-cock the device the cocking ring  188  is moved in the direction of the arrow  248 , thus moving the piston  196  and re-engagement of the sear  238  with the piston rear head  234 . 
         [0079]    As illustrated in  FIG. 23 , the cocking ring may include guides  252  for preventing rotation thereof. 
         [0080]    With reference to  FIG. 24 , there is shown still another embodiment  258  generally including a housing  260 , an injection head  262 , a vial  264  for containing a medicament, a cocking grip  266 , and a trigger  268 . 
         [0081]    As shown in  FIGS. 25-27 , the housing  260  includes a distal end  274  and a proximal end  276  with a chamber  278  disposed within the housing at the distal end  274 . 
         [0082]    The injection head  282 , which may be of conventional design, is disposed at the housing distal end  274  and is in fluid communication with the chamber  278 . 
         [0083]    A vial  286  may support a replaceable container  288  containing a medicament, not shown, as hereinabove referenced and is in fluid communication with the chamber  278  through a dip tube  290  and a one-way valve  292 . 
         [0084]    A piston  296  is slidably disposed within the housing  260  and includes a piston head  298  slidably disposed within the chamber  278  and a separately moveable stem  302  disposed in the housing  260 . The piston head  298  is fitted within the chamber  278  in order to draw medicament from the vial  286  into the chamber  278  through the one-way valve  292  and dip tube  290  upon movement of the piston head  298  from a first position, as shown in  FIG. 26 , to a second position shown in  FIG. 27 . 
         [0085]    Medicament is forced through the injection head  282  by movement of the piston head from the second position, as shown in  FIG. 25 , to the first position as shown in  FIG. 26  with the injected medicament being indicated by the arrow  306 . A head  308  on the piston stem  302  couples the stem  302  in a slidable manner with the piston head  298  between a fore plate  402  an aft plate  404  of the piston head  298 . 
         [0086]    As shown in  FIGS. 25-27 , a spring  406  disposed around the piston stem  302  between the aft plate  404  and an end plate  408  which is compressed by the cocking grip  266  which is slidably disposed over the housing proximal end  276 . Reciprocal movement of the cocking grip  266  causes compression of the spring  406 , as illustrated in the figures. A sear  410  is provided for releasably holding the piston  296  in the second position with the spring  406  compressed by engagement with the aft plate  404 , as shown in  FIGS. 25 and 26 . 
         [0087]    The trigger  268  is pivotally disposed on a housing  260  and in an operational relationship with the sear  410  for releasing the spring  406  in order to drive the piston  296  along with fore plate  402  to the first position, thus ejecting a metered dose of medicament determined by the chamber  278  volume. 
         [0088]    With reference to  FIGS. 28 and 29 , there is shown a twist-set needleless injector generally including a housing  416 , an injection head  418 , a vial  420  for containing a medicament, a rotatable grip  422  and a trigger  424 . 
         [0089]    As shown in  FIGS. 30-32 , the housing  416  includes a distal end  428  and a proximal end  430  with a chamber  432  disposed within the housing at the distal end  428 . 
         [0090]    The injection head  418 , which may be of conventional design, is disposed at the housing distal end  428  and is in fluid communication with the chamber  432 . 
         [0091]    The vial  420  may support a replaceable container  434  containing a medicament, not shown, as hereinabove referenced and is in fluid communication with the chamber  432  through a dip tube  436  and a one-way valve  440 , for example a duckbill valve. 
         [0092]    A piston  442  is slidably disposed within the housing  416  and includes a piston head  444  slidably disposed within the chamber and a moveable stem  446  disposed in the housing  416 . The piston head  444  is fitted within the chamber  432  in order to draw medicament from the vial  420  into the chamber  432  through the one-way valve  440  and dip tube  436  upon movement of the piston head  444  from a first position, as shown in  FIG. 31 , to a second position shown in  FIG. 32 . 
         [0093]    Medicament is forced through the injection head  418  by movement of the piston head  444  from the second position, as shown in  FIG. 31 , to the first position as shown in  FIGS. 30 and 32  with the injected medicament being indicated by the arrow  450 . A head  452  on the piston stem  446  couples the stem  446  in a slidable manner with the piston head  444  between a fore plate  456  an aft plate  458 . 
         [0094]    As shown in  FIGS. 30-31 , a spring  460  disposed around the piston stem  446  between the aft plate  458  and an end plate  462  which is compressed by the rotating grip  422  which is threadably disposed at the housing proximal end  430 . Rotational movement of the cocking grip  422  causes compression of the spring  460 , as illustrated in the figures. A sear  466  is provided for releasably holding the piston  442  in the second position with the spring  460  compressed by engagement with the aft plate  458 , as shown in  FIG. 30 . 
         [0095]    The trigger  424  is pivotally disposed on the housing  416  and in an operational relationship with the sear  466  for releasing the spring  460  in order to drive the piston  442  along with fore plate  456  to the first position, thus ejecting a metered dose of medicament determined by the chamber  432  volume. 
         [0096]    With reference to  FIGS. 33 and 34 , there is shown an inline needleless injector  510  having a hollow casing  512  with a proximal end  514  and a distal end  516 , an injection head  518  is disposed at the casing distal end  516  and a vial  520  for containing a medicament, is disposed within the casing  512  at the proximal end  514  thereof. 
         [0097]    A drug manifold  522  or line communicates with the vial  520  through a dip tube  524  and a chamber  528  for transport of medicament from the vial  520  into the chamber  528 . A one-way valve  530 , such as, for example, a duckbill valve, disposed in the drug manifold  522  prevents transport of medicament into the vial  520  from the chamber  528 . 
         [0098]    A piston  532  is provided and slidably disposed within the chamber  528  for forcing medicament through the injection head  518  and withdrawing medicament from the vial  520  into the chamber  528  through the manifold  522 . A gas manifold  536  is provided behind a proximal end  538  of the piston  532  for introducing gas from a line behind the piston proximal end  538  in order to drive the piston  532  toward the casing distal end  516  thereby forcing medicament through the injection head  518 . 
         [0099]    In the embodiment  510 , a cocking stud  540  may be provided in order to move the piston  532  toward the casing proximal end  514  in order to withdraw medicament from the vial  520  and into the chamber  528  for subsequent injections. 
         [0100]    With reference to  FIGS. 35 and 36 , there is shown another embodiment  544  of an inline needleless injector in accordance with the present invention. Common reference characters represent identical or substantially similar elements, as hereinabove described in connection with the injector as shown in  FIGS. 33 and 34 . 
         [0101]    A manually operated gas valve  546 , not shown, in  FIGS. 33 and 34 , is disposed proximate the casing  512  for enabling control of a gas through a gas line  548  into the manifold  522 . In the embodiment, a spring  552  is provided as a means for moving the piston  532  toward the casing proximal end  514  after discharge of medicament through the injection head  518  in order to withdraw medicament from the vial  520  through the drug manifold  522 . 
         [0102]    Operation of the injector is illustrated in  FIGS. 35 and 36  respectively. In  FIG. 35 , the chamber  528  which is filled with medicament, is ready for injection with the piston disposed with its proximal end  538  adjacent the gas manifold  536 . Opening of the gas valve  546  causes gas to drive the piston toward the casing distal end  516  forcing medicament through the injection lead  518 , as shown in  FIG. 36 . 
         [0103]    With referenced to  FIGS. 37 and 38 , there is shown a needleless injector  556  in accordance with the present invention including a housing  558  having a proximal end  560  and a distal end  562  with a cylinder  566  disposed in the housing  558  at the distal end  562  thereof along with an injection head  568  disposed at one end of the cylinder  566 . A vial  510  for containing a medicament, is disposed within the housing  558  at the proximal end  560  thereof. A manifold  522  interconnects the cylinder with the vial for transport of medicament from the vial  510  to the cylinder  566  utilizing a dip tube  524  disposed within the vial  510 . 
         [0104]    A plunger  578  includes a first end, or piston,  582  slidably disposed within the cylinder  566  for forcing medicament in the cylinder  566  through the injection head  568  upon movement of the plunger  578  toward the injection head  568  and for withdrawing medicament from the vial  510  into the cylinder  566  upon movement of the plunger  578  away from the injection head  568 . As hereinafter described, the plunger  578  is operable, or moveable, through the application of a magnetic flied provided by a solenoid  586 . The solenoid  586  is disposed around the plunger  518  between the first end  582  and a second end  590  of the plunger  518 . The solenoid  586  is disposed in an operational manner for forcing the plunger  578  toward the injection head  568  upon application of electrical current controlled by a trigger switch  594  interconnected with a power supply such as, for example, a 110-volt AC line. 
         [0105]    A spring  598  is disposed around the plunger  578  between the solenoid  586  and the second end  590  for forcing a plunger  578  away from the injection head  568  after electrical current is not applied to the solenoid  586  in order to withdraw medicament from the vial  510  into the cylinder  566 , as hereinabove noted. 
         [0106]    As more clearly shown in  FIGS. 39 and 40 , the vial  510  may be removable from the housing  558  through a coupling  602  between the proximal end  560  and distal end  562  of the housing  558 . 
         [0107]    Operation of the device is illustrated in  FIGS. 39 and 40 , with  FIG. 39  illustrating the injector in a charged state with the plunger  518  disposed at a proximal end  560  of the cylinder  566 . 
         [0108]    Upon energizing the solenoid  586  through the application of electrical current controlled by the trigger switch  594 , the plunger  578  is forced to a distal end of the cylinder  566  as shown in  FIG. 40  forcing medicament through the injector head  568  as indicated by the arrow  606 . Electrical wiring, (not shown), conventionally interconnects trigger  594  and solenoid  586 . 
         [0109]    After injection of medicament through the injection head  568 , power is removed from the solenoid  586  through the switch  594  enabling the spring  598  to force the plunger  578  away from the injector head  568  with the first end, or piston,  582  thereof withdrawing to the proximal end of the cylinder  566 . 
         [0110]    Although there has been hereinabove described specific intraocular delivery instruments and a method in accordance with the present invention for the purpose of illustrating the manner in which the invention may be used to advantage, it should be appreciated that the invention is not limited thereto. That is, the present invention may suitably comprise, consist of, or consist essentially of the recited elements. Further, the invention illustratively disclosed herein suitably may be practiced in the absence of any element which is not specifically disclosed herein. Accordingly, any and all modifications, variations or equivalent arrangements which may occur to those skilled in the art, should be considered to be within the scope of the present invention as defined in the appended claims.