Abstract:
An ophthalmic injection device includes a dispensing chamber housing with an inner surface that partially defines a dispensing chamber for holding a substance, a plunger fluidly sealed to the interior surface of the dispensing chamber housing, and a needle fluidly coupled to the dispensing chamber. A temperature control device partially surrounds the dispensing chamber housing and alters a temperature of the substance. A piston is coupled to the plunger at one end and to a spring at the other end. The spring provides a force to drive the piston and the plunger. An actuator is coupled to the lockout bar with which a button is configured to interface. The actuator moves the lockout bar when the substance reaches a temperature, thereby allowing the button to be activated so that the spring provides the force to drive the plunger. An incorporated stop whose measurements may vary allow the expelled dosage to vary accordingly.

Description:
RELATED APPLICATIONS 
       [0001]    This Application is a continuation-in-part of U.S. patent application Ser. No. 11/832,301 filed Aug. 1, 2007, U.S. patent application Ser. No. 11/832,333 filed Aug. 1, 2007, U.S. patent application Ser. No. 11/832,243 filed Aug. 1, 2007, U.S. patent application Ser. No. 11/832,364 filed Aug. 1, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a single-use medical device and more particularly to a two-piece ophthalmic drug delivery device with a disposable tip end containing a sintered ceramic chamber. 
         [0003]    Several diseases and conditions of the posterior segment of the eye threaten vision. Age related macular degeneration (ARMD), choroidal neovascularization (CNV), retinopathies (e.g., diabetic retinopathy, vitreoretinopathy), retinitis (e.g., cytomegalovirus (CMV) retinitis), uveitis, macular edema, glaucoma, and neuropathies are several examples. 
         [0004]    These, and other diseases, can be treated by injecting a drug into the eye. Such injections are typically manually performed using a conventional syringe and needle.  FIG. 1  is a perspective view of a prior art syringe used to inject drugs into the eye. In  FIG. 1 , the syringe includes a needle  105 , a luer hub  110 , a chamber  115 , a plunger  120 , a plunger shaft  125 , and a thumb rest  130 . As is commonly known, the drug to be injected is located in chamber  115 . Pushing on the thumb rest  130  causes the plunger  120  to expel the drug through needle  105 . 
         [0005]    In using such a syringe, the surgeon is required to pierce the eye tissue with the needle, hold the syringe steady, and actuate the syringe plunger (with or without the help of a nurse) to inject the fluid into the eye. The volume injected is typically not controlled in an accurate manner because reading the vernier is subject to parallax error. Fluid flow rates are uncontrolled during injection and tissue damage may occur due to an “unsteady” injection. Reflux of the drug may also occur when the needle is removed from the eye. 
         [0006]    An effort has been made to control the delivery of small amounts of liquids. A commercially available fluid dispenser is the ULTRA™ positive displacement dispenser available from EFD Inc. of Providence, R.I. The ULTRA dispenser is typically used in the dispensing of small volumes of industrial adhesives. It utilizes a conventional syringe and a custom dispensing tip. The syringe plunger is actuated using an electrical stepper motor and an actuating fluid. With this type of dispenser, the volumes delivered are highly dependent on fluid viscosity, surface tension, and the specific dispensing tip. Parker Hannifin Corporation of Cleveland, Ohio distributes a small volume liquid dispenser for drug discovery applications made by Aurora Instruments LLC of San Diego, Calif. The Parker/Aurora dispenser utilizes a piezo-electric dispensing mechanism. While precise, this dispenser is expensive and requires an electrical signal to be delivered to the dispensing mechanism. 
         [0007]    U.S. Pat. No. 6,290,690 discloses an ophthalmic system for injecting a viscous fluid (e.g. silicone oil) into the eye while simultaneously aspirating a second viscous fluid (e.g. perflourocarbon liquid) from the eye in a fluid/fluid exchange during surgery to repair a retinal detachment or tear. The system includes a conventional syringe with a plunger. One end of the syringe is fluidly coupled to a source of pneumatic pressure that provides a constant pneumatic pressure to actuate the plunger. The other end of the syringe is fluidly coupled to an infusion cannula via tubing to deliver the viscous fluid to be injected. 
         [0008]    It would be desirable to have a portable hand piece for injecting a drug into the eye. Such a hand piece can include a limited reuse assembly attachable to and removable from a disposable tip segment. The disposable tip segment contains the drug, a needle for administering the drug, and a temperature control device, such as a heater, for altering the temperature of the drug. In order to safely operate such a device, a mechanical lockout feature may be desirable. In addition, for lower cost, spring actuation may also be desirable. 
       SUMMARY OF THE INVENTION 
       [0009]    In one embodiment consistent with the principles of the present invention, the present invention is an ophthalmic injection device including a dispensing chamber housing, a plunger, a needle, a spring, a safety actuator, a lockout bar, and a button. The dispensing chamber housing has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for receiving a quantity of a substance. The plunger is fluidly sealed to an interior surface of the dispensing chamber housing. The needle is fluidly coupled to the dispensing chamber. The spring provides a force to drive the plunger. The actuator is coupled to the lockout bar. The button interfaces with the lockout bar. The actuator moves the lockout bar when a condition is met, thereby allowing the button to be activated so that the spring provides the force to drive the plunger. 
         [0010]    In another embodiment consistent with the principles of the present invention, the present invention is an ophthalmic injection device including a dispensing chamber housing, a plunger, a needle, a temperature control device, a spring, a piston, an actuator, a lockout bar, and a button. The dispensing chamber housing has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for receiving a quantity of a substance. The plunger is fluidly sealed to an interior surface of the dispensing chamber housing. The needle is fluidly coupled to the dispensing chamber. The temperature control device alters a temperature of the substance. The spring provides a force to drive the plunger. The piston is coupled to the plunger at one end and to the spring at the other end. The actuator is coupled to the lockout bar. The button interfaces with the lockout bar. The actuator moves the lockout bar when the substance reaches a temperature, thereby allowing the button to be activated so that the spring provides the force to drive the plunger. 
         [0011]    In another embodiment consistent with the principles of the present invention, the present invention is a method of injecting a substance into an eye, the method comprising: altering the temperature of a substance to be injected into an eye; after the substance reaches a temperature, activating an actuator to move a lockout bar; moving the lockout bar to allow a spring to be activated; and activating the spring to produce a force that pushes a plunger to deliver the substance into the eye. 
         [0012]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The following description, as well as the practice of the invention, set forth and suggest additional advantages and purposes of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. 
           [0014]      FIG. 1  is a perspective view of a prior art syringe. 
           [0015]      FIG. 2  is a cross section view of an ophthalmic medical device including a disposable tip segment and a limited reuse assembly according to the principles of the present invention. 
           [0016]      FIG. 3  is a cross section view of an embodiment of a disposable tip segment and safety linear actuator lockout mechanism according to the principles of the present invention. 
           [0017]      FIGS. 4A and 4B  are views of a safety linear actuator lockout mechanism according to the principles of the present invention. 
           [0018]      FIG. 5  is a side view of a lockout bar according to the principles of the present invention. 
           [0019]      FIGS. 6A and 6B  are perspective views of a lockout mechanism according to the principles of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Reference is now made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying figures. Wherever possible, the same reference numbers are used throughout the figures to refer to the same or like parts. 
         [0021]      FIG. 2  is a cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention.  FIG. 2  shows how tip segment  205  interfaces with limited reuse assembly  250 . In the embodiment of  FIG. 2 , tip segment  205  includes plunger  415 , dispensing chamber housing  425 , tip segment housing  215 , temperature control device  450 , thermal sensor  460 , needle  210 , dispensing chamber  405 , button  335 , piston  345 , spring  355 , stop  360 , interface  530 , and tip interface connector  520 . Limited reuse assembly  250  includes safety actuator  515 , lockout bar  365 , power source  505 , controller  305 , limited reuse assembly housing  255 , interface  535 , temperature control device activation button  337 , and limited reuse assembly interface connector  525 . 
         [0022]    In tip segment  205 , one end of plunger  415  forms one end of dispensing chamber  405 . Plunger  415  is adapted to slide within dispensing chamber  405 . An outer surface of plunger  415  is fluidly sealed to the inner surface of dispensing chamber housing  425 . Dispensing chamber housing  425  surrounds the dispensing chamber  405 . Typically, dispensing chamber housing  425  has a cylindrical shape. As such, dispensing chamber  405  also has a cylindrical shape. 
         [0023]    Needle  210  is adapted to deliver a substance, such as a drug, into an eye. Needle  210  may be of any commonly known configuration. Preferably, needle  210  is designed such that its thermal characteristics are conducive to the particular drug delivery application. For example, when a heated drug is to be delivered, needle  210  may be relatively short (several millimeters) in length to facilitate proper delivery of the drug based on thermal characteristics. 
         [0024]    Needle  210  is fluidly coupled to dispensing chamber  405 . In such a case, a substance contained in dispensing chamber  405  can pass through needle  210  and into an eye. Temperature control device  450  at least partially surrounds dispensing chamber housing  425 . Interface  530  connects temperature control device  450  with tip interface connector  520 . 
         [0025]    In various embodiments of the present invention, temperature control device  450  is a heating and/or a cooling device. Temperature control device  450  is in thermal contact with dispensing chamber housing  425 . As such, temperature control device  450  is capable of changing the temperature of the substance in dispensing chamber  405 . Interface  530  and tip interface connector  520  couple temperature control device  450  to a limited reuse assembly. In such a case, temperature control device  450  can be powered and controlled by the limited reuse assembly. Temperature control device activation button  337  can be used to activate temperature control device  450 . 
         [0026]    A substance to be delivered into an eye, typically a drug, is located in dispensing chamber  405 . In this manner, the substance is contacted by the inner surface of dispensing chamber housing  425  and one face of plunger  415 . Typically, dispensing chamber  405  is cylindrical in shape. Temperature control device  450  is in thermal contact with dispensing chamber housing  425 . In this manner, temperature control device  450  is adapted to control the temperature of the contents of dispensing chamber  425 . Thermal sensor  460  provides temperature information to assist in controlling the operation of temperature control device  450 . 
         [0027]    In one embodiment of the present invention, the substance located in dispensing chamber  405  is a drug that is preloaded into the dispensing chamber. In such a case, disposable tip segment  205  is appropriate as a single use consumable product. Such a disposable product can be assembled at a factory with a dosage of a drug installed. 
         [0028]    When a drug is preloaded into dispensing chamber  405 , a set quantity of the drug can be preloaded. For example, 100 microliters of a drug can be loaded into dispensing chamber  405 , and any quantity up to 100 microliters can be dispensed. In such a case, the plunger  415  can be moved a precise distance to deliver a precise dosage of drug from the dispensing chamber  405 , through the needle  210 , and into an eye. This provides for flexibility of dosing and for ease of assembly. 
         [0029]    Spring  355  is coupled to piston  345 , which in turn is coupled to plunger  415 . Spring  355  is adapted to drive piston  345  upward when button  335  is activated. In this manner, spring  355  provides the force necessary to move piston  345  and plunger  415  upward to dispense the substance contained in dispensing chamber  405 . Spring  355  is selected (generally by selecting its spring constant) to provide a force that drives plunger  415  at a pre-selected rate. For example, if spring  355  has a relatively high spring constant, the rate at which plunger  415  is driven is relatively high—resulting in a fast delivery of the substance in dispensing chamber  405 . If spring  355  has a relatively low spring constant, the rate at which plunger  415  is driven is relatively low—resulting in a slow delivery of the substance in dispensing chamber  405 . 
         [0030]    Button  335  engages lockout bar  365  (as described in further detail below). In this manner, lockout bar  365  traverses piston  345 . In this embodiment, lockout bar  365  is inserted into an opening in piston  345 . Button  335  also enters piston  335  through an opening that is generally perpendicular to the opening through which lockout bar  365  travels. 
         [0031]    A stop  360  is also provided to stop the movement of piston  345  and plunger  415 . In this manner, stop  360  can be used as a mechanical dosing device. The location and length of stop  360  determines how far piston  345  and plunger  415  can travel, thus limiting the amount of substance dispensed from dispensing chamber  405 . 
         [0032]    The components of tip segment  205 , including piston  345 , spring  355 , stop  360 , dispensing chamber housing  425 , temperature control device  450 , and plunger  415  are at least partially enclosed by tip segment housing  215 . In one embodiment consistent with the principles of the present invention, plunger  415  is sealed to the interior surface of dispensing chamber housing  425 . This seal prevents contamination of any substance contained in dispensing chamber  405 . For medical purposes, such a seal is desirable. This seal can be located at any point on plunger  415  or dispensing chamber housing  425 . 
         [0033]    In limited reuse assembly  250 , power source  505  provides power to safety actuator  515 . An interface (not shown) between power source  505  and safety actuator  515  serves as a conduit for providing power to safety actuator  515 . Safety actuator  515  is connected to lockout bar  365 . 
         [0034]    Controller  305  is connected via interface  535  to limited reuse assembly interface connecter  525 . Limited reuse assembly interface connecter  525  is located on a top surface of limited reuse assembly housing  255 . In this manner, limited reuse assembly interface connector  525  is adapted to be connected with tip interface connector  520 . 
         [0035]    Controller  305  and safety actuator  515  are connected by an interface (not shown). This interface (not shown) allows controller  305  to control the operation of safety actuator  515 . In addition, an interface (not shown) between power source  505  and controller  305  allows controller  305  to control operation of power source of  505 . In such a case, controller  305  may control the charging and the discharging of power source  505  when power source  505  is a rechargeable battery. 
         [0036]    Controller  305  is typically an integrated circuit with power, input, and output pins capable of performing logic functions. In various embodiments, controller  305  is a targeted device controller. In such a case, controller  305  performs specific control functions targeted to a specific device or component, such as a temperature control device or a power supply. For example, a temperature control device controller has the basic functionality to control a temperature control device. In other embodiments, controller  305  is a microprocessor. In such a case, controller  305  is programmable so that it can function to control more than one component of the device. In other cases, controller  305  is not a programmable microprocessor, but instead is a special purpose controller configured to control different components that perform different functions. While depicted as one component, controller  305  may be made of many different components or integrated circuits. 
         [0037]    Safety actuator  515  is typically a linear actuator or linear driver. In such a case, safety actuator  515  may be a spring or spring driven mechanism, a geared DC motor with a rotary sensor coupled to a linear drive or a dc motor coupled to a linear drive with a linear sensor, or a linear stepper motor. Other types of motors, like a rotational permanent magnet motor, may also be used for safety actuator  515 . 
         [0038]    Tip segment  205  is adapted to mate with or attach to limited reuse assembly  250  as previously described. In the embodiment of  FIG. 2 , tip interface connector  520  is adapted to connect with limited reuse assembly interface connector  525 . In addition, an interface is formed between controller  305  and temperature control device  450 . A signal can pass from controller  305  to temperature control device  450  through interface  535 , limited reuse assembly interface connector  525 , tip interface connector  520 , and interface  530 . 
         [0039]    In addition, controller  305  controls the operation of temperature control device  450 . Temperature control device  450  is adapted to heat and/or cool dispensing chamber housing  425 . Since dispensing chamber housing  425  is at least partially thermally conductive, heating or cooling dispensing chamber housing  425  heats or cools a substance located in dispensing chamber  405 . Temperature information can be transferred from thermal sensor  460  to controller  305  via any of a number of different interface configurations. This temperature information can be used to control the operation of temperature control device  450 . When temperature control device  450  is a heater, controller  305  controls the amount of current that is sent to temperature control device  450 . The more current sent to temperature control device  450 , the hotter it gets. In such a manner, controller  305  can use a feed back loop utilizing information from thermal sensor  460  to control the operation of temperature control device  450 . Any suitable type of control algorithm, such as a proportional integral derivative (PID) algorithm, can be used to control the operation of temperature control device  450 . 
         [0040]    In operation, when tip segment  205  is connected to limited reuse assembly  250 , controller  305  controls the operation of temperature control device  450  and safety actuator  515 . First, the substance in dispensing chamber  405  is heated or cooled (as the case may be). When the substance reaches the proper temperature, controller activates safety actuator  515 . Safety actuator  515  moves lockout bar  365  to a position that allows button  335  to be depressed. Depressing button  335  allows spring  355  to drive piston  345  and plunger  415 , thus dispensing the substance contained in dispensing chamber  405 . In this manner, safety actuator  515  only allows an injection to take place when the substance is in the proper temperature range. An upper and/or lower temperature limit (or both—i.e. a range) can be provided to control safety actuator  515 . Safety actuator  515  moves the lockout bar  365  when the temperature condition is met. In other embodiments of the present invention, other conditions may be met before safety actuator  515  moves lockout bar  365 . For example, various safety conditions (tip segment properly attached to limited reuse assembly, properly functioning mechanics or electronics, proper dosage selection, etc.) may be met before safety actuator  515  moves lockout bar  365 . 
         [0041]    While depicted as being a part of tip segment  205 , piston  345 , spring  355 , lockout bar  365 , and button  335  or any combination of them may be found in limited reuse assembly  250 . For example, in one embodiment consistent with the principles of the present invention, piston  345 , spring  355 , lockout bar  365 , and button  335  are all a part of limited reuse assembly  250 . In this configuration, piston  345  interfaces with plunger  415  or a shaft attached to the bottom of plunger  415 . In this manner, tip segment contains fewer parts than depicted in  FIG. 2  resulting in fewer parts that are discarded after an injection. 
         [0042]      FIG. 3  is a cross section view of an embodiment of a disposable tip segment and safety linear actuator lockout mechanism according to the principles of the present invention. The tip segment  205  of  FIG. 3  includes a few additional features not pictured in  FIG. 2 . These new features include an internal housing  370 , window  375 , indicator  380 , vent  385 , and one or more o-rings  390 . The remaining components of tip segment  205  are described with reference to  FIG. 2 . 
         [0043]    Internal housing  370  at least partially encloses piston  345 . In this manner, internal housing  370  provides a space in which piston  345  travels. Typically, this space is generally cylindrical, as is piston  345 . A window  375  is included in tip segment housing  215  to allow indicator  380  to be seen. Indicator  380  is a mechanical indicator that moves with piston  345 . In this manner, as piston  345  moves (moving plunger  415  and dispensing the substance from dispensing chamber  405 ), indicator  380  also moves. Indicator  380  has colors, numbers, or the like that are designed to visually confirm the success or failure of an injection. For example, if piston  345  moves properly (and is stopped by stop  360 ), then indicator  380  moves upward so that an indication of a successful injection is displayed through window  375 . 
         [0044]    Vent  385  is located in internal housing  370 . One or more o-rings  390  provide a seal between piston  345  and the interior of internal housing  370 . Both vent  385  and o-rings  390  are optional. Vent  385  is provided to allow air to escape from the interior of internal housing  370 . This allows piston  345  to move upward. When one or more o-rings  390  are used (or another suitable seal is formed between piston  345  and the interior surface of internal housing  370 ), the size of vent  385  can determine how fast piston  345  is allowed to move. For a given force provided by spring  355 , the size of vent  385  acts to damp the movement of piston  345  (which movement is constrained by the rate at which the air entrapped in internal housing  370  escapes through vent  385 ). In this manner, a controlled movement of piston  345  can be achieved. 
         [0045]      FIGS. 4A and 4B  are views of a safety linear actuator lockout mechanism according to the principles of the present invention.  FIGS. 4A and 4B  show the movement of lockout bar  365  and the position of button  335  with respect to lockout bar  365 . Safety actuator moves lockout bar  365  downward revealing an opening through which one end of button  335  passes. This opening is shown in  FIG. 5 .  FIG. 5  is a side view of a lockout bar according to the principles of the present invention. 
         [0046]      FIGS. 6 and 6B  are perspective views of a lockout mechanism according to the principles of the present invention.  FIGS. 6A and 6B  show the shapes and relative movement of button  335  and lockout bar  365 . As shown, one end of button  335  is shaped and/or sized to fit through an opening in lockout bar  365 . Safety actuator  515  is coupled to lockout bar  365 . After a certain condition is met (such as the substance reaching the proper temperature), safety actuator  515  moves lockout bar  365  so that one end of button  335  can pass through lockout bar  365 . When button  335  passes through lockout bar  365 , piston  345  is allowed to move. Spring  355  drives piston  345  and plunger  415  to dispense the substance contained in dispensing chamber  405 . 
         [0047]    From the above, it may be appreciated that the present invention provides an improved system for delivering precise volumes of a substance into an eye. The present invention provides a single use, disposable delivery device tip segment that is capable of delivering a precise dosage. The tip segment interfaces with a limited reuse assembly. A safety actuator prevents the substance from being dispensed until a certain condition is met. When the condition is met, the safety actuator moves a lockout bar that allows the injection to take place. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. 
         [0048]    Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.