Abstract:
A disposable injection device includes a dispensing chamber, a plunger, a fuse in series with a light, and a housing. The dispensing chamber has an inner surface and an outer surface. The inner surface defines a cavity for receiving a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber, is capable of sliding in the cavity of the dispensing chamber, and is fluidly sealed to the inner surface of the dispensing chamber. The housing at least partially encloses the dispensing chamber and the plunger. After the substance has been delivered from the dispensing chamber, the fuse is blown causing the light to go out and disabling the device.

Description:
RELATED APPLICATIONS 
       [0001]    This Application is a continuation-in-part of U.S. patent application Ser. No. ______, which claims priority to U.S. Provisional Patent Application No. ______, converted from U.S. patent application Ser. No. 11/581629 filed Oct. 16, 2006, and which is a continuation-in-part of U.S. patent application Ser. No. 11/435,906 filed May 17, 2006. 
     
    
     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 fuse assembly. 
         [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 made 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 puncture 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 the vernier on the syringe is not precise relative to the small injection volume. Fluid flow rates are uncontrolled. Reading the vernier is also subject to parallax error. Tissue damage may occur due to an “unsteady” injection. 
         [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 has 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 various other components. In order to prevent infection, the needle of tip segment needs to be sterile. The tip segment could come prepackaged in a sterile pack. In order to insure that the disposable tip segment is used only once, it would be desirable to have a fused light that prevents the reuse of the disposable tip segment. 
       SUMMARY OF THE INVENTION 
       [0009]    In one embodiment consistent with the principles of the present invention, the present invention is a disposable injection device including a dispensing chamber, a plunger, a fuse in series with a light, and a housing. The dispensing chamber has an inner surface and an outer surface. The inner surface defines a cavity for receiving a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber, is capable of sliding in the cavity of the dispensing chamber, and is fluidly sealed to the inner surface of the dispensing chamber. The housing at least partially encloses the dispensing chamber and the plunger. After the substance has been delivered from the dispensing chamber, the fuse is blown causing the light to go out and disabling the device. 
         [0010]    In another embodiment consistent with the principles of the present invention, the present invention is an ophthalmic injection system including a tip segment and a limited reuse assembly. The tip segment includes a dispensing chamber, a plunger, a fuse in series with a light, and a housing. The dispensing chamber has an inner surface and an outer surface. The inner surface defines a cavity for receiving a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber, is capable of sliding in the cavity of the dispensing chamber, and is fluidly sealed to the inner surface of the dispensing chamber. The plunger also has an end with a first mechanical linkage interface. The housing at least partially encloses the dispensing chamber and the plunger. The limited reuse assembly includes a power source, a controller for controlling the operation of the system, a actuator having a shaft, a second mechanical linkage interface located on an end of the shaft, and a second housing at least partially enclosing the controller and the actuator. After the substance has been delivered from the dispensing chamber, the fuse is blown causing the light to go out and disabling the device. 
         [0011]    In another embodiment consistent with the principles of the present invention, the present invention is a method of operating an ophthalmic injection system. The method includes recognizing a connection between a tip segment and a limited reuse assembly and determining if a fuse has been blown. If the fuse has not been blown, then a light is illuminated indicating that the tip segment is ready to be used. After the tip segment has been used, a current to the fuse is increased thus causing the fuse to be blown. 
         [0012]    In another embodiment consistent with the principles of the present invention, the present invention is a medical device having a single use component and a limited reuse assembly. The single-use component has a fuse connected in series with a light and an interface for receiving electric current that is provided to the fuse and the light. The limited reuse assembly is attachable to and removable from the single-use component. The limited reuse assembly has a controller for controlling the operation of the single-use component and a power source for providing the electric current to the fuse and the light via the interface. After the single-use component has been used, the fuse is blown thus disabling the single use component. 
         [0013]    In another embodiment consistent with the principles of the present invention, the present invention is a single-use medical device including a fuse connected in series with a light and an interface for receiving electric current. The electric current is provided to the fuse and the light. After the device has been used, the fuse is blown thus disabling the device. 
         [0014]    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 
         [0015]    The accompanying drawings, 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. 
           [0016]      FIG. 1  is a perspective view of a prior art syringe. 
           [0017]      FIG. 2  is a view of an ophthalmic hand piece including a drug delivery tip segment and a limited reuse assembly according to an embodiment of the present invention. 
           [0018]      FIG. 3  is a diagram of a fused light for use in a drug delivery tip segment according to an embodiment of the present invention. 
           [0019]      FIG. 4  is an exploded cross section view of a drug delivery tip segment for an ophthalmic hand piece according to an embodiment of the present invention. 
           [0020]      FIG. 5  is cross section view of a drug delivery tip segment and a limited reuse assembly according to an embodiment of the present invention. 
           [0021]      FIG. 6  is a flow chart depicting one method of operation of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    Reference is now made in detail to the exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used throughout the drawings to refer to the same or like parts. 
         [0023]      FIG. 2  depicts one view of an ophthalmic hand piece including a drug delivery tip segment and a limited reuse assembly according to an embodiment of the present invention. In  FIG. 2 , the hand piece includes a tip segment  205  and a limited reuse assembly  250 . The tip segment  205  includes a needle  210 , a housing  215 , a plunger connection  225 , and an optional light  275 . The limited reuse assembly  250  includes a housing  255 , a switch  270 , a lock mechanism  265 , and a threaded portion  260 . 
         [0024]    Tip segment  205  is capable of being connected to and removed from Limited reuse assembly  250 . In this embodiment, tip segment  205  has a threaded portion on an interior surface of housing  215  that screws onto the threaded portion  260  of limited reuse assembly  250 . In addition, lock mechanism  265  secures tip segment  215  to limited reuse assembly  250 . Lock mechanism  265  may be in the form of a button, a sliding switch, or a cantilevered mechanism. Other mechanisms for connecting tip segment  205  to limited reuse assembly  250 , such as those involving structural features that mate with each other, are commonly known in the art and are within the scope of the present invention. 
         [0025]    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. 
         [0026]    Switch  270  is adapted to provide an input to the system. For example, switch  270  may be used to activate the system or to turn on a heater. Other switches, buttons, or user-directed control inputs are commonly known and may be employed with limited reuse assembly  250  and/or tip segment  205 . 
         [0027]    Optional light  275  is illuminated when tip segment  205  is ready to be used. Optional light  275  may protrude from housing  215 , or it may be contained within housing  215 , in which case, optional light  275  may be seen through a clear portion of housing  215 . In other embodiments, optional light  275  may be replaced by an indicator, such as a liquid crystal display, segmented display, or other device that indicates a status or condition of the tip segment. For example, optional light  275  may also pulse on and off to indicate other states such as but not limited to a system error, fully charged battery, insufficiently charged battery or faulty connection between the tip segment  205  and limited use assembly  250 . 
         [0028]      FIG. 3  is a diagram of a fused light for use in a drug delivery tip segment according to an embodiment of the present invention. In  FIG. 3 , optional light  275  and fuse  375  are connected in series with power source  310 . Controller  305  controls the operation of power source  310 . 
         [0029]    In the embodiment of  FIG. 3 , optional light  275  is a light emitting diode of any appropriate color. In other embodiments, optional light  275  may be a lamp, a phosphorescent light, or any other similar electric or electronic light source. In other embodiments, optional light  275  is any type of indicator, such as a liquid crystal display or a segmented display. 
         [0030]    Fuse  375  is a fuse with a current rating greater than the operating current of optional light  275 . Fuse  375  may be a common glass encapsulated fuse, a trace fuse on a printed circuit board, or other similar structure that provides the function of a fuse. For example, a switch or switching circuit may be used to provide the functionality of fuse  375 . 
         [0031]    Power source  310  is typically a rechargeable battery with associated electronics. In other cases, power source  310  is a disposable battery or simply a connection to an independent power source, such as a switch mode power supply. In this embodiment, power source  310  also includes the charging and current driving electronics associated with it. 
         [0032]    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 heater or a power supply. For example, a heater controller has the basic functionality to control a heater. 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. In the embodiment of  FIG. 3 , controller  305  controls power supply  310  and reads data from memory device  315 . While depicted as one component in  FIG. 1 , controller  305  may be made of many different components or integrated circuits. 
         [0033]      FIG. 4  is an exploded cross section view of a drug delivery tip segment for an ophthalmic hand piece according to an embodiment of the present invention. In  FIG. 4 , the drug delivery tip segment includes housing  215 , needle  210 , optional light  275 , fuse  375 , plunger shaft  410 , plunger tip  415 , mechanical linkage interface  420 , dispensing chamber  405 , dispensing chamber housing  425 , heater  450 , thermal sensor  460 , and optional luer  430 . 
         [0034]    In the embodiment of  FIG. 4 , mechanical linkage interface is located on one end of plunger shaft  410 . Plunger tip  415  is located on the other end of plunger shaft  410 . Plunger shaft  410  and plunger tip  415  collectively form a plunger. Dispensing chamber  405  is enclosed by dispensing chamber housing  425  and plunger tip  415 . Plunger tip  415  forms a fluid seal with the interior surface of dispensing chamber housing  425 . Needle  210  is fluidly coupled to dispensing chamber  405 . In this manner, a substance located in dispensing chamber  405  can be contacted by plunger tip  415  and pushed out of needle  210 . Needle  210  may be secured to the drug delivery tip segment by an optional luer  430  or may be permanently attached. Heater  450  is located on dispensing chamber housing  425  and at least partially surrounds dispensing chamber  405 . Housing  215  forms an outer skin on the drug delivery tip segment and at least partially encloses plunger shaft  410 , plunger tip  415 , dispensing chamber  405 , and dispensing chamber housing  425 . Optional light  275  is visible from outside of housing  215 . Optional light  275  may be illuminated, for example, when the tip segment is ready to be used. Fuse  375  is connected in series with optional light  275 . 
         [0035]    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 tip  415 . Typically, dispensing chamber  405  is cylindrical in shape. Heater  450  is in thermal contact with dispensing chamber housing  425 . In this manner, heater  450  is adapted to heat the contents of dispensing chamber  425 . Current is applied to heater  450  through an electrical interface (not shown). Thermal sensor  460  provides temperature information to assist in controlling the operation of heater  450 . 
         [0036]    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, the drug delivery tip segment 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. A precise volume of a substance can be preloaded into the delivery device. 
         [0037]    When the 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 (plunger shaft  410  and plunger tip  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. 
         [0038]    In operation, the drug delivery tip segment of  FIG. 4  is attached to a limited reuse assembly (not shown). The limited reuse assembly provides power to the tip segment and illuminates optional light  275 . In such a case, a current passes through optional light  275  and fuse  375 . Mechanical interface  420  mates with a mechanical interface on the limited reuse assembly. When a force is applied to plunger shaft  410 , plunger tip  415  is displaced. The displacement of plunger tip  415  in turn displaces the substance contained in dispensing chamber  405 . The substance is pushed out of needle  210 . After the dosage is delivered, the controller (not shown) directs an increased current to be sent through fuse  375  and optional light  275 . This increased current burns out fuse  375  indicating that the tip segment has been used and is to be discarded. Any number of commonly known methods can be used to increase the current to blow fuse  375 . Since the tip segment of the depicted embodiment is a single use tip segment, once fuse  375  is blown, the tip segment is no longer operable. 
         [0039]      FIG. 5  is cross section view of a drug delivery tip segment and a limited reuse assembly according to an embodiment of the present invention.  FIG. 5  shows how tip segment  205  interfaces with limited reuse assembly  250 . In the embodiment of  FIG. 5 , tip segment  205  includes fuse assembly  555 , mechanical linkage interface  420 , plunger  505 , dispensing chamber housing  425 , tip segment housing  215 , heater  450 , thermal sensor  460 , needle  210 , dispensing chamber  405 , interface  530 , and tip interface connector  520 . Limited reuse assembly  250  includes mechanical linkage  545 , actuator shaft  510 , actuator  515 , power source  310 , controller  305 , limited reuse assembly housing  255 , interface  535 , and limited reuse assembly interface connector  525 . 
         [0040]    In tip segment  205 , mechanical linkage  420  is located on one end of plunger  505 . The other end of plunger  505  forms one end of dispensing chamber  405 . Plunger  505  is adapted to slide within dispensing chamber  405 . An outer surface of plunger  505  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. In tip segment  205 , fuse assembly  555  includes a fuse and an optional light connected in series as shown in  FIG. 3 . 
         [0041]    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. Heater  450  at least partially surrounds dispensing chamber housing  425 . In this case, heater  450  is adapted to heat dispensing chamber housing  425  and any substance contained in dispensing chamber  405 . In other words, heater  450  is in thermal contact with dispensing chamber housing  425 . Interface  530  connects heater  450  with tip interface connector  520 . 
         [0042]    The components of tip segment  205 , including dispensing chamber housing  425 , heater  450 , and plunger  505  are at least partially enclosed by tip segment housing  215 . In one embodiment consistent with the principles of the present invention, a seal is present on a bottom surface of tip segment housing  215 . In this manner, plunger  505  is sealed to tip segment housing  215 . 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  505  or on dispensing chamber housing  425 . In such a case, tip segment housing  215  maybe connected to dispensing chamber housing  425  to form an air tight or fluid tight seal. In another embodiment, tip segment housing  215  may be sealed to plunger  505  near the end on which mechanical linkage interface  420  resides. In such a case, an air tight or fluid tight seal may be formed between a location on plunger  505  and tip segment housing  215 . 
         [0043]    In addition, tip segment  205  may contain a plunger stop mechanism. As shown in  FIG. 5 , the bottom portion of plunger  505  (the portion on which mechanical linkage interface  420  resides) is adapted to contact the bottom portion of dispensing chamber housing  425 . In such a case, as plunger  505  advances upward toward needle  210 , mechanical linkage interface  420  also advances upward toward needle  210 . A top surface of mechanical linkage interface  420  contacts a bottom surface of dispensing chamber housing  425 . In this embodiment, the protrusions on the bottom end on plunger  505  and the bottom surface of dispensing chamber housing  425  form a plunger stop mechanism. Plunger  505  cannot be advanced any further than the point at which the top surface of mechanical linkage interface  420  contacts the bottom surface of dispensing chamber housing  505 . Such a plunger stop mechanism can provide a safety feature, such as to prevent plunger  505  from contacting needle  210  and possibly dislodging it. In another embodiment consistent with the principles of the present invention, such a plunger stop mechanism may also include a locking mechanism so that plunger  505  cannot be retracted or moved away from needle  210  when needle  210  is removed from the eye. Such a plunger lock mechanism helps to prevent reflux of the substance when needle  210  is removed. 
         [0044]    In limited reuse assembly  250 , power source  310  provides power to actuator  515 . An interface (not shown) between power source  310  and actuator  515  serves as a conduit for providing power to actuator  515 . Actuator  515  is connected to actuator shaft  510 . When actuator  515  is a stepper motor, actuator shaft  510  is integral with actuator  515 . Mechanical linkage interface  545  is connected to actuator shaft  510 . In this configuration, as actuator  515  moves actuator shaft  510  upward toward needle  210  mechanical linkage  545  also moves upward toward needle  210 . 
         [0045]    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  adjacent to mechanical linkage interface  545 . In this manner, both limited reuse assembly interface connector  525  and mechanical linkage interface  545  are adapted to be connected with tip interface connector  520  and mechanical linkage interface  420  respectively. 
         [0046]    Controller  305  and actuator  515  are connected by an interface (not shown). This interface (not shown) allows controller  305  to control the operation of actuator  515 . In addition, an optional interface (not shown) between power source  310  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  310  when power source  310  is a rechargeable battery. Controller  305  may also control the current provided to fuse assembly  555  in order to illuminate the optional light and blow the fuse. Controller  305  may also detect if the fuse has been blown. 
         [0047]    Tip segment  205  is adapted to mate with or attach to limited reuse assembly  250  as previously described. In the embodiment of  FIG. 5 , mechanical linkage interface  420  located on a bottom surface of plunger  505  is adapted to connect with mechanical linkage interface  545  located near a top surface of limited reuse assembly housing  255 . In addition, tip interface connector  520  is adapted to connect with limited reuse assembly interface connector  525 . When tip segment  205  is connected to limited reuse assembly  250  in this manner, actuator  515  and actuator shaft  510  are adapted to drive plunger  505  upward toward needle  210 . In addition, an interface is formed between controller  305  and heater  450 . A signal can pass from controller  305  to heater  450  through interface  535 , limited reuse assembly interface connector  525 , tip interface connector  520 , and heater interface  530 . 
         [0048]    In operation, when tip segment  205  is connected to limited reuse assembly  250 , controller  305  controls the operation of actuator  515 . Actuator  515  is actuated and actuator shaft  510  is moved upward toward needle  210 . In turn, mechanical linkage interface  545 , which is connected to mechanical linkage interface  420 , moves plunger  505  upward toward needle  210 . A substance located in dispensing chamber  405  is then expelled through needle  210 . 
         [0049]    In addition, controller  305  controls the operation of heater  450 . Heater  450  is adapted to heat an outside surface of dispensing chamber housing  425 . Since dispensing chamber housing  425  is at least partially thermally conductive, heating dispensing chamber housing  425  heats a substance located in dispensing chamber  405 . Temperature information can be transferred from thermal sensor  460  through interface  530 , tip interface connector  520 , limited reuse assembly interface connector  525 , and interface  535  back to controller  305 . This temperature information can be used to control the operation of heater  450 . Typically, controller  305  controls the amount of current that is sent to heater  450 . The more current sent to heater  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 heater  450 . Any suitable type of control algorithm, such as a proportional integral derivative (PID) algorithm, can be used to control the operation of heater  450 . 
         [0050]    Controller  305  is also adapted to operate fuse assembly  555 . In this manner, controller  305  directs current to flow from power source  310  to fuse assembly  555 . As previously depicted in  FIG. 3 , fuse assembly  555  includes a fuse and an optional light connected in series. A current passing through optional light  275  and fuse  375  illuminates optional light  275 . After the tip segment  205  has been used (after the substance has been dispensed), controller  305  directs an increased current to blow fuse  375  and extinguish optional light  275 . This indicates that the tip segment  205  has been used and that it should be discarded. In addition, controller  305  may check fuse  375  to see if it is blown. In such a case, tip segment  205  is rendered inoperable. Alternatively, fuse  375  may be placed such that when it is blown, no power is delivered to the tip segment. In such a case, once fuse  375  is blown, optional light  275  is extinguished and the tip segment is rendered inoperable. Other indicators on the limited reuse assembly  250  or the charging base (not shown) may indicate that the fuse  375  is blown. 
         [0051]      FIG. 6  is a flow chart depicting one method of operating the present invention. In  605  a connection between a tip segment and a limited reuse assembly is recognized. In  610 , a determination is made as to whether or not a fuse has been blown. If the fuse has been blown, then in  640 , the tip segment is prevented from being used. If the fuse has not been blown, then in  615 , an optional light is illuminated indicating that the tip segment is ready to be used. In  620 , after the tip segment has been used, the fuse is blown by an increased current. In  625 , the optional light is extinguished. In  630 , the tip segment is prevented from being reused. 
         [0052]    From the above, it may be appreciated that the present invention provides an improved system and methods 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 universal hand piece limited reuse assembly. The disposable tip segment is provided with a fuse that indicates whether or not it is ready to be used. The fuse prevents the reuse of the disposable tip segment. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. 
         [0053]    While the present invention is described in the context of a single-use drug delivery device, the present invention encompasses any single-use medical device that interfaces with a source of electric power. 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.