Abstract:
An ophthalmic injection device has a dispensing chamber housing, a plunger, a needle fluidly coupled to a dispensing chamber, a temperature control device, a power source for providing power to the temperature control device, a controller for controlling the temperature control device, and a mechanical linkage mechanism. The interior surface of the dispensing chamber housing partially defines a dispensing chamber for holding a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. A plunger shaft is coupled to the plunger. The temperature control device can alter the temperature of the substance contained therein. The mechanical linkage mechanism has at least two pivots and at least two shafts and transfers force from a lever to the plunger.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of U.S. patent application Ser. No. 11/581,629 filed Oct. 16, 2006 and 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 an ophthalmic drug delivery device with a mechanical linkage mechanism. 
         [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. 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. 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. Ypsomed, Inc. of Switzerland produces a line of injection pens and automated injectors primarily for the self-injection of insulin or hormones by a patient. This product line includes simple disposable pens and electronically-controlled motorized injectors. 
         [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 that includes reliable technology. A mechanical lever can be utilized to provide accurate translation of a plunger to deliver a substance. The lever configuration can be such that it is activated by a finger or thumb to deliver a precise dosage. The hand piece may be a single piece unit or a two-piece device. Placing the more expensive components, including electronics and a battery, in a reusable assembly, while keeping the sterile components in a disposable assembly, improves the efficiency and cost-effectiveness of a drug delivery system. However, a single piece device with a relatively simple structure is also feasible. Such a system provides numerous benefits over prior art injectors. 
       SUMMARY OF THE INVENTION 
       [0009]    In one embodiment consistent with the principles of the present invention, the present invention is an ophthalmic injection device having a dispensing chamber housing, a plunger, a needle, a temperature control device, a power source for providing power to the temperature control device, a controller for controlling the temperature control device, and a mechanical linkage mechanism. The dispensing chamber housing has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. A plunger shaft is coupled to the plunger. The needle is fluidly coupled to the dispensing chamber. The temperature control device at least partially surrounds the dispensing chamber housing and is capable of altering the temperature of the substance in the dispensing chamber. The mechanical linkage mechanism has at least two pivots and at least two shafts and transfers force from a lever to the plunger. 
         [0010]    In another embodiment consistent with the principles of the present invention, the present invention is an ophthalmic injection device having a tip segment attachable to and removable from a limited reuse assembly. The tip segment has a dispensing chamber housing, a plunger, a needle, and a temperature control device. The limited reuse assembly has a power source for providing power to the temperature control device, a controller for controlling the temperature control device, and a mechanical linkage mechanism. The dispensing chamber housing has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. The plunger has a plunger interface for coupling with a plunger shaft. The needle is fluidly coupled to the dispensing chamber. The temperature control device at least partially surrounds the dispensing chamber housing and is capable of altering the temperature of the substance in the dispensing chamber. The mechanical linkage mechanism has at least two pivots and at least two shafts and transfers force from a lever to the plunger. 
         [0011]    In another embodiment consistent with the principles of the present invention, the present invention is an ophthalmic injection device having a tip segment attachable to and removable from a limited reuse assembly. The tip segment has a dispensing chamber housing, a plunger, a needle, a temperature control device, and a mechanical linkage mechanism. The dispensing chamber housing has an inner surface and an outer surface. The inner surface partially defines a dispensing chamber for holding a quantity of a substance. The plunger is engaged with the inner surface of the dispensing chamber housing, is capable of sliding in the dispensing chamber housing, and is fluidly sealed to the inner surface of the dispensing chamber housing. The plunger has a plunger interface for coupling with a plunger shaft. The needle is fluidly coupled to the dispensing chamber. The temperature control device at least partially surrounds the dispensing chamber housing and is capable of altering the temperature of the substance in the dispensing chamber. The mechanical linkage mechanism has at least two pivots and at least two shafts and transfers force from a lever to the plunger. The limited reuse assembly has a power source for providing power to the temperature control device and a controller for controlling the temperature control device. 
         [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 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. 
           [0014]      FIG. 1  is a perspective view of a prior art syringe. 
           [0015]      FIG. 2  is one view of an ophthalmic medical device including a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. 
           [0016]      FIG. 3  is a cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. 
           [0017]      FIG. 4  is an exploded cross section view of a tip segment for an ophthalmic medical device according to an embodiment of the present invention. 
           [0018]      FIG. 5  is a cross section view of an ophthalmic injection device according to the principles of the present invention. 
           [0019]      FIG. 6  is a cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. 
           [0020]      FIGS. 7A and 7B  are cross section views of a mechanical linkage mechanism according to the principles of the present invention. 
           [0021]      FIGS. 8A-8C  are diagrams showing the trigonometric relationship of a mechanical linkage mechanism according to the principles 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  is one view of an ophthalmic medical device including a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. In  FIG. 2 , the medical device includes a tip segment  205  and a limited reuse assembly  250 . The tip segment  205  includes a needle  210 , a housing  215 , and an optional light  275 . The limited reuse assembly  250  includes a housing  255 , a switch  270 , a lock mechanism  265 , a lever  350 , 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 disposable tip segment  205 . 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 . While shown on tip segment  205 , optional light  275  or other indicator may be located on limited reuse assembly  250 . 
         [0028]      FIG. 3  is cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention.  FIG. 3  shows how tip segment  205  interfaces with limited reuse assembly  250 . In the embodiment of  FIG. 3 , tip segment  205  includes dispensing chamber housing  425 , tip segment housing  215 , thermal sensor  460 , needle  210 , dispensing chamber  405 , plunger  415 , plunger shaft  380 , temperature control device  450 , interface  530 , tip interface connector  453 , and a mechanical linkage mechanism comprising lever  350 , pivot  365 , shaft  355 , coupling  370 , shaft  360 , and pivot  375 . Limited reuse assembly  250  includes power source  505 , controller  305 , limited reuse assembly housing  255 , interface  535 , and limited reuse assembly interface connector  553 . 
         [0029]    In tip segment  205 , plunger  415  is adapted to slide within dispensing chamber  405 . The 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. 
         [0030]    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 . In this case, temperature control device  450  is adapted to heat and/or cool dispensing chamber housing  425  and any substance contained in dispensing chamber  405 . Interface  530  connects temperature control device  450  with tip interface connector  453 . 
         [0031]    Optional thermal sensor  460  provides temperature information to assist in controlling the operation of temperature control device  450 . Thermal sensor  460  may be located near dispensing chamber housing  425  and measure a temperature near dispensing chamber housing  425  or may be located in thermal contact with dispensing chamber housing  425 , in which case it measures a temperature of dispensing chamber housing  425 . Thermal sensor  460  may be any of a number of different devices that can provide temperature information. For example, thermal sensor  460  may be a thermocouple or a resistive device whose resistance varies with temperature. Thermal sensor is also electrically coupled to interface  530  or other similar interface. 
         [0032]    The components of tip segment  205 , including 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  is typically a rechargeable battery, such as a lithium ion battery, although other types of batteries may be employed. In addition, any other type of power cell is appropriate for power source  505 . Power source  505  provides current to dispensing chamber housing  425  to heat it and change its shape. Optionally, power source  505  can be removed from housing  255  through a door or other similar feature (not shown). 
         [0034]    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 current delivered to dispensing chamber housing  425 . 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 in  FIG. 4 , controller  305  may be made of many different components or integrated circuits. 
         [0035]    Controller  305  is connected via interface  535  to limited reuse assembly interface connecter  553 . Limited reuse assembly interface connecter  553  is located on a top surface of limited reuse assembly housing  255 . In this manner, limited reuse assembly interface connector  553  is adapted to be connected with tip interface connector  453  to provide an electrical connection between tip segment  205  and limited reuse assembly  250 . 
         [0036]    An interface between power source  505  and controller  305  allows controller  305  to control operation of power source  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. 
         [0037]    In operation, when tip segment  205  is connected to limited reuse assembly  250 , the device is ready to be used for an injection. When lever  350  is actuated, coupling  370  moves towards tip segment housing  215 . Shaft  360  is rotated moving pivot  375  and plunger  415  upward toward needle  210 . A substance located in dispensing chamber  405  is then expelled through needle  210 . 
         [0038]    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  and its contents. 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  through interface  530 , tip interface connector  453 , limited reuse assembly interface connector  553 , and interface  535  back to controller  305 . 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 . 
         [0039]    A substance to be delivered into an eye, typically a drug suspended in a phase transition compound, is located in dispensing chamber  405 . In this manner, the drug and phase transition compound are contacted by the inner surface of dispensing chamber housing  425 . The phase transition compound is in a solid or semi-solid state at lower temperatures and in a more liquid state at higher temperatures. Such a compound can be heated by the application of current to temperature control device  450  to a more liquid state and injected into the eye where it forms a bolus that erodes over time. 
         [0040]    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, 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. 
         [0041]      FIG. 4  is an exploded cross section view of a tip segment for an ophthalmic medical device according to an embodiment of the present invention. In  FIG. 4 , tip segment  205  includes dispensing chamber housing  425 , tip segment housing  215 , thermal sensor  460 , needle  210 , dispensing chamber  405 , plunger  415 , plunger shaft  380 , temperature control device  450 , interface  530 , tip interface connector  453 , an optional luer  430 , and a mechanical linkage mechanism comprising lever  350 , pivot  365 , shaft  355 , coupling  370 , shaft  360 , and pivot  375 . Optional luer secures needle  210  to dispensing chamber housing  425 . 
         [0042]    In the embodiment of  FIG. 4 , temperature control device  450  is activated to bring a substance in dispensing chamber  405  to the proper temperature. Thermal sensor  460  provides temperature information to controller  305  (not shown) to control temperature control device  450 . After the substance has reached the proper temperature, lever  350  is actuated to drive plunger toward needle  210  to dispense a substance contained in dispensing chamber  405 . 
         [0043]    The mechanical linkage mechanism that includes lever  350  is designed to use a force applied to lever  350  to translate plunger  415  within dispensing chamber housing  425 . Lever  350  is hand actuated with a finger or thumb. In one embodiment, a thumb is used to rotate lever  350  about pivot  365 . Since lever  350  is rigidly connected to shaft  355 , when lever  350  is rotated upward about pivot  365 , shaft  355  rotates downward about pivot  365 . This in turn causes coupling  370  to rotate downward about pivot  365 . Shaft  360  rotates downward about pivot  375  moving plunger shaft  380  (and plunger  415  to which plunger shaft  380  is rigidly connected) toward needle  210 . The movement of plunger  415  dispenses the substance contained in dispensing chamber  405 . 
         [0044]      FIG. 5  is a cross section view of an ophthalmic injection device according to the principles of the present invention. In  FIG. 5 , the injection device is integrated into a single unit. The single piece device of  FIG. 6  operates in the same manner as the two piece device previously described. In  FIG. 6 , the device includes dispensing chamber housing  425 , dispensing chamber  405 , needle  210 , thermal sensor  460 , interface  536 , controller  305 , power source  505 , and housing  216 . In  FIG. 6 , a single interface  536  is used instead of two separate interfaces ( 530  and  535 ) and two separate connectors ( 453  and  553 ). Housing  216  encloses the components pictured. 
         [0045]      FIG. 6  is cross section view of a disposable tip segment and a limited reuse assembly according to an embodiment of the present invention. In  FIG. 6 , the mechanical linkage mechanism is in limited reuse assembly  250  and not in tip segment  205  as depicted in  FIG. 3 . In  FIG. 6 , plunger shaft  380  interfaces with plunger  415  at plunger interface  420 . Any number of different interfaces can be used including interfaces that are rigidly connected when engaged or those in which force is only transferred in a single direction (as shown in  FIG. 6 ). The embodiment of  FIG. 6  has the characteristics and operates in the same manner as the embodiment of  FIG. 3 . 
         [0046]      FIGS. 7A  and B are cross section views of a mechanical linkage mechanism according to the principles of the present invention. In  FIG. 7A , lever  350  has not been actuated. In  FIG. 7B , lever  350  has been actuated and a substance  650  has been dispensed from dispensing chamber  405 . 
         [0047]    In  FIGS. 7A and 7B , lever  350  is rigidly connected to shaft  355 . Pivot  365  is disposed between lever  350  and shaft  355  so as to provide a first rotation point. Pivot  365  is stationary. A rotatable coupling  370  joins shaft  355  to shaft  360 . In this manner, shaft  355  can rotate with respect to shaft  360 . Pivot  375  connects shaft  360  to plunger shaft  380 . In this manner, shaft  360  rotates about pivot  375 . Pivot  375  moves in a direction along plunger shaft  380 . Since plunger shaft  380  is constrained to move only in a direction along dispensing chamber housing  425 , plunger shaft  380  does not rotate. Instead, when shaft  360  rotates about pivot  375 , plunger shaft  380  moves in dispensing chamber housing  425 . 
         [0048]    When a force is applied to lever  350 , lever  350  and shaft  355  rotate about pivot  365 . When the force rotates lever  350  upward, shaft  355  is rotated downward. Coupling  370  is moved downward along the arc of a circle with a radius equal to the length of shaft  355  and with its center at pivot  365 . As coupling  370  moves, shaft  360  also moves. In this case, shaft  360  moves generally downward and rotates about pivot  375 . Pivot  375  moves along an axis defined by plunger shaft  380 . As shaft  360  moves downward, pivot  375  moves toward needle  210 . Plunger  415  moves in dispensing chamber housing  425  to expel substance  460  as shown in  FIG. 6B . 
         [0049]      FIGS. 8A-8C  are diagrams showing the trigonometric relationship of a mechanical linkage mechanism according to the principles of the present invention. In  FIGS. 8A-8C , Φ measures the angle of the arc through which coupling  370  travels. This is also the angle through which lever  350  and shaft  355  rotates. The point (X 370 , Y 370 ) is the position of coupling  370 . The angle α is the complement of the angle through which shaft  360  travels. In other words, α measures the angle from an axis defined by plunger shaft  380  to shaft  360 . L 1  is the length of shaft  360 , L 2  is the length of plunger shaft  380 , and L 3  is the length of shaft  355 . Pivot  365  is stationary and pivot  375  moves only in a direction along the dashed straight arrow. The point (X 375 , Y 375 ) is the position of coupling  375 . The distance D Y  is the distance between pivot  365  and the dashed line along which plunger shaft  380  travels. Given these parameters, a simple trigonometric relationship among the various components is shown. 
         [0050]    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 mechanical linkage mechanism that can be easily actuated by the hand to deliver a substance into an eye. In one embodiment, a disposable tip segment that interfaces with a limited reuse assembly is employed. In another embodiment, a single unit is employed. The present invention is illustrated herein by example, and various modifications may be made by a person of ordinary skill in the art. 
         [0051]    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.