Abstract:
A punctal plug is disclosed, wherein the punctal plug includes a body portion and a retaining portion. The body portion is defined by an open distal end, an open proximal end and a wall portion. The wall portion further includes at least one window extending therethrough. The retaining flange is configured to have an outer periphery that is larger than the outer periphery of the body portion. A method of delivering a therapeutic agent to a patient using a punctal plug is also disclosed.

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to the field of implantable ocular devices, pharmaceutics, and methods of drug delivery to the eye. More particularly, the present disclosure relates to implantable ocular devices for sustained delivery of a therapeutic compound to the eye. 
     BACKGROUND 
     Glaucoma is the leading cause of blindness worldwide and the most common cause of optic neuropathy. Various forms of glaucoma leads to elevated intraocular pressure, and may also lead to damage to the optic nerve. If glaucoma or ocular hypertension is detected early and treated promptly with medications that effectively reduce elevated intraocular pressure, loss of visual function or its progressive deterioration can generally be ameliorated. Drug therapies that have been proven useful for the reduction of intraocular pressure include both agents that decrease aqueous humor production and agents that increase the outflow facility. Such therapies may be administrated in a number of different ways. 
     One example of administrating suitable therapies includes topical application to the eye, such as eye drops. However, one of the limitations of topical therapy is inadequate and irregular delivery of the therapeutic agent to the eye. For example, when an eye drop is applied to the eye, a substantial portion of the drop may be lost due to overflow of the lid margin onto the cheek. Moreover, compliance with a necessary drug regime is also always an issue with this method. For example, for some medications, 4 to 5 applications a day are required to achieve therapeutic drug levels. 
     Other suitable delivery mechanisms for therapeutic devices include injection at the pars plana. However, aside from discomfort for the patient, this method also requires that the patient return monthly. 
     Various ocular drug delivery implants have also been employed in an effort to improve and prolong drug delivery. One such example includes a reservoir drug-delivery device. A reservoir drug-delivery device is a device that contains a receptacle or chamber for storing the drug while implanted in the eye. However, reservoir drug devices are difficult to manufacture, difficult to achieve drug content uniformity (i.e., device to device reproducibility, particularly with small ocular devices), and carry the risk of a “dose dump” if they are punctured. 
     Another type of drug delivery device is a punctal plug device that is inserted into one or more of the tear ducts within the eye. However, because the geometry of the tear duct varies from person to person, there have been problems with plugs migrating within the tear duct. Other issues occur whereby the punctal plugs may inadvertently fall out of the eye. 
     Accordingly, there exists a need for a therapeutic delivery mechanism that allows for controlled and sustained release of ophthalmic drugs over a predetermined period of time, while sufficiently securing the delivery device within the eye so as to prevent inadvertent migration or removal of the delivery device. 
     BRIEF SUMMARY 
     A punctal plug is disclosed, wherein the punctal plug includes a body portion and a retaining portion. The body portion is defined by an open distal end, an open proximal end and a wall portion. The wall portion further includes at least one window extending therethrough. The retaining flange is configured to have an outer periphery that is larger than the outer periphery of the body portion. A method of delivering a therapeutic agent to a patient using a punctal plug is also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present disclosure will now by described by way of example in greater detail with reference to the attached figures, in which: 
         FIG. 1  is a perspective view of a distal end of a delivery device with a punctal plug releasably connected thereto; 
         FIG. 2  is a perspective view of an exemplary embodiment of a punctal plug; 
         FIG. 3  is a perspective view of the punctal plug of  FIG. 2  with an exemplary therapeutic compound disposed therein; 
         FIG. 4  is a front, partially sectional view of a lacrimal duct system of a mammalian eye with a punctal plug disposed therein; and 
         FIG. 5  is an enlarged front sectional view of the lacrimal canaliculi of  FIG. 4 , with a punctal plug disposed therein. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the discussion that follows and also to the drawings, illustrative approaches to the disclosed devices and methods are shown in detail. Although the drawings represent some possible approaches, the drawings are not necessarily to scale and certain features may be exaggerated, removed, or partially sectioned to better illustrate and explain the present disclosure. Further the descriptions set forth herein are not intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and configurations shown in the drawings and disclosed in the following detailed description. 
     Referring to  FIGS. 1-5 , an exemplary arrangement of a punctal plug  10  is illustrated. Punctal plug  10  includes a body portion  12  and a retaining flange  14 . Body portion  12  includes an open distal end  16  and an open proximal end  18  that is in communication with retaining flange  14 . Formed within body portion  12  is at least one window  20 . In one exemplary arrangement, a plurality of windows  20  are formed, separated by land members  22 . Windows  20  may be formed so as to be spaced equi-distant from one another. Body portion  12  of punctal plug  10  may be made from a biocompatible material such as titanium, stainless steel, plastics, elastomers or any other material which may be formed into body portion  12 . 
     In one exemplary arrangement, at least one cross-member  24  is disposed within body portion  12 . Alternatively, a pair of cross-members  24  is provided. Each cross-member  24  is defined by ends  25  that are fixedly secured to an inner wall  26  of body portion  12 . In one exemplary arrangement, cross-members  24  are arranged within body portion  12  in an intersecting manner, such that one cross-member  24   a  is disposed above the other cross-member  24   b . In another exemplary arrangement, cross-members  24   a ,  24   b  are integrally connected together so as to lie along a common plane (not shown). Cross-members  24  are also constructed of a biocompatible material, whereby the material allows for some degree of flexibility, as will be explained below in further detail. 
     Retaining flange  14  is defined by a distal end  28  and a proximal end  30 . Distal end  28  is defined by a diameter that generally corresponds to the diameter of proximal end  18  of body portion  12 . Proximal end  30  is defined by a diameter that is larger than the diameter of distal end  28  and body portion  12 . In one exemplary arrangement, an interior surface  32  slopes outwardly from distal end  28  to proximal end  30 . 
     As shown in  FIG. 1 , a delivery device  34  is shown releasably connected to punctal plug  10 . More specifically, delivery device  34  includes a delivery cannula  36  having a distal end that secures to interior surface  32  of retaining flange  14 . In one exemplary arrangement, the distal end of delivery cannula  36  includes retaining apertures (not shown) that releasably receives retaining members  38  that extend from interior surface  32 . More specifically, retaining members  38  may be constructed of a flexible material that permits selective engagement and disengagement between punctal plug  10  and delivery cannula  36 . Alternatively, the distal end of delivery cannula  36  may be provided with retaining members that engage complementary retaining apertures (not shown) formed on interior surface  32 . Other suitable mechanisms for releasably securing punctal plug  10  to deliver cannula  36  are also within the scope the present disclosure. 
     Turning now to  FIGS. 4 and 5 , the lacrimal duct system  100  of a mammalian eye  102  will be described. System  100  includes a lower punctum  104  connected to a lower lacrimal canaliculus  106 , and an upper punctum  108  connected to an upper lacrimal canaliculus  110 . Canaliculli  106  and  110  are connected to a lacrimal sac  112  and a nasolacrimal duct  114 . A lacrimal gland  116  is connected to eye  102  via a lacrimal duct  118 . In general, tears are produced by lacrimal gland  116  and are provided to eye  102  via lacrimal duct  118 , and tears are drained from  102  via punctum  108  and canaliculus  110 , punctum  104  and canaliculus  106 , and nasolacrimal duct  114 . 
     In operation, punctal plug  10  is secured to the distal end of delivery cannula  36 . Delivery cannula  36  is secured to a suitable drug supply. Once secured to delivery cannula  36 , but before a drug  40  is injected into punctal plug  10  via delivery cannula  36 , distal end  16  is implanted into either lower or upper punctums  104 ,  106 . In  FIGS. 4 and 5 , distal end  16  of body portion  12  of punctal plug  10  is implanted into lower punctum  104  until retaining flange  14  contacts an outer surface of the eye. Once positioned, a suitable therapeutic drug is injected through delivery cannula  36  and into punctal plug  10 . More specifically, a phase transition drug formulation  40  is injected through delivery cannula  36  into punctal plug  10 . Because body portion  12  includes at least one window  20 , a portion of phase transition drug formulation  40  flows through window  20  and some also flows out distal end  16  of body portion  12 , as shown in  FIG. 3 . This action causes drug formulation to conform to the irregular shape of the walls of lower punctum  104 . As drug formulation  40  cools, it solidifies into a drug bolus such that the drug formulation  40  serves to lock punctal plug  10  into place in lower punctum  104 , thereby preventing migration of punctal plug  10 , as well as preventing inadvertent dislodgement of punctal plug  10  from punctum  104 . As shown in  FIG. 5 , because drug formulation is able to conform to the irregularities in shape of the punctum, puntal plug  10  is able to adapt to various contours of the respective punctums without requiring unique geometry for each plug  10  for each individual into which the puntal plug  10  is inserted. 
     Further, when injected, drug formulation  40  also flows around cross-members  24 . Because cross-members  24  have some degree of flexibility, as drug formulation  40  flows into punctal plug  10 , cross-members  24  serve to generally retain the basic shape of punctal plug  10  to keep punctal plug  10  properly positioned within the punctum  104 , but allow some degree of flexing of body portion  12 . Further, as drug formulation  40  cools, the drug bolus attaches to cross-members  24 , thereby locking the drug bolus into punctal plug  10 , such that the drug bolus itself is prevented from migrating down punctums  104  and  106 . Windows  20  also may aid in the locking effort. 
     Once drug formulation  40  has been injected and permitted to solidify, punctal plug  10  is released from delivery cannula  36 , thereby leaving punctal plug  10  in place within the eye. In one embodiment, forceps may be utilized to release delivery cannula  36  from punctal plug  10 . Drug formulation  40 , which is retained within punctal plug  10 , is configured to allow for sustained release of ophthalmic drugs over a predetermined period of time (e.g., 3-6 months). Other predetermined time periods are also possible (e.g., 1-2 days, 1-2 months, 1 year, etc). As drug formulation  40  is released into the patient over time, the drug bolus shrinks such that punctal plug detaches from the interior wall of punctum  104 ,  106 . Once so released, punctal plug  10  may be easily removed in a non-invasive manner. 
     It will be appreciated that the devices and methods described herein have broad applications. The foregoing embodiments were chosen and described in order to illustrate principles of the methods and apparatuses as well as some practical applications. The preceding description enables others skilled in the art to utilize methods and apparatuses in various embodiments and with various modifications as are suited to the particular use contemplated. In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been explained and illustrated in exemplary embodiments. 
     It is intended that the scope of the present methods and apparatuses be defined by the following claims. However, it must be understood that this invention may be practiced otherwise than is specifically explained and illustrated without departing from its spirit or scope. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the claims without departing from the spirit and scope as defined in the following claims. The scope of the invention should be determined, not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that future developments will occur in the arts discussed herein, and that the disclosed systems and methods will be incorporated into such future examples. Furthermore, all terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those skilled in the art unless an explicit indication to the contrary is made herein. In particular, use of the singular articles such as “a,” “the,” “said,” etc. should be read to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. In sum, it should be understood that the invention is capable of modification and variation and is limited only by the following claims.