Abstract:
A microsurgical instrument used in ophthalmic surgery to remove proliferative membranes during a surgical procedure treating proliferative vitreoretinal membrane disorders and other macular diseases where the microsurgical instrument has a instrument handle, a tip, and abrasive particles attached to a scraping edge projecting beyond the tip. The microsurgical instrument may be fitted with infusion, aspiration, or illumination sources, and these sources are directed to the surgical site in proximity to the scraping edge, the abrasive particles on the edge scrape membranes to remove tissue at the surgical site. In one embodiment, the microsurgical instrument may be configured with a retractable/extendable pick where the relative stiffness of the pick and the edge may be adjusted. In another embodiment the edge may also be angularly positionable as it is retracted/extended from the microsurgical instrument.

Description:
This application is a continuation of provisional patent application serial No. 60/153,574 filed Sep. 13, 1999, presently pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a type of microsurgical instrument used in treatment of intraocular diseases such as proliferative vitreoreitnal disorders. The microsurgical tool may be configured to provide the surgeon with improved methods for the removal of proliferative membranes from the surface of the retina or for the removal of residual cortical vitreous proliferative membranes from the areas surrounding the macular hole. 
     2. Description of the Background 
     Proliferative vitreoretinal disorders are manifested in the intraocular cavity of the eye by the growth of proliferative membranes on the neurosensory retina. In the conventional treatment for vitreoretinal disorders, the membranes are removed from the neurosensory membranes with various microsurgical instruments such as intraocular forceps and intraocular picks. The microsurgical instruments are introduced into the intraocular cavity through an incision in the eye, and the membranes are carefully removed from the neurosensory surface of the retina without causing tears or hemorrhages. 
     Depending on the stage of the disorder and the growth of the membranes, the membranes have a different texture and composition. Mature membranes tend to be removed with less complication when compared with the removal of immature membranes. With conventional intraocular forceps and picks, the surgeon is generally able to remove mature membranes from the surface of the retina as a film. When the mature membranes are removed as a film, more complete removal from the surface of the retina is possible with a lower chance of membranes remaining on the surface. On the other hand, immature membranes tend to be friable in nature because they have not acquired the necessary cross-section to be removed with conventional intraocular picks and intraocular forceps. Being friable in texture, the immature membranes do not peel of as a film, and consequently, immature membranes, which are not fully removed during surgery, may be a nidus for future membrane formation, causing the patient to undergo future operations for removal of these membrane formations. 
     A recent invention, effective in the treatment of proliferative vitreoretinal disorders, has been developed to mechanically remove mature and immature proliferative membranes from the neurosensory surface of the retina without the use of intraocular picks or intraocular forceps. This invention described by Tano, et al. (U.S. Pat. No. 5,921,998 (&#39;998), incorporated herein by reference) uses an abrasive media on a tip of the microsurgical instrument to scrape the membranes from the surface of the retina. The advantages of this invention are a reduced chance of retinal tearing and hemorrhaging and the ability to remove membranes despite the stage of the growth of the membrane. 
     The abrasive media of the &#39;998 instrument is affixed on the distal end of a straight probe. The straight probe is introduced into the eye through a cannula that is inserted through an incision into the intraocular cavity in the eye. The abrasive media described in the &#39;998 patent may be diamond, silicone carbide, quartz, or alumina. The abrasive particles are biologically inert and bonded to the distal end of the probe in a manner such that the shedding of particle into the retinal tissue is avoided. By using different instruments having tips with varying types of abrasive particles, it is possible for the surgeon to more carefully separate and remove these proliferative membranes from the retina without causing damage to the retina. The removal rate may be varied depending upon the type of particles that are bonded to the tip of the microsurgical instrument, where the rate of tissue removal is in proportion to the coarseness of the particles bonded to the tip. The surgeon may more carefully control the removal rate of the proliferative membranes ensuring retinal tears and other damage to the retina does not occur, in distinction to other methods that use intraocular picks and forceps to remove the proliferative membranes. 
     During surgery for the treatment of vitreoretinal disorders, the surgeon may use in conjunction with these previously mentioned surgical instruments other more common surgical instruments to execute the other functions required during the operation. These microsurgical instruments are also introduced into the intraocular cavity through the cannula. A common instrument is one that is designed to deliver an aspiration source locally to an area to remove tissue. Another common instrument is used to provide infusion to the surgical area for irrigation and flushing as required. The surgeon may use a combination of these instruments and techniques to condition the surface of the retina and remove membranes by the devices previously mentioned. In some conventional instruments, a single instrument capable of performing both of these functions has been used to perform both aspiration and infusion functions. 
     Other common instruments aid in the visualization of the surgical site. Often the surgeon wishes to illuminate the surgical site or surface of the retina for more complete visualization of the membranes. In conventional instruments, the surgical site may be illuminated or visualized by a fiber optic cable fitted into a probe that is inserted through the cannula into the eye. The fiber optic cable may also be fitted onto a conventional probe to transmit a video picture signal back to a display to give the surgeon a visual image of the surgical site on the surface of the retina. This enhanced visual representation of the surface of the retina allows the surgeon to evaluate the operation and to more completely remove the proliferative membranes during the operation. 
     Generally, during the course of the operation, the surgeon must alternate between probes to carry out the specific function required at a particular stage of the operation. When changing probes, the old probe must be removed from the cannula and a new probe must be inserted. Generally, the type of cannula used is either straight or curved depending upon the instruments to be used during the surgery and the location of the surgical site in relation to the incision site. Curved probes cannot be inserted through straight cannulas, and straight probes cannot be inserted through curved cannulas. In a surgical procedure using these conventional instruments, the surgeon must make an initial choice to the style or cannula and instrument to be used during the operation. 
     Sometimes, the surgeon will find that during the course of the operation, a surgical instrument having a straight probe will not efficiently deliver aspiration or infusion to the target area. This may be due to the positioning of the incision or instrument entry site in the eye relative to the target surgical site. The surgeon may decide that a curved probe would provide better range to deliver infusion or aspiration to the surgical site. This change also requires a change in the style of cannula or the use of the probe through the eye incision itself. Such a changeover complicates the operation and often produces additional and sometimes harmful stresses on the eye. Similarly, the delivery of the optical fiber to the surgical site is generally through a straight probe so that the surgeon may directly visualize or illuminate the affected area. Curved probes may also be used with curved cannulas that are aimed to the surgical site. The changeover also complicates the operation and often produces additional and sometimes harmful stresses on the eye. 
     To overcome these disadvantages of prior art microsurgical instruments used during ophthalmic surgical operations, what is needed is a microsurgical instrument, which combines the functions of infusion and aspiration with abrasive membrane scraping or the functions of illumination with abrasive membrane scraping. The invention could be provided in an adjustable curved member that is adaptable to a straight cannula, thus providing the surgeon with increased range for membrane scraping. The invention could also be provided in a pick and scraping device that could increase the versatility of the instrument introduced to the surgical site. Such an invention would thereby increase the likelihood of success of an operation for removal of vitreoretinal proliferative membrane disorders and other intraocular diseases without undue stress on the tissue surrounding the entry incision. 
     SUMMARY OF THE INVENTION 
     The microsurgical instrument of the present invention allows the surgeon to treat proliferative vitreoretinal membrane disorders more effectively with less chance of hemorrhaging and tearing. The microsurgical instrument of the present invention combines the advantages of abrasive membrane scraping with the features of aspiration/infusion, and the advantages of abrasive membrane scraping with illumination. In the preferred embodiments of the invention, the microsurgical tool is configured with abrasive particles that are made from synthetic diamond. The diamond particles are preferably contained on a film that is bonded to the distal end portion of the microsurgical instrument. The microsurgical instrument may then be introduced into the intraocular cavity through a straight cannula inserted in through an incision in the eye. 
     In one embodiment of the apparatus of the invention, the illuminated diamond dusted membrane scraper, the microsurgical instrument has the ability to scrape the membrane surface while providing illumination of the surface to be treated. In this embodiment the apparatus of the invention includes an instrument handle, a tip extending outward and away from the instrument handle, and an adapter fitted onto a distal end of the tip. Preferably, the adapter is cylindrical in shape and has a bevel section-cut across its outside cylindrical surfaces. The abrasive particles are bonded to the outermost tip of the adapter. The instrument handle, tip, and adapter have hollow interiors that are configured to receive and encase an optical fiber. The optical fiber is capable of transmitting/receiving visual imagery or providing illumination. The optical fiber may be positioned through the bevel section-cut in the adapter to illuminate the adapter or transmit/receive visual images of the surgical site. Preferably, the adapter is a flexible and translucent member to facilitate scraping and transillumination. 
     The second embodiment of the present invention, the illuminated diamond dusted membrane scraper, is similarly constructed. In this embodiment of the invention, the microsurgical instrument includes an instrument handle and a tip extending outward and away from the instrument handle. The instrument handle and tip have a hollow interior; however, in this configuration, the adapter is affixed to a bracket connected to the distal end of the tip, and the adapter is positioned at an acute angle to the tip with the adapter distal end projecting away from the tip distal end. The abrasive particles are deposited on the outermost edge of the adapter. The optical fiber is positioned in the hollow interior of the instrument handle and the tip such that the operative end of the optical fiber is positioned at the distal end of the tip. In this configuration, the optical fiber may illuminate the surgical site or transmit/receive visual imagery of the surgical site. The path of transmission/receipt from the optical fiber intersects the adapter distal end. The surgical site may be illuminated or visualized directly while the surface is scraped by the adapter. 
     An additional embodiment of the apparatus of the invention has the ability to scrape membranes, while providing infusion or aspiration to the surgical site. In this configuration the microsurgical instrument includes an instrument handle, a tip extending outward and away from the instrument handle, and an adapter fitter on the distal end of the tip. The abrasive particles are contained on the adapter. The instrument handle, tip and adapter have hollow interiors. The hollow interior of the instrument handle may be configured to accept an interface from an external infusion source or an aspiration source. The microsurgical instrument may be introduced into the intraocular cavity, and the adapter may be used to scrape the retinal surfaces. The hollow interiors of the instrument handler, tip and adapter form a channel inside the microsurgical instrument to deliver infusion/aspiration functions to the surgical site. 
     In another embodiment of the apparatus of the invention, a diamond dusted membrane scraper having a pick with an adjustable stiffness is provided. In this embodiment of the invention, the microsurgical instrument includes an instrument handle, a tip extending outward and away from the instrument handle and an adapter fitted onto the tip. The instrument handle, tip, and adapter have hollow interiors that are configured receive and encase a pick that may be retracted or extended from a hole in the outermost end of the adapter. The pick has a relative stiffness that is indirectly proportional to a length of the pick exposed from the outermost end of the adapter. When the length of the exposed pick is increased, the stiffness of the pick decreases. The stiffness of the pick is adjustable through a control mechanism on the instrument handle that adjusts the length of the pick exposed from the outermost end of the adapter. The amount of stiffness of the pick is controlled by the surgeon to allow the surgeon more flexibility in removing membranes affixed to the surface of the retina. The pick may be fully retracted into the hollow interior of the microsurgical instrument so that the surgeon may utilize the scraping capability provided by abrasive particles deposited on the adapter. The surgeon may also vary the relative stiffness of the adapter by controlling the length of the pick retained in a portion of the hollow interior of the adapter. 
     In a similar embodiment of the apparatus of the invention, a directional endoscopic abrasive aspiration instrument is provided. In this embodiment of the invention, the microsurgical instrument includes an instrument handle and a tip extending outward and away from the instrument handle. The instrument handle and tip have hollow interiors that are configured to receive and encase a tube that may be retracted or extended from a hole in the distal end of the tip. The extension of the tube is adjustable through a control mechanism on the instrument handle that adjusts the length of tube exposed from the outermost end of the tip. Abrasive particles are deposited on the exterior of the tube at its distal end. Preferably, an elastic nitinol tube is used and pre-formed with a curved distal end. The curvature of the tube may be controlled by controlling the length of tube that is retracted or extended from the tip. In the fully retracted position, the tube is fully contained within the tip and may be inserted into a straight cannula into the incision in the eye. When inside the eye cavity, the tube may be extended from the tip allowing the tube to bend and curve to reach areas that may have been unreachable by a straight instrument. The hollow interior of the instrument handle may be configured to accept an external device to provide aspiration/infusion functions at the distal end of the tube. Simultaneously, the surgeon may remove membranes by scraping the retinal surfaces with the distal end of the tube. The retinal surfaces may be conditioned as required through infusion and tissue may be removed through aspiration. 
     With the constructions and arrangements of the ophthalmic microsurgical tools mentioned above, it is possible to more effectively remove the vitreoretinal proliferative membranes without excessive damage to the retina and without undue stress to the entry incision into the intraocular cavity. 
    
    
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     Further objectives and features of the invention are revealed in the following detailed description of the preferred embodiment of the invention and in the drawing figures wherein: 
     FIG. 1A is cross sectional view of one embodiment of the present invention, an infusion/aspirating diamond dusted membrane scraper; 
     FIG. 1B is an enlarged, partial view of an embodiment of an adapter for the infusion/aspirating membrane scraper of FIG. 1A; 
     FIG. 1C is an enlarged, partial view of a second embodiment of an adapter for the infusion/aspirating membrane scraper of FIG. 1A; 
     FIG. 2 is a cross sectional view of a second embodiment of the current invention, an illuminated membrane scraper; 
     FIG. 3A is a cross sectional view of a third embodiment of the present invention, an illuminated membrane scraper; 
     FIG. 3B is a enlarged, partial view of the adapter used on the illuminated membrane scraper of FIG. 3A; 
     FIG. 4A is a cross sectional view of a fourth embodiment of the present invention, a membrane scraper with adjustable stiffness pick, the pick shown in a retracted position; 
     FIG. 4B is a cross sectional view of the membrane scraper with adjustable stiffness pick of FIG. 4A, the pick shown in an extended position; 
     FIG. 5A is a cross sectional view of a fifth embodiment of the present invention, a directional endoscopic abrasive membrane scraper connected to an external aspiration source, a tip shown in a retracted position; and 
     FIG. 5B is a cross sectional view of the directional endoscopic abrasive membrane scraper of FIG. 5A, a tip shown in an extended position. 
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1A shows one embodiment of the apparatus of the present invention, an infusion and aspiration microsurgical instrument. The microsurgical instrument  10 A consists of an instrument handle  13  with opposite distal  16  and proximal ends  19 . The instrument handle  13  is a hollow cylinder arranged with an internal passage  21  running through its center axis. The instrument handle  13  may be disposable or re-useable, and is to be constructed from light-weight material compatible with common sterilization processes. The internal passage  21  provides communication between the opposite proximal  19  and distal  16  ends. At the proximal end  19  of the instrument handle  13 , the internal passage  21  is outwardly and frustoconically shaped to create a luer taper  24  for attachment to external aspiration or infusion sources  27 . Preferably, the distal end  16  of the instrument handle  13  has a counter bore  30 , and the diameter of the counter bore  30  is dimensioned so that the tip  33  may be securely press fit into the instrument handle  13 . The length of the counter bore  30  is set to provide minimum deflection of the tip  33  and to anchor the tip  33  to the instrument handle  13 . However, other methods of attaching the tip  33  to the instrument may be used. Additionally, it is possible to form the instrument handle and the tip as a monolithic unit to avoid the need to firmly secure the tip to the instrument handle. 
     The tip  33  is a tube with opposite proximal and distal ends  36 ,  39 . Preferably, the tip  33  is made from a stainless steel hypodermic tube. The tip  33  is attached to the instrument handle  13  by inserting and adhering a proximal end  36  of the tip in the counter bore  30  on the instrument handle  13  such that the distal  39  end extends outward and away from the instrument handle  13 . The distal end  39  of the tip is configured to accept an adapter  42 A. The tip  33  has a hollow core  45  that allow communication into the internal passage  21  of the instrument handle  13 . Preferably, the diameter of the hollow core  45  matches the diameter of the handle internal passage  21  to allow the smooth flow of liquid through the instrument handle  13  to the tip  33  of the microsurgical instrument  10 A. 
     As shown in FIG. 1A, the distal end  39  of the tip is provided with the adapter  42 A. Preferably, the adapter  42 A is a cylindrically shaped member having proximal and distal ends  48 ,  51  and an internal chamber  54  running between proximal and distal ends  48 ,  51 . The internal chamber  54  provides communication from the distal end  51  of the adapter  42 A into the hollow core  45  of the tip  33  and into the internal passage  21  of the instrument handle  13 . Preferably, the portion of the internal chamber  54  at the proximal end  48  of the adapter  42 A is configured to slide over the exterior of the distal end  39  of the tip  33  and securely seat on the tip  33 . Preferably, the adapter  42 A is elastic and expands to fit over the distal end of the tip  33  and is adhered in place. To maintain the flexibility of the adapter  42 A during scraping the distal end  39  of the tip  33  is only partially inserted into the internal chamber  54  of the adapter. This allows the distal end  51  of the adapter  42 A to flex as required during scraping. The length of insertion into the internal chamber  54  of the adapter  42 A is preferably set to securely fit the adapter  42 A onto the tip  33  while maintaining flexibility for scraping. 
     The distal end  51  of the adapter  42 A has a curved beveled surface  57  that exposes the internal chamber  54  of the adapter. This is best shown in FIGS. 1B and 1C. The curved open surface optimizes delivery of aspiration or infusion sources. This bevel surface  57  also provides better visualization of the surgical site and increased flexibility for scraping with the distal edge  51 . The adapter distal end  51  can be configured in a flat arrangement as shown in FIG. 1B or tapered arrangement as shown in FIG. 1C to facilitate fluid manipulation around the surface of the retina. 
     As shown in FIGS. 1B and 1C, the distal end  51  of the adapter has abrasive particles  60  adhered thereon. The film of abrasive particles  60  in the preferred embodiment consists of synthetically-made diamond particles. Other similar types of particles and other types of abrasive surfaces may be employed. The particles may be arranged in a film that is bonded to the adapter  42 A such that the particles are not loosened and disassociated from the film and the distal end  51  of the adapter during the scraping operation. Preferably, the adapter  42 A is made from a flexible, biologically inert rubber or other similar material that is compatible with the bonding methods used for the chosen abrasive particles. The film of abrasive particles  60  is bonded to the distal end  51  of the adapter such that all exposed edges of the distal end  51  of the adapted are coated while the distal end  51  of the adapter is maintained in communication with the internal chamber  54 . In the axial direction of the adapter  42 A, the abrasive particles are preferably attached 1 mm to 2 mm back from the distal end  51 . The particles adhered to the distal end  51  may be chosen for their coarseness and texture to create the desired effect for membrane scraping and removal rates. As shown in FIG. 1A, an external infusion/aspiration source  27  may be interfaced at the taper  24  in the internal passage  21  of the instrument handle  13  and directed into the hollow core  45  of the tip, into the internal chamber  54  of the adapter, and through the bevel surface  57 . 
     In FIG. 2, a similar embodiment of the apparatus of the invention shown in FIG. 1A is depicted. In this embodiment, the microsurgical instrument  10 B is an illuminated membrane scraper. The instrument handle  13 , adapter  42 B, and tip  33  are constructed much in the same way as previously mentioned. The differences between the two embodiments will be discussed to avoid repetition of the same features and modes of operation. As shown in FIG. 2, the illuminated microsurgical instrument  10 B contains an optical fiber  66  that is directed through the internal passage  21  of the instrument handle, into the hollow core  45  in the tip, and through the internal chamber  54  in the adapter  42 B. In this configuration, the instrument handle  13  is configured slightly different than shown in FIG. 1A with the outwardly conical shaped taper  24  omitted from the proximal end  19  of the instrument handle. Preferably, the distal end  16  of the instrument handle contains the same counter-bore  30  into which the proximal end  36  of the tip is securely press fit. 
     Preferably, the optical fiber  66  is directed through the internal passage  21  of the instrument handle through the hollow core  45  of the tip to the internal chamber  54  of the adapter. The portion of the optic fiber  66  outside the instrument is covered with a protective cladding and the portion of the optic fiber that enters the instrument has had its cladding removed. The adapter  42 B is positioned on the distal end  39  of the tip. The optical fiber  66  may be made from glass or plastic, as is common in the art. Preferably, the adapter  42 B is made from a translucent, inert, elastic material, which will glow and provide illumination of the surgical site when the optical fiber  66  is illuminated. The adapter  42 B contains the same bevel surface  57  across the internal chamber  54  of the adapter as shown in FIG.  1 B and FIG.  1 C. In this application, the bevel surface  57  has an additional design consideration in that the surface  57  is made in a manner so as to provide a desired illumination pattern for the surgical site. The distal end  69  of the optical fiber slightly protrudes from the hole created by the bevel surface  57  across the internal chamber  54  in the adapter. The distal end  69  of the optical fiber  66  may also be shaped to create the desired illumination pattern at the surgical site. For example, the distal end  69  of the optical fiber  66  may be rounded. 
     In FIG. 3A, an illuminated membrane scraper  10 C is shown. In this embodiment, the construction is very similar to the device shown in FIG. 2 in that the instrument handle  13  is adapted to accept an optical fiber  66  running through the internal passage  21  in the instrument handle. The tip  33  is press fit and adhered in the counter-bore  30  on the distal end  16  of the instrument handle. However, in this embodiment the adapter  42 C is moved to a location where it is positioned above the distal end  39  of the tip by a bracket  72 . The bracket  72  is preferably made of a surgical grade steel wire or resilient plastic and is attached to the distal end  39  of the tip. The bracket  72  positions the adapter  42  at an acute angle with the tip  33 . The acute angle is chosen to hold the adapter  42  away from the distal end  39  of the tip such that the optical fiber  66  can effectively illuminate the distal end  51  of the adapter and the surgical site. The bracket  72  holds the adapter  42  at the acute angle such that the distal end  51  of the adapter intersects the path of illumination while preserving an overall low cross section for the microsurgical instrument  10  that permits introduction into a straight cannula. 
     In this embodiment of the invention, the adapter  42 C may be provided with an internal chamber  54  similar to the adapters shown in FIGS. 1A,  1 B,  1 C, and  2 . In this configuration, the bracket  72  may be inserted into the internal chamber  54  of the adapter  42 C in a manner similar to the arrangement of the tip and the adapter described previously. The bracket may penetrate the internal chamber  54  of the adapter  42 C to a depth that preserves the flexibility of the adapter  42 C for scraping while maintaining a secure fit on the bracket  72 . However, the adapter also may be a solid member with no internal chamber and the bracket may be pressed into the proximal end of the adapter and adhered thereto. 
     As shown in FIG. 3A, the distal end  69  of the optical fiber protrudes from the hollow core  45  of the tip. The distal end  69  of the optical fiber is shaped to provide the desired illumination pattern at the surgical site. As shown in FIG. 3B, the adapter  42 C also has abrasive particles  60  bonded to its distal end  51 . With this arrangement of the microsurgical instrument  10 C, the surgeon may scrape the membranes while directly illuminating the surgical site. 
     FIGS. 4A and 4B show another embodiment of the present invention, a membrane scraper  10 D with an adjustable stiffness pick  75 . The microsurgical instrument has the construction of an instrument handle  13  with tip  33  and adapter  42 D as previously described. In the embodiment shown in FIGS. 4A and 4B, the microsurgical instrument  10 D has an adjustable pick  75  received in the internal passage  21  of the instrument handle  13 , the hollow core  45  of the tip  33 , and in the internal chamber  54  of the adapter  42 D. This pick  75  is secured in the handle passage  21  by a set screw (not shown) or by other equivalent means. The length of the pick  75  exposed from the bevel section cut of the adapter  42 D may be varied between an extended position in which the pick  75  is exposed from the distal end  51  of the adapter  42 D and a retracted position in which the pick  75  is retracted into the hollow core  45  of the tip  33 . The length of the pick  75  exposed from the adapter controls the relative stiffness of the pick  75 . When a longer length of the pick  75  is exposed from the distal end  51  of the adapter  42 D, the pick  75  is more flexible and less stiff. As the pick  75  is retracted, the pick  75  becomes stiffer. 
     To adjust the stiffness in the pick  75 , the instrument handle  13  is constructed with a slide mechanism  78  located in an axial slot  82  cut in the outer cylindrical wall of the instrument handle  13 . The axial slot  82  provides communication between the outer surface of the cylindrical wall of the instrument handle  13  and the internal passage  21  of the instrument handle. To aid the surgeon in manipulating the slide mechanism  78 , a grip  83  may be formed on the exterior of the cylinder wall of the instrument handle  13 . Additionally, the diameter of the internal passage  21  in the distal end portion  16  of the instrument handle is increased to allow the tip  33  to slide freely through the distal end  16  portion of the instrument handle  13 . 
     The slide mechanism  78  preferably includes a finger pad  85  connected to the proximal end  36  of the tip  33 . The finger pad  85  is positioned in the axial slot  82  for axial sliding movement of the finger pad  85  through the axial slot  82  between a pushed forward position of the finger pad and a pulled back position of the finger pad. The finger pad  85  is preferably constructed of the same material as the instrument handle  13 , a disposable medical grade plastic. The proximal end  36  of the tip  33  is received at the distal end  16  of the instrument handle  13  and positioned in the axial slot  82  in the instrument handle  13 . 
     Preferably, the finger pad  85  has a hole  88  into which the proximal end  36  of the tip is inserted. A set screw  91  may then be used to secure the finger pad  85  to the proximal end  36  of the tip. Thus, moving the finger pad  85  to its pushed forward position will also move the tip  33  through the distal end  16  portion of the instrument handle to its forward most position or pushed forward position relative to the instrument handle  13  where the distal end  39  of the tip  33  projects its greatest distance from the instrument handle distal end  16 . Moving the finger pad  85  to its pulled back position will also move the tip  33  to its pulled back position relative to the instrument handle  13  where the tip distal end  39  projects its shortest distance from the instrument handle distal end  16 . In the preferred embodiment of the invention, the travel distance of the finger pad in the axial slot  82  and of the tip distal end  39  is 25 mm. 
     As shown in FIGS. 4A and 4B, a medical grade plastic pick  75  having distal  94  and proximal  97  ends is directed from the bevel surface  57  across the internal chamber  54  of the adapter, into the hollow core  45  of the tip and into a portion of the instrument handle internal passage  21 . The overall length of the pick  75  is preferably slightly larger than the combined length of the tip  33  and the adapter  42 . The pick  75  is preferably positioned in the internal chamber  54  of the adapter, the hollow core  45  of the tip, and the instrument handle internal passage  21  so that the distal end  94  of the pick is positioned just inside the adapter proximal end  48  when the tip  33  and adapter  42  are moved to their forward most positions. 
     As shown in FIG. 4A, the pick  75  preferably passes through the axial slot  82  in the side of the instrument handle  13  and extends for a short distance through the internal passage  21  of the instrument handle behind the terminal point of the axial slot  82 . The pick proximal end  97  is preferably secured stationary relative to the instrument handle  13  by a set screw that passes through the side of the instrument handle  13  and engages against the exterior of the pick  75 . With the pick distal end  94  being positioned just inside the proximal end  48  of the adapter when the tip  33  and adapter  42 D are moved to their pushed forward positions as shown in FIG. 4A, a distal end  94  portion of the pick projects from the adapter distal end  51  when the finger pad  85 , and the tip  33  and adapter  42 D are moved to their pulled back positions as shown in FIG.  4 B. The distal end  94  portion of the pick that projects from the adapter distal end  51  is shown in FIG.  4 B. This distal end  94  portion has a variable stiffness as the length of the pick  75  exposed from the bevel surface  57  in the adapter is adjusted. As the length of pick  75  is increased, the relative stiffness of the pick  75  is decreased. As the pick  75  is drawn into the bevel surface  57  in the adapter  42 D as the finger pad  85  is moved to its pushed forward position as shown in FIG. 4A, the relative stiffness of the pick  75  increases. 
     In a like manner, the position of the pick distal end  94  inside the adapter  42 D adjusts the stiffness of the adapter  42 D. In the previous embodiments of the invention, the stiffness of the adapter was controlled by the adapter&#39;s material and dimensions, the bevel surface, and the depth of penetration of the tip into the adapter or by the bracket into the adapter. With the pick distal end positioned in the adapter adjacent the adapter distal end, the pick may also serve to stiffen the adapter. Retracting the pick toward the adapter proximal end reduces the stiffness of the adapter. The combined action of the pick  75  and the abrasive particles  60  in the distal end  51  of the adapter  42 D, allow the surgeon to better control the rate of membrane removal while giving the flexibility to either use the film of abrasive particles  60  or the pick  75  for actual removal. 
     To assist the sliding of the tip  33  over the distal end  94  portion of the pick, the hollow core  45  of the tip is preferably coated with a layer of a sliding material such as Teflon®. The Teflon® layer preferably extends only a short distance in the hollow core  45  of the tip adjacent the tip distal end  39 . The remainder of the hollow core  45  of the tip may be dimensioned slightly larger than the exterior diameter of the pick  75  providing an air gap between the pick exterior and the hollow core  45  of the tip that reduces actuation drag and enhances the ease of sliding the tip  33  over the exterior of the pick  75 . 
     It is not the intention of this invention to limit the configuration of this embodiment to where the pick is stationary and the tip and adapter move relative to the pick. It is also possible to move the pick in relation to the tip and adapter to achieve the stiffness required to effectively scrape membranes. 
     In FIGS. 5A and 5B, the embodiment of the apparatus of the invention is shown where the pick of FIGS. 4A and 4B is replaced with a tube  103  and the adapter is removed from the distal end  39  of the tip. In this configuration, the embodiment of the microsurgical instrument  10 E in FIGS. 5A and 5B is termed a directional endoscopic abrasive aspiration membrane scraper. In this embodiment, the instrument handle  13  is configured much as it was in the FIGS. 4A and 4B. The internal passage  21  is provided in the instrument handle  13  and the distal end  16  portion of the instrument handle is adapted for sliding motion of the tip  33  therethrough into the axial slot  82 . The instrument handle is preferably configured with a grip  83  to allow the surgeon to manipulate the sliding mechanism  78 . The instrument handle  13  contains an axial slot  82  in the outer cylindrical wall located toward the distal end  16  of the instrument handle  13  for locating the sliding mechanism  78 . A finger pad  85  is preferably inserted into the axial slot  82 . The finger pad  85  has a hole  88  into which the proximal end of the tip is inserted. The set screw  91  preferably secures the finger pad  85  to the proximal end  36  of the tip. Thus, moving the finger pad  85  to its pushed forward position will also move the tip  33  through the distal end  16  portion of the instrument handle to its forward most position or pushed forward position relative to the handle where the distal end  39  of the tip projects its greatest distance from the instrument handle distal end  16 . Moving the finger pad  85  to its pulled back position will also move the tip  33  to its pulled back position relative to the instrument handle  13  where the tip distal end  39  projects its shortest distance from the instrument handle distal end  16 . In the preferred embodiment of the invention, the travel distance of the finger pad  85  in the slot  82  and the tip distal end  39  is 25 mm. 
     Located in the internal passage  21  of the instrument handle is the tube  103  with a pre-formed bend  106  on its distal end  107 . Preferably, the tube is constructed of nitinol. The proximal end  109  of the tube is directed into and through the hollow core  45  of the tip, and into the internal passage  21  of the instrument handle. The proximal end  109  of the tube  103  may be connected to an aspiration or infusion source  27 . A distal end  107  portion of the tube is pre-formed with a bend  106  through a 90° angle relative to the distal end  39  of the tip. Around the distal end  107  of the tube, the abrasive particles  60  are deposited, covering the exterior of the cylindrical portion of the tube  103  back 1 mm to 2 mm from the distal end  107  of the tube as well as the circumferential annular edge at the distal end of the tube  107 . 
     As shown in FIG. 5A, when the finger pad  85  on the instrument handle  13  is pushed forward, it extends the tip  33  to its pushed forward position in which the distal end portion of the tube  107  is completely contained inside the hollow core  45  of the tip and is held in the straight configuration of the hollow core  45  of the tip. As shown in FIG. 5B, when the finger pad  85  is moved to its pulled back position, the tip  33  is also moved back to its pulled back position causing the bend portion  106  of the distal end  107  of the tube contained therein to be gradually exposed at the distal end of the tip  39 . As the tube  103  is exposed at the distal end of the tip  39 , the tube  103  gradually bends from the initial straight configuration of the tip  33  toward the 90° pre-bent configuration of the tube  103 . In this manner, the tube  103  may be adjustably positioned through any angle between 0° when the tube  103  is entirely contained in the tip  33  at its pushed forward position, to a 90° bend when the tube  103  projects from the tip distal end  39  with the tip  33  moved to its pulled back position. 
     In use of the directional membrane scraper in the scraping of obscured retinal membranes, the finger pad  85  is moved to its pushed forward position. The tube  103  is contained in the tip  33 , which projects in a straight line from the distal end  16  of the instrument handle. The tip  33  is then inserted through a cannula positioned in an incision in the eye. The finger pad  85  is then slowly moved toward the rear of the instrument handle  13  causing the tip  33  to slowly move toward its pulled back position relative to the instrument handle  13 . This, in turn, causes the pre-bent  106  distal end  107  portion of the tube to gradually bend from its straight configuration toward its 90° configuration. The bending of the tube  103  allows optimal positioning of the film of abrasive particles  60  to areas where a straight scraping adapter  42  shown in the embodiments of FIGS. 1,  2 ,  3 , and  4  may not reach. Rotation of the entire instrument about its center axis may be necessary to further direct the tube. Once the proper location of the distal tube is achieved, the surgeon may begin scraping and treating the surgical site with aspiration/infusion functions supplied via the tube. Retraction of the tip  33  is performed by first pushing the finger pad  85  forward causing the tip  33  to move toward its pushed forward position and causing straightening of the bent portion  106  of the tube projecting from the tip  33 . With the tube  103  contained in the tip  33 , the tip  33  is then pulled back through the surgical entry site. 
     In alternate embodiments of the invention, the actuation mechanism provided by the finger pad may be replaced with other types of mechanisms that would produce the same axial movement of the tip, for example by a trigger mechanism manipulated by the surgeon&#39;s finger or by a squeeze mechanism that is squeezed by the surgeon&#39;s hand. In addition, a fiducial mark may be provided on the tip adjacent its distal end to indicate to the surgeon which direction the distal end portion of the tube will bend as it is extended out of the distal end of the tip. This would be useful to the surgeon in accurately positioning the tip in the interior of the eye before the bending movement of the tube is commenced. 
     The intent of this embodiment of the invention is not only to work in the intraocular cavity, this microsurgical tool may be used in operations where the treatment tool must be inserted into a cavity where the spatial arrangement of the cavity obscures treatment surfaces, for example, in brain tumor removal. 
     While the present invention has been described by reference to specific embodiments, it should be understood that modifications and variations of the invention may be constructed without departing from the scope of the invention defined in the following claims.