Patent Publication Number: US-2019192340-A1

Title: Manufacturing an articulating ophthalmic surgical probe

Description:
This application is a continuation of U.S. Non-Provisional application Ser. No. 14/612,576, filed Feb. 3, 2015, which is entitled “Manufacturing An Articulating Ophthalmic Surgical Probe” (which is hereby incorporated by reference in its entirety as though fully and completely set forth herein) and claims priority to U.S. Provisional Application No. 61/936,434 filed Feb. 6, 2014, which is entitled “Manufacturing An Articulating Ophthalmic Surgical Probe”. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to ophthalmic surgical equipment and more particularly to posterior segment ophthalmic surgical probes. 
     BACKGROUND OF THE INVENTION 
     Microsurgical instruments typically are used by surgeons for removal of tissue from delicate and restricted spaces in the human body, particularly in surgery on the eye, and more particularly in procedures for removal of the vitreous body, blood, scar tissue, or the crystalline lens. Such instruments include a control console and a surgical handpiece with which the surgeon dissects and removes the tissue. With respect to posterior segment surgery, the handpiece may be a vitreous cutter probe, a laser probe, or an ultrasonic fragmenter for cutting or fragmenting the tissue and is connected to the control console by a long air-pressure (pneumatic) line and/or power cable, optical cable, or flexible tubes for supplying an infusion fluid to the surgical site and for withdrawing or aspirating fluid and cut/fragmented tissue from the site. The cutting, infusion, and aspiration functions of the handpiece are controlled by the remote control console that not only provides power for the surgical handpiece(s) (e.g., a reciprocating or rotating cutting blade or an ultrasonically vibrated needle), but also controls the flow of infusion fluid and provides a source of vacuum (relative to atmosphere) for the aspiration of fluid and cut/fragmented tissue. The functions of the console are controlled manually by the surgeon, usually by means of a foot-operated switch or proportional control. 
     During posterior segment surgery, the surgeon typically uses several handpieces or instruments during the procedure. This procedure requires that these instruments be inserted into, and removed out of the incision. This repeated removal and insertion can cause trauma to the eye at the incision site. To address this concern, hubbed cannulae were developed at least by the mid-1980s. These devices consist of a narrow tube with an attached hub. 
     The tube is inserted into an incision in the eye up to the hub, which acts as a stop, preventing the tube from entering the eye completely. Surgical instruments can be inserted into the eye through the tube, and the tube protects the incision sidewall from repeated contact by the instruments. In addition, the surgeon can use the instrument, by manipulating the instrument when the instrument is inserted into the eye through the tube, to help position the eye during surgery. 
     Many surgical procedures require access to the sides or forward portion of the retina. In order to reach these areas, the surgical probes must be pre-bent or must be bendable intra-operatively. Various articulating optical surgical probes for providing laser and/or illumination light are known. See for example, U.S. Pat. No. 5,281,214 (Wilkins, et al.) and U.S. Pat. No. 6,984,130 (Scheller, et al.). The articulation mechanism, however, adds extra complexity and expense. One flexible laser probe needing no articulation mechanism is commercially available, but this device uses a relatively large diameter optical fiber sheathed in a flexible tube comprising the distal tip, resulting in a large bend radius and large distal tip diameter with significant bend stiffness. These characteristics require that the distal tip contain a non-bent straight portion for ease of insertion of the bent portion, which must flexibly straighten as it passes through the hubbed cannula. The straight portion of the distal tip allows the bent portion to flexibly pass through the hubbed cannula before the distal cannula of the handpiece enters the hubbed cannula, to allow maximum bending clearance of the flexible portion, thereby minimizing the bending strain and corresponding frictional insertion forces. Such a large bend radius, large diameter flexible tube, and straight distal tip causes the useable portion of the fiber to extend a relatively long distance from the distal tip of the probe and limits access of the probe. 
     A further disadvantage in the known art is the flexibility of the distal cannula, which is a function of the material properties and cross sectional moment of inertia, as determined by the gauge size of the outside diameter of the cannula to fit within the hubbed cannula, and the inside diameter of the cannula to accept the flexible tube. For any given material, the outer and inner diameters of the cannula determine the flexibility of the cannula. This flexibility limits the surgeon&#39;s ability to use the instrument to manipulate the position of the eye during surgery. 
     A flexible-tip probe is disclosed in U.S. Patent Application Publication 2009/0093800 (Auld, et al.) that does not require a straight portion of flexible tube, which thus provides a more compact useable tip length, thereby allowing greater access to internal posterior structures of the eye without compromising insertion forces. The flexible-tip probe provides increased rigidity of the distal cannula to facilitate manipulation of the position in the eye during surgery. While this probe provides a relatively smaller cross section as compared to the previous probes, such as those disclosed by Scheller et al., it does not provide controllable articulation over a range of angles in the manner those probes do. 
     A more recent approach described in U.S. Patent Application Publication 2013/0035551 (Auld, et al.), which is incorporated herein by reference, discloses a single cannula with a flexible tip that is articulable using a pull-wire. This combines the advantages of a very small diameter with controllable articulation of the probe tip. This approach combines advantages of other previous alternatives and provides a simple alternative. Any improvements to the ability to manufacture such probes with increased ease and reliability would therefore be valuable. 
     BRIEF SUMMARY OF THE INVENTION 
     In particular embodiments of the present invention, an articulating ophthalmic surgical probe includes a handle formed from a rigid plastic material and sized to fit in a single hand, a rigid cannula extending from the handle having a diameter of 20 Ga or less, and a slotted tip at a distal end of the cannula. The probe further includes at least one optical fiber extending through the handle, the single rigid cannula, and the slotted tip. A pull-wire is permanently attached to the slotted tip, When the pull-wire exerts tension on the slotted tip, the slotted tip will deviate from straight to a bend angle controlled by the tension in the pull-wire, and the slotted tip is formed from a resilient material that will restore to the straight position when the tension exerted by the pull-wire is released. The probe further includes an anchor permanently attached to a distal end of the pull wire, and a weld pin secured within the handle welded to the anchor. 
     In other embodiments, a method of manufacturing an articulating ophthalmic surgical probe includes providing a cannula having an outer diameter of 20 Ga or less and a slotted tip, permanently attaching a pull wire to the slotted tip, permanently attaching a metal anchor to a distal end of the pull wire, positioning a weld pin within a handle assembly that is sized to fit within a single hand, and welding the metal anchor to the weld pin within the handle assembly. 
     Other objectives, features and advantages of the present invention will become apparent with reference to the drawings, and the following description of the drawings and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of an articulating optical surgical endoprobe, according to a particular embodiment of the present invention; 
         FIG. 2  illustrates a pull wire, cannula and handle assembly according to a particular embodiment of the present invention; 
         FIG. 3  illustrates a key feature and keypath pocket of a handle assembly according to a particular embodiment of the present invention; 
         FIGS. 4A-4B  illustrate a cannula with a flared proximal end according to a particular embodiment of the present invention; 
         FIGS. 5 and 6  illustrate a thumb switch for adjusting tension in a pull wire according to a particular embodiment of the present invention; 
         FIG. 7  illustrates a protective cover with a thumb switch according to a particular embodiment of the present invention; and 
         FIGS. 8A-8B  is a flow chart illustrating an example method for assembling an articulating ophthalmic surgical probe according to a particular embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Various embodiments of the present invention may allow improved reliability and simplicity in the manufacture of articulating ophthalmic surgical probes. Articulating ophthalmic surgical probes with a single rigid cannula having a slotted tip of resilient material secured to a pull wire have been described in U.S. Patent Application Publication 2013/0035551. Tension in the pull wire causes the slotted tip to bend in a particular direction, while releasing the tension allows the resilient tip to restore to its straight position. Pull-wire technology has been used previously to deviate a distal end of a surgical catheter, but not in a small-diameter, rigid cannula used in handheld optical surgical probes nor with the degree of angular movement used in the relatively small spaces found within the interior of an eye. Consequently, the application of pull-wire tension in the context of hand-held surgical probes is uniquely advantageous. 
     Such probes can be manufactured by the use of adhesives or similar assembly techniques to connect metal parts of the probe (including the pull wire and cannula) to a plastic housing. Particularly given the small components and relatively small contact are between them, the strength of the adhesive bond may be highly variable. In particular, factors such as inconsistent application, surface contamination, heat, moisture, or age may cause the adhesive bonds to fail. Additionally, given the small scale of the components and the relatively stringent manufacturing tolerances required combined with the additional requirements of alignment so that the probe can articulate in the correct direction, even aligning the components of the probe is relatively challenging. Various embodiments of the present invention provide improvements in manufacturing processes for an articulating ophthalmic surgical probe that uses a pull wire for articulation. 
       FIG. 1  is a schematic of an articulating optical surgical endoprobe  10 , according to a particular embodiment of the present invention, with a handle  12  suitable for being held in a single hand and a cannula  14 . (For ease of illustration, the handle  12  and cannula  14  are not shown to scale and certain external features of the handle  12 , such as the control mechanism for an internal pull-wire, are not shown.) The handle  12  is formed of one or more rigid plastic materials, such as acrylonitrile butadiene styrene (ABS), acetal homopolymer, or polypropylene. The proximal end of the endoprobe  10  is connected to one or more light sources (not shown) that provide laser and/or illumination light by connection to at least one optical fiber running through the interior of the endoprobe  10 . The cannula  14  is formed of a rigid biocompatible metal, such as stainless steel. The cannula  14  has a slotted tip  20  at a distal end (referring to the end farthest from the surgeon during use). The slotted tip  20  may articulate in a selected direction in a controllable manner by applying tension to a pull wire secured within the slotted tip  20  (not shown in  FIG. 1 ). 
     The metal components of the probe  10  (namely, the pull wire and the cannula) can be attached to one another by welding, and given the high precision required, this preferably would use laser welding. This can be used to attach the pull wire to the cannula, for example. Metal weld points, such as stainless steel pins, can be molded, inserted or otherwise positioned in the plastic handle  12  so that the pull wire can also welded to the handle  12 . But the pull wire has such a narrow diameter (0.004 inches or less) that the increased heat from the welding can cause the wire to break if it is under significant tension. Thus, the pull wire could be broken if it is welded while it is threaded within the housing in the correct position to be able to exert tension on the flexible tip, so the secure attachment of the pull wire within the handle  12  may remain problematic. 
       FIG. 2  illustrates a pull wire  100  coupled to cannula  14  which advantageously resolves this problem according to a particular embodiment of the present invention. The pull wire  100 , which has a diameter of 0.004 inches or less, is permanently attached to a metal anchor  102 , preferably by laser welding (where “permanently attached” in this specification refers to two components are joined by a physical bond that can be broken only by damage or destruction of the bond). The metal anchor  102  may be formed from any suitable metal, including stainless steel. The pull wire  100  is likewise permanently attached, preferably by laser welding, to the inside of the cannula  14  at the slotted tip  20 , which will allow the pull wire  100  to exert tension to bend the slotted tip  20  when the probe  10  is fully assembled. 
     The anchor  102  is welded to a weld pin  104  within the housing. Another weld pin  104  is used for the cannula  14 . The weld pins  104  may include any fixed metal piece that is held securely in the handle  12  when welded to the respective component (anchor  102  or cannula  14 ), and the weld pins  104  need not be the same shape or size. In a particular example, the weld pins  104  may include U-shaped grooves on an end or side of the weld pin  104  so that the anchor  102  or cannula  14  fits within the U-shaped groove of the respective weld pin  104  for welding. Although U-shaped grooves can be advantageous for cylindrical symmetry of the cannula  14  and anchor  102 , other shapes could also be used, including different grooves (for example, V-shaped or rectangular grooves), flat surfaces, rails, or other features to facilitate secured welds to the weld pins  104 . In an alternative example, the weld pins  104  may be ends of an integral assembly, such as a support wire, that is held securely in the handle  12  after welding. Such an assembly can act as a heat sink to remove heat from the weld pins  104  in order to reduce the possibility of damage to the plastic handle  12 . In other embodiments, a separate heat sink, such as a metal rod, can be placed in contact with the weld pin  104 , anchor  102  or cannula  14  during welding to conduct heat away from the weld pin  104 . 
     The cannula  14  likewise has additional features that facilitate assembly of the probe  10 . Specifically, the cannula  14  has a key feature  105  permanently attached to an exterior of the cannula  14 . As shown in  FIG. 3 , the key feature  105  is an asymmetrical structure extending away from the cannula that fits into a matching keyway pocket  106  at a distal end of the plastic handle  12  (“distal” referring to the end of the handle  12  that would face away from the surgeon during use, as opposed to “proximal”). The key feature  105  can be part of a sleeve permanently attached to the cannula  14 , or it may be directly attached to the cannula  14 . 
     During assembly of the probe  10 , the cannula  14  slides into the distal end of the handle  12  until the key feature  105  reaches the keyway pocket  106 . The asymmetry of the key feature  105  assures correct rotational alignment of the cannula  14 , so that the slotted tip  20  articulates in the correct direction. The key feature  105  also acts as a stop to prevent further movement of the cannula  14  once the key feature  105  reaches the keyway pocket  106 , assuring correct axial positioning of the cannula  14  within the handle  12 . 
     The cannula  14  also includes a flared proximal end  108 , which is shown in greater detail in the magnified view of  FIGS. 4A-4B . The flared proximal end  108  is placed relative to a guide pin  110  within the handle  12  over which one or more optical fibers  112  within the handle  12  that hold the optical fibers  112  in place. In particular, the optical fibers  112  are held away from an outer edge  109  of the flared proximal end  108  when positioned over the guide pin  110 . This prevents the optical fibers  112  from contacting the corner of the cannula  14 , which could cause the optical fibers  112  to be nicked or broken. Additionally, the guide pin  110  is placed at a sufficient distance from the flared proximal end  108  to prevent the optical fibers  112  from bending with a bend radius less than a minimum critical radius (i.e., the bend radius at which the fiber will be unable to properly transmit light and/or will be damaged). For small-gauge single-mode laser fibers (0.004 inch diameter) and multimode illumination fibers (0.007 inch diameter), the minimum bend radius may be around 0.193 inches. Given conventional dimensions for a hand-held probe  10  and suitable placement of the light source connector near the proximal end of the handle  12 , the bend radius can be kept above 0.690 inches by the guide pin  110 , which provides a significant safety margin for small-gauge optical fibers  112 . 
       FIGS. 5 and 6  illustrate a tension mechanism for the pull wire according to a particular embodiment of the present invention. In the depicted embodiment, a thumb switch  114  is used to advance a slider pin  116  along a ramp  118  to adjust tension in the pull wire  100 , causing the slotted tip  20  to articulate to an angled position. The thumb switch  114  is snap fit into a slot  115  in the handle  12 , allowing the switch  114  to slide. Due to manufacturing tolerances, there may be slight variations in the fit of the switch  114  within the slot. This may result in variability of the force required to advance the switch  114  and thus to articulate the slotted tip  20 . Therefore, a compressible insert  118  is placed in the switch  114  that contacts the slot, providing a uniform frictional force. Preferably, this material is a low-friction silicone, so that the force required to advance the switch  114  is low but uniform. 
     The slot  115  in the handle  12  includes a widened portion  120  corresponding to the position of the compressible insert  118  when the switch  114  is in its rearmost (i.e., farthest proximal) position. This allows the compressible insert  114  to expand so as to retain the switch  114  in this rearmost position until the probe  10  is used, which reduces the chance of the switch  114  advancing during storage or transport. 
       FIG. 7  illustrates a protective cover  122  that also helps to maintain the switch  114  in the rearmost position. In the depicted embodiment, the protective cover  122  includes a tapered slot  124 , which reduces any drag on the switch  114  due to friction when the protective cover  122  is removed. The protective cover  122  is held in place by retention tabs  126 . 
       FIGS. 8A-B  is a flow chart  200  illustrating an example method for manufacturing a probe  20  according to a particular embodiment of the present invention. At step  202 , a cannula with a diameter of 20 Ga or less having a slotted tip is provided. At step  204 , a pull wire is permanently bonded to the slotted tip, such as by laser welding, so as to allow the tip to articulate when tension on the pull wire is increased. At step  206 , a key feature is permanently attached to the cannula. Then, at step  208 , a metal anchor is permanently bonded to the pull wire, such as by laser welding. Steps  202 - 208  form the cannula assembly that will be welded to the handle assembly in forming the probe. 
     At step  210 , a handle assembly is provided. The handle assembly has a keypath pocket at a distal end matching the key feature. At step  212 , weld pins are inserted into the handle assembly. At step  214 , the pull wire is threaded into the handle assembly until the key features fits into the keypath pocket. The cannula is welded to a distal weld pin at step  216 . 
     At steps  218 - 224 , the tension in the pull wire is adjusted to produce the correct bend in the slotted tip of the cannula. At step  218 , a slider pin is inserted into a ramp of the handle assembly. At step  220 , the tension in the pull wire is adjusted to produce a calibrated bend in the slotted tip. The anchor on the pull wire is then welded to the proximal weld pin at step  222 . Any excess pull wire may be trimmed away at step  224 . 
     Although the aforementioned steps are directed to placement of the pull wire, one skilled in the art will recognize that this is not a comprehensive guide to the steps of assembling the probe. Thus, for example, the optical fiber will may be threaded into the handle assembly and bonded in place, and the handle assembly may likewise be bonded together. Likewise, guide pins may be placed and/or bonded before or after wire placement, and the slider pin can likewise be placed before or after the wire tension is set. 
     At step  226 , a thumb switch is snap fit into a slot in the handle assembly, where it fits onto the slider pin. The thumb switch is placed into a rearmost position at step  228 , where a compressible insert in the thumb switch expands into a widened portion of the slot to retain the thumb switch in the rearmost position. A protective cover is placed onto a distal end of the probe at step  228 , which also is configured to retain the thumb switch in the rearmost position. 
     While certain embodiments of the present invention have been described above, these descriptions are given for purposes of illustration and explanation. Variations, changes, modifications and departures from the systems and methods disclosed above that would be apparent to one skilled in the art may be adopted without departure from the scope of the present invention as recited in the following claims.