Patent Publication Number: US-2021161610-A1

Title: Distance indication for invasive microsurgical instruments

Description:
PRIORITY CLAIM 
     This application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 62/315,278 titled “DISTANCE INDICATION FOR INVASIVE MICRO SURGICAL INSTRUMENTS,” filed on Dec. 3, 2019, whose inventor is Ivan Filipin, which is hereby incorporated by reference in its entirety as though fully and completely set forth herein. 
    
    
     TECHNICAL FIELD 
     The present invention generally relates to the field of microsurgical instruments and, more particularly, to microsurgical instruments having one or more distance indication members. 
     BACKGROUND OF THE INVENTION 
     Many microsurgical procedures require precision cutting and/or removal of various body tissues. For example, ophthalmic surgery often requires cutting, removal, dissection, delamination, coagulation, or other manipulation of delicate tissues such as the vitreous humor, traction bands, membranes, and/or the retina. Therefore, cutting, removal, and/or other manipulation of the eye must be done with great care to avoid traction on the retina, the separation of the retina from the choroid, a retinal tear, or, in the worst case, cutting and removal of the retina itself. 
     Microsurgical instruments, such as vitrectomy probes, fiber optic illuminators, infusion cannulas, aspiration probes, scissors, forceps, and lasers are typically utilized during ophthalmic surgery. These devices are generally inserted through one or more surgical incisions in the sclera near the pars plana and/or via cannulas. 
     To reduce potential damage to surgical sites and reduce recovery time, care must be taken to avoid inadvertently contacting tissue surfaces such as the retina. Because the operator of the microsurgical instruments is viewing the operation through a microscope or a viewing screen, knowing the depth of an instrument and its distance from a tissue surface may be difficult to ascertain precisely. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, a microsurgical instrument comprising a microsurgical tool and at least one distance indication member is provided. In a particular embodiment, the microsurgical tool, such as a forceps or scissors, is operatively positioned within a tubular member. The distal end of the tubular member is coupled to the proximal end of the distance indication member. The distal portion of the distance indication member is located a predetermined distance from the distal end of the tubular member, and is configured to transition from a first, undeflected position of use to a second, deflected position of use when a predetermined force is applied thereto. In this second, deflected position of use, the distal portion is angled relative to the remaining portion of the distance indication member, giving the operator of the instrument a visual indication that the distance indication member has encountered a surface and that the microsurgical tool is in close proximity to the surface. 
     In another embodiment, the microsurgical instrument comprises a microsurgical tool and a first distance indication member coupled to, and extending beyond a distal end of, the microsurgical tool. A distal portion of the first distance indication member is configured to deflect when in contact with a tissue surface, without causing damage to the tissue surface, to provide the operator a visual indication that the distal end of the microsurgical tool is in proximity to the tissue surface. The distal portion of the distance indication member is further configured to return to a non-deflected configuration when no longer in contact with the tissue surface. In particular embodiments, the microsurgical tool further comprises a second distance indication member coupled to, and extending beyond the distal end of, the microsurgical tool. This second distance indication member also has a distal portion configured to deflect when in contact with the tissue surface, without causing damages to the tissue surface, to provide the operator a visual indication that the distal end of the microsurgical tool is in proximity to the tissue surface, and to return to a non-deflected configuration when no longer in contact with the tissue surface. 
     One of ordinary skill in the art will appreciate the lengths of the distance indication members in embodiments that employ more than one distance indication member can vary. More specifically, in some applications, the intended tissue of contact may be curved, wherein it may be beneficial to provide the operator indication of curvature by providing distance indication members of different lengths. In other applications, it may be desirous to contact the tissue surface with the first distance indication member initially followed by contact with the second distance indication member, wherein the tip of the first distance indication member would be bent to a greater degree. This aspect of some embodiments of the present invention would allow the operator to fine-tune the initial distance setting to a more preferred spacing from the tissue surface. 
     The distance indication members may also prevent the distal end of the microsurgical tool from accidentally contacting a tissue surface such as the retina. The distance indication members may provide a warning to the operator of the microsurgical instrument that the distal end of the microsurgical tool is in close proximity to the tissue surface and thereby reduce the likelihood of accidentally contacting the tissue surface with the distal end of the microsurgical tool. 
     The contemplated distance indication members may be made of any suitable material that is capable of bending upon minimal pressure. In some embodiments, the distance indication member employs a thinned portion that acts as a “living hinge” that facilitates bending. The distance indication member may also possess areas of varying colors or patterns (e.g., stripes, dots) to help the operator better ascertain when the distal portion of the distance indication member is touching or adjacent to the tissue surface. And in a related aspect of some embodiments, the distance indication member, or portions thereof, may be constructed of a piezoelectric material that creates an electrical charge when compressed or bent, which may provide feedback to the operator. 
     It is one aspect of some embodiments of the present invention to provide a distance indication member made of a material that changes color when compressed or bent, such as chromogenic or piezochromic polymers. Further, the distal portion of the distance indication member may be made of material that provides operator feedback (e.g., a color change) when it contacts tissue or the components thereof (e.g., certain proteins). One of ordinary skill in the art will appreciate that the distance indication member may include one or more of the active indicators or more passive indicators described herein. 
     It is another aspect of some embodiments of the present invention to provide a distance indication member that dissolves after a predetermined amount of time when exposed to, for example, the fluids of the eye. Preselected portions of the distance indication member may be made of such material, such as the distal portion of the distance indication member. 
     It is still yet another aspect of some of the embodiments of the present invention described herein to provide a distance indication member that is selectively integrated with the surgical tool and does not affect the operation thereof. Accordingly, the distance indication member or members of some embodiments may be selectively removed from the surgical tool when not needed. 
     By providing a microsurgical instrument with distance indication members, particular embodiments of the present invention are able to provide enhanced functionality to surgeons. For example, particular embodiments of the present invention may allow a surgeon to accurately determine the distance of the microsurgical tool from the surface of a surgical area, such as a retina. Particular embodiments may also help the surgeon prevent accidental damage to the surgical area due to inadvertent touching of the surgical area by the microsurgical tool. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The appended figures depict certain aspects of the one or more embodiments of the present invention and are therefore not to be considered limiting of the scope of this disclosure. 
         FIG. 1A  is a top plan view of a microsurgical instrument comprising a forceps and distance indication members in accordance with one embodiment of the present invention. 
         FIG. 1B  is a side elevation view of the microsurgical instrument shown in  FIG. 1A . 
         FIG. 2A  is a side elevation of a microsurgical instrument comprising a probe with scissors functionality and distance indication members in accordance with one embodiment of the present invention. 
         FIG. 2B  is a top plan view of the microsurgical instrument shown in  FIG. 2A . 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the drawings. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     In accordance with the teachings of the present invention, a microsurgical instrument comprising a microsurgical tool and at least one distance indication member is disclosed. In a particular embodiment, the microsurgical tool, such as a forceps or scissors, is operatively positioned within a tubular member. The distal end of the tubular member is coupled to the proximal end of the distance indication member. The distal portion of the distance indication member is located a predetermined distance from the distal end of the tubular member, and is configured to transition from a first, undeflected position of use to a second, deflected position of use when a predetermined force is applied thereto. In this second, deflected position of use, the distal portion is angled relative to the remaining portion of the distance indication member, giving the operator of the instrument a visual indication that the distance indication member has encountered a surface and that the microsurgical tool is in close proximity to the surface. 
     In another embodiment, the microsurgical instrument comprises a microsurgical tool and a first distance indication member coupled to, and extending beyond a distal end of, the microsurgical tool. A distal portion of the first distance indication member is configured to deflect when in contact with a tissue surface, without causing damage to the tissue surface, to provide the operator a visual indication that the distal end of the microsurgical tool is in proximity to the tissue surface. The distal portion of the distance indication member is further configured to return to a non-deflected configuration when no longer in contact with the tissue surface. In particular embodiments, the microsurgical tool further comprises a second distance indication member coupled to, and extending beyond the distal end of, the microsurgical tool. This second distance indication member also has a distal portion configured to deflect when in contact with the tissue surface, without causing damages to the tissue surface, to provide the operator a visual indication that the distal end of the microsurgical tool is in proximity to the tissue surface, and to return to a non-deflected configuration when no longer in contact with the tissue surface. 
     By providing a microsurgical instrument with distance indication members, particular embodiments of the present invention are able to provide enhanced functionality to surgeons. For example, particular embodiments of the present invention may allow a surgeon to accurately determine the distance of the microsurgical tool from the surface of a surgical area, such as a retina. Particular embodiments may also help the surgeon prevent accidental damage to the surgical area due to inadvertent touching of the surgical area by the microsurgical tool. 
       FIGS. 1A and 1B  illustrate a microsurgical instrument  100  comprising a set of forceps  102  with two distance indication members,  104  and  106 , respectively. Although  FIGS. 1A and 1B  illustrate forceps  102 , other microsurgical tools are also contemplated within the teachings of the present invention, including but not limited to scissors, scrapers, spatulas, scalpels, diathermy probes, vitrectomy probes, fiber optic illuminators, infusion cannulas, aspiration probes, and laser probes. The distance indication members  104  and  106  are sometimes referred to herein as upper distance indication member  104  and lower distance indication member  106 .  FIG. 1A  shows two distance indication members but any number of distance indication members may be employed.  FIG. 1A  illustrates the forceps  102  in an expanded position in a top-down view from a position orthogonal to the plane in which the forceps  102  open.  FIG. 1B  illustrates the forceps  102  in a side view from the plane in which the forceps  102  open. 
     As shown in  FIGS. 1A and 1B , microsurgical instrument  100  includes a tubular member  108  with a shaft  110  coaxially extending therethrough. Forceps  102  are coupled to shaft  100  and actuated by the movement of tubular member  108  through movement of the shaft  110  within and relative to tubular member  108 . 
     In particular embodiments, distance indication members  104  and  106  are attached to forceps  102 , wherein at least a portion of the distance indication members  104  and  106  extend beyond the distal end of the forceps  102 . In some embodiments, the upper distance indication member  104  and the lower distance indication member  106  may be coupled to inner portions of the arms of the forceps  102 . Alternatively, distance indication members  104  and  106  may be coupled to outer portions of the forceps  102 . In other embodiments, distance indication members  104  and  106  may be coupled directly to the shaft  110 . And in yet other embodiments, distance indication members  104  and  106  may be coupled to tubular member  108 , for example, in embodiments where forceps  102  is be fixed in relation to the tubular member  108 . 
     In particular embodiments, tubular member  108  may be made of a metal or another substantially rigid material. The tubular member  108  may be designed to penetrate the eye or inserted into a small cannula (e.g., smaller than 20 gauge) that has penetrated the eye so that the forceps  102  and distance indication members  104 ,  106  can reach the surgical site. In some examples, distance indication members  104 ,  106  may be relatively small. For example, in some embodiments, distance indication members  104 ,  106  may each have a width within a range of about 0.05 to 0.3 mm. Other sizes, both larger and smaller, are contemplated within the teachings of the present disclosure. 
     The distance indication members  104  and  106  are configured to provide a visual indication to the operator of the microsurgical instrument  100  that the distal end of the forceps  102  are approaching a tissue surface, such as a retina, before the distal end of the forceps  102  contact the tissue surface. In general, the distance indication member may extend a greater distance than the distal end of the microsurgical tool along any axis to provide a visual distance indication to the operator of the microsurgical instrument  100 . In particular embodiments, upper distance indication member  104  and lower distance indication member  106  may extend the same distance beyond the distal end of forceps  102  as each other (as measured along the longitudinal axis of the surgical tool). For example, in a particular embodiment upper and lower distance indication members  104  and  106  may extend about 0.3 to 1.0 mm beyond the distal end of the forceps  102 . In another embodiment, distance indication members  104 ,  106  may extend about 0.5 to 0.8 mm beyond the distal end of forceps  102 . And, in yet another embodiment, distance indication members  104 ,  106  may extend about 0.6 mm beyond the distal end of forceps  102 . Other suitable distances may be readily ascertained by persons of ordinary skill with the benefit of the present disclosure. 
     In other embodiments, upper distance indication member  104  may extend a first distance beyond the distal end of forceps  102 , whereas lower distance indication member  106  extends a second, different distance beyond the distal end of forceps  102 . In such an embodiment, upper and lower distance indication members  104  and  106  may each provide a graduated, or staged, indication of the proximity of forceps  102  to the tissue surface. For example, in a particular embodiment upper distance indication member  104  may extend about 0.6 to 1.0 mm beyond the distal end of forceps  102 , while lower distance indication member  106  may extend about 0.3 to 0.6 mm beyond the distal end of forceps  102 . In another embodiment, upper distance indication member  104  may extend about 1.0 mm beyond the distal end of forceps  102 , while lower distance indication member  106  may extend about 0.5 mm beyond the distal end of forceps  102 . Again, other suitable distances may be readily ascertained by persons of ordinary skill with the benefit of the present disclosure. 
     In general, the upper and lower distance indication members  104  and  106  also provide sufficient radial clearance for the microsurgical tool, so as not to interfere with the operation of the tool (e.g., the opening and closing of the forceps). The specific amount of radial clearance provided by the distance indication members  104  and  106  may vary depending on the specific type of microsurgical tool employed. However, the appropriate amount of radial clearance may be readily ascertained by persons of ordinary skill with the benefit of this disclosure. 
     In other embodiments, different configurations in the location and shape of distance indication members  104 ,  106  could be employed. For example, rather than using two distance indication members (e.g., upper and lower distance indication members  104  and  106 ) a single distance indication member could be used. Similarly, three or more distance indication members could be used. In addition, the orientation of the distance indication member(s) could be modified. For example, the distance indication members  104  and  106  could be located coplanar or orthogonal with the arms of the forceps  102 . In one example, shown in  FIG. 1B , upper distance indication member  104  may be curved above the plane in which the forceps  102  open and close, whereas lower distance indication member  106  is shown to curve below the plane in which the forceps  102  open and close. In such an embodiment, this allows the forceps  102  to open and close with minimal, or at least reduced, interference from upper and lower distance indication members  104  and  106 , respectively. 
     In general, distance indication members  104  and  106  are configured to contact and interface with a tissue surface such as a retina. As the distal end of the microsurgical tool approaches the tissue surface, a portion of the distance indication member  104 ,  106  initially contacts the tissue surface and moves, or deflects, from a first position of use to a second position of use. The operator of the microsurgical tool provides the necessary force to position the microsurgical tool closer to the tissue surface and to deflect the distance indication member  104 ,  106  from the first position to the second position. Deflection of the distance indication member  104 ,  106  into the second position provides the operator of the microsurgical instrument  100  the visual indication of the distance from the distal end of the microsurgical tool to the tissue surface. The force necessary to cause the deflection of the distance indication member  104 ,  106  can be predetermined and differing levels of force may produce different levels of deflection by the distance indication member  104 ,  106 . Once a distance indication member  104 ,  106  is removed from contact with the tissue surface, the distance indication member  104 ,  106  will return to the non-deflected, first position of use. 
     The distance indication members  104 ,  106  may assume many possible configurations when contacting the tissue surface. In one example, as shown in  FIG. 1A , the distal portion  112  of a distance indication member  104  is angled. As also shown in  FIG. 1A , the majority of a distance indication member  104  is substantially parallel to the longitudinal axis of the microsurgical tool and, thus, much of the distance indication member  104  would not be readily visible to the microsurgical instrument operator when the distance indication member  104  is not in contact with a tissue surface. The angle of the distal portion  112  of distance indication member  104  forces the distal portion  112  of the distance indication member  104  to spread outwardly from the longitudinal axis of the microsurgical tool when the distance indication member  104  contacts the tissue surface. As the operator moves the distal end of the microsurgical tool (e.g., forceps  102 ) closer to the tissue surface, the deflection of the distance indication member  104  will increase and the distal portion  112  of distance indication member  104  will become more visible to the operator. Thus, in this configuration, the amount the distance indication member  104  readily visible to the operator is related to the distance the distal end of the microsurgical tool is from the tissue surface—the closer the microsurgical tool is to the tissue surface, the greater the amount of distance indication member  104  that will be readily visible to the user. When the microsurgical tool is moved away from the tissue surface, the distal portion  112  of the distance indication member  104  will return to a non-deflected configuration and the operator will know the microsurgical tool is no longer in contact with the tissue surface. 
     In another possible configuration, the distal portion  112  of a distance indication member  104  will not spread outwardly when it contacts the tissue surface, but rather the distal portion  112  of a distance indication member  104  remains stationary and at least an intermediate portion of the distance indication member  104  (e.g., between the distal and proximal ends of the member) deflects, or bows out, to provide the visual distance indication to the operator regarding the proximity of the microsurgical tool to the tissue surface. 
     In particular embodiments, distance indication members  104 ,  106  may be formed of a flexible material. Because the distance indication members  104 ,  106  are intended to contact sensitive tissue surfaces (e.g., the retina), the material may be extremely flexible to avoid damaging sensitive tissue surfaces within the eye. The material can also possess considerable elasticity to resume the desired shape after microsurgical tool  100  is compressed to pass through a cannula. Suitable materials for distance indication members  104 ,  106  may include EPDM (ethylene-propylene-diene monomer rubber), PHA (poly-hydroxy-alkanoate), and/or PHB (poly-hydroxy-butyrate). In particular embodiments, distance indication members  104 ,  106  may comprise a material that dissolves after a predetermined amount of time when exposed to, for example, the fluids of the eye. Such a material could prevent contamination of the eye if portions of distance indication members  104 ,  106  broke off, or were separated from, the microsurgical instrument  100  during surgery. Preselected portions of distance indication members  104 ,  106  may be made of such materials, such as the distal portion  112  of distance indication member  104 . 
     In particular embodiments, distance indication members  104 ,  106  may employ a thinned or narrowed portion that acts as a “living hinge” that facilitates bending of the distance indication members  104 ,  106 . The thinned or narrowed portion of the distance indication members  104 ,  106  could be more prone to bending than the remaining portions of the distance indication members  104 ,  106  in order to facilitate bending of the distance indication members  104 ,  106  in a prescribed manner. Other materials that provide the desired flexibility, elasticity, and visibility that may be used as well would be known to a person of skill in the art with the benefit of this disclosure. 
     The distance indication members  104 ,  106  may also be designed to be capable of being easily seen by an operator of the microsurgical instrument  100 . For example, in particular embodiments, the distance indication members  104 ,  106  may be a color, such as green, that enhances visibility relative to the tissue surface. Similarly, the distance indication members  104 ,  106  may be covered with a visual pattern, such as stripes or dots that enhances visibility. In particular embodiments, the color or visual markings on the distance indication members  104 ,  106  may differ at different points on the member to give the operator more discrete information about the proximity of the distal end of the microsurgical tool (e.g., forceps  102 ) to the tissue surface. For example, a distal portion  112  of distance indication member  104  may be green, an intermediate portion may be yellow, and a more proximal portion may be red. As the distance indication member  104  deflects outward, the green will first become visible to the operator, followed by the yellow as the microsurgical tool advances closer to the tissue surface, followed by the red as the microsurgical tool advances even closer to the tissue surface. In particular embodiments, portions of distance indication members  104 ,  106  may be enlarged in area to aid the operator of the microsurgical instrument  100  to view the distance indication members  104 ,  106 . 
     In particular embodiments, distance indication members  104 ,  106  may be designed of materials capable of providing additional feedback to an operator of the microsurgical instrument  100 . It is one aspect of some embodiments of the present invention to provide distance indication members  104 ,  106  made of material that changes color when compressed or bent, such as chromogenic or piezochromic polymers. Such a material would allow an operator to determine by the color change of the distance indication members  104 ,  106  the amount of force being applied to the distance indication members  104 ,  106  by the operator and may highlight to the operator that the distance indication members  104 ,  106  have been deflected. Further, the distal portion  112  of the distance indication members  104 ,  106  may be made of material that provides operator feedback (e.g., a color change) when it contacts tissue or the components thereof (e.g., certain proteins). Such a material would allow an operator to determine by the color change of the distance indication members  104 ,  106  the type of surface in contact with the distance indication members  104 ,  106 . In particular embodiments, the distance indication members  104 ,  106 , or portions thereof, may be constructed of a piezoelectric material that creates an electrical charge when compressed or bent. This electrical charge could be utilized to provide feedback to the operator through a surgical console or through the microsurgical instrument  100 . One of ordinary skill in the art will appreciate that the distance indication members  104 ,  106  may include one or more of the active indicators or more passive indicators described herein. 
     There are a variety of possible configurations of distance indication members  104  that could be implemented for a given microsurgical instrument  100 . Generally, the distance indication member  104  may surround the microsurgical tool (e.g., forceps  102 ) with a three-dimensional structure that exceeds the length and width of the microsurgical tool without impairing the intended functionality of the microsurgical tool. The design of distance indication members  104 ,  106  may provide an operator with an accurate visual distance indication from a tissue surface while not damaging the tissue surface through contact by distance indication members  104 ,  106  while meeting the mechanical requirement of being able to be retracted to fit through a small incision or cannula. 
       FIGS. 2A and 2B  illustrate a microsurgical instrument  200  in accordance with another embodiment of the present invention.  FIGS. 2A and 2B  illustrate microsurgical instrument  200  comprising scissors  214  and three distance indication members  204 ,  206 , and  208 .  FIG. 2A  illustrates the microsurgical instrument  200  in a side view orthogonal to the plane in which scissors  214  open, while  FIG. 2B  illustrates microsurgical instrument  200  in a top-down view parallel to the plane in which scissors  214  open. Although  FIG. 2A  illustrates three distance indication members, one of ordinary skill in the art, with the benefit of this disclosure, should appreciate that any number of distance indication members may be employed without departing from the teachings of the present disclosure. 
     As shown in  FIGS. 2A and 2B , scissors  214  comprises a first blade  216  and a second blade  218 , and may be at least partially received within a tubular member  210 . In particular embodiments, first blade  216  may be fixed relative to the tubular member  210 , e.g., by welding, while second blade  218  may be configured to move longitudinally within the tubular member  210 , relative to the first blade  216 . 
     Microsurgical instrument  200  also includes a shaft  212  that extends coaxially through tubular member  210 . In particular embodiments, shaft  212  may be used as an attachment point for distance indication members  204 ,  206 , and  208 . For example, first distance indication member  204  and third distance indication member  208  are shown attached to shaft  212  in a coplanar manner, whereas second distance indication member  206  is attached to a shaft  212  orthogonal to the plane in which distance indication members  204  and  208  are attached. Other possible attachment points, such as the outer portions of the scissors  214  or portions of the tubular member  210 , as also possible within the teachings of the present invention, provided that the distance indication members should be attached in such a manner that the distance indication members extend further than the distal end of the microsurgical tool (e.g., scissors  214 ) to which they are coupled. 
     Similar to the distance indication members  104  and  106  described above with respect to  FIGS. 1A and 1B , distance indication members  204 ,  206 , and  208  are configured to provide the operator of microsurgical instrument  200  with a visual indication that scissors  214  is in close proximity to a tissue surface. For example, as also shown in  FIG. 2A , the majority of a distance indication member  204  is substantially parallel to the longitudinal axis of microsurgical instrument  200  and, thus, much of the distance indication member  204  would not be readily visible to the microsurgical instrument operator when the distance indication member  204  is not in contact with a tissue surface. However, the distal portion  220  of distance indication member  204  is angled slightly outward. When the distal portion  220  of the distance indication member  204  contacts the tissue surface, the angle of the distal portion  220  of distance indication member  204  forces the distance indication member  204  to spread outwardly from the longitudinal axis of microsurgical instrument  200 . As the operator moves the distal portion  220  of scissors  214  closer to the tissue surface, the deflection of the distance indication member  204  will increase and the distal portion  220  of the member will be more readily visible to the operator. Thus, in this configuration, the greater the amount of distance indication member  204  that is readily visible to the operator, the closer the distal end of scissors  214  is to the tissue surface. When scissors  214  is moved away from the tissue surface, the distal portion  220  of the distance indication member  204  is configured return to a non-deflected configuration, thus giving the operator a visual indication that scissors  214  is no longer in close proximity to the tissue surface. Distance indication members  206  and  208  may be configured similarly to distance indication member  204 . 
     In another possible configuration, the distal portion  220  of the distance indication members  204 ,  206  and  208  will not spread outwardly when they contact the tissue surface. Instead, the distal portions  220  of distance indication members  204 ,  206 , and  208  may remain stationary and an intermediate portion of each distance indication member  204 ,  206  and  208  (between the distal portion and a more proximal portion), may deflect, or bow out, to provide the visual indication to the operator regarding the proximity of the microsurgical tool (e.g., scissors  214 ) to the tissue surface. 
     In particular embodiments, the distal portions  220  of distance indication members  204 ,  206 , and  208  extend beyond the distal end of scissors  214  by a predetermined amount. For example, in a particular embodiment distance indication members  204 ,  206 , and  208  extend beyond the distal end of scissors  214  by about 0.2 to 0.7 mm. In another embodiment, distance indication members  204 ,  206 , and  208  may extend about 0.5 mm beyond the distal end of scissors  214 . In other embodiments, the distance indication members may extend a greater or smaller distance beyond the distal end of scissors  214 . In  FIGS. 2A and 2B , distance indication members  204 ,  206  and  208  are also shown having the same length. However, in particular embodiments, distance indication members  204 ,  206 , and  208  may each have a different length. Moreover, in some embodiments, distance indication members  204 ,  206 , and  208  may be easily frangible or include perforated or thinned areas that allow the operator to selectively reduce the length of each distance indication member individually. Providing a microsurgical instrument  200  with distance indication members  204 ,  206 ,  208  of different lengths may increase the accuracy of the visual distance indication to the operator regarding the depth of the microsurgical instrument  200 . 
     Distance indication members  204 ,  206 , and  208 , are also positioned with sufficient radial clearance around scissors  214  so as not to interfere with the operation of scissors  214 . The amount of radial clearance between the distance indication members  204 ,  206 , and  208  and scissors  214  that is sufficient for a particular embodiment may be readily ascertained by persons of ordinary skill with the benefit of this disclosure. 
     Because distance indication members  204 ,  206 , and  208  are intended to contact and interface with a sensitive tissue surface, such as a retina, distance indication members  204 ,  206 , and  208  are designed to be capable of touching the tissue surface without damaging it. For example, distance indication members  204 ,  206 , and  208  are formed of a flexible material to avoid damaging sensitive tissue surfaces within the eye. The material can also possess considerable elasticity to resume the desired shape once a distance indication member  204  is passed through an entry cannula to gain access to the interior of an eye. In particular embodiments, the distance indication members  204 ,  206 , and  208  may be made of EPDM (ethylene-propylene-diene monomer rubber), PHA (poly-hydroxy-alkanoate), and/or PHB (poly-hydroxy-butyrate). Other materials that provide the desired flexibility, elasticity, and visibility that may be used as well would be known to a person of skill in the art with the benefit of this disclosure. 
     In particular embodiments, distance indication members  204 ,  206 , and/or  208  may also be comprised of a material that dissolve after a predetermined amount of time when exposed to, for example, the fluids of the eye. Such a material could prevent contamination of the eye if portions of one of the distance indication members  204 ,  206 , and/or  208  broke off or were separated from the microsurgical instrument  200  during surgery. Preselected portions of the distance indication members  204 ,  206 , and/or  208  may be made of such materials, such as the distal portion  220 . 
     The distance indication members  204 ,  206 , and  208  may also be designed to be capable of being easily seen by an operator of the microsurgical instrument  200 . For example, in particular embodiments, the distance indication members  204 ,  206 , and  208  may be a color, such as green, that enhances the visibility of the member relative to the tissue surface. Similarly, the distance indication members  204 ,  206 , and  208  may be covered with a visual pattern, such as stripes or dots that enhances visibility. In particular embodiments, the color or visual markings on the distance indication members  204 ,  206 , and  208  may differ at different points on the members to give the operator more discrete information about the proximity of the distal end of the microsurgical tool to the tissue surface. For example, a distal portion  220  of distance indication member  204  may be green, an intermediate portion may be yellow, and a more proximal portion may be red. As the distance indication member  204  deflects outward, the green will become visible first to the operator, followed by the yellow as the microsurgical tool advances closer to the tissue surface, followed by the red as the microsurgical tool advances even closer to the tissue surface. In particular embodiments, portions of distance indication members  204 ,  206 , and/or  208  may be enlarged in area to be more visible to the operator of the microsurgical instrument  200 . 
     In particular embodiments, distance indication members  204 ,  206 , and/or  208  may comprise materials capable of providing additional feedback to the operator of the instrument. For example, distance indication members  204 ,  206 , and/or  208  may made of a material that changes color when compressed or bent, such as chromogenic or piezochromic polymers. Such a material would allow an operator to determine by the color change the amount of force being applied to the distance indication members  204 ,  206 , and/or  208  and may highlight to the operator that the distance indication members  204 ,  206 , and/or  208  have been deflected. Further, the distal portion  220  of the distance indication members  204 ,  206 , and/or  208  may be made of material that provides operator feedback (e.g., a color change) when it contacts tissue or the components thereof (e.g., certain proteins). Such a material would allow an operator to determine by the color change of the distance indication members  204 ,  206 , and/or  208  the type of surface in contact with the distance indication members. In particular embodiments, the distance indication members  204 ,  206 , and/or  208  (or portions thereof) may be constructed of a piezoelectric material that creates an electrical charge when compressed or bent. This electrical charge could be utilized to provide feedback to the operator through a surgical console or through the microsurgical instrument  200 . One of ordinary skill in the art will appreciate that the distance indication members  204 ,  206 , and/or  208  may include one or more of the active indicators or more passive indicators described herein. 
     By providing a microsurgical instrument with distance indication members, particular embodiments of the present invention are able to provide enhanced functionality to surgeons. For example, particular embodiments of the present invention may allow a surgeon to accurately determine the distance of the microsurgical tool from the surface of a surgical area, such as a retina. Particular embodiments may also help the surgeon prevent accidental damage to the surgical area due to inadvertent touching of the surgical area by the microsurgical tool. 
     The foregoing description is provided to enable any person skilled in the art to practice the various embodiments described herein. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments. Thus, the claims are not intended to be limited to the embodiments shown herein, but are to be accorded the full scope consistent with the language of the claims.