Patent Publication Number: US-2021186478-A1

Title: Ocular surgical instrument

Description:
RELATED APPLICATIONS 
     The present application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Application 62/724,098 filed on Aug. 29, 2018 the disclosure of which is incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the invention relate to an apparatus for performing ocular surgery. 
     BACKGROUND 
     “Crossed-eyes” formally referred to by the medical profession as “strabismus” is a condition in which gaze directions of both of a person&#39;s eyes do not simultaneously align to a same point of regard. Gaze direction of a person&#39;s eye is controlled by six ocular muscles, referred to as extra-ocular muscles, that extend from a fibrous ring at the back of the eye orbit to respective attachment regions on the sclera the eye. The ocular muscles include four recti muscle (superior, inferior, lateral and medial) and two oblique muscles (inferior and superior). 
     Strabismus may be surgically corrected by strengthening or weakening of one or more extra ocular muscles to realign both eye in primary gaze position. In order to strengthen a muscle a procedure referred to as a resection procedure is usually performed, which involves excising a portion of the muscle near an attachment region of the muscle to the sclera of the eyeball and reattaching the muscle shortened by the excision to or near to the original “native” attachment region. Conversely in order to weaken the muscle, a procedure referred to as a recession procedure is performed, in which the muscle is detached from its native attachment region on the sclera then reattached at a new attachment region located behind the native attachment region and closer to the fibrous ring at the back of the eye&#39;s orbit. 
     Spatial accuracy in excising a portion of an ocular muscle and in reattaching an ocular muscle is advantageously performed to tolerances of less than or equal to about a millimeter or two. Surgical correction of strabismus is a relatively complex procedure that typically requires the hands of a qualified surgeon, and due to the technical difficulties involved in in the procedure the hands of a skilled assistant to help retract and constrain the positions of the muscle and the eye so that the surgeon may operate safely. 
     SUMMARY 
     An aspect of an embodiment of the disclosure relates to providing a strabismus ocular surgical instrument, optionally referred to by the acronym “OSIN”, for performing surgery on an ocular muscle that aids in efficiency and accuracy of performing strabismus surgery. In an embodiment OSIN comprises a support housing configured to be placed on an eye during eye surgery to correct strabismus and to hold an ocular muscle hook that is used during strabismus surgery to lift an ocular muscle of the eye away from the surface of the eyeball so that the muscle can be operated on. For holding the ocular muscle hook, OSIN may comprise a muscle hook holder and lock that enables the ocular muscle hook after being manipulated to engage the ocular muscle to be translated substantially along an axis of the hook to elevate the muscle by a desired distance from the eyeball and thereafter lock the ocular muscle hook in place to maintain the muscle elevated by the desired distance. In an embodiment the housing and/or the ocular muscle hook comprises graduation markings that may be used to determine a distance by which the ocular muscle hook is translated and the muscle displaced. The support housing is formed having at least one open access aperture through which a surgeon can introduce and operate a tool, such as a scalpel or surgical needle, to perform a step of a strabismus resection or recession procedure. 
     In an embodiment to facilitate reattachment of an elevated ocular muscle in a resection or recession procedure by gluing a region of the muscle to a desired reattachment location on the sclera, the housing comprises a clamping foot configured to be used to clamp the region of the elevated muscle to the reattachment location on the sclera for a setting period of the glue. Optionally, the housing comprises a foot stop against which the clamping foot can be pressed when clamping the region of the muscle to the reattachment location on the sclera. In an embodiment the clamping foot is formed at an end of a shank, which is attached to the housing and can be rotated to position the clamping foot to contact and clamp the muscle region to the desired reattachment location on the sclera. 
     In the discussion and claims, unless otherwise stated, adjectives such as “substantially” and “about” modifying a condition or relationship characteristic of a feature or features of an embodiment of the disclosure, are understood to mean that the condition or characteristic is defined to within tolerances that are acceptable for operation of the embodiment in an application for which the embodiment is intended. The word “or” is considered to be the inclusive “or” rather than the exclusive or, and indicates at least one of, or any combination of more than one of items it conjoins. 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF FIGURES 
       Non-limiting examples of embodiments of the disclosure are described below with reference to figures attached hereto that are listed following this paragraph. Identical features that appear in more than one figure are generally labeled with a same label in all the figures in which they appear. A label labeling an icon representing a given feature of an embodiment of the disclosure in a figure may be used to reference the given feature. Dimensions of features shown in the figures are chosen for convenience and clarity of presentation and are not necessarily shown to scale. 
         FIGS. 1A-1C  schematically show perspective views from different vantage points of a OSIN for use having a clamping foot and configured to reinsert an ocular muscle by gluing in a strabismus surgery, in accordance with an embodiment of the disclosure; 
         FIG. 1D  schematically shows an exploded view of the OSIN shown in  FIGS. 1A-1C  that shows detail of a muscle hook holder and lock, in accordance with an embodiment of the disclosure; 
         FIG. 1E  schematically shows an ocular muscle hook, in accordance with an embodiment of the disclosure; 
         FIG. 1F  schematically shows a cutaway view of the OSIN shown in  FIGS. 1A-1D  with the ocular muscle hook shown in  FIG. 1E  mounted to the OSIN, in accordance with an embodiment of the disclosure; 
         FIG. 1G and 1H  schematically shows operation of a muscle hook holder and lock similar to the muscle hook holder and lock shown in  FIG. 1D , in accordance with an embodiment of the disclosure; 
         FIGS. 2A-2F  schematically show a OSIN similar to that shown in  FIGS. 1A-1H  being used to perform a recession of a rectus muscle of an eye in which the rectus muscle is reinserted in a gluing operation near the muscle&#39;s native attachment location on the eye&#39;s sclera, in accordance with an embodiment of the disclosure; 
         FIG. 3A  schematically shows a clamping foot and a foot stop of comprised in a variation of the OSIN shown in  FIGS. 2A-2F   
         FIG. 3B  schematically shows a clamping foot and a foot configured to reinsert by stapling an ocular muscle in a strabismus resection operation in accordance with an embodiment of the disclosure; 
         FIGS. 4A-4H  schematically show an OSIN configured to reinsert an ocular muscle in a strabismus operation by suturing and operation of the OSIN in resecting a superior rectus muscle of an eye, in accordance with an embodiment of the disclosure; 
         FIGS. 5A and 5B  schematically show features of variations of an OSIN, in accordance with an embodiment of the disclosure; and 
         FIGS. 6A and 6B  schematically show operation of a variation of an OSIN, in accordance with an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the detailed description below construction and features of an OSIN having a clamping foot in accordance with an embodiment of the disclosure are described with reference to  FIGS. 1A-1H . A resection procedure of a superior rectus muscle using the OSIN shown in  FIGS. 1A-H  is illustrated and discussed with reference to  FIGS. 2A-2F . A variation of an OSIN having in addition to a clamping foot a foot stop is discussed with reference to  FIG. 3A . A variation of an OSIN in which a clamping foot is configured to facilitate stapling an ocular muscle to reattach the muscle to an eye is discussed with reference to  FIG. 3B . Discussion of an OSIN configured for performing a strabismus operation in which an ocular muscle is reattached by suturing is shown and discussed with reference to  FIGS. 4A-4C .  FIGS. 4D-4H  illustrate a strabismus operation using the OSIN shown in  FIGS. 4A-4C , and references to the figures are made in a discussion of the operation.  FIGS. 5A and 5B  show optional accessories to an OSIN for use in a strabismus operation in which a rectus muscle is reattached to an eye by suturing. Another variation of an OSIN and use of the variation are shown and discussed with reference to  FIGS. 6A and 6B . 
       FIGS. 1A-1C  schematically show different perspective views of an OSIN  20  operable to hold an ocular muscle hook for lifting an ocular muscle away from an eye during a strabismus operation, and to aid in reattaching the ocular muscle by gluing, in accordance with an embodiment of the disclosure.  FIG. 1D  schematically shows an exploded view of OSIN  20  that illustrates details of the construction of OSIN  20 , in accordance with an embodiment of the disclosure that are not shown in  FIGS. 1A-1C .  FIG. 1E  schematically shows an ocular muscle hook in accordance with an embodiment of the disclosure, and  FIG. 1F  schematically shows a perspective cutaway of OSIN  20  holding the ocular muscle hook shown in  FIG. 1E . Not all features of OSIN  20  are labeled or shown in all of  FIGS. 1A-1H . Figures of  FIGS. 1A-1H  in which a feature of OSIN  20  is best exhibited may be referenced for attention in the discussion below where the feature is discussed. 
     In an embodiment, OSIN  20  ( FIGS. 1A-1C ) comprises a tube-shaped support housing  22  optionally characterized by a substantially elliptical cross-section and formed having an access aperture  24  and glue injection ports  25  at a bottom end  26  of the housing, and a muscle hook holder  40  and lock  50  at a top end  27  of the housing. A bottom edge  28  of OSIN  20  may be formed to have a curvature matched to curvature of an eyeball of an eye for which OSIN is to be used to perform an operation and on which the bottom edge is placed during the operation. A set  31  of graduation markings that may be used to determine a distance by which an ocular muscle hook held by OSIN  20  is translated to elevate an ocular muscle during a strabismus operation may be located at bottom end  26  and extend in a direction towards top end  27  from a location near bottom edge  28 . Optionally, adjacent graduation markings are spaced apart by equal distances. Bottom edge  28  may be covered with a layer (not shown) of a suitable biocompatible soft elastomer to prevent damage to the eye on which the bottom edge is placed. 
     OSIN  20  comprises a clamping foot  60  at an end of a shank  62  optionally connected to support housing  22  at a junction  63  ( FIG. 1C ) and integrally formed with support housing  22  to elastically splay outward from the housing. Clamping foot  60  may be connected to shank  62  by a relatively thin junction  61  that functions as a hinge to allow rotation of clamping foot  60  in directions indicated by arrow-head arc  61 * shown in  FIG. 1A . Shank  62  optionally comprises a ramp  64  and an arched segment  65 . A shank slider  70  may be mounted to housing  20  by snap clips  72  shown in the exploded view of OSIN  20  in  FIG. 1D  that snap into slide slots  29  formed in the housing. Shank slider  70  is manually movable along slide slots  29  ( FIGS. 1C, 1D ) from a position near top end  27  of housing  20  in a direction towards bottom end  26  of housing  22  to press on ramp  64  of shank  62  and force the ramp and thereby the shank to rotate toward access aperture  24 . Arched segment  65  may be configured to provide added bendability to the shank and clearance room to prevent interference with an ocular muscle hook held by muscle hook holder  40  when the hook is raised and the shank rotated towards the access aperture  24 . 
     Muscle hook holder  40 , shown in greater detail in  FIG. 1D  may protrude from a cap plate  41  that closes top end  27  of housing  22 . The muscle hook holder is optionally formed to have a u-shaped cross-section and an open side  42 , and the cap plate is optionally formed to have a slot  43 . Open side  42  and slot  43  facilitate introducing an ocular muscle hook into OSIN  20 , removing the ocular muscle hook from OSIN, and manipulating the ocular muscle hook during an operation when the ocular muscle hook is held by muscle hook holder  40 . Muscle hook holder  40  may have at least one friction pad  44  mounted on an internal surface  45  of the holder. The at least one friction pad, which may be advantageously formed from a resilient elastomer, is configured to press snugly onto and hold a handle of an ocular muscle hook inserted into the holder, and operates to prevent free, unwanted motion of the ocular muscle hook. Optionally, muscle hook holder  40  comprises a pair of friction pads  44  on opposite regions of internal surface  45  of the muscle hook holder. The pair of friction pads may press onto a handle of an ocular muscle hook mounted in the muscle hook holder to sandwich and hold the handle between them. 
     In the perspective of  FIGS. 1A-1C  only a single friction pad  44  of a pair of friction pads is seen.  FIG. 1D , and  FIGS. 1G and 1H  discussed below, schematically show both friction pads  44  of a pair of friction pads that muscle hook holder  40  may comprise.  FIG. 1E  schematically shows an ocular muscle hook  80  having a handle  82  and a hook  84 , and  FIG. 1F  schematically shows a perspective cutaway of OSIN  20  in which the ocular muscle hook shown in  FIG. 1E  is mounted in OSIN and at least one friction pad  44  presses on handle  82  of the ocular muscle hook. 
     Optionally, handle  82  of ocular muscle hook  80  comprises a set of graduation markings  85 . When mounted in muscle hook holder  40  as shown in  FIG. 1E , the graduation markings may be referenced to an edge  49  of muscle hook holder  40  to determine a distance by which ocular muscle hook  80  is translated to elevate an ocular muscle during a strabismus operation. 
     Lock  50  mounted to muscle hook holder  40  optionally comprises an elliptical or an eccentric circular locking wheel  52  that protrudes through a lock aperture  46  in the muscle hook holder to contact a friction pad  44  comprised in the muscle hook holder. The locking wheel, which by way of example is shown as an elliptical locking wheel, may be rotated to increase pressure on the friction pad that the locking wheel contacts and thereby pressure with which friction pads  44  holds the handle of the ocular muscle hook. Locking wheel  52  may be mounted to muscle hook holder  40  by any of various configurations of brackets for example, U-brackets  56  shown in  FIGS. 1G and 1H . Optionally, lock  50  has a handle  54  for rotating locking wheel  52  and operating the lock. 
       FIGS. 1G and 1H  schematically show cross-section views of lock  50  in open and closed positions respectively. Lock  50  has by way of example an elliptical locking wheel  52  and is mounted to muscle hook holder  40  by U-brackets  56 . In the figures muscle hook holder  40  is holding handle  82  of ocular muscle hook  80  ( FIG. 1E ). In the open position shown in  FIG. 1G , friction pads  44  sandwich ocular muscle hook handle  82  between them so that the ocular muscle hook does not freely slide in hook holder  40  but can be moved during use in an operation by application of a modicum of manual force. In the closed position shown in  FIG. 1H , friction pads  44  sandwich hook handle  82  between them with force sufficient to lock the handle to the hook holder and operate to prevent motion of ocular muscle hook  80  relative to the friction pads. A modicum of manual force is a force that a surgeon using OSIN finds practical to apply to adjust position of muscle hook  80  during an ocular operation, such as a strabismus operation. A force sufficient to lock the handle to the muscle hook holder is a force which requires the surgeon to unlock the lock to enable adjustment of the position of the ocular muscle hook by application of the modicum of manual force. 
       FIGS. 2A-2F  schematically show OSIN  20  being used in a strabismus resection operation on an eye  100 , in accordance with an embodiment of the disclosure. 
       FIG. 2A  schematically shows a cross-section of ocular muscle hook  80  mounted to OSIN  20  and extending out from bottom  26  of OSIN at an initial stage of the operation before OSIN is brought into contact with eye  100  and after the ocular muscle hook has engaged, by way of example, a superior rectus ocular muscle  102  of eye  100 . In  FIG. 2A  lock  50  is in the open position and shank slider  70  is located near to top  27  of OSIN  20  and does not apply force to shank ramp  64 . In  FIG. 2B  OSIN  20  has been lowered to contact eye  100  along bottom edge  28  of OSIN in preparation for raising ocular muscle hook  80  to elevate ocular muscle  102  away from eye  100 . As noted above, bottom edge  28  may be configured to have a curvature that substantially matches curvature of eye  100  and may be covered with a suitable soft biocompatible elastomer that operates to prevent the eye from being injured by contact with the bottom edge. 
       FIG. 2C  schematically shows a perspective cutaway view of OSIN  20 , ocular muscle hook  80 , and eye  100  as shown in the cross-section view of  FIG. 2B .  FIG. 2C  schematically shows graduation markings  31  on OSIN  20  and graduation markings  85  on ocular muscle hook  80 . The figure illustrates the relation of graduation markings  31  to the position of hook  84  of ocular muscle hook  80  , and the position of graduation markings  85  relative to edge  49  of ocular muscle hook holder  40 . 
       FIG. 2D  shows a cross-section of OSIN  20  and eye  100  after ocular muscle hook  80  has been raised to elevate superior rectus muscle  102  to a desired distance above eye  100 . In accordance with an embodiment, an amount by which ocular muscle hook  80  has been raised and rectus muscle  102  elevated may be determined by referencing change of position of the ocular muscle hook to graduation markings  31  and/or  85 . For example, an inset  91  in  FIG. 2D  shows a perspective view of ocular muscle hook handle  82 , markings  85 , and a portion of muscle hook holder  40  that includes edge  49 , after ocular muscle hook  80  has been raised. Comparison of the position of graduation markings  85  relative to edge  49  in the inset with the position of markings  85  relative to edge  49  in  FIG. 2C  shows that ocular muscle hook  80  has been raised in  FIG. 2D  by five graduation markings relative to the position of the ocular muscle hook in  FIG. 2C . Assuming by way of example that adjacent graduation markings  85  are spaced apart by 1 mm (millimeter), ocular muscle hook  80  has been raised by 5 mm in  FIG. 2D  relative to the position of ocular muscle hook  80  in  FIG. 2C . 
     Following raising of ocular muscle hook  80  as shown in  FIG. 2D , in  FIG. 2E  lock  50  is closed to lock ocular muscle hook  80  to OSIN  20  and lock rectus muscle  102  elevated to the desired distance and an amount of a topical biological glue is deposited on a reattachment region on the eye at which rectus muscle  102  is to be reattached. The glue may be deposited on the reattachment region by using a syringe introduced to the region through a glue injection port  25  to inject the glue onto the region. In  FIG. 2E  and figures that follow the deposited glue is schematically represented by a bold line  110 . Following injection of glue  110 , in  FIG. 2F  shank slider  70  is slid downward in a direction indicated by a block arrow  75  to press onto shank ramp  64  and rotate shank  62  clockwise in the plane of the figure to bring clamping foot  60  to press a region  103  of raised superior rectus muscle  102  into contact with glue  110  in the reattachment region on eye  100  and with a portion  104  of the rectus muscle at the native attachment region  105  of the rectus muscle. Clamping foot  60  is maintained in the position shown in  FIG. 2F  for sufficient time to allow glue  110  to set and bond regions  103  and  104  to each other and the reattachment region of eye  100 . Following setting of glue  110 , excess tissue of superior rectus muscle  102  folded into a loop  107  of muscle tissue  102  by operation of clamping foot  60  may be excised by cutting through the excess tissue with a scalpel, optionally using clamping foot  60  as a cutting anvil against which to cut the muscle tissue. 
     In an embodiment, an OSIN similar to OSIN  20  may be configured to have a foot stop against which a clamping foot, such as a clamping foot  60  shown in  FIG. 2F , may compress together portions of ocular muscle tissue when clamping a region of an ocular muscle to glue the region to a gluing region of an eye. By way of example  FIG. 3A  schematically shows a cross-section of a portion of an OSIN  20 - 2  having a foot stop  66  against which clamping foot  60  compresses portions  108  and  109  of superior rectus muscle  102  together when gluing a region  103  of the rectus muscle to eye  100  in a neighborhood of native attachment region  105  of the rectus muscle. As schematically shown in  FIG. 3A , foot stop  66  may aid in sandwiching a quantity  111  of glue  110  between muscle portions  108  and  109  and bonding the portions together to provide a strong anchor of muscle region  103  of rectus muscle  102  to eye  100 . 
     In an embodiment an OSIN may comprise a clamping foot and foot stop that are configured to staple portions of an ocular muscle together to perform a strabismus resection operation in accordance with an embodiment of the disclosure.  FIG. 3B  schematically shows a cross-section of a portion of an OSIN  120  having a support housing  122 , and a clamping foot  160  and matching foot stop  166  configured to staple together portions of an ocular muscle in a resection operation. By way of example OSIN  120  is shown stapling portions  108  and  109  of superior rectus muscle  102  together. 
     Clamping foot  160  is formed having a staple channel  161  for receiving a staple  170  pushed into the channel by a staple hammer  171  and directing the staple to a recess  167  formed in foot stop  166  and shaped to operate as a crimping recess. As staple hammer  171  is operated to push staple  170  into and through channel  161 , legs (not shown) of staple  170  penetrate muscle regions  108  and  109  and are forced into crimping recess  167  where the staple legs are bent to staple regions  108  and  109  together. In an embodiment, staple hammer  171  may hold staple  170  by a magnetic force or by an adhesive applied to a region of the staple hammer and be manually operated to push staple  170  through staple channel  161  and muscle regions  108  and  109 . Optionally, staple hammer  171  is hinged to support housing  122  of OSIN  120  or to a portion of shank  162  to which clamping foot  160  is attached. 
       FIGS. 4A-4C  schematically show a perspective view, a perspective cutaway view, and a transparent “see-through” view respectively of an OSIN  200  configured to be used in a strabismus operation in which an ocular muscle is reattached to an eye by suturing, in accordance with an embodiment of the disclosure. 
     OSIN  200  optionally comprises a support housing  202 , having a muscle hook holder  40  optionally protruding from a cap  41  at a top end  27  of the support housing, a lock  50  attached to the holder, and at a bottom end  26  of the housing optionally two access apertures  24  and graduation markings  31 . Cut away view of OSIN  200  in  FIG. 4B  schematically shows OSIN  200  positioned on an eye  100  and holding a ocular muscle hook  80  optionally comprising a hook  84  and a handle  82  having graduation markings  85 . In the figure ocular muscle hook  80  has been manipulated to engage superior rectus muscle  102  of eye  100 . In see-through image of OSIN  200  shown in  FIG. 4C  ocular muscle hook  80  has been raised to elevate rectus muscle from eye  100  by a desired distance. 
       FIGS. 4D-4H  schematically illustrate OSIN  200  being used to perform a strabismus resection operation on rectus muscle  102  after the muscle has been elevated as shown in  FIG. 4C , in accordance with an embodiment of the disclosure. 
       FIG. 4D  schematically shows a posterior view of a portion of eye  100  and superior rectus muscle  102  following securing a region  103  of muscle  102  with a double armed surgical suture  300  having a spatulated needle  310  at each end of the suture. Lengths of suture  300  that lie on top side of muscle  102  are shown in solid lines. Lengths of suture  300  that lie on an underside of muscle  102  are shown in dashed lines. Regions of muscle  102  through which the suture passes from one side to the other side of the muscle are indicated by solid circles  302 . A loop  304  in a section of suture  300  indicates that the section lies over a section of suture  300  that passes through the loop. An inset  309  schematically shows an enlarged view of suture  300  that secures muscle  102 . 
       FIG. 4E  schematically shows a perspective posterior view of all of eye  100 , a portion of OSIN  200 , and superior rectus muscle  102  following securing region  103  of muscle  102  with double armed suture  300 .  FIG. 4F  schematically shows eye  100  and muscle  102  shown in  FIG. 4E  from a perspective anterior view of eye  100 .  FIG. 4G  schematically shows spatula needles  310  being used to puncture the top tissue layer, the sclera (not separately shown), of eye  100  and a region  104  of rectus muscle  102  to suture region  103  of the muscle to the sclera (not shown) near the native attachment region  105  of the muscle. Following puncturing and threading suture  300  through the sclera, suture  300  is drawn taut as schematically shown in  FIG. 4H  to pull and suture region  103  to region  104  and to region  105  the eye&#39;s sclera. After being drawn taut, suture  300  may be knotted and excess tissue from muscle  102  excised to complete the resection operation. 
     Care is advantageously taken when using a spatula needle  310  to suture muscle  102  to eye  100  to prevent the spatula needle from puncturing through the eye&#39;s sclera and damaging an internal tissue of the eye. In an embodiment an OSIN, such as OSIN  200  may be configured as schematically shown in  FIG. 5A  having needle guides  210 , each formed having a guide slot  211  curved to match the curve of a spatula needle  310  and into which the spatula needle may be inserted. Each needle guide  210  is positioned to orient its guide slot  211  so that the inserted needle  310  may be guided along the slot to penetrate, move through, and exit the sclera along a curved path in the sclera having a maximum depth that is less than the thickness of the sclera and advantageous for attaching muscle  102  to the eye without perforating the eye&#39;s globe. 
     In an embodiment an OSIN, such as OSIN  200 , may have a pair of muscle stops  212 , as schematically shown in  FIG. 5B , that are formed as a part of housing  202  to aid in positioning the housing during a strabismus operation. The muscle stops are located, optionally inside housing  202 , so they may be positioned, by way of example, over rectus muscle  102  before the muscle is elevated by ocular muscle hook  80 . Stops  212  are separated by a distance indicated by a double arrowhead line labeled “D”, that allows ocular muscle hook  80  to forcibly pull muscle  102  through space D when elevating the muscle. After muscle  102  is elevated, muscle stops  212  lie under the muscle and behind native attachment region  105  of the muscle. The stops then operate to prevent displacement of housing  202  in a direction towards native attachment region  105  beyond the native attachment region. In an embodiment distance D is determined so that the ends of muscle stops  212  that face each other catch edges of muscle  102 . By way of numerical example D may be between about 3 mm to about 3.5 mm. 
       FIG. 6A  schematically shows an OSIN  250  in accordance with an embodiment that is similar to OSIN  200  but comprises a roll-bar  260  which bridges aperture  24  at bottom  26  of support housing  202  near to or at bottom edge  28 , in accordance with an embodiment of the disclosure. Roll bar  260  optionally has an omega-like shape comprising a base segment  261  and two raised wing segments  262 . By way of example OSIN  250  is shown in  FIG. 6A  being used with ocular muscle hook  80  to perform a strabismus resection on rectus muscle  102 . After ocular muscle hook  80  is operated to elevate muscle  102  as shown in  FIG. 6A , OSIN  250  may be rotated around roll bar  260  optionally by about 90° as shown in  FIG. 6B  to trap a loop of muscle  102  on base segment  261  between wing segments  262 . Opposite tissue regions of the loop may be joined, for example by suturing, gluing and/or stapling. together along a region indicated by dashed lines  270  to shorten the length of muscle tissue in muscle  102  and correct for strabismus. 
     There is therefore provided according to an embodiment of the disclosure an apparatus for performing an ocular surgery, the apparatus comprising: a support housing having a bottom configured to be positioned on the sclera of an eye during performance of an ocular surgery; a muscle hook holder connected to the support housing and configured to hold an ocular muscle hook so that the ocular muscle hook may be translatable to elevate an ocular muscle away from the eye during performance of the surgery; and a set of graduation markings on the support housing useable to determine a distance that the ocular muscle hook may be translated to elevate the ocular muscle. Optionally, the set of graduation markings is located near the bottom of the housing. Optionally, adjacent graduation markings are spaced apart by a same distance. 
     In an embodiment, the housing is formed having at least one access aperture through which a tool to perform the surgery is introduced and manipulated. 
     In an embodiment, the muscle hook holder is configured to hold the ocular muscle hook with force that operates to prevent unwanted motion of the ocular muscle hook during performance of the surgery but enables application of a modicum of force to adjust the position of the ocular muscle hook during the surgery. Optionally, the muscle hook holder comprises at least one friction pad that contacts the ocular muscle hook and applies the force to prevent the unwanted motion of the ocular muscle hook. 
     In an embodiment, the muscle hook holder comprises a lock operable to be locked and apply force to the ocular muscle hook sufficient to lock the ocular muscle hook to the muscle hook holder. Optionally, the lock comprises a locking wheel rotatable to lock the lock. Optionally, the muscle hook holder comprises at least one friction pad that contacts the ocular muscle hook and when rotated the locking wheel contacts and presses on a friction pad of the at least one friction pad to lock the lock. 
     In an embodiment the apparatus comprises a roll bar at the bottom of the housing about which the housing is rotatable to pull the elevated muscle to form a loop of muscle tissue having two regions of muscle tissue pressed to each other, so that the pressed muscle regions can be joined together to perform a resection of the ocular muscle. 
     In an embodiment the apparatus comprises at least one needle guide having a guide slot curved to match the curve of a needle used to suture a region of the ocular muscle to the sclera and along which needle guide the needle is guidable to suture the region of the ocular muscle to the sclera without perforating the eye globe. 
     In an embodiment the apparatus comprises at least one muscle stop located at the bottom of the housing which when the bottom is placed on the sclera operates to prevent displacement of the housing in a direction towards a native attachment region of the ocular muscle beyond the native attachment region. 
     In an embodiment, the housing comprises a clamping foot operable to clamp a region of an ocular muscle to the sclera. 
     There is further provided according to an embodiment of the disclosure an apparatus for performing an ocular surgery, the apparatus comprising: a support housing having a bottom configured to be placed on the sclera of an eye during performance of an ocular surgery; a muscle hook holder connected to the support housing and configured to hold an ocular muscle hook so that the ocular muscle hook is translatable to elevate an ocular muscle away from the eye during performance of the surgery; and a clamping foot operable to clamp a region of the ocular muscle to the sclera. Optionally or additionally, the clamping foot is formed at an end of a shank coupled to the support housing and rotatable to a position that clamps a region of the ocular muscle to the sclera. Optionally, the shank comprises a ramp to which force is applicable to rotate the shank. Optionally, the housing comprises a shank slider operable to be moved along the housing to apply force to the ramp to rotate the shank. Optionally, the housing is formed having a slot and the shank slider having a snap clip which is snap clipped into the slot to mount the shank slider to the housing. 
     In an embodiment, the housing comprises a foot stop to which the clamping foot is pressable by rotation of the shank. In an embodiment, the housing is formed having at least one glue injection port through which a topical biological glue is injectable onto the sclera. 
     There is further provided according to an embodiment of the disclosure an ocular muscle hook comprising graduation markings that are referenceable to determine a distance to which the ocular muscle hook is translated to elevate an ocular muscle during an ocular surgery. 
     In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of components, elements or parts of the subject or subjects of the verb. 
     Descriptions of embodiments of the disclosure in the present application are provided by way of example and are not intended to limit the scope of the disclosure. The described embodiments comprise different features, not all of which are required in all embodiments of the disclosure. Some embodiments utilize only some of the features or possible combinations of the features. Variations of embodiments of the disclosure that are described, and embodiments of the disclosure comprising different combinations of features noted in the described embodiments, will occur to persons of the art. The scope of the disclosure is limited only by the claims.