Page 180 - Manual of Equine Field Surgery
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CHAPTER                                                                   32









                              Nerve Blocks for Ophthalmic Procedures: Lacrimal, Zygomatic,





                                          lnfratrochlear, Palpebral, and Supraorbital Nerve Blocks








                                                                                                                      Laurence  E.  Galle

























                            INDICATIONS                                                                                                                ANATOMY







                            The  indications  for the lacrimal,  zygomatic,  and                                                                        The  lacrimal,  zygomatic,  infratrochlear,  and


                            infratrochlear  nerve  blocks  are  to  provide  local                                                                      frontal nerves  provide  sensory  innervation  to the


                            anesthesia  to  the  dorsolateral,  ventrolateral,  and                                                                     eyelids of the horse.  The  lacrimal  nerve innervates


                            ventromedial  eyelids. These  sensory nerve blocks                                                                          the dorsolateral  third  of the eyelid,  the  zygomatic



                            are  primarily used  for  minor  diagnostic  or thera-                                                                      nerve  innervates  the  ventrolateral  eyelid,  the


                            peutic  procedures  such  as  subpalpebral  lavage                                                                          infratrochlear  nerve  innervates  the  medial  can-


                            tube placement,  conjunctiva!  biopsy,  or eyelid lac-                                                                      thus  and  ventromedial  aspect  of  the  eyelids,


                             eration  repair.  These  blocks  do  not  provide  aki-                                                                    and the frontal nerve  innervates  the dorsomedial


                            nesia  of the eyelids."?                                                                                                    two  thirds  of the eyelids  (Figure  32-1).  The  zygo-


                                   The  supraorbital  nerve  block provides  sensory                                                                    matic  nerve  is  a branch  of the  maxillary  branch



                             anesthesia  of the  dorsomedial  two  thirds  of  the                                                                      of  the  trigeminal  nerve  (CN  V),  whereas  the


                             eyelid  to facilitate  examination  or minor  surgical                                                                     lacrimal,  infratrochlear,  and  frontal  nerves  are


                            procedures.  This block does  not  provide  akinesia                                                                        branches  of the  ophthalmic  branch  of the trigem-


                             of the  eyelids."!                                                                                                         inal  nerve.':"  The  lacrimal,                                          zygomatic,                   and


                                   The  palpebral  nerve  block  is  used  to  provide                                                                  infratrochlear nerves  exit  the  orbit  from  beneath


                             eyelid akinesia  for ophthalmic  examination and to                                                                        the  orbital  rim  adjacent  to  the areas  they  inner-



                            facilitate  diagnostic or minor  surgical  procedures.                                                                      vate, whereas  the frontal  nerve  exits the orbit  with


                            It  does  not,  however,  provide  sensory anesthesia                                                                       the  frontal  artery  and vein  through  the supraor-

                             of the eyelids."?                                                                                                          bital  foramen  of  the  supraorbital  process  of the



                                                                                                                                                        frontal bone.


                                                                                                                                                              The  palpebral nerve  is a branch  of the  auricu-



                             EQUIPMENT                                                                                                                  lopalpebral  branch  of the  facial  nerve  ( CN VII)


                                                                                                                                                        and  innervates  the  orbicularis  oculi  muscle.  The



                            A  5-mL  syringe,                     5/8-inch         25-gauge  needle,  and 2°/o                                          palpebral  nerve is most easily palpated as it crosses


                            lidocaine.                                                                                                                  the  dorsal  border  of the zygomatic  arch"  (Figure

                                                                                                                                                        32-2).








                             PREPARATION AND  POSITIONNG                                                                                                PROCEDURE
                                                                                                      I






                             These procedures may be performed  in restrained                                                                           The  lacrimal  nerve  block  is performed  by palpat-


                             patients  but are  facilitated  by sedation.                                                                               ing the dorsolateral  orbital rim.  Using  a 25-gauge






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