Page 180 - Manual of Equine Field Surgery

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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