SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
of these toxic effects that the application of topical anaesthetics is contraindicated for
the treatment of painful ocular conditions.
REGIONAL ANAESTHETIC OF THE EYELIDS
Two to five millilitres of lignocaine are injected at the specific site to induce akinesia
or analgesia. The time of onset of anaesthesia is 4-6 minutes and the duration of
effect is 40-60 minutes in most cases. Regional nerve blocks are used to block both
motor and sensory nerves of the eyelids.
The orbicularis oculi muscle encircles the eyelids and is responsible for closing them.
Paralysis of the orbicularis oculi muscle is indicated during small surgical procedures
to allow subconjunctival injections and to facilitate diagnostic procedures including
examination of the eye. The orbicularis oculi muscle of large animals is powerful and
it can easily prevent the examination of the eye. Blepharospasm is a common
presenting sign of corneal ulceration. If the eyelids are forcefully opened in the case
of a deep corneal ulcer, rupture of the cornea may occur with possible loss of the
eye. Analgesia of the eyelids is indicated for manipulative and surgical procedures of
the eyelids for example resection of an eyelid tumour or placement of a subpalpebral
lavage system.
Auriculopalpebral nerve block:
This procedure will block the motor [Facial nerve, CN VII] control to the eyelids. It is
probably the most useful and widely used block. The auriculopalpebral nerve may be
blocked at two sites,
1.
Lignocaine is injected just lateral to the highest point of the zygomatic
arch.
2.
Palpate the caudal border of the ramus of the mandible and zygomatic
arch. A depression can be felt and the nerve may be palpated as it
passes the bone. Lignocaine is injected in a fan like manner in this area.
Akinesis is evident by narrowing of the palpebral fissure and drooping of the upper
eyelid.
Sensation to the eyelids is provided by the ophthalmic and maxillary divisions of the
Trigeminal nerve (CN V). The frontal, lacrimal, and infratrochlear nerves arise from
the ophthalmic branch of CN V, whereas the zygomatic nerve arises from the
maxillary branch of CN V.
Frontal (Supraorbital) nerve block: This blocks the sensory innovation [Frontal
nerve, CN V] of the central upper eyelid. Landmarks are the supraorbital foramen,
situated as a palpable depression midway across the supraorbital process where it
begins to widen. A one inch 22 gauge needle is inserted into the foramen, 2ml
lignocaine is injected into the foramen as the needle is withdrawn.
Zygomatic nerve block: This blocks sensory innervation [Maxillary branch CN V] to
the lower eyelid except to the medial canthus. Landmarks are a point just medial to
75