98
46TH
ANNUAL
CONGRESS
OF
THE
SAEVA
SKUKUZA
16-‐20
FEBRUARY
2014
Anatomy:
The periorbita is a conical shaped structure stretching from the bony orbit
caudomedially and apexes toward the foramina ethmoidale, fissure orbitalis, canalis
opticus and foramen rotundum. All nerves carrying sensory, sympathetic and motor
sensation to the structures of the eye are found within this fascia. Cranial nerves III,
IV, V (ophthalmic branch) and VI, internal ophthalmic artery and vein are situated
within the periorbita. The sensory innervation to the globe and anexa is carried by
the ophthalmic branch of the trigeminal nerve (cranial nerve V).
Figure 2: Student performing a retrobulbar block in a horse (Campoy 2012. WCVA Order of
Proceedings).
Procedure:
There are two approaches to the periorbita: The modified retrobulbar technique
and the Peterson block.
The modified retrobulbar block:
The Modified retrobulbar technique requires advancement of a needle bent 5o
curvomedially at 4 separate sites around the globe through the conjunctiva. The
needle is insterted at the lateral and medial canthi as well as dorsal and ventral
margin of the eye. The needle should be advanced until a pop is felt as it passes
through the periorbital fascia. The syringe is aspirated and the local anaesthetic is
injected.
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