Retrobulbar block

A retrobulbar block is a regional anesthetic nerve block into the retrobulbar space, the area located behind the globe of the eye. Injection of local anesthetic into this space constitutes the retrobulbar block. This injection provides akinesia of the extraocular muscles by blocking cranial nerves III, IV, and VI, thereby preventing movement of the globe. It also provides sensory anesthesia of the conjunctiva, cornea and uvea by blocking the ciliary nerves. This block is most commonly employed for cataract surgery, but also provides anesthesia for other intraocular surgeries.

Side effects and complications
Complications associated with this block are either ocular or systemic. Local ocular complications include hematoma formation, optic nerve damage and perforation of the globe with possible blindness. Systemic complications include local anesthetic toxicity, brainstem anesthesia, and stimulation of the oculocardiac reflex. Most commonly, patients will report discomfort during the performance of the block, such as the sensation of the needle during insertion and/or pressure behind the eye during injection.

Technique
Resuscitative equipment, monitoring and personnel must be immediately available prior to performance of this block. The retrobulbar block is performed with the patient either seated or supine and looking straight ahead. The head should be maintained in a neutral position. A needle (22-27 Gauge, 3cm long) is inserted at the inferolateral border of the bony orbit and directed straight back until it has passed the equator of the globe. It is then directed medially and cephalad toward the apex of the orbit. Occasionally a 'pop' is felt as the needle tip passes through the muscle cone delineating the retrobulbar space. Following a negative aspiration for blood, 2-4mls of local anesthetic solution is injected and the needle is withdrawn. Akinesia and anesthesia quickly ensue within minutes with a successful retrobulbar injection.