Ultrasound Guided Peribulbar Anaesthesia - A Novel Dual Quadrant Injection Technique

Peribulbar anesthesia is widely used for anterior and posterior chamber ophthalmic procedures. It is a blind technique which is traditionally carried out by inserting a needle in the infero-lateral aspect of the orbit below the globe and injecting a volume of 8 - 12 mL of local anesthetic in the periorbital space. The goal of this inejction is to achieve akinesia and anesthesia of the eye sufficient for surgery. The technique has a relatively high failure rate of up to 30%. A failure or insufficient block requires a second or rarely a third peribulbar injection to achieve success. Ultrasound can be used to guide needles in the human body and has been successfully used in many anatomic locations for anaesthesia. This study will assess whether ultrasound can guide the block needle in ophthalmic anesthesia to deliver local anesthetic via a single entry into two discrete locations within the periorbital space - the first in the infero-lateral quadrant and the second in the infero-medial quadrant. If this can be done the investigators may achieve a higher success rate for this block with a lower volume potentially improving the quality of the block and its safety.

Inclusion criteria

• ASA score less than III and ability to provide a written informed consent
• 22 patients presenting for opthalmic surgery

Exclusion criteria

• Coagulation disorder or anticoagulated with INR > 1.5
• Platelet count < 75 X 10*9/L
• Significant Myopia (axial length > 28mm)
• Patients unable to lie supine for 2 hours
• Patients with recent gas or silicone injections in/around the eye