Which peri‑ocular anesthetic blocks are used for cataract surgery?

Peri-Ocular Anesthetic Blocks for Cataract Surgery

The primary anesthetic blocks used for cataract surgery are peribulbar block, retrobulbar block, and sub-Tenon's block, with peribulbar and sub-Tenon's blocks being preferred over retrobulbar due to comparable efficacy and improved safety profiles. 1, 2

Main Anesthetic Block Techniques

Peribulbar Block

• Involves injection of local anesthetic outside the muscle cone, avoiding penetration into the retrobulbar space 1
• Provides effective anesthesia and akinesia comparable to retrobulbar block 1, 3
• Associated with increased conjunctival chemosis compared to retrobulbar block (RR 2.11,95% CI 1.46-3.05) 1
• Lower risk of globe perforation and retrobulbar hemorrhage compared to retrobulbar approach 1, 2
• Typically administered via two-injection transconjunctival technique with volumes around 5 mL 4, 3

Retrobulbar Block

• Involves injection of anesthetic within the muscle cone, directly into the retrobulbar space 1, 2
• Has been progressively phased out in favor of peribulbar and sub-Tenon's blocks due to higher complication risk 2
• Associated with increased lid hematoma compared to peribulbar (RR 0.36,95% CI 0.15-0.88) 1
• Carries risk of globe perforation, particularly in patients with myopic staphyloma 2
• Retrobulbar hemorrhage, though rare, occurs more frequently with this technique 1

Sub-Tenon's Block (STB)

• Surgical approach to accessing sub-Tenon's space that avoids needle penetration of the globe 2, 5
• Involves dissection of superior quadrants followed by direct infusion of retrobulbar space using a blunt 19-gauge cannula 5
• When deep anesthesia is required, low-volume STB appears to be the technique of choice in terms of efficacy 2
• Increasing anesthetic volume provides reproducible akinesia 2
• Demonstrated to be safe, simple, and effective for achieving rapid ocular anesthesia 5

Clinical Considerations

Efficacy Comparison

• No significant difference exists in pain perception during surgery between retrobulbar and peribulbar techniques 1
• Both peribulbar and retrobulbar blocks provide comparable complete akinesia 1
• Supplemental anesthesia requirements are similar: 21% for retrobulbar versus 28% for peribulbar 3
• Patient comfort assessments show no significant differences between techniques 3

Anesthetic Agents

• Prilocaine 2% plain is equally effective as lignocaine 1% with bupivacaine 0.5% for peribulbar anesthesia 4
• Prilocaine offers low toxicity and effectiveness without adrenaline 4
• Hyaluronidase is the most useful adjuvant to local anesthetic 2

Modern Surgical Context

• The requirement for very deep block with total akinesia has greatly decreased with phacoemulsification, allowing for topical anesthesia or low-volume sub-Tenon's block 2
• Non-akinesia techniques may result in impaired surgical conditions with potential for surgical complications 2

Safety Profile

Severe local or systemic complications are rare for all block types 1. The main risks include:

• Globe perforation (primarily with needle-based techniques in myopic patients) 2
• Retrobulbar hemorrhage (rare, predominantly with retrobulbar block) 1
• Chemosis (more common with peribulbar) 1
• Lid hematoma (more common with retrobulbar) 1

Correct teaching and training are mandatory to prevent complications, as needle misplacement represents the primary risk factor 2.