Retrobulbar Block Technique for Cataract Surgery
Critical Safety Note
Retrobulbar anesthesia has been progressively phased out in favor of safer alternatives (peribulbar block, sub-Tenon's block, or topical anesthesia) due to the risk of serious complications including globe perforation, optic nerve injury, and retrobulbar hemorrhage. 1 However, when retrobulbar block is specifically indicated, the following technique should be employed:
Patient Positioning and Preparation
- Position the patient supine with the head stabilized and comfortable 2
- Use primary eye position during injection (Unsöld technique) rather than superonasal gaze (Atkinson technique), as this significantly reduces the risk of optic nerve lesion 2
- Apply topical anesthetic to the conjunctiva before needle insertion 3
- Leave the pupil undilated initially to monitor anesthetic effect 3
Injection Technique
Needle Placement
- Insert a sharp, appropriately sized needle (typically 25-27 gauge, 31-38mm length) at the inferotemporal orbital rim 2
- Direct the needle within the orbital muscle cone to achieve true retrobulbar placement 2
- Advance the needle posteriorly while maintaining primary gaze position to avoid the optic nerve 2
- Stop advancement just past the equator of the globe, typically 25-31mm depth 2
Anesthetic Administration
- Inject approximately 0.25 ml of anesthetic initially and wait until the pupil dilates before injecting the remaining volume 3
- Total volume should be approximately 5 ml of local anesthetic mixture 2
- This controlled injection technique is nearly painless and prevents increased intraocular pressure 3
Anesthetic Selection
Recommended Mixture
- Use a bupivacaine-lidocaine combination to achieve both rapid onset (lidocaine) and prolonged duration (bupivacaine) 2
- Add hyaluronidase to the mixture, as it is highly effective for preventing vitreous bulging 2, 1
- Consider adding adrenaline (epinephrine) to prolong anesthetic action, reduce hemorrhage risk, and decrease intraoperative vitreous bulging 2
Alternative Agents
- Lidocaine or prilocaine for short procedures (advantages: good tissue penetration, low toxicity) 2
- Mepivacaine for intermediate duration with pronounced vasoconstrictor activity 2
- Bupivacaine alone provides excellent postoperative analgesia but has higher cardiac toxicity risk 2
Adjunctive Facial Nerve Block
- Perform a Nadbath/Rehman modified facial nerve block for superior orbicularis akinesia 2
- Inject 5 ml of etidocaine-lidocaine mixture just inferior to the earlobe 2
- This technique blocks both upper and lower portions of the peripheral facial nerve, providing better lid akinesia than O'Brien or van Lint techniques 2
Post-Injection Management
- Apply oculopression (gentle orbital compression) for approximately 20 minutes after injection 2
- This enhances anesthetic spread and improves akinesia 2
- Massage or compression to soften the eye is NOT required with the controlled injection technique 3
- Apply short-acting mydriatics after the injection is complete 3
Expected Outcomes
- Complete corneal anesthesia should be achieved in nearly all cases 2
- Retrobulbar block provides superior globe akinesia compared to peribulbar techniques, even when larger volumes are used for peribulbar injection 2
- Lid closure force should be zero with proper facial nerve blockade 2
Critical Contraindications and High-Risk Factors
- Myopic staphyloma is the main patient risk factor for inadvertent globe perforation 1
- Severe coagulopathy increases hemorrhage risk 4
- Prior orbital trauma may distort anatomy 4
- Uncontrolled hypertension increases bleeding complications 4
- Infection at the injection site is an absolute contraindication 4
Important Caveats
Modern cataract surgery with phacoemulsification has greatly reduced the requirement for deep akinesia, making less invasive techniques (topical anesthesia, low-volume sub-Tenon's block) increasingly preferred. 1 The choice of retrobulbar block should be reserved for specific clinical scenarios where deep anesthesia and complete akinesia are essential, and only when performed by properly trained practitioners. 1
Sedation with intravenous sodium thiopental (pentothal) immediately prior to the block can enhance patient comfort and amnesia during needle insertion. 5