Ocular Anaesthesia: Blocks, Complications and Exam Essentials
Last updated: October 2026
Choosing the safest anaesthesia for eye surgery, recognising block complications early, and the anaesthetic facts examiners love: drug doses, the oculocardiac reflex, malignant hyperthermia and gas bubbles.
Techniques
| Technique | Best for | Advantages | Risks |
|---|---|---|---|
| Topical ± intracameral lidocaine | Phaco in cooperative patients | No needle, quick visual recovery | Patient movement; not for long or complex surgery |
| Sub-Tenon (blunt cannula) | Phaco, vitrectomy, trabeculectomy | Good akinesia and analgesia, very low risk of globe perforation | Chemosis, subconjunctival haemorrhage |
| Peribulbar (needle outside the cone) | Most intraocular surgery | Good akinesia | Globe perforation, retrobulbar haemorrhage (lower than retrobulbar) |
| Retrobulbar (needle inside the cone) | Rapid deep block | Fast, small volume | Brainstem anaesthesia, optic nerve injury, retrobulbar haemorrhage, globe perforation |
| General anaesthesia | Children, open globe, very anxious or uncooperative patients, long surgery | Full control | Systemic risks; postoperative nausea |
Block complications to recognise
- Globe perforation: higher in axial lengths over 26 mm, staphyloma and previous buckle; prefer sub-Tenon or topical in such eyes.
- Retrobulbar haemorrhage: tense proptosis and raised IOP; decompress with lateral canthotomy if vision is threatened.
- Brainstem anaesthesia: within minutes: confusion, contralateral amaurosis, cranial nerve palsies, apnoea. Support the airway and circulation until it wears off; monitor every patient after a needle block.
- Local anaesthetic systemic toxicity: perioral tingling, seizures, arrhythmias; give 20% lipid emulsion (1.5 mL/kg bolus) and follow resuscitation guidelines.
Drugs and doses
| Drug | Use | Maximum dose (adult) |
|---|---|---|
| Lidocaine 2% | Fast onset, about 1–2 hours | 3 mg/kg without adrenaline; 7 mg/kg with adrenaline |
| Bupivacaine 0.5% | Slow onset, long action | 2 mg/kg |
| Hyaluronidase | Speeds spread of the block | Rare allergy can mimic orbital cellulitis |
Physiology and exam favourites
- Oculocardiac reflex: traction on muscles (especially the medial rectus) or pressure on the globe causes bradycardia; afferent trigeminal, efferent vagus. Release traction; give atropine if it persists. Commoner in children.
- Effect on IOP: suxamethonium, ketamine, coughing and straining raise IOP; propofol, thiopentone and volatile agents lower it. Avoid suxamethonium in open globe injury if possible.
- Malignant hyperthermia: triggered by suxamethonium and volatile agents; rising end-tidal CO2, rigidity and fever; treat with dantrolene 2.5 mg/kg. More common in patients with strabismus and some myopathies.
- Intraocular gas: nitrous oxide diffuses into SF6 or C3F8 bubbles and can raise IOP dangerously; avoid it for the life of the bubble. No flying either.
- Anticoagulants: usually continued for topical, intracameral and sub-Tenon anaesthesia; check INR for warfarin; avoid sharp-needle blocks where possible.
Related: cataract pre-op checklist, lateral canthotomy, ocular pharmacology.
Key sources
- Royal College of Anaesthetists and Royal College of Ophthalmologists. Local Anaesthesia for Ophthalmic Surgery. Joint guidelines, 2012
- Association of Anaesthetists. Management of severe local anaesthetic toxicity (2010, updated guidance)
- Kumar CM, Dodds C. Ophthalmic regional block. Ann Acad Med Singapore 2006;35:158–67
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