Ophthalmic regional blocks: retrobulbar, peribulbar, sub-Tenon

Model answer

Compare (6). Intraconal retrobulbar gives rapid dense akinesia with the highest serious risk; extraconal peribulbar uses larger volumes with slower onset and lower needle risk; sub-Tenon via blunt cannula is the safety default with good analgesia but variable akinesia — each technique has its own risk-benefit profile and the choice is individualised to patient, surgery, and operator skill.^[1] Sub-Tenon blocks have gained popularity through an improved safety profile over other regional blocks; topical offers analgesia without akinesia.^[3] Hyaluronidase breaks down hyaluronic acid to hasten onset of anaesthesia and akinesia, with conflicting efficacy evidence.^[4] Needle blocks for anterior segment surgery can proceed without stopping antiplatelet or anticoagulant treatment per local guidance.^[5]

Complications (4). Globe perforation (long myopic eye), retrobulbar haemorrhage (pain, progressive proptosis, tight orbit, rising IOP — canthotomy pathway), oculocardiac reflex (typical moderate trigemino-vagal bradycardia on extraocular muscle tension; profound bradycardia in almost 10 percent of strabismus cases without anticholinergic; reduced by deeper inhaled agents, hypocarbia, anticholinergics and orbital block; augmented by rapid opioids), and brainstem anaesthesia.^[1][6]

Brainstem (5). Minutes after injection: drowsiness, contralateral eye signs, seizures, apnoea, unresponsiveness, cardiovascular instability — an airway emergency, not sedation. Call for help, ventilate with 100 percent oxygen, intubate if needed, support circulation, continue ALS-level support until the LA redistributes; such life-threatening complications are why an anaesthesiologist must be available. Cancel surgery, document, review monitoring culture.^[1][2]