SUB-TENON’S ANAESTHESIA

Ocular Anaesthesia Retrobulbar (intraconal) Peribulbar (extraconal) Topical Sub-conjunctival Sub-Tenon’s

Use of “sharp instruments” in the peribulbar and retrobulbar anaesthesia has been quoted as causing possible serious and even vision threatening complications globe perforation orbital haemorrhage optic nerve damage subarachnoid diffusion

A relative new and safer technique Sub-Tenon block

Sub-Tenon’s Space Tenon´s capsule: thin layer of connective tissue which surrounds the globe. Anteriorly it lies in close apposition to the conjunctiva and fuses with it at the level of the limbus. Posteriorly surrounds the globe and fuses with the dura of the optic nerve

Anatomy of Sub-Tenon’s Space

The sub-Tenon´s space is a virtual space between the capsule and the sclera. The instillation of local anaesthetic into this space produces analgesia and akinesia by diffusing posteriorly into the retro-orbital space to block the traversing sensory and motor nerves.

Contraindications (Relative) Large vascular nasal pterygium Recent pterygium surgery (with graft) Scleral buckle surgery Previous or planned Glaucoma Drainage implants Previous or planned Trabeculectomy Ocular Cicatricial Pemphigoid Steven-Johnson’s syndrome

Sub-Tenon Cannula

Procedure

Complications Minor Slight pain Overspill of anaesthetic Chemosis Conjunctival haemorrhage

Complications Significant Diplopia Orbital or Retrobulbar haemorrhage Scleral perforation Optic neuropathy, choroidal and retinal vascular occlusion (rare) Cardiorespiratory collapse

Conclusion Reliable and low risk profile anaesthetic technique Highly suitable for day care surgical settings Largely accepted by both the surgeons and anaesthetists