Safer methods of ophthalmic block.

Sir,

We thank Dr Kannan for highlighting the risk of globe perforation due to two-injection technique for peribulbar block in our report.[12] Although medial canthus block has lower incidence of globe perforation, we suggest that sub-tenon block is an another safer alternative for primary ophthalmic block.[3] Sub-tenon block indications are same as of peribulbar block. Sub-tenon block can be administered in patients with long axial length where peribulbar block is avoided due to increased chances of globe rupture.[3] Volume of local anaesthetic varies from 3 to 10 ml depending on the type of surgeries. It results in lesser increase in intraocular pressure than peribulbar block.

Before the ophthalmic block, ultrasound (USG) of the globe can be done especially in myopic eye to rule out staphyloma and to evaluate the axial length. B-mode USG can improve the quality and safety of ophthalmic block by guiding the needle trajectory and spread of local anaesthetic. Monitoring of needle path with USG may prevent globe perforation with needle blocks. Najman et al. used B-scan liner array transducer of 12 MHz and 25 mm long 23G needle to administer 6 ml of 0.75% levobupivacaine periconal block.[4] They found that USG-guided block reduces the rate of intraconal needle tip placement along with reduction of needle length insertion into the orbit and concluded that USG-guided block is safer to reduce chances of globe perforation, especially in high myopic eyes.

We suggest that apart from medial canthus block, sub-tenon block and USG can be used to decrease the incidence of globe perforation.

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Conflicts of interest

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