Sykes and Presland [1]describe overfilling of the upper eyelid during a sub-Tenon injection which resulted in failed surgical access to the eye.  However, they make no mention of using gentle ocular pressure to assist dispersal of local anaesthetic from peri-orbital structures. This can be applied manually using massage, or alternatively using a purpose designed ocular weight or balloon. Externally applied ocular pressure is commonly used with peribulbar anaesthesia to facilitate spread of local anaesthetic around the globe. However, it may also prove useful following sub-Tenon anaesthesia to deal with dispersal of local anaesthetic from peri-orbital structures.

Extravasation of local anaesthetic into peri-orbital structures is not always unwanted. It may be used to advantage in patients who exhibit tight eye squeezing using their orbicularis oculi muscle. Surgery may be impossible in these patients despite an otherwise adequate block, even when ptosis is present. These patients are easily identified as they exhibit  marked intolerance, with eye squeezing, when the ocular speculum is first inserted for the sub-Tenon block. The block is often difficult to perform and these patients may require sedation. However, if a large volume sub-Tenon block (5ml) is used, extravasation into periorbital structures will result in  paralysis of the orbicularis oculi muscle, preventing eye squeezing during surgery. The only other alternative, in these circumstances, is to block the zygomatic branch of the facial nerve  at the lateral orbital rim by a subcutaneous injection of local anaesthetic, which may be painful.

Dr TA King

East Sussex Hospitals NHS Trust

East Sussex

Reference

 1. Sykes OT, Presland A. Trabeculectomy postponed due to volume of sub-Tenon local anaesthetic. Anaesthesia 2009; 64: 100-1.