Regional Anesthesia in Ophthalmology

Routine preoperative testing is not recommended for patients undergoing cataract surgery, because testing neither decreases adverse events nor improves outcomes. We sought to assess adherence to this guideline, estimate expenditures from potentially unnecessary testing, and identify patient and health care system characteristics associated with potentially unnecessary testing.

A new technique of local anesthetic administration has been used for 50 patients undergoing cataract extraction. The simple technique involves direct transconjunctival infiltration of local anaesthetic directly to the sub-Tenon's space, in the inferior-nasal quadrant, using a blunt 19-gauge Southampton cannula. This method seeks to avoid the risks of retrobulbar haemorrhage, perforation of the globe, damage to the optic nerve, and injection into the subarachnoid space, whilst providing prolonged and reliable anaesthesia. Akinesia is achieved by the inferior-nasal placement of solution and if not sufficient, a top-up can easily be given. Patients graded any discomfort or pain using a 10 cm visual analogue graphical pain score chart with numerical and descriptive rating scale. The delivery of 50:50 mixture of lignocaine 2% and bupivacaine 0.5% anaesthetic was evaluated by patients with a median response of 'slight discomfort'. The operative procedure was graded with a median of 'no pain or discomfort', both for extracapsular cataract extraction and phakoemulsification. This is a new, modified, sub-Tenon technique which is simple, reliable, and which offers excellent anaesthesia and akinesia and avoids a sharp instrument being passed into the orbit.

The advent of a new technique that is considered much safer than previously established one leads to its rapid adoption. This usually leads to the identification of previously unreported complications of the new technique, and a re-assessment of its position in clinical care, which is precisely the state of play with the sub-Tenon's block. The sub-Tenon's block was introduced into the clinical practice in early 1990. A systematic recent search of subject headings such as complications of sub-Tenon's block, subtenon, orbital block, orbital block complications, and orbital anaesthesia was performed in Medline, EMBASE, and Cochrane database. Indeed there are complications of sub-Tenon's block published as case reports and the exact incidence of these complications is not known. Management and preventive measures of these complications are described. Although the sub-Tenon's block appears to be relatively safer than needle-based blocks but a proper prospective, randomized, double-blind controlled trial is essential for scientific proof that sub-Tenon's block is better than needle-based blocks.