"No-needle" sub-Tenon's anaesthesia
- 1Department of Ophthalmology, Taunton and Somerset NHS Trust, Musgrove Park, Taunton TA1 5DA, UK
- 2Department of Anaesthesia
We read with interest the letter from Amin et al,1 suggesting a modification of the sub-Tenon local anaesthetic injection procedure. They advocate the use of a Venflon needle to penetrate the conjunctiva, with subsequent advancement of the cannula before anaesthetic injection. We are concerned that the use of a sharp needle should be recommended so close to the eye. Amin et al point out that the needle tip is clearly visible at all times and therefore at “minimal risk” of puncturing the eye. However, once under the conjunctiva, the needle is not necessarily “clearly” visible, and if subconjunctival haemorrhage should occur then it will quickly become obscured. We do not think it sensible to place a sharp needle this close to the eye when an effective and well proved alternative delivery system has already stood the test of time.2
In his editorial on local anaesthetic injection techniques for cataract surgery, Smerdon3 rightly emphasises the risk of ocular penetration for all techniques involving needles, and highlights the Royal College of Ophthalmologists' local anaesthesia survey4 which demonstrated the relative safety of sub-Tenon's and topical anaesthesia. We agree with him that when discussing an anaesthetic technique with a potential for high volume, it is not the expert anaesthetist/ophthalmologist who should be borne in mind, but rather the less skilled person, possibly less familiar with ophthalmic anaesthetic techniques, or in training, who may be required to administer a block. It is in this setting that the use of a needle very close to the eye is, in our opinion, an unwarranted risk. Surely the “no needle” sub-Tenon's technique is just as effective, and safer.
