Cataract is the commonest cause of blindness worldwide; it is usually due to the normal ageing process. Cataract is the loss of the natural transparency of the lens of the eye. A cataract is treated by surgery to remove the lens and replace it with an artificial one. Cataract surgery is usually performed under local anaesthetic. There is debate as to which form provides better pain relief and operating conditions for the surgery.
Topical anaesthesia is performed by placing drops or gel of local anaesthetics on the surface of the eye. During the operation this may be supplemented by using a blunt needle to inject local anaesthetic to the front part of the eye through the operation incision (intracameral). Sub-Tenon anaesthesia is performed by first numbing the surface of the eye with local anaesthetic drops. The patient is then asked to look up and out. The membrane lining the front of the eye is held with blunt tweezers and a small nick is made in it with curved blunt-ended scissors. A small blunt sub-Tenon cannula is passed through this hole, round towards the back of the eye and alongside the globe to inject local anaesthetic in the sub-Tenon space.
This review was based on seven studies involving 617 patients.
The review showed that sub-Tenon anaesthesia provided better pain relief than topical anaesthesia during an operation for cataract surgery. The administration of topical anaesthesia was slightly less painful than sub-Tenon. Surgeons and patients both preferred sub-Tenon anaesthesia and there were more serious complications with topical than for sub-Tenon anaesthesia, although sub-Tenon anaesthesia tended to cause more minor, aesthetic problems. There was no report of any life threatening complications in any of the studies. Five of the seven studies used weak clinical methods.