Post Operative Pain Management Following Pterygium Surgery

A pterygium is a noncancerous growth on the front surface of the eye (cornea) which can cause redness, irritation and distortion in vision. The aim of surgery is to restore the normal curvature of front of the eye by peeling the pterygium off the cornea. This is done under local anaesthesia, in the form of eye drops and an anaesthetic injection into the pterygium. The medicine commonly used for injection are lidocaine or bupivacaine, the latter has a slightly greater duration of effect. The anaesthetic wears off shortly after the surgery after which the eye becomes uncomfortable, especially for the first 24 hours following surgery. This is because the cornea is more sensitive than any other structure in the body and the takes 3-7 days to heal. Unfortunately most conventional oral pain relief medicines do not effectively reduce eye pain. There are other ways of numbing the eye including a subtenons block where an anaesthetic medicine (mentioned above) is injected around the eye at the time of surgery. This is easily done once the pterygium has been removed as the subtenons space becomes accessible. This type of anaesthetic not only numbs the eye but temporally impairs ocular motility, causes drooping of the upper lid and can impair vision for up to 8 hours. The latter is not an issue as a pad covers the eye for the first 24hrs after surgery. This type of regional anaesthesia is very safe and is routinely performed for patients undergoing intraocular procedures such as cataract surgery. Anecdotal evidence suggests this mode of anaesthesia may provide better postoperative pain control for patients undergoing pterygium surgery. The aim of our study is to determine wheather a subtenons block given at the time of surgery, in addition to topical and injected anaesthesia, provides better short term post-operative pain control for patients undergoing pterygium surgery compared to traditional methods of anaesthesia.