The use of orbital morphine for postoperative analgesia in pterygium surgery

A prospective double-blind study compared the analgesic effectiveness of peribulbar lignocaine with peribulbar morphine and lignocaine for postoperative analgesia in pterygium surgery. Twenty patients were randomly divided to receive a peribulbar injection preoperatively of either 1% lignocaine 2 ml or 1% lignocaine 1.6 ml and 4 mg morphine. Effects on pain at injection and pain at 24 hours and 48 hours postoperatively were measured with a visual analog pain scale. Effects of the injections on sedation, pupil size and unwanted side-effects were also recorded. The groups were comparable for age, weight and surgical technique. There was a significantly lower pain score at 24 hours after operation in the morphine group (P = 0.035). There were no significant differences in sedation or side-effects between the groups. The physiological effects of morphine on the eye are reviewed. The study suggests that orbital morphine may be an effective and safe form of analgesia for corneal surgery and further investigation is warranted.