RESPONSE OF INTRAOCULAR-PRESSURE TO RETROBULBAR AND PERIBULBAR ANESTHESIA

BACKGROUND AND OBJECTIVE: To evaluate the response of intraocular pres sure (IOP) to retrobulbar and peribulbar anesthesia. PATIENTS AND METH ODS: Patients were prospectively masked and randomized to receive eith er 4 cc of retrobulbar anesthesia (X = 29) or 6 cc of peribulbar anest hesia (X = 30), each consisting of a 50:50 mixture of 2% xylocaine and 0.75% bupivacaine with 150 units of hyaluronidase. IOPs were measured pre-anesthesia and 1, 2, and 5 minutes postanesthesia in nonglaucoma patients undergoing cataract extraction and intraocular lens implantat ion. RESULTS: Mean IOPs in the retrobulbar group as determined with a tonometer were 18.24, 18.66, 19.14, and 17.86 mm Hg pre-anesthesia and 1, 2, and 5 minutes post-anesthesia, respectively. In the peribulbar group, the mean IOPs were 18.53, 21.20, 20.40, and 19.20 mm Hg, respec tively. The 1-minute pressures in the two groups were statistically di fferent (P = .023). Within the peribulbar group, the 1- and 2-minute p ressures were statistically different from the pre-anesthesia IOP (P = .001 and P = .018, respectively). CONCLUSION: Peribulbar anesthesia, with its higher volume of anesthetic (6 vs 4 cc), results in a higher initial IOP. This difference was slight and short lived, and occurred in the absence of any external ocular compression. This study may have application in avoiding elevation of IOP in select patients undergoin g a local procedure.