Effect of Retrobulbar Anesthesia on Ocular Tension

VOL. 93, NO. 6

CORRESPONDENCE

Effect of Retrobulbar Anesthesia on Ocular Tension Editor; In their abstract, "Effect of retrobulbar anesthesia on ocular tension" (Am. J . Ophthalmol. 92:739, 1981), S. Hershenfeld and C. W. Breslin stated that after injecting 2% lidocaine with hyaluronidase and, in most cases, epinephrine, they concluded that retrobulbar anesthesia does not produce a statistically or clinically significant reduction in ocular tension, although this procedure is usually considered to have a hypotensive effect. A colleague and I studied the effect of retrobulbar anesthesia on intraocular pressure in 40 patients with senile cataracts the day before surgery. Interference with intraocular pressure caused by preoperative sedatives, carbonic anhydrase inhibitors, mydriatics, akinesia of the orbicularis oculi muscle, and the like was eliminated. We randomly divided the patients into four groups of ten each based on the type of anesthetic solution used. Group 1 received 2% lidocaine; group 2, 2% lidocaine with 1:200,000 epinephrine; group 3, 0.5% bupivacaine; and group 4, 0.5% bupivacaine with 1:200,000 epinephrine. The volume injected was 2 ml. Ipsilateral mydriasis after the injection disclosed the exact placement of the anesthetic solution. We used the noninjected eye as the control and measured intraocular pressure with the Perkins hand-held applanation tonometer before and one, five, ten, 20, 30, 40, and 60 minutes after the retrobulbar anesthesia was administered. There was a statistically significant difference between the values for the test eyes and the control eyes in all groups except group 1. The reduction caused by bupivacaine was significantly greater than that caused by lidocaine. The intraocular pressure decreased more when the anesthetic solution contained epineph-

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rine. The greatest decrease in intraocular pressure occurred five minutes after the injection of bupivacaine with epinephrine. However, this decreased value was only 23.63% less than the value recorded before the injection. Therefore, I agree with Drs. Hershenfeld and Breslin that retrobulbar anesthesia does not cause a clinically relevant reduction in intraocular pressure. 1

FERNANDO L . C . TRINDADE,

Belo Horizonte,

M.D.

Brazil

REFERENCE 1. Trindade, F. L. C , and Calixto, N.: Açâo da anestesia retrobulbar sobre a pressäo intra-ocular. Rev. Bras. Oftalmol. 40:45, 1981.

Reply Editor: We agree with Dr. Trindade that retrobulbar anesthesia does not cause a clinically relevant reduction in intraocular pressure before cataract extraction. Some cataract surgeons omit digital massage because they are confident of the pressure-decreasing effect of retrobulbar injection. We studied 50 patients, ranging in age from 24 to 87 years, chosen at random before undergoing cataract surgery. We measured intraocular pressure before the administration of intravenous sedation or retrobulbar injection and remeasured it four minutes after the retrobulbar injection with the EMT 20 electronic digital applanation tonometer. The noninjected eye served as the control. Patients were given either 2% lidocaine or 2% lidocaine with epinephrine 1:200,000. The mean decrease in intraocular pressure in the operated on eyes that received 2% lidocaine without epinephrine retrobulbarly was 0 mm Hg, a value significantly different from that noted in the control eyes. The mean decrease in intraocular pressure in the operated on eyes that received 2% lidocaine with epinephrine