97th DOG Annual Meeting 1999
THE EFFECT OF RETROBULBAR ANESTHESIA ON VISUAL EVOKED RESPONSES
T. Heuermann1, N. Anders1, D. T. Pham2, J. Wollensak1
Retrobulbar anesthesia in ocular surgery blocks ocular motility and reduces the sensitivity of the cornea, conjunctiva and deep sensation of the eye. Furthermore it leeds to a temporary sensory blockade of the nervus opticus. The purpose of this study was to investigate the effect and duration of this anesthesia on the visual system and to find out, if there does exists any relation to the patients age, oral premedication, time of oculopression and the axial length of the operated eye.
Methods: A total of 57 patients with a mean age of 77.4±21.5 years were included in the study. All patients received retrobulbar injection of 4cc Xylonest 2%®/Dur-Anest 1%® (3:1). Cataract surgery was performed by using phacoemulsification technique and IOL implantation in the posterior chamber. Visual evoked potential (VEP) was recorded before and short after retrobulbar anesthesia and several times after cataract surgery (55 min to 6 hours after surgery). The latency time and amplitude of the P100 deflection of the VEP were analyzed. A possible correlation to the above mentioned variables has been evaluated statistically.
Results: Directly after retrobulbar injection of the anesthetic and at the first postoperative VEP recordings the VEP recordings showed a decreased amplitude and an increased latency time. All measurements returned to normal within 2 hours after the retrobulbar injection, proving that the conduction block of the optic nerve was temporary. There was a poor correlation between patients age, ocular length of the operated eye and the degree of reduction of the recorded VEP. No correlatioen could be found between time of oculopression, premedication and the alteration of the VEP.
Conclusion: Retrobulbar anesthesia with 4cc of a mixture of Xylocain/Dur-Anest leeds to a temporary conduction block in the optic nerve for about 2 hours. Patients should be informed about a possible temporary visual loss after retrobulbar anesthesia.
1Dept. of Ophthalmology, Charité, Campus Virchow-Klinikum, D-13353 Berlin
2Dept. of Ophthalmology, Hospital Neukölln, Rudowerstr. 48, D-12313 Berlin