[The effect of retrobulbar anaesthesia on visual evoked responses].
BACKGROUND
Retrobulbar anaesthesia in ocular surgery leads to a temporary sensory blockade of the nervus opticus. The purpose of this study was to investigate the effect and duration of this anaesthesia on the visual system and to find out whether there is any relation to the patient's 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 +/- 9.5 years were included in the study. All patients received retrobulbar injection of 4cc Xylonest(R) 2 %/Dur-Anest(R) 1 % (3 : 1). Visual evoked potential (VEP) was recorded before and shortly after retrobulbar anaesthesia and several times after cataract surgery (45 min to 6 hours after surgery). The latency period and amplitude of the P100 deflection of the VEP were analysed. A possible correlation to the above-mentioned variables was evaluated statistically.


RESULTS
Directly after retrobulbar injection of the anaesthetic and at the first postoperative VEP recordings the VEP recordings showed a decreased amplitude and an increased latency period. All measured values returned to normal within 2 hours after the retrobulbar injection, proving that the conductivity 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 correlation could be found between time of oculopression, premedication and the alteration of the VEP.


CONCLUSIONS
Retrobulbar anaesthesia with 4cc of a mixture of Xylocain/Dur-Anest leads to a temporary conductivity block in the optic nerve for about 2 hours.
Heuermann
Tim
T
Universitätsaugenklinik Charité, Medizinische Fakultät der Humboldt-Universität zu Berlin, Campus Virchow-Klinikum, Berlin, Germany.
Anders
Norbert
N
Pham
Duy-Thoai
DT
Wollensak
Josef
J
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000772:Anesthesia, Local; D002387:Cataract Extraction; D004569:Electroencephalography / Q000187:drug effects; D005074:Evoked Potentials, Visual / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007910:Lenses, Intraocular; D008012:Lidocaine; D008297:Male; D009900:Optic Nerve / Q000187:drug effects* / Q000503:physiopathology; D011183:Postoperative Complications / Q000503:physiopathology; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012016:Reference Values; D012307:Risk Factors; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D008012:Lidocaine