Change in flash visual evoked potentials in New Zealand albino rabbits after sub-tenon's anesthesia.

Context: The occurrence of amaurosis during ophthalmic anesthesia is well known. The reason for this manifestation has not been studied.Purpose: To investigate the effect of sub-tenon's anesthesia on visual conduction in rabbit eyes.Methods: Fifteen right eyes of 15 New Zealand albino rabbits were included. 2% lidocaine hydrochloride and 0.75% bupivacaine hydrochloride (1ml, 1:1 mixture) was injected in the sub-tenon's space of 8 eyes while the control group (n=7) was injected with 1ml physiological saline. Flash visual evoked potentials (FVEP) were performed with Roland reti-scan system before and, 5min, 15min, and 5 days after injection. The natural pupillary diameter and minimal pupillary diameter with light reflex were recorded.Results: In the anesthesia group, N1 latency, P1 latency, and P1 amplitude were 17.131.13ms, 28.251.83ms, 13.45 +/- 4.36v respectively before injection; 21.75 +/- 3.06ms, 29.63 +/- 2.67ms, 7.24 +/- 4.64v at 5min after injection; 22.25 +/- 1.39ms, 29.50 +/- 2.51ms, 7.54 +/- 4.47v at 15min after injection, and, 17.75 +/- 0.71ms, 28.13 +/- 2.42ms, 13.17 +/- 4.08v 5 days after injection. When compared with baseline, N1 latency at 5min and 15min after injection showed prolongation (p=0.019 and p=0.001, respectively). Likewise, P1 amplitude decreased at 5min and 15min after injection (p<0.001, p<0.001, respectively). Both N1 latency and P1 amplitude recovered 5 days after the injection. Pupillary light reflex (PLR) constriction amplitude was 35.42% and 0.00% before and at 5min after injection (p=0.012). After 5 days it recovered to 33.33%. The FVEP and PLR constriction amplitude did not change significantly after injection in the control group.Discussion: Sub-tenon's anesthesia was associated with changes in the FVEP and pupullary light reflex in rabbit eyes in our study.Conclusions: The data from this study suggested that sub-tenon's anesthesia could reversibly block visual conduction in rabbit's eyes.