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

Abstract

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 (1 ml, 1:1 mixture) was injected in the sub-tenon’s space of 8 eyes while the control group (n = 7) was injected with 1 ml physiological saline. Flash visual evoked potentials (FVEP) were performed with Roland reti-scan system before and, 5 min, 15 min, 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 17.13 ± 1.13 ms, 28.25 ± 1.83 ms, 13.45 ± 4.36 μv respectively before injection; 21.75 ± 3.06 ms, 29.63 ± 2.67 ms, 7.24 ± 4.64 μv at 5 min after injection; 22.25 ± 1.39 ms, 29.50 ± 2.51 ms, 7.54 ± 4.47 μv at 15 min after injection, and, 17.75 ± 0.71 ms, 28.13 ± 2.42 ms, 13.17 ± 4.08 μv 5 days after injection. When compared with baseline, N1 latency at 5 min and 15 min after injection showed prolongation (p = 0.019 and p = 0.001, respectively). Likewise, P1 amplitude decreased at 5 min and 15 min 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 5 min 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.

Keywords:

• Ophthalmic anesthesia
• sub-tenon’s anesthesia
• visual potential

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article. (1) Joint Shantou International Eye Center of SUMC & CUHK (grant No.14-002). (2) Innovation Project of Colleges Reinforcement of Guangdong Province.