Abstract

Topical vecuronium has been used as a mydriatic in avian species including parrots, cockatoos, and kestrels.^1,3 The initial purpose of this study was to evaluate the efficacy of vecuronium bromide (Norcuron®)² as a mydriatic in the South African black-footed penguin (Spheniscus demersus). After the penguin trials, we decided to evaluate its use in the common loon (Gavia immer) and the double crested cormorant (Phalacrocorax auritus).

Seven adult South African black-footed penguins from the Mystic Marine life Aquarium were used in the first part of the study. Initial pupil diameters were measured using a home made pupil gauge consisting of different sized (3-15 mm) semi-circles. Responsiveness to a bright light was also evaluated and recorded. Responsiveness was assessed by a subjective grade scale: 1- no response, 2- barely responds, 3- moderate response, 4- slow but complete response, and 5 normal pupillary light reflex. A total of 150 vecuronium bromide (4 mg/ml) was applied to one eye. This amount was given by applying one 30ml drop every 5 minutes. The opposite eye was used as a control by applying l50ml of saline in the same manner. Measurements of pupil diameter and responsiveness were made at 5 minute intervals for the first 30 minutes and at 15 minute intervals for the next 30- 60 minutes.

A juvenile common loon which was donated to the UFCVM and two adult double crested cormorants from Sea World of Florida was used in the second part of the study. A protocol similar to that used for the penguins was used. A total of 60mL vecuronium bromide (4mg/mL), given as two drops at 15 minute intervals, was placed in the conjunctival fornix of one eye and the same amount of saline into the control eye. Pupillary diameter and responsiveness for each eye were recorded at 10-15 minute intervals.

In the penguins, we compared the measurements and responsiveness of the test eye with the control eye at 15 minute intervals. Pupil diameter and responsiveness of the test eye before instillation of vecuronium were also compared to those measured at 15 minute intervals. Using a t-test or Mann-Whitney rank sum test,⁴ we calculated that there was no statistically significant difference (p > 0.05) within these values. Therefore, the drug was ineffective at producing mydriasis in this species of penguin.

In the loon, the first change in pupil size was observed at approximately 40 minutes. The test pupil reached a diameter of 7 mm (90% dilated) and remained that size for at least 45 minutes. During this period, the pupil no longer responded to direct light stimulation.

In the cormorants, mydriasis was first noted at 30 minutes. Maximum dilation was obtained after 75 minutes and lasted for more than two hours. The drug was effective in both of these species at producing adequate mydriasis.

References

1.  Mikaelian, I., I. Paillet, and D. Williams. 1994. Comparative use of various mydriatic drugs in kestrels (Falco tinnunculus). American Journal of Veterinary Research 55:270-272.

2.  Norcuron (Organon Incorporated, West Orange, New Jersey).

3.  Rainer, J.C., J. Paul-Murphy, D. Brunson, and C.J. Murphy. 1996. Effects of mydriatic agents in cockatoos, African gray parrots, and blue-fronted Amazon parrots. Journal of the American Veterinary Medical Association 208(2):227-230.

4.  SigmaStat for Windows version 2.0 (Jandel Corporation, San Rafael, California).