Effect of mydriasis with topical rocuronium bromide on electroretinography in domestic pigeons (Columba livia)

Abstract

This study aimed to investigate the effect of mydriasis using topical rocuronium bromide on electroretinography (ERG) in domestic pigeons (Columba livia). Scotopic mixed rod and cone, photopic cone, and photopic flicker ERG were performed on nine eyes of nine healthy adult pigeons under sedation. Each pigeon underwent two sets of ERG recordings. First, without the induction of mydriasis (control) and the second time with the induction of mydriasis using topical rocuronium bromide (treatment). The results were compared using either the Student's t-test or Wilcoxon rank-sum test, where a P-value of <0.05 was considered statistically significant. No significant differences were observed in the a- and b-wave implicit times and amplitudes during scotopic ERG between the two groups. The a- and b-wave amplitudes in the photopic cone were significantly higher in the treatment group (63.83 ± 32.33 and 191.75 ± 94.46 µV) compared to the control group (46.15 ± 27.60 and 116.76 ± 70.65 µV; P=0.045 and P=0.032, respectively). The photopic flicker amplitude was also significantly higher in the treatment group (76.23 ± 48.56 µV) than in the control group (42.18 ± 31.18 µV; P=0.044). No statistically significant differences were observed in the photopic cone and flicker implicit times between both groups. In conclusions, mydriasis induced by rocuronium bromide in pigeon resulting in higher amplitudes during the photopic ERG but not scotopic ERG.

Keywords: avian; electroretinography; mydriasis; pigeon; rocuronium bromide.

Fig. 1.

Representative electroretinography of domestic pigeons with and without rocuronium bromide to induce mydriasis. The scotopic mixed rod and cone response: (A) without rocuronium bromide, and (B) with rocuronium bromide to induce mydriasis. The photopic cone response: (C) without rocuronium bromide, and (D) with rocuronium bromide. The photopic flicker response: (E) without rocuronium bromide, and (F) with rocuronium bromide. The letters a and b denote the a- and b-waves, respectively. N1 denotes the implicit time, and P1 denotes the amplitude of the photopic flicker response. The bar in between the waves of photopic flicker represents the introduction of light stimulus except for the first stimulus (on E and F). Oscillatory potentials (OP) were observed during on the ascending slope between the a- and b-waves (arrows; A, B, C and D).