Characterization of the normal dark adaptation curve of the horse
Article first published online: 12 JUL 2011
© 2011 American College of Veterinary Ophthalmologists
Volume 15, Issue 1, pages 42–45, January 2012
How to Cite
Ben-Shlomo, G., Plummer, C., Barrie, K. and Brooks, D. (2012), Characterization of the normal dark adaptation curve of the horse. Veterinary Ophthalmology, 15: 42–45. doi: 10.1111/j.1463-5224.2011.00923.x
- Issue published online: 18 JAN 2012
- Article first published online: 12 JUL 2011
Objective The goal of this work is to study the dark adaptation curve of the normal horse electroretinogram (ERG).
Procedures The electroretinographic responses were recorded from six healthy female ponies using a contact lens electrode and a mini-Ganzfeld electroretinographic unit. The horses were sedated intravenously with detomidine, an auriculopalpebral nerve block was then performed, and the pupil was fully dilated. The ERG was recorded in response to a low intensity light stimulus (30 mcd.s/m2) that was given at times (T) T = 5, 10, 15, 20, 25, 30, 40, 50, and 60 min of dark adaptation. Off-line analysis of the ERG was then performed.
Results Mean b-wave amplitude of the full-field ERG increased continuously from 5 to 25 min of dark adaptation. The b-wave amplitude peaked at T = 25, however, there was no statistical significance between T = 20 and T = 25. The b-wave amplitude then remained elevated with no significant changes until the end of the study at T = 60 (P > 0.49). The b-wave implicit time increased continuously between T = 5 and T = 20, then gradually decreased until T = 60. No distinct a-wave was observed during the testing time.
Conclusions Evaluation of horse rod function or combined rod/cone function by means of full-field ERG should be performed after a minimum 20 min of dark adaptation.