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Vet Ophthalmol. 2012 Jan;15(1):42-5. doi: 10.1111/j.1463-5224.2011.00923.x. Epub 2011 Jul 12.

Characterization of the normal dark adaptation curve of the horse.

Author information

1
Veterinary Clinical Sciences, Iowa State University Department of Small and Large Animal Clinical Sciences, University of Florida, Gainesville, FL, USA. gil.benshlomo@yahoo.com

Abstract

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/m(2) ) 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.

[Indexed for MEDLINE]

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