J Vet Sci.  2009 Sep;10(3):233-238. 10.4142/jvs.2009.10.3.233.

The normal electroretinogram in adult healthy Shih Tzu dogs using the HMsERG

• Lee JS
• Kim KH
• Jang HY
• Lee B
• Kim JY
• Jeong SW

• KMID: 1726923
• DOI: http://doi.org/10.4142/jvs.2009.10.3.233

Abstract

Electroretinography (ERG) is a reliable diagnostic tool for the diagnosis of retinal disease. It measures electric potentials occurring in the retina in response to light stimulation. In this study, we examined the normal electroretinogram using the Handheld Multispecies ERG (HMsERG) in Shih Tzu dogs. ERG recordings were performed in twelve eyes of six healthy Shih Tzu dogs. Dogs were anesthetized with a combination of medetomidine and ketamine. Proparacaine eye drops were also applied as a topical anesthetic. Tropicamide eye drops were applied for mydriasis. After 20 min of dark adaptation, we recorded the amplitudes and implicit times of the b-waves of the rod, standard rod and cone (Std R&C), high-intensity rod and cone (Hi-int R&C), and cone systems, and responses of the cones and inner retina by flicker light stimulation (cone flicker). Results showed that mean the amplitudes of a-waves of Std R&C, Hi-int R&C, and the cone responses were 141.25 microV, 173.00 microV, and 12.92 microV, respectively. The b-waves of the rod responses ranged from 141.58 to 155.25 microV; the Std R&C was 314.75 microV, the Hi-int R&C was 329.42 microV, the cones were 37.75 microV, and the flicker responses were 64.08 microV. The b/a ratios for the Std R&C, Hi-int R&C, and the cone response were 2.29, 1.94, and 3.71, respectively. Mean implicit time of the a-wave of the Std R&C was 15.12 ms, of Hi-int R&C was 13.42 ms, and of the cone response was 7.22 ms. The b-wave of the rod responses ranged from 68.12 to 72.68 ms, of Std R&C were 37.28 ms, of Hi-int R&C were 41.90, of the cone responses were 38.12 ms, and of the cone flicker responses were 22.80 ms. We believe that these parameters can be used as reference "normal" ERGs ranges for Shih Tzu dogs using the HMsERG under medetomidine and ketamine anesthesia.

Keyword

electroretinogram; HMsERG; Shih Tzu dog

MeSH Terms

Animals
Dog Diseases/diagnosis
Dogs/*physiology
Electroretinography/instrumentation/*veterinary
Retinal Diseases/diagnosis/veterinary
Time Factors

Figure

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  Fig. 1 Representative waveforms of the ERG results using the dog diagnostic protocol of the Handheld Multispecies electroretinography (HMsERG) in adult Shih Tzu dogs showing normal retinal function. (A-E: rod response, F: standard rod and cone (Std R&C) responses, G: high-intensity (Hi-int) R&C responses, H: cone response, I: cone flicker response).

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  Fig. 2 a-wave amplitudes (mean ± SE) using the diagnostic protocol with the HMsERG equipment in adult Shih Tzu dogs showing normal vision. Std R&C: standard rod and cone, Hi-int R&C: high-intensity rod and cone.

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  Fig. 3 b-wave amplitudes (mean ± SE) using the dog diagnostic protocol with the HMsERG equipment in adult Shih Tzu dogs showing normal vision. Std R&C: standard rod and cone, Hi-int R&C: high-intensity rod and cone.

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  Fig. 4 b/a ratio of amplitudes (mean ± SE) using dog diagnostic protocol of HMsERG equipment in adult Shih Tzu dogs showing normal vision. Std R&C: standard rod and cone, Hi-int R&C: high-intensity rod and cone.

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  Fig. 5 a-wave implicit time (mean ± SE) using dog diagnostic protocol of HMsERG equipment in adult Shih Tzu dogs showing normal vision. Std R&C: standard rod and cone, Hi-int R&C: high-intensity rod and cone.

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  Fig. 6 b-wave implicit time (mean ± SE) using dog diagnostic protocol of HMsERG equipment in adult Shih Tzu dogs showing normal vision. Std R&C: standard rod and cone, Hi-int R&C: high-intensity rod and cone.

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