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

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 µV, 173.00 µV, and 12.92 µV, respectively. The b-waves of the rod responses ranged from 141.58 to 155.25 µV; the Std R&C was 314.75 µV, the Hi-int R&C was 329.42 µV, the cones were 37.75 µV, and the flicker responses were 64.08 µV. 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.

Clinical utility of a complete diagnostic protocol for the ocular evaluation of free‐living raptors

“…patients more practical and feasible. [28][29][30] The present study demonstrates that harvesting ERGs in awake, manually restrained raptors is simple and easy to perform, eliminating the need for general anesthesia which can be both expensive and high risk in the raptor patient. 31 Anesthetic drugs can impact the ERG, so performing ERG with manual restraint alone also eliminates pharmacological confounders.…”

“…The ERG is the summation of the electrical potentials and currents generated within the cells of the retina and is widely used in veterinary ophthalmology for assessing retinal function 27 . Traditional ERG units are bulky and nonportable; however, a new hand‐held ERG system makes electrodiagnostic assessment of nontraditional patients more practical and feasible 28–30 . The present study demonstrates that harvesting ERGs in awake, manually restrained raptors is simple and easy to perform, eliminating the need for general anesthesia which can be both expensive and high risk in the raptor patient 31 .…”

Normal values of b-wave responses of full-field electroretinogram in Lhasa Apso dogs with cataracts according to age

“…In a study to standardize the ERG values in Shih Tzu dogs, Lee et al (2009) also demonstrated lower values of amplitude, when confronted with the same data of the Lhasa Apso dogs. However, the legitimacy of such comparison is questionable, not only due to differences in the sedation protocol, in the adaptation time and in the response pattern recorded, but also due to the electroretinograph (Handheld Multispecies ERG) used.…”

“…The extrinsic factors consist mainly of the duration and intensity of light stimuli, dark/light adaptation period, anesthetic protocol, positioning and electrode type, recording equipment and environmental condition. All these factors are variables among different veterinary clinics, laboratories or hospitals (Ekesten 2007, Lee et al 2009). Therefore, it is highly recommended that each laboratory establishes its own normal parameters to avoid misinterpretation of results (Mentzer et al, 2006, Noman et al 2008.…”

<b>Padronização do eletrorretinograma de campo total em cães da raça Yorkshire Terrier</b>

“…A sedação por nós utilizada foi eficaz para a realização dos exames, fato corroborado por outros estudos (KOMÁROMY; SMITH; LEE et al, 2009;LIN et al, 2009;SAFATLE et al, 2010a, b, c;FREEMAN et al, 2013;GÓES et al, 2015). A recuperação foi, em geral, rápida e os animais foram liberados aos proprietários com capacidade motora completa.…”