Equis ISSN 2398-2977

Eye: electroretinography

Synonym(s): ERG

Contributor(s): Tim Knott, Ruth Morgan

Introduction

  • Equine ophthalmology is an ever advancing field of veterinary medicine.
  • Equine recurrent uveitis   Uveitis: recurrent  is one of the most common conditions of the horse and can result in retinal dysfunction and visual impairment.
  • Retinal function is difficult to assess in veterinary species and visible changes to the retina do not always accurately reflect changes in function.
  • Electroretinography (ERG) is a technique used to record and assess the electrical function of the retina, the optic nerve and the central visual pathways. Visual function can only currently be assessed as a behavioral response.
  • ERG works by recording electrical potentials generated by the retinal cells when light reaches them.
  • The electrical potentials are detected by an electrode placed on the cornea.
  • By varying the light adapted state of the retina and the properties of the light stimulus the ERG trace can give information about specific photoreceptor dysfunction.

Uses

  • The objective assessment of the function integrity of the retina, optic nerve and central visual pathways.
  • Assessment of retinal function prior to cataract surgery   Lens: cataract 08 - mature  .
  • Diagnosis of specific retinal disease, eg congenital stationary night blindness in the Appaloosa   Eye: night blindness  .
  • Investigation of sudden onset blindness where retina may be normal, eg optic   Optic nerve: neuritis  , ischemic optic neuropathy   Eye: ischemic optic neuropathy  .

Advantages

  • It provides an objective assessment of retinal function and can help with prognosticating in cases of equine recurrent uveitis or other diseases affecting the retina.

Disadvantages

  • Specialized expertise and equipment are required to perform ERG.

Requirements

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Preparation

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Procedure

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Komoromy A M, Andrew S E, Sapp H L et al (2003) Flash electroretinography in standing horses using the DTL microfiber electrode. Vet Ophthal (1), 27-33 PubMed.
  • Narfstrom K, Ekesten B, Rosolen S G et al (2002) Guidelines for clinical electroretinography in the dog. Docu Ophthalmol 105 (2), 83-92 PubMed.
  • Gouras P (1970) Electroretinography: Some basic principles. Invest Ophthal (8), 557-569 PubMed.


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