Equis ISSN 2398-2977

Eye: night blindness

Synonym(s): Congenital Stationary Night Blindness

Contributor(s): Dennis E Brooks, Alison Clode, Tim Knott, Graham Munroe

Introduction

  • Congenital, non-progressive visual disturbance most obvious in conditions of poor light.
  • Incidence: inherited in Appaloosa   Appaloosa  but rare and sporadic in Thoroughbred, Paso Finos, Standardbred.
  • Cause: defect in neural transmission within retina.
  • Signs: suckling foal or yearling with abnormal night vision and associated behavior in specific breeds.
  • Diagnosis: no abnormalities on full ophthalmic examination but pathognomonic abnormal electroretinography (ERG).
  • Treatment: none.
  • Prognosis: guarded to poor.

Pathogenesis

Etiology

  • Inherited in the Appaloosa by, as yet, an unidentified pattern - thought to be either autosomal recessive, or sex-linked recessive, with the defect on the X chromosome.
  • Sporadic in other breeds including the Thoroughbred, Standardbred and Paso Fino - cause not known.

Specific

Pathophysiology

  • A congenital, non-progressive disease which produces visual disturbance in reduced light conditions, probably due to a defect in neural transmission from the photoreceptor cell to the bipolar and Muller cells.
  • The mode of transmission has not been defined, but may be a sex-linked recessive trait.
  • Defect in neural transmission from photoreceptor cell to the bipolar and Muller cells.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Roberts S M (1992) Congenital ocular anomalies. Vet Clin N A Equine Pract (3), 459-478 PubMed.
  • Bistner S (1984) Fundus examination of the horse. Vet Clin N A Equine Pract (3), 541-551 PubMed.
  • Witzel D A et al (1978) Congenital stationary night blindness - an animal model. Invest Ophthal Vis Sci 17 (8), 788-795 PubMed.
  • Joyce J R (1977) Equine night blindness. JAVMA 170 (9), 878-880 PubMed.

Other sources of information

  • Brooks D E (1999) Equine Ophthalmology. In: Veterinary Ophthalmology. Ed: Gelatt K N. 3rd edn. 1053-1116.


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