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Basics ⬇

Outline

BASICS

Overview!!navigator!!

  • Atrophy of the optic nerve as a sequela to infarction or injury to the vascular supply to the optic nerve
  • Systems affected—ophthalmic

Signalment!!navigator!!

N/A

Signs!!navigator!!

  • Acute blindness
  • Dilated pupil
  • Absent pupillary light reflex
  • Absence of ocular pain
  • Following sudden loss of blood supply, the optic disk at first appears normal, but the eye is blind. Within 24 h, there is swelling and mild hyperemia of the optic disk. Focal white, raised lesions overlying the optic nerve and its margins are observed within 48 h, and may be associated with peripapillary hemorrhages. After several weeks, there are ophthalmoscopic signs of optic nerve atrophy with pallor and vascular attenuation of the optic disk
  • Peripapillary depigmentation may be observed as the disease progresses, and represents early retinal atrophy. With time, there are increasing signs of retinal atrophy

Causes and Risk Factors!!navigator!!

Any condition that may result in sudden hypoxia of the optic nerve, such as:

  • Acute hypovolemia
  • Thromboembolic diseases
  • Surgical ligation of the internal carotid, external carotid, and greater palatine arteries for treatment of epistaxis caused by guttural pouch mycosis

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Traumatic optic neuropathy
  • Exudative optic neuropathy
  • Proliferative optic neuropathy
  • Optic nerve atrophy

CBC/Biochemistry/Urinalysis!!navigator!!

N/A

Other Laboratory Tests!!navigator!!

N/A

Imaging!!navigator!!

N/A

Other Diagnostic Procedures!!navigator!!

The electroretinogram will be normal initially but will be reduced to absent as the ischemia becomes prolonged.

Pathologic Findings!!navigator!!

Peripapillary retinal ischemia results in microinfarcts of the nerve fiber layer, which appear clinically as depigmentation. These are areas of a thickened nerve fiber layer consisting of aggregates of ruptured and swollen axons.

Treatment ⬆ ⬇

TREATMENT

There is no treatment for the condition itself; however, treatment of the underlying cause is recommended, if possible.

Medications ⬆ ⬇

MEDICATIONS

Contraindications/Possible Interactions

N/A

Follow-up ⬆ ⬇

FOLLOW-UP

Expected Course and Prognosis

Poor prognosis for return of vision.

Miscellaneous ⬆ ⬇

MISCELLANEOUS

Suggested Reading ⬆ ⬇

Brooks DE. Retinopathies and ocular manifestations of systemic diseases in the horse. In: Brooks DE, ed. Ophthalmology for the Equine Practitioner, 2e. Jackson, WY: Teton NewMedia, 2008:207–225.

Gilger BC. Equine ophthalmology. In: Gelatt KN, Gilger BC, Kern TJ, eds. Veterinary Ophthalmology, 5e. Ames, IA: Wiley Blackwell, 2013:1560–1609.

Nell B, Walde I. Posterior segment diseases. Equine Vet J Suppl 2010;37:69–79.

Wilkie DA. Diseases of the ocular posterior segment. In: Gilger BC, ed. Equine Ophthalmology, 2e. Maryland Heights, MO: Elsevier Saunders, 2011:367–396.

Author(s) ⬆

Author: Bianca C. Martins

Consulting Editor: Caryn E. Plummer

Acknowledgment: The author and editor acknowledge the prior contribution of Maria Källberg and Dennis E. Brooks.