Felis ISSN 2398-2950

Optic neuritis

Contributor(s): Dennis E Brooks, Paul Evans, Newman Lorna, Philip K Nicholls, David Williams

Introduction

  • Optic neuritis is an inflammation of the optic nerve and often arises secondary to an underlying systemic illness. It usually occurs as an extension of inflammation from the brain and meninges, or from the choroid and retina.
  • Cause: certain infective agents, eg Toxoplasma gondii  Toxoplasma gondii, FIP Feline infectious peritonitis, as well as lymphosarcoma Lymphoma.
  • Signs: sudden onset blindness if bilateral, mydriasis, changes in the appearance of the eye with intraocular inflammation, possible cranial nerve abnormalities, possible other neurologic deficits.
  • Diagnosis: clinical examination, laboratory tests.
  • Treatment: treatment of the underlying disease.
  • Prognosis: dependent on the etiology.

Pathogenesis

Etiology

  • Infective agents that may cause optic neuritis include Toxoplasma gondii, cryptococcosis, histoplasmosis, blastomycosis Blastomyces dermatitidis, and FIP.
  • Feline lymphosarcoma that affects the brain may also affect the optic nerves.
  • Other intracranial neoplasms, eg meningiomas, may physically impinge upon the optic nerves, but usually cause an optic neuropathy rather than an optic neuritis.
  • Optic neuritis may also occur with systemic diseases that arise in the presence of FeLV Feline leukemia virus and FIV Feline immunodeficiency virus infections, but neither virus is known to directly affect the optic nerve.

Predisposing factors

General

  • Immunosuppression from FeLV and FIV infections may predispose to systemic illnesses and infections that can indirectly affect the CNS and optic nerves, but this is an uncommon occurrence.

Pathophysiology

  • The optic nerves are really extensions of the brain and are more closely related to tracts of the central nervous system than peripheral nerves. As such they may be affected by infections or inflammation of the brain and meninges.
  • The optic disk (papilla) is closely associated with the sclera, choroid and retina of the eye. Infection or inflammation that originates in these tissues may also affect the optic nerves.
  • Inflammation of the portion of the optic nerve that lies in the posterior aspect of the eye is called papillitis.

Timecourse

  • The onset of blindness can be acute (48-72 hours).
  • The onset of systemic signs can be gradual and insidious.
  • In retrospect most cats are ill for several weeks prior to presentation.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Lappin M R Feline Toxoplasmosis. Waltham Focus 4, 2-8.
  • Lappin M R, Greene C E, Winston S et al (1989) Clinical feline toxoplasmosis - serologic diagnosis and therapeutic management of 15 cases. JVIM (3), 139-143 PubMed.

Other sources of information

  • Barnett K C & Crispin S M Veterinary Ophthalmology, Chapters 14 and 15 Fundus and Optic Nerve, 2nd edn. Ed. Gelatt K N.
  • Petersen-Jones S & Crispin S (2002) BSAVA Manual of Small Animal Ophthalmology. 2nd edn. British Small Animal Veterinary Association. ISBN 0 905214 54 4


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