Canis ISSN: 2398-2942

Chorioretinitis

Synonym(s): Retinochoroiditis, Retinitis, Choroiditis

Contributor(s): Dennis E Brooks, David L Williams

Introduction

  • Inflammatory reaction of vascular choroid and secondarily the neurosensory retina (NSR) (chorioretinitis) or retina first and subsequently the choroid (retina choroiditis).
  • Cause: all causes of uveitis including infectious agents (bacteria, viruses), trauma, neoplasia, reflex uveitis secondary to corneal surface disease, septicemia, penetrating injury, immune mediated.
  • Signs: in absence of anterior uveitis, chorioretinitis diagnosed only ophthalmoscopically.
  • Diagnosis: ophthalmoscopic signs confirm clinical entity, underlying cause may be identified by full clinical examination, history, hematology and/or biochemistry. Vitreocentesis may be helpful with PCR or bacteriological culture.
  • Treatment: attempt to identify and treat underlying cause.
  • Prognosis: depends on extent/distribution of lesions and underlying cause. Often even large lesions appear to have little effect on vision.

Pathogenesis

Etiology

  • Bacteria:Leptospira,Brucella Brucellosis ,Borrelia Borrelia burgdorferi.
  • Parasites:Toxocara canis Toxocara canis (chronic inflammatory retinal granuloma).
  • Viruses: Canine distemper Canine distemper disease (most common cause of retinochoroiditis).
  • Protozoa:Toxoplasma gondii Toxoplasmosis andLeishmania donovaniand migrating Dipteran larvae (retinal inflammation).
  • Rickettsia: Tropical canine pancytopenia and Rocky Mountain spotted fever (retinitis and retinal hemorrhage).
  • Fungi: Blastomycosis , Histoplasma, coccidiodes, protothecocis and Cryptococcus (retinal inflammation).
  • Neoplasia.
  • Trauma.
  • Foreign bodies.

Pathophysiology

  • Choroid usually focus of inflammation.
  • Retina and vitreous usually secondarily affected. Choroiditis alone is rare.
  • Vitreal haze may preclude visualization of fundus in active chorioretinitis.
  • Acute inflammation is followed by resolution and retinal scarring, usually seen as increased reflectivity (in tapetum) with or without ectopic pigment deposition Post-inflammatory retinopathy 02 Labrador 8 years. Scars referred to as post-inflammatory retinopathy/chorioretinitis.
  • UDS = auto-immune reation to melanin, resulting in:
    • Uveitis.
    • Vitiligo (depigmentation of skin especially mucocutaneous junctions - lids, lips, nose).
    • Poliosis (whitening of hair).
  • Nomenclature reflects structure where inflammation commences:
    • Chorioretinitis = choroid primarily involved, seconday spread to nsr (most common).
    • Retinochoroiditis = nsr primarily involved, secondary spread to choroid (seen with neurotropic viruses such as distemper.)
    • Retinitis = NSR only involved.
    • Choroiditis (or posterior uveitis) = choroid only involved.
  • Distinctions difficult to make clinically, usually made on histology.
  • Early in inflammatory process, exudates accumulate around retinal blood vessels, forming perivascular opacities Post-inflammatory retinopathy 08 English Springer Spaniel 3 years.
  • As exudates increase in quantity, retina becomes edematous, nsr may separate from retinal pigment epithelium (RPE) retinal detachment, exudate may extend into vitreous → vitreal opacification may preclude visualization of fundus.
  • Hemorrhage may accompany severe inflammation Retinal hemorrhage Crossbred 6 years. Shape of hemorrhage defines its location: subretinal - diffuse (between nsr and rpe); deep retinal - 'dot and blot' (confined by cell bodies and axons); superficial retinal - flame shaped (following distribution of fibers in nerve fiber layer); preretinal - keel shaped, following gravitational forces (between nsr and vitreal face).
  • Healing is mediated by tissue macrophages and rpe. Connective tissue elements may proliferate leading to folding in retina. Nsr atrophies, causing hyper-reflectivity in tapetal region, pallor in nontapetal. In atrophic area, there may be inceased pigmentation. Borders of lesion usually very distinct. Blood vessls crossing lesion may be attenuated or tortuous.
  • UDS: autoimmune response to melanin pigment.

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

Other sources of information

  • Michau T M, Breitschwerdt E B, Gilger B C and Davidson M G (2003) Bartonella vinsonii subspecies berkhoffi as a possible cause of anterior uveitis and choroiditis in a dog. Vet Ophthalmol (4), 299-304 PubMed.
  • Gelatt K N (1999)Veterinary Ophthalmology.3rd edn. Williams & Wilkins.


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