Canis ISSN: 2398-2942

Cornea: opacity

Synonym(s): Blue eye

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

Introduction

  • Cause:
    • Edema
    • Pigment.
    • Calcium.
    • Lipid.
    • Scarring.
    • Cellular infiltrate.
    • Symblepharon.
  • Signs: opacity of eye.
  • Diagnosis: confirm opacity to be affecting cornea - identify underlying cause.
  • Treatment: depends on nature of opacity.
  • Prognosis: good to poor for resolution depending on nature and size of opacity.

Pathogenesis

Etiology

Corneal edema
  • May result from dysfunction of the corneal endothelium or epithelium, or changes in intraocular pressure, accumulation of fluid within the corneal stroma which is normally relatively dehydrated.
  • Potential causes of endothelial dysfunction include iatrogenic resulting in compromise, endothelial dystrophy Cornea: endothelial dystrophy , uveitis and glaucoma Glaucoma (through alterations in intraocular pressure) and canine adenovirus 1 infection (also known as 'blue eye') Canine adenovirus type 1 disease Cornea edema - Airedale 4 months.
  • Breaches in corneal epithelium allow fluid from the precorneal tear film to gain access to the stroma.
  • Edema - congenital: persistent pupillary membranes - variable size/distribution of affected areas +/- lens involvement Persistent pupillary membrane.
  • Edema - acquired: iatrogenic endothelial compromise, endothelial dystrophy, uveitis Uveitis , glaucoma, lens luxation Lens: luxation , canine adenovirus 1 infection, secondary to erosion/ulceration.
  • Cellular infiltrate: chronic superficial keratitis Chronic superficial keratitis.
  • Pigment: pigmentary keratitis Pigmentary keratitis.
  • Lipid deposition: corneal lipidosis Cornea: lipidosis , corneal lipid dystrophy.
  • Symblepharon: adhesion between cornea and conjunctiva, or conjunctiva/conjunctiva, may obliterate fornix Symblepharon.
  • Scarring Cornea: opacity.
  • Calcium deposition associated with dystrophic calcification or secondary response to trauma.
Iatrogenic corneal endothelial dysfunction
  • Damage to endothelial cells during intraocular surgery.
Uveitis
  • Corneal endothelial cells are damaged by the associated intraocular inflammation.
'Blue eye' associated with canine adenovirus 1 infection
  • Glaucoma/uveitis.
  • Changes in intraocular pressure affect fluid dynamics and result in over-hydration of the stroma.
  • A proportion of infected dogs will develop endothelial damage.
  • Antibody/antigen deposits form within the corneal endothelial cells.
  • This does not occur with canine adenovirus 2 infection Canine adenovirus type 2 disease.

Predisposing factors

General
  • Breeds at risk of glaucoma.
  • Breeds at risk of lens luxation.

Specific

  • Breed for endothelial dystrophy or blue eye with CAV-1 infection.

Pathophysiology



Endothelial dystrophy
  • Degeneration of corneal endothelial cells results in loss of endothelial cell pump function and subsequent bilateral corneal edema.
  • Fluid accumulation underneath the corneal epithelium leads to the formation of bullae which rupture, resulting in corneal ulceration Ulcerative keratitis.
'Blue eye' associated with CAV-1 infection
  • Affected dogs intially develop an anterior uveitis which is of variable severity Uveitis.
  • Antibody/antigen deposits form within the endothelial cells 10-14 days post-infection, resulting in a disruption of normal function.

Timecourse

  • Most blue eye cases resolve in 30 days.
  • Slow progression to total corneal edema in endothelial dystrophies (worsens with age).
  • Endothelial cell pump damage, irrespective of cause, results in loss of corneal detergescence.

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

  • Gelatt K N (1999)Veterinary Ophthamology.3rd edn: Williams & Wilkins.


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