Corneal Dystrophy

Dystrophy is any disorder due to defective or faulty nutrition. Corneal dystrophy is an inherited eye disease characterized by development of gray-white or silver crystalline opacities in or around the central area of the cornea. The preferred veterinary term for this condition is Crystalline Corneal Opacities (CCOs). The opacities are produced by cone-shaped crystals that form in the cornea and spread across the surface of the eye, potentially interfering with the dog's vision. The symmetrical opacities are almost always present in the same area of both eyes with no accompanying inflammation or systemic illness. Dystrophies differ from corneal degenerations because they usually affect both eyes as in bilateral cataracts (though not simultaneously or to the same degree in every incidence), appear in certain breeds, do not have inflammation, often affect connective and supportive tissue constituting the thickest layer of the cornea (stroma) and rarely cause blindness.



The corneal dystrophies are divided into:

  • Epithelial and basement membrane which usually present as non-healing ulsers and can be initiated by slight trauma to the epithelial surface of the eye;
  • Stromal deposits of lipids commonly seen as an inherited condition in several breeds; these deposits often cause swelling of the cornea. Stromal dystrophies seldom lead to loss of vision, except in middle aged Airedale Terriers and aged Siberian Huskies. Treatment is usually unnecessary.
  • Endothelial dystrophy is associated with progressive corneal edema (abnormal fluid accumulation in tissues or body cavities that appears as swelling), which can lead to corneal ulcers. Unless the edema becomes severe enough to cause ulceration, the disease is nonpainful. Treatment with hyperosmotic 5% sodium chloride ointment applied 4 times a day daily may reduce edema. A surgical procedure called "thermokeratoplasty" may be beneficial in advanced cases. It involves creation of multiple superficial corneal burns to create superficial corneal fibrosis that leads to formation of a scar.2

If the dystrophy affects the deepest layer of the cornea, as it does in Boston Terriers, Chihuahuas and Dachshunds, it can lead to blindness. Most dystrophies are more superficial, such as those seen in Siberian Huskies, Beagles and King Charles Spaniels. Affected dogs should not be bread in order to avoid perpetuating the affect.

References

  1. Cooley PL, Dice PF. Corneal dystrophy in the dog and cat.
  2. David J. Maggs, Paul E. Miller, Ron Ofri, Douglas H. Slatter. Slatter's Fundamentals of Veterinary Ophthalmology
  3. Small Animal Ophthalmology: What's Your Diagnosis. Heidi Featherstone, Elaine Hol




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