CORNEAL ENDOTHELIAL DEGENERATION
A bluish haze to the cornea caused by loss of the deepest corneal cells.
The corneal endothelial cells line the inner portion of the cornea. One of their main functions is to pump fluid from the cornea to keep it relatively dehydrated. The dehydrated state and regular arrangement of tissue maintains clarity. The cells have poor regenerative capacity when damaged. There is age-related decline in these cells. In some animals, cellular loss is accelerated and/or extreme. When function is impaired, fluid builds in the cornea, causing it to swell.
Opacity of both corneas is usually the initial sign and this often starts at the lateral aspect of the eye and progresses to involve the entire cornea. Some dogs may show visual impairment, but this is usually mild, except in advanced cases. Often, painful corneal ulcers develop due to the rupture of fluid-filled vesicles (bullae) and/or poor corneal health.
Advanced age, breed, intraocular inflammation and/or intraocular surgery can be contributing factors. It is most often seen in Boston terriers, Dachshunds, and Chihuahuas.
Slit-lamp examination reveals thickening of the cornea. Bullae and/or ulcers can be seen when they are present. It is important to evaluate the interior of the eye for inflammation, and to measure intraocular pressure as high pressure or intraocular inflammation can also cause corneal opacity.
Medical treatment is possible with topical hyperosmotic agents, such as 5% NaCl (sodium chloride). The high salt content draws fluid out of the cornea. It is most effective to limit ulcer formation but is not effective in all patients and some patients show discomfort with application; clearing of the corneal cloudiness should not be expected with its use. Ulcers are treated with topical antibiotics and pain management. Procedures to aid ulcer healing are commonly needed.
Surgeries to tack areas by scarring with thermal cautery (thermokeratoplasty) or to place a thin conjunctival graft over the area are used. Both leave scarring, which can impair vision, but can be effective to prevent ulcerations. In human beings with analogous conditions, a full-thickness or endothelial corneal transplant replaces the lost endothelial cells. In dogs, graft rejection is usually severe and this procedure is not routinely performed.
Once the condition forms, it is life-long. Many dogs do not require treatment of any kind. Most dogs are managed well with medications and/or surgeries to control ulcer formation.