This dog gradually developed bilateral corneal edema over a period of 2- 3 months. During this period there were no signs of ocular discomfort or inflammation. On presentation the patient was blind and developed acute onset blepharospasm.
Corneal endothelial dystrophy / degeneration.
The corneal endothelial cells line the inside surface of the cornea. These cells are responsible for keeping the cornea dehydrated and consequently transparent. There is an energy-dependent Na – K pump in these cells that actively pumps fluid out of the cornea into the anterior chamber.
Endothelial dystrophy is inherited in Chihuahuas and Boston terriers and in these breeds it occurs in young dogs.
Causes for endothelial cell degeneration include senile degeneration, uveitis, glaucoma, and iatrogenic surgical damage during intraocular surgery from turbulence of irrigating fluid.
The endothelial cells do not have a regenerative ability in adult dogs. If this condition is left untreated severe edema may result in the development of fluid filled bullae in the corneal stroma. These bullae may rupture leading to painful corneal ulcers.
A number of treatment options have been described including 360 degree conjunctival grafts and thermal keratoplasty. These procedures will prevent bullae from rupturing and consequently will keep the patient comfortable. In a large number of cases we get good results with 5 % NaCl ointment which, by means of its hydroscopic action, leads to dehydration of the cornea. The dose is dependant on the extent of damage to the endothelial cells, but most cases are treated twice daily. 5 % NaCl ointment is available through Kyron Laboratories.