Corneal Endothelial Degenration - Corneal Oedema

Corneal oedema is fluid retention in the cornea.

Clinical Signs

The appearance of corneal oedema is a blue or cloudy cornea.

Causes
1. inflammation of the cornea (keratitis)
2. corneal ulcers
3. age-related corneal endothelial degeneration
4. breed-related corneal endothelial degeneration

Breeds more commonly affected include
1. Welsh Springer Spaniel
2. Basset Hound
3. Chihuahua
4. Dachshund

Some may be affected in middle age eg 5-6 years of age.

The inner surface of the cornea is called the endothelium. In young dogs and cats there are in excess of 3000 cells, however this number reduces with age. These cells act as pumps whose role is to pump fluid out of the cornea to keep it in a dehydrated state. This lack of water results in the cornea being clear and transparent.

In some breeds and especially in older animals, these pumps may start to fail. The result is fluid retention in the cornea, or corneal oedema, and the cornea becomes cloudy.

In severe cases, the corneal oedema is so severe that vision may be affected. Furthermore, blisters may form just under the surface of the cornea (epithelium). If the surface is disrupted, superficial ulcers may result. These ulcers may be slow to heal.

Treatment

Treatment of corneal endothelial degeneration is the use of hypertonic saline drops. These drops work by drawing fluid out of the cornea, and they must be administered four times daily. In most cases the oedema can be reduced, and maintenance therapy is continued at a frequency of twice daily. The initial treatment of corneal ulceration is topical hypertonic saline drops four times daily.

Oral anti-inflammatory treatment, eg Rimadyl tablets, may also be commenced. If the ulceration fails to heal, surgery may be required to excise the non-healing ulcer. Following this surgery, the cornea is covered with a third eyelid flap. In severe cases when this surgery fails, thermal burns are used to encourage the ulcers to heal. This also works to control the fluid retention by forming a barrier layer of scar tissue. One complication following surgery is scarring, which can be unpredictable. However, in most cases if the ulceration and oedema are severe, vision has already been affected for some time. In these cases surgery is performed in order to reduce pain.

Topical treatment in most cases is life long, as this is a problem we can control rather than cure. If cloudiness reduces, increase the frequency of the drops back to four times daily. If an eye suddenly becomes sore, do the same and contact us as soon as convenient, as this suggests ulceration has occurred.