Corneal dystrophy may
be elusive diagnosis

CORNEAL dystrophy is is for the most part inherited and can affect either just one, or both of the dog's eyes. There are three corneal layers in the eye - the epithelium or outer layer, the stroma or centre layer which is the thickest layer, and the endothelium or inner layer. The layer that is affected will depend on the type of dystrophy your dog has.

Most forms of dystrophy do not cause the dog any discomfort, except in some cases where the outer layer is affected and may rupture or become ulcerated. It is very important to have your vet evaluate your dog's eyes at the onset as your dog may have dystrophy or may also have ulcers, cataracts, or even an eye injury causing scar tissue in the under layers. The appearance of any of these conditions can be very similar.

Your dog's eyes may seem to have white through to grey or blue-grey areas or a cloudy appearance and when the eyes are magnified there can be crystals in the deeper layers. The cloudiness may be concentrated at the centre of the cornea, or around the periferal areas of the eye. The main thing that your vet will need to check is to be sure that your dog has no ulceration. If it has, this must be treated at once.

Different breeds seem to have different ages of onset, and also different types of the condition. For instance, airedale terriers can show signs from just four months old, but in chihuahuas the onset can be as late as 13 years old. Opacities usually progress, but in some cases they do not progress at all. Progression can be very slow and may or may not lead to eventual blindness. This form of the condition is common in cocker spaniels, poodles, samoyeds, Siberian huskies, pointers, German shepherds and bichon frises. Progression may also be quite fast and lead to blindness - this type more common in airdale terriers, Boston terriers, chihuahuas and dachshunds. For many breeds the way the disease is genetically inherited is as yet unknown, but in the airedale terrier it is thought to be a sex-linked trait while in the Siberian husky it is a recessively inherited trait.

There is no treatment for dystrophy in general. The opaque deposits can be removed by surgery but they usually return fairly quickly. Because the bulk of dogs with this condition do not go blind or suffer any pain or irritation they are best left alone. However, if the outer layer is affected your dog may suffer irritation and tearing and this may progress to ulceration.

Stromal dystrophy
This form may be the result of a corruption of the normal lipid metabolism in the cornea. Stromal deposits usually do not cause problems. The opacity in your dog's eye/s may become more noticeable over time, but in the greater number of cases there is no impairment of vision. However, in some breeds such as airedales and beagles the vision may eventually be impaired.

Epithelial dystrophy
This form of the disease often causes painful ulcerations or tears or scratches in the cornea. For some breeds there appear to be a number of smaller areas of opacity which can all erupt into ulcers. Older boxers are susceptible to a chronic ulceration which is hard to clear up, painful and often returns. The deposits have been shown to be largely made-up of cholesterol. For dogs that suffer from this type of eye eruption the treatment is mainly medication to clear up the erosion. In this type, surgery may be considered if the ulceration persists.

Endothelial dystrophy
Endothelial dystrophy affects the function of the cells of that layer and may result in a build-up of fluid in the cornea which may decrease vision. Edema (fluid build-up) may cause the eye to appear blue. Recurring non-healing shallow corneal ulcers can as well in this form of the condition. Over time, the fluid build-up causes inflammation of the cornea and reduced vision. This can be compared to a water blister forming under the skin layers. No treatment is needed in the early stages, but once the liquid builds-up your dog will require treatment.

Dogs affected by any form of corneal dystrophy should not be used for breeding as the condition can be passed on to progeny in various forms.