Pannus is a disorder that affects the eye of the greyhound, and will eventually lead to blindness if it’s not managed. It is not painful in its early stages, causes no discharge from the eye, and may be hard to see unless you look closely at your greyhound’s eyes in a good light. If it is not diagnosed or treated, the disease will slowly cover the clear part of the eye (the ‘cornea’) until the dog can no longer see.
Pannus is seen most commonly in German Shepherd’s, but is also found in Collies, Poodles, Dachshunds and Greyhounds. There is thought to be a significant genetic inheritance, with certain families and lines within a breed more severely affected, but environmental factors also play a part in the development of the disease.
Pannus is a concern in greyhounds, not only because it causes sight loss, but also because the normal treatments for the disease can lead to the risk of returning a positive swab. GAR Rule 74(3) also allows a track veterinarian to scratch a greyhound from a race if it is ‘found to have or suspected of having impaired vision in one or both eyes’. This makes pannus a very serious disease for a racing greyhound.
Pannus symptoms generally start to appear when the dog reaches 2-5 years of age. In the beginning you may only notice that the edge of the cornea seems more pigmented (coloured) than before – kind of like ‘freckles’ developing near the edge of the eye – or there may be a hazy/greyish colour to the edge of the clear part of the eye. Generally the disease will occur in both eyes, starting at about the same time, but the lesions do not necessarily look the same.
As the disease progresses, Pannus lesions may simply look like brown pigment ‘growing’ onto the surface of the eye, or it may appear more inflamed with a ‘greyish-pink’ colour (which is the eye’s version of scar tissue). If you look closely, you might even see small blood vessels growing onto the eye surface. The colour change to the clear part of the eye starts at the outside edges and spreads inwards until the entire eye surface is covered, leaving no clear window for light to enter the eye – making the dog blind.
Pannus is thought to be an auto-immune disease. This means the body actually starts to attack itself. The genetic predisposition to develop pannus is inherited – so it tends to affect certain breeds and certain families within these breeds more than others.
The other factor thought to contribute to pannus is exposure to Ultra-Violet (UV) light. This exposure to UV light is thought to trigger the start of the reaction, or to make the reaction worse, so it is important to keep affected dogs out of bright light, especially in the summer months when the UV level is high. Even if exposure to UV light is not the cause of the disease, the rate of progression increases with exposure to high levels of UV light (from sun light, or reflected light from water).
Once the disease has started, there is no ‘cure’ that completely eliminates pannus. All treatments are directed at slowing the progression of the pigmented lesions and to prevent flare-ups. The most commonly used treatment is cortisone eye drops, which are administered daily. The cortisone slows the immune reaction that causes the pigment, and hence slows the progression of the disease. Cortisone may also be combined with cyclosporine drops which also help control the symptoms.
All corticosteroids (cortisones) are considered a ‘prohibited substance’ under the rules of racing (cortisones can also be used to mask pain), so the problem lies with keeping the dog’s eyes under control. For a greyhound to race, it has to be free of this drug at the time of racing. This means the greyhound has to stop medication at the right time prior to the race to make sure that the drug is completely out of its system on race day. The problem with this is that the dog is then at risk of a pannus flare-up or worsening of the condition – so it won’t be long before the greyhound will have to be retired from racing.
Ideally, no greyhound with pannus would be used at stud. Unfortunately, because of its later onset, there are some litters bred from affected animals which may not have had any eye lesions at the time of breeding. This means that the disease continues to be present within the gene pool.
The first thing to do is to consult your greyhound veterinarian. They will be able to do an eye examination, and discuss the disease with you. They can also refer you to a veterinary ophthalmologist (eye specialist for dogs) who can give more specific advice and recommend treatments for more severe cases. Getting to the disease early gives the best chance of treatment, so don’t hesitate – take the greyhound to the vet for a check up.