Progressive retinal atrophy (PRA) is a genetic and progressive disease of dogs which sadly leads to blindness over a period of time. PRA can be diagnosed in any dog breed. However there are certain breeds which are more genetically predisposed than others to developing this condition. This article will review and explore what PRA is, how it is diagnosed and how it is managed.
Table of contents
What is PRA?
To fully understand what PRA is, we must first recap the normal anatomy of the mammalian eye. The retina is a structure containing photoreceptor cells (rod and cone cells) within the eye. Its main function is to convert the light that enters the eye into electrical signals. These electrical signals are then sent to the brain via the optic nerve and processed as a visual picture. The retina is often described as the ‘film within the camera.’
PRA is a group of degenerative diseases that directly affects these photoreceptor cells in both eyes. If the retina degenerates, it consequently loses its ability to convert light into visual images; which is why this disease sadly leads to progressive blindness. This blindness may either occur suddenly or gradually over a period of time.
There are two types of PRA recognised in dogs, early onset PRA vs an inherited form. The inherited form is not always referred to as PRA and is often named ‘retinal dysplasia’. Early onset PRA generally occurs in younger puppies around 2-3 months of age. Whereas the inherited form (retinal dysplasia) usually manifests in adult dogs. In some cases, affected dogs may also develop cataracts which can be a secondary follow-on condition in PRA patients.
Which dog breeds are susceptible to PRA?
As briefly mentioned above, PRA can affect any dog breed. However, there are genetic predispositions and PRA appears to be an ‘autosomal recessive’ condition. This means that affected dogs must have inherited the defective gene from both parents.
Below lists some of these commonly affected breeds (this list is not exhaustive):
- Bedlington terriers
- Golden/Labrador retrievers
- Cavalier King Charles Spaniels
- Toy poodles
- Tibetan terriers
What are the clinical signs of PRA?
Recognising the signs of PRA can be difficult; especially early on in the disease process as the clinical signs can be subtle.
Owners of PRA dogs may notice initially that their dog’s vision is reduced at night time (night blindness) when light levels are at their lowest. This can make your dog behave and act differently. You may notice that they appear more nervous when moving around their home environment. Typical signs of vision loss include a lack of spatial awareness; and they may start to bump into objects in their surroundings.
Further along the disease process it may become more apparent that your dog has complete or partial vision loss. PRA is a non-painful condition. As a result of this your dog is unlikely to display signs of ocular discomfort, unless cataracts are present. Their eyes may appear more reflective than normal and their pupils may be more dilated.
Of course there are also a multitude of other diseases and conditions that can also look identical to the clinical signs of PRA and your Vet will differentiate between these.
How is PRA diagnosed by my Vet?
When you take your dog to see your Vet, they will take a thorough clinical history and perform a hands-on physical examination of your pet. Once they have performed a general health check, they will then focus on the ophthalmic examination. Your Vet will examine the back of the eye to assess the retina using an ophthalmoscope and they will be looking for any characteristic signs of PRA. Additionally, accurately assessing the retina can often prove challenging and suspected cases are sometimes referred to a specialist Veterinary ophthalmologist who will investigate further with specialist equipment.
The advancement of Veterinary medicine now allows a more specific diagnostic test to be performed which can accurately measure the electrical activity of the retina in response to light. This test is called an electroretinogram (ERG).
Like many other genetic conditions, DNA testing is now also available to aid with disease screening to try to protect the health of future generations.
Can PRA be treated?
Sadly in current times this condition cannot be treated and there is no cure. Affected dogs should absolutely never be bred from. In affected dogs, they will experience visual impairment and gradual vision loss and this can be difficult for their Owners to experience.
In those canine patients who also develop secondary cataracts, consideration for cataract removal surgery may be discussed (only if your dog is a suitable patient for this of course!). Furthermore, your dog may require lifelong medication in the form of topical eye drops to support ocular health and to reduce inflammation and pain associated with cataracts.
Tips for people living with a blind dog
As an Owner, receiving the news from your Vet that your dog is blind I can only imagine is extremely overwhelming. If you have never lived with a blind dog before, most people will share an initial thought about how they will manage and cope with caring for their blind pet. Thankfully nowadays, there are many resources available to provide tips, guidance and support to people caring for blind dogs. I won’t explore this topic in too much detail in this article, but I will briefly discuss some points that have been known to help Clients who are caring for their blind dog.
An important factor to minimise for a blind dog is change. Keeping their routine and home environment stable is hugely beneficial. Secondly, animals with poor vision have more hazards to be aware of, such as access to stairs etc and ensuring their safety is crucial. Animals with vision loss often experience a heightening of their other senses such as hearing, therefore it is important to utilise your voice and use voice commands to assist them. Additionally, blind dogs are often startled easily so please be mindful of this.
To conclude, PRA is a progressive disease of dogs which inevitably results in vision loss or complete blindness in your canine friend. Unfortunately, there is no available treatment for this condition but with support and management your dog will be able to live a long and happy life. If you are concerned that your dog may be showing signs of vision loss, please seek advice from your Vet.