What is PRA or Progressive Retinal Atrophy?


PRA in Dogs is a shortened term for Progressive Retinal Atrophy in Dogs. There are a number of variations of PRA, all of them creating vision difficulties, particularly in low lighting situations and there are a number of these PRA conditions that lead to complete blindness. Although most of the causes are known and understood, there is no known cure for dogs. A hereditary condition often progressed by age it is a blindness that is slow to take effect, there are two main types of PRA, which are GPRA and CPRA and a number of other lesser known types such as RPED.

The retina is a highly specialized tissue found inside the eye and its good condition is critical for good vision. It is responsible for integrating light into vision and is comparable to that of film in a camera.

When light enters the animal’s eyes, it is focused onto the retina by the lens, where it then gets converted into electrical impulse signals which are then sent to the dog’s brain for processing and interpretation. If the eye is devoid of adequate retinal function, vision becomes difficult or impossible.

A Retinal Scan can show Degeneration in the tissue

As the name implies, Progressive Retinal Atrophy (PRA) is a degeneration or atrophy of retinal tissue. In most cases for many dogs, the condition’s progression is slow, and the early signs are generally missed or overlooked.

The loss of sight is slow, similar to dimming a light switch to reduce brightness in a room, but the process can take several months.

Imagine a light dimming over several months

Your vet might recommend an eye exam if your dog is having vision trouble or experiencing challenges moving around at night. If it’s still in its early stage, a retinal test (ERG) may also help diagnose progressive retinal atrophy.

The condition of Progressive retinal atrophy itself is painless, even if walking into doors is not. The vision loss progresses slowly, and dogs normally adjust to this physical handicap quite well.

Unfortunately, there is no available cure for PRA. Irreversibly blind animals due to PRA can still enjoy a normal lifespan with an excellent quality of life provided they receive some extra help from their owners. 

Forms of Progressive Retinal Atrophy

Progressive retinal atrophy that affects dogs manifests in two main forms, but both are considered hereditary.

GPRA

Generalized Progressive Retinal Atrophy (GPRA) is the most common form of PRA. It can occur in both old and young dogs. In early GPRA, the dog’s cones and rods within the eyeball have not developed properly, and the dog has difficulty seeing details, more so over distance and in low lighting. 

In cases of late-onset GPRA, the dog’s loss of vision is very gradual as the cone and rod cells formed correctly but have simply deteriorated over time. Usually, this form isn’t noticed until the dog is at least three years old, and often older still, when they start exhibiting symptoms of vision impairment.

CPRA (or RPED)

Central Progressive Retinal Atrophy is also referred to as retinal pigment epithelial dystrophy (RPED) and is less common. A rare type of PRA, it causes deterioration of the pigmented layer of the dog’s retina and makes it difficult for your pet to see in environments of low light. CPRA is mostly seen in older dogs, and it does not always lead to complete blindness.

SARD type PRA

Another form of PRA is Sudden Acquired Retinal Degeneration (SARD), of which the cause is unknown. This PRA is different from the nominal inherited progressive retinal atrophy, and it generally affects middle-aged dogs and seniors. It is characterized by unexpected blindness occurring within days to weeks. 

Symptoms of PRA

Progressive retinal atrophy is not a painful medical condition, and because of that, it’s rarely noticed during the early stages of development. Owners tend to notice things are wrong with their dogs when dogs are reactive to things such as bites from a flea.

Until a dog walks into something or perhaps is afraid to go outside in the dark, owners tend not to notice that their is a problem. Usually, the first sign noticed in a dog with this disease is night blindness. Dogs affected by PRA may display reluctance to venture into dark rooms, or they can be nervous to go out at night, or bump into things in poorly lit places.

Dog owners with pets that are developing progressive retinal atrophy will often observe that their dog’s eyes become very reflective when a light is shined on them. The pupils become more dilated than usual, and it affects both eyes. 

Notice the reflection return in the flash photograph

If you take a photo with a flash and there appears an over reflective appearance to the eyes, get your dog checked out with a vet.

In some cases, the dog owner might notice nothing abnormal when at home with their dog but may gradually begin to notice that their four-legged pal is becoming clumsier when in unfamiliar settings. Familiarity within the home can help them avoid bumping into things, just like any blind person can navigate their own home without problems.

For dogs with SARD, the suddenly acquired form of PRA, the initial symptom might only be a day’s loss or sudden complete blindness, this would obviously be very noticeable.

Causes of PRA

Progressive retinal atrophy is a broad term that covers a range of hereditary defects primarily affecting photoreceptors within the eye. In most forms, it’s the rod photoreceptors that are initially affected, leading to impaired night-vision. As the condition progresses, cone vision also deteriorates, resulting in daylight vision impairment and eventually total blindness. 

PRA is an inherited disease common in purebred dogs, although it may occur in mixed breeds. In most dog breeds, the medical condition is inherited by what is known as autosomal recessive mode in which one bad gene is passed from both parents.

Neither parent might be affected by PRA, but both must be carriers of the genetic trait. To prevent the spread of PRA within the breed, identification of affected breeding dogs is essential for breeders. 

The age of onset tends to vary between affected breeds. Some demonstrate clinical signs within their early years, while others may be seniors before vision loss is observed.

PRA Diagnosis 

The speed of progression depends on the form of disease and breed. In most cases, a dog experiences complete vision loss over a period lasting 1-2 years. Based on a general ophthalmic exam, if a dog has dilated pupils and shows sluggish pupillary light responses, your vet may suspect PRA.

In the early stages of the condition, it may not be easy to see any noticeable changes to the retina. However, as the PRA progresses, ophthalmoscope examination of the back of the eye will display increased reflectivity of the ‘tapetum lucidum,’ a portion of the retina. This is because of changes in the retinal blood vessels and the optic nerve. 

A scan shows the change in Retinal Blood vessels

In some cases your vet will refer you to a veterinary ophthalmologist for diagnosis confirmation. This is through additional sophisticated and advanced testing like an electroretinogram (ERG). It also rules out other possible causes of the blindness in your dog. The ERG test is sensitive enough to detect progressive retinal atrophy in pets even before obvious symptoms manifest themselves.

In some cases, it may be necessary to conduct genetic screening for inherited PRA to detect disease carriers.

Treatment and Prevention

In all living things, the retina is akin to the film in a camera and contains photoreceptors that are responsible for converting light into nerve signals. Progressive retinal atrophy causes the photoreceptors to die prematurely. Both eyes become blind over time, giving the dog time to adjust to the vision loss changes slowly. However, PRA is not painful. 

There is tons of research taking place to help both humans and pets affected with progressive retinal atrophy. Unfortunately, currently, there are no effective treatments available for the most common types of pet PRA.

Because PRA is a hereditary disease, it’s a condition that dogs can be born with if the parents had it. To eliminate canines that show symptoms of PRA, selective breeding should be encouraged to safeguard the gene pool.

Cataracts (cloudiness of the lens or opacification) are the more common secondary complication associated with PRA.

Cataract beginning to form in one eye

If a condition such as retinal detachment or cataracts has been diagnosed as the cause of dog blindness, treating this underlying cause may help prevent further vision loss. However, removal is not typically recommended as it may not improve vision, and cataracts could deteriorate following surgery. 

Living with a Blind Dog

Because dogs’ vision is the third most important sense after smelling and hearing, most do very well even when blind. Because progressive retinal atrophy in dogs develops slowly, most have time to hone their other senses, memorize their living environment, and adjust to living without vision. Dogs can be so good at it that you may find it hard to pinpoint when they finally went completely blind.

It’s not difficult to live with a PRA-affected dog. Your reaction to the vision loss is likely to be even stronger than the victim. The dog doesn’t require any medication as the eyes are not painful. Besides, PRA doesn’t affect the rest of a dog’s life as other more painful causes of blindness are likely to do.

There are several things you can do to help make the life of your PRA-affected dog much easier. Don’t rearrange the furniture in your home, and you will be surprised at how well your dog will remember all the details about the floor plan — he will even manage going up and down the stairs. Always keep the food bowls in the same location. Teach your children not to leave items such as toys and clothes on the dog’s usual pathways. 

A blind dog can continue playing its role as a loving companion in every way. Balconies and swimming pools present particular hazards, and it may be necessary to erect some barriers in such situations. Like the ones used for babies, safety gates may help keep your blind dog from falling downstairs and other mishaps. 

If you have other dogs in the household, they will serve as the ‘seeing eye’ for their blind companion. Your blind dog will pick up cues from them or follow the sighted dog around the house.

Remember that progressive retinal atrophy is not a death sentence for your pet. Because the loss of vision is gradual, most dogs learn to adapt, and they go on to enjoy happy, fulfilling lives. As long as your attitude to his condition is positive, and you encourage him along, he will remain healthy and happy.

General Breeds Affected by PRA

Many dog breeds can get progressive retinal atrophy. However, the more common breeds prone to PRA are;

  • Akita
  • Alaskan Malamute
  • American Cocker Spaniel
  • American Eskimo Dog
  • American Water Spaniel
  • Australian Cattle Dogs
  • Basenji
  • Bernese Mountain Dog
  • Border Collies
  • Cocker Spaniels
  • Curly Coated Retriever
  • Dalmatian
  • English Springer Spaniel
  • Field Spaniel
  • Finnish Lapp Hund
  • Flat Coated Retriever
  • German Shepherd Dog
  • German Spitz
  • Gordon Setter
  • Greyhound
  • Griffon Bruxellois
  • Hungarian Kuvasz
  • Hungarian Puli
  • Hungarian Vizsla
  • Irish Setter
  • Japanese Chin
  • Labrador Retriever
  • Lhasa Apso
  • Lowchen
  • Maltese
  • Miniature Pinscher
  • Miniature Schnauzer
  • Miniature and Toy Poodles
  • Nova Scotia Duck (yes it is a dog)
  • Papillion
  • Pomeranian
  • Portuguese Water Dog
  • Pug
  • Samoyed
  • Siberian Husky
  • Soft Coated Wheaten Terrier
  • Swedish Vallhund
  • Welsh Springer Spaniel
  • Other less commonly affected breeds include :
  • Tibetan Terriers
  • Tibetan Spaniel
  • Yorkshire Terriers
  • All Dachshunds
  • Elkhounds

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