What Is Progressive Retinal Atrophy (PRA) In Dogs?
Progressive Retinal Atrophy (PRA) in dogs refers to a cluster of genetic conditions leading to eventual vision loss. Typically, dogs experience complete blindness within 1-2 years of symptom onset. PRA manifests either by the failure of retina development shortly after birth (early onset PRA) or the atrophy of retinal cells in adulthood (late onset PRA). The retina, a crucial layer of cells at the back of the eye, converts incoming light into signals interpreted by the brain. Photoreceptor cells, namely rods and cones, play pivotal roles in this process.
Rods facilitate black and white vision and motion detection, particularly in low light, aiding dogs in night vision. Cones, on the other hand, support color vision in well-lit environments. Dogs possess a higher number of rods and fewer cones compared to humans, granting them superior night vision but diminished color perception.
PRA typically impacts rods first, followed by cones, often noticeable when dogs struggle to see in dim lighting. While PRA can affect any dog breed or age group, certain breeds are at higher risk due to genetic mutations. Although vision loss is distressing for pet owners, PRA itself is not a painful process compared to other conditions resulting in blindness. Efforts are ongoing to understand how genetic mutations interact with various breeds in the development of PRA.
Two Forms of PRA in Dogs
Early-onset PRA, also known as retinal dysplasia, typically manifests in puppies around the time of weaning, generally between 8 to 12 weeks of age. In these young dogs, the rods and cones fail to develop correctly, resulting in a rapid decline in their ability to see.
Late-onset PRA, on the other hand, affects adult dogs aged between 3 to 9 years. This form represents a genuine atrophy, where the rods and cones gradually lose their functionality over time, leading to vision loss.
The symptoms of Progressive Retinal Atrophy (PRA) in dogs can vary depending on the individual dog and the speed at which the disease progresses. Some changes that pet parents may observe include:
- Reluctance to venture outside at night or enter dark rooms.
- Increased clumsiness, leading to bumping into objects, especially in dimly lit areas, unfamiliar surroundings, or following changes in furniture arrangement.
- Dilated pupils that gradually contract when exposed to light.
- Enhanced reflectivity of the eyes in darkness, causing them to appear more luminous than usual when photographed with flash.
- The presence of cataracts, which could be among the initial signs noticed by pet parents.
Symptoms
Symptoms of Progressive Retinal Atrophy (PRA) in dogs can vary based on the individual dog and the pace of the disease’s progression. Pet owners may observe the following changes:
- Reluctance to venture outside during nighttime or to enter poorly lit rooms.
- Increased clumsiness leading to bumping into objects, especially in dimly lit environments, unfamiliar surroundings, or after furniture rearrangement.
- Dilated pupils that slowly contract when exposed to light.
- More reflective eyes in low light conditions, noticeable by increased glow when captured in flash photography.
- Onset of cataracts, which might be the initial sign prompting pet owners’ attention.
Causes
Causes of Progressive Retinal Atrophy (PRA) in dogs stem from an inherited disorder with no viable treatment options. In the majority of cases, PRA is triggered by an autosomal recessive trait. This means that a dog must inherit a faulty gene from both parents to develop the condition.
In certain dog breeds, PRA manifests as a dominant gene, where only one defective gene copy is needed for the condition to emerge. Additionally, some breeds exhibit a gender-linked version of PRA, with males being more susceptible than females.
While various genetic disorders leading to PRA have been pinpointed and can be identified through genetic testing, certain mutations remain unidentified. Therefore, negative genetic test results for PRA don’t guarantee immunity to the condition.
In dogs with PRA, the initial deterioration typically affects the rods, diminishing their functionality and leading to decreased vision in low light conditions. Eventually, the cones also atrophy, resulting in complete vision loss once all rods and cones have degenerated.
The onset and pace of atrophy vary depending on the specific genetic mutation, but most affected pets become blind within 1-2 years after the onset of symptoms.
Certain breeds are at a heightened risk of early-onset PRA/Retinal Dysplasia, while others face a risk of late or adult-onset PRA. These breeds include a range of terriers, herding dogs, retrievers, spaniels, and others, with differing levels of susceptibility across genders.
Diagnosis
The diagnosis of Progressive Retinal Atrophy (PRA) in dogs typically involves an examination of the retina using an indirect ophthalmoscope. This optical device is worn by the veterinarian on their head or attached to their eyeglasses, allowing them to visualize the back of the eye.
During the examination, the veterinarian will assess the retina and optic nerve for any discernible changes. They may observe an increased reflection in the part of the eye that appears to “glow” in photographs when exposed to light. In some dogs, these changes may be subtle and may necessitate referral to a board-certified veterinary ophthalmologist. It’s important to note that both eyes are usually affected equally in PRA cases.
If cataracts or other ocular issues hinder the veterinarian’s ability to examine the retina, they may resort to a specialized diagnostic procedure known as an electroretinogram (ERG). This test evaluates the retinas’ response to light stimuli.
Furthermore, genetic tests utilizing a blood sample may be conducted to identify the presence of specific genetic mutations associated with PRA. This helps confirm the diagnosis and provides valuable information for treatment and management strategies.
Treatment
Regrettably, Progressive Retinal Atrophy (PRA) in dogs cannot be treated, ultimately resulting in the loss of vision. Consequently, it’s imperative that dogs diagnosed with PRA, as well as their relatives, refrain from breeding to prevent the inheritance of the condition.
Although there is limited scientific evidence supporting their efficacy, some veterinarians may suggest the use of antioxidants or a supplement known as Ocu-Glo following a diagnosis of PRA.
In cases where cataracts develop as a result of PRA, they are typically left untreated as vision improvement is not feasible. However, cataracts can sometimes precipitate eye inflammation or glaucoma, which can cause discomfort. In such instances, special eyedrops may be prescribed to alleviate pain and manage the associated complications.
Recovery and Management
After the onset of blindness due to Progressive Retinal Atrophy (PRA), dogs require adjustments to adapt, but they can maintain a high quality of life relying on their heightened sense of smell and acute hearing. Here are some strategies to support dogs with reduced vision or blindness:
- Establishing a familiar, safe environment where furniture and objects remain stationary. Maintain consistency by keeping beds, food dishes, and water bowls in fixed locations. Consider using a fountain or bubbler for their water dish to enable them to locate it by sound.
- Securing hazardous areas like stairs with baby gates and covering sharp corners and objects with protective materials. Get down to the dog’s eye level to identify potential hazards.
- Implementing training techniques based on verbal cues and gentle touches. Utilize simple directional commands such as left, right, up, down, stop, go, and slow to assist dogs in navigating their surroundings.
- Maintaining a routine to promote a sense of safety and security. Leave the TV or radio on to provide comforting background noise.
- Engaging in modified playtime activities with toys that emit noise or contain treats with strong scents to stimulate their senses.
- Using a leash and harness to guide dogs through the house, yard, and unfamiliar areas. Consider investing in a specialized harness with a halo to help dogs detect obstacles better.
- Informing others about the dog’s blindness and discussing preferred approaches for interaction. Explain verbal commands used to signal your presence and the preferred method of touch.