Section: Overview
What to Watch For
Dilated pupils
Bumping into objects, reluctance to go out at night, reluctance to go down stairs in dim light, or other signs of blindness
Poor vision in dim light or darkness
More readily visible eye shine from the back of the eye due to dilation of the pupils
Diagnosis
Diagnostic tests are needed to recognize PRD/PRA and exclude other diseases. Your veterinarian will probably take a complete medical history and perform a thorough physical examination.
A complete ophthalmic examination is indicated and involves all of the following tests. Your veterinarian may refer your dog to a veterinary ophthalmologist for completion of some of these tests:
Tests to evaluate vision, such as observing the dog as he navigates an obstacle course in both bright and dim light, and certain neurologic reflex testing
Pupillary light reflex testing
A Schirmer tear test and fluorescein staining of the cornea
Tonometry to measure the pressure within the eye
Specialized examination of the front chamber of the eye, the iris and lens, the vitreous and the retina.
If your veterinarian is concerned that some disease other than PRA is the source of the dog's blindness, then medical tests to rule out other causes may include the following:
A complete blood count (CBC) and serum blood tests
Blood tests for some of the tick borne diseases, fungal diseases and toxoplasmosis to look for the presence of infectious diseases
A measurement of systemic arterial blood pressure to rule out high blood pressure
Possibly chest and abdominal X-rays
PRA can sometimes be confirmed at the time of retinal examination because it causes characteristic changes in the appearance of the retina. Early stages of the disease can be more difficult to diagnose, and in that instance the disease can be detected with the following test:
An electroretinogram to evaluate the function of the photoreceptor cells when they are stimulated with flashes of light. If the electroretinogram is abnormal, then the retina is diseased. If the electroretinogram is normal, then the origin of blindness is somewhere other than the retina.
Treatment
No therapy is available to prevent, slow the progression of, or reverse the degenerative changes of PRD/PRA.
Early diagnosis of PRD using electroretinography or genetic testing is important in kennels to eliminate individuals from the breeding pool that are either clinically affected or represent genetic carriers of the disease.
Home Care
Care consists of providing a consistent and safe environment for pets with vision loss. Considerations include:
Establish a known location for the food and water bowls and guide your pet to them until he can memorize the locations.
Place barriers across staircases, over hot tubs and around pools.
Restrict activity on balconies so that small dogs cannot fall through the space between the guardrails and large dogs cannot unwittingly jump off the balcony.
Avoid changing the location of the furniture and leaving chairs or other objects out of place in the house. Your pet will memorize a familiar environment in a relatively short time.
Purchase toys that squeak, balls that contain bells, or other noisemakers to encourage and help blind dogs to play.
Pets affected with PRD lose their vision in dim lighting first. Therefore, night-lights or plug-in hall lights are helpful for negotiating in the house at night.
Preventative Care
No preventive care is available for an individual because PRA is genetic. Do not breed affected animals.
Genetic testing is available for about 15 breeds of dogs affected with PRA. Testing performed on a blood sample can identify which dogs are affected and which are carriers of the disease. This information can then be used by breeders to decide which dogs may or may not be used for breeding. In addition, dogs can be examined on a yearly basis by a veterinary ophthalmologist and certified to be clinically free of the disease. The certification is valid for a period of one year from the time of examination.
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