Progressive Retinal Degeneration (PRD) in Cats

Overview of Feline Progressive Retinal Degeneration (PRD)

Progressive retinal degeneration or atrophy (PRD, PRA) is premature degeneration (deterioration) of the photoreceptor cells of the retina. There are two types of photoreceptors in the retina and these are the light-sensitive rods and cones. They are responsible for detecting light and converting it into an electrical signal that travels to the brain. When the photoreceptor cells deteriorate, vision is lost because the animal has no way to generate an image from the light reaching the retina.

PRA/PRD is in cats initially affects the rods. The rods are responsible for dim light vision; therefore, the cat loses its nighttime vision first. The disorder is progressive and eventually the cones are affected. Over time, the cat slowly goes completely blind. The disease affects both eyes at the same time.

Most cats are seen in the late stages of disease and have advanced changes in their retinas because they compensate very well as their vision slowly deteriorates. Sometimes the blindness can appear to be sudden in onset (even though it has been developing for months) because the cat may show almost no signs until the last bit of vision has been lost.

PRA in cats is rare in the United States. It is seen most often in purebred cats, such as the Abyssinian, Persian, and Siamese. It is seen sporadically in domestic shorthair and other mixed breed cats. In the Abyssinian, the disease is inherited as a dominant trait, but the inheritance pattern is unknown for other cats.

Below is an overview of Progressive Retinal Degeneration (PRD) in Cats followed by more detailed information on the diagnosis and treatment of this disease.

What to Watch For

Diagnosis of Progressive Retinal Degeneration (PRD) in Cats

Diagnostic tests are needed to recognize PRA/PRD 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 cat to a veterinary ophthalmologist for completion of some of these tests:

If your veterinarian is concerned that some disease other than PRA is the source of the cat’s blindness, then medical tests to rule out other causes may include the following:

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:

Home Care

Care consists of providing a consistent and safe environment for pets with vision loss. Considerations include:

Preventative Care

No preventive care is available for an individual because PRA is genetic. Do not breed affected animals.
Breeders can obtain certification from a veterinary ophthalmologist that certifies an individual is free of inherited eye disease. The certification is valid for a period of one year from the time of examination.

In-depth Information on Progressive Retinal Degeneration (PRD) in Cats

Poor vision in dim lighting conditions (nyctalopia) is usually the first behavioral sign of PRA. Good vision may be maintained for some time under bright light conditions. The visual impairment induced by PRA eventually progresses to blindness in all lighting conditions, and this clinical course often takes place over 18 to 24 months. As the retinas deteriorate the pupils (hole in the center of the iris) become increasingly dilated and often a greenish-yellow sheen or reflection is noted because the eye shine of the retina is more easily seen through the enlarged pupils.

Other ophthalmic diseases or conditions can mimic the signs of PRD by also inducing blindness. Some of these diseases cause acute blindness, while others cause a slow onset of blindness.

It is important to exclude these conditions before establishing a conclusive diagnosis:

In-depth Information on the Diagnosis of Progressive Retinal Degeneration (PRD) in Cats

Veterinary care often includes diagnostic tests to confirm the presence of PRD and to exclude other diseases. Tests may include:

– Tests to evaluate vision, such as observing the cat 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.

Treatment In-depth for Feline Progressive Retinal Degeneration

There is no treatment for PRA/PRD. It is very important not to breed affected animals.