Progressive Retinal Atrophy, Bardet-Biedl Syndrome

A dog with decreased vision may be reluctant to go down stairs or into a dark room or outside at night. They may bump into door frames or corners and have difficulty fetching toys. You may notice a characteristic eyeshine due to increased reflectivity of the eye. Affected dogs may also react more slowly, or not at all, to sudden light or movement. In addition to PRA, this variant may cause an upturned nose, dental abnormalities, and a wavy coat.

The age of onset of clinical signs of PRA varies. However, dogs whose age was documented were diagnosed with PRA at over six years. An upturned nose, an abnormal coat of a wavy texture, and dental abnormalities become increasingly noticeable as dogs develop, becoming more apparent around the age of six months.

A diagnosis of PRA is made by examination of the back of the eye (the "fundus"). In the early stages, it may be difficult to observe any obvious changes to the retina, but as the disease progresses, a veterinarian will observe increased reflectivity of the eye, thinning of the retinal blood vessels, and atrophy of the optic nerve. A veterinary ophthalmologist can perform an electroretinogram (ERG), which measures the electrical activity of the retina. Since cataracts often develop secondary to PRA, an ERG is crucial to evaluate for PRA prior to considering cataract surgery.

Currently, there is no widespread treatment for progressive retinal atrophy; however, gene therapy is an evolving field.

Talk to your vet about your dog’s PRA result so you can work together to plan their ongoing care and monitoring.

Schedule regular eye exams with your vet or a veterinary ophthalmologist to monitor for changes or complications such as cataracts.

If your dog’s vision changes, help them adjust by keeping furniture and routines consistent, using verbal cues, and keeping them on a leash in unfamiliar areas.

Products such as protective halos can also help dogs navigate safely if their vision declines.

This variant was first identified in Shetland Sheepdogs.

Penetrance: PRA is inherited in an autosomal recessive manner, meaning that affected dogs must have two copies of the variant to show clinical signs from it.

Gene

BBS2 Exon 11

Inheritance type

recessive

Clinical category

Ophthalmologic

Citations

1. Hitti-Malin et al 2021
2. Mellersh 2014

• Shetland Sheepdog