> I had never heard of dna for testing pra
Depending on breed there may be a PRA DNA test available. We have one for the prcd-PRA form since the end of 2008.
Unfortunately there are many breeds and many forms of this group of eye disorders where the gene has not been identified so the only available test is the standard CLINICAL eye test, which can only tell you if there are 'clinical signs' not whether the dog is a carrier clear or affected.
For example in my breed a dog affected by prcd-PRA could show no clinical signs for some years and get an unaffected certificate on clinical exam, as the disease is late onset.
The DNA tests are in most cases patented and can only be done by the labs that hold the patent (or under license from the patent holder), in many cases that is Optigen in the USA.
DNA can be tested from cheek swabs, but blood is more reliable to get a testable sample.
For most eye problems or to monitor for any emerging problem the clinical BVA/KC/ISDS eye scheme test is still needed.