Progressive Retinal Atrophy, otherwise known as Retinitis Pigmentosa (RP) is a group of genetic disorders that affect the retina's ability to respond to light, leading to a gradual loss of vision. While most information regarding RP in humans is well documented, specific details about Retinitis Pigmentosa in Lapponian Herder dogs may not be as extensively studied or easily accessible.

The Lapponian Herder is a Finnish breed of herding dog traditionally used by the Sami people for herding reindeer. If there is a specific variant of Retinitis Pigmentosa in Lapponian Herder dogs, it would likely be tied to a particular genetic mutation.

Typically, in dogs, genetic disorders like RP are often inherited in an autosomal recessive pattern. This means that a dog would need to inherit two copies of the mutated gene (one from each parent) to exhibit symptoms of the disease.

For accurate and detailed information on Retinitis Pigmentosa in Lapponian Herder dogs, including genetic testing, diagnosis, and breeding advice, consulting a veterinary geneticist or a specialist in canine ophthalmology would be the best course of action. They might refer to databases or publications specific to veterinary genetics that document canine hereditary diseases comprehensively. Furthermore, genetic testing laboratories might offer specific tests to identify carriers of genes associated with RP in various dog breeds, including the Lapponian Herder.