Cone Degeneration

General Information: Cone Degeneration is a genetic eye disease that affects dogs, leading to the loss of cone photoreceptor cells, which are essential for vision in bright light. Affected dogs typically begin to show symptoms between 8 and 12 weeks of age, developing day blindness (inability to see in bright light) and photophobia (sensitivity to light). Despite these issues, they retain normal vision in low light conditions, as rod photoreceptors, which are responsible for night vision, remain unaffected. An eye examination of affected dogs will show that the inner eye structures appear normal. Normal cone cell function can be detected via Electroretinogram (ERG) before six weeks of age, but this function becomes abnormal between 6 and 12 weeks, and is completely absent in adult dogs, indicating a total loss of cone cells. This condition severely limits a dog’s ability to see in daylight but does not affect their vision in dim light.

How to Read Your Dog's Test Results for this Genetic Variant:

Two Variants Detected: Dog Likely Affected

One Variant Detected: Dog Unlikely Affected

No Variants Detected: No Effect

Gene / Testing Information: Genetic testing for the CNGB3 gene is crucial for identifying carriers and dogs affected by Cone Degeneration. This disorder is inherited in an autosomal recessive pattern, meaning that a dog must inherit two copies of the mutated gene, one from each parent, to develop the disease. Carrier dogs, which possess one normal and one mutated gene, do not exhibit symptoms but can pass the mutation to their offspring. Breeding two carriers poses a risk of producing affected puppies, with each pup having a 25% chance of developing the disease and a 50% chance of being a carrier. Reliable genetic testing for the CNGB3 mutation allows breeders to make informed decisions, avoiding the pairing of two carriers to prevent the production of affected puppies. This approach helps eliminate the mutation from breeding lines and ensures the health and well-being of future generations. It is important to note that while a clear result for the CNGB3 gene reduces the risk of Cone Degeneration, there may be other genetic causes for similar conditions. Comprehensive genetic screening is vital to maintain the overall eye health and quality of life for dogs susceptible to this disorder.