Although blue eyes are considered quite rare among most dogs, you're more likely to seem them occur in these breeds.

This is because the eyes contain a wealth of information about the body's health. Retinal imaging can help to detect signs of diseases such as Alzheimer's, Parkinson's, and multiple sclerosis .

Blue eyes have been around for at least 7,000 years but we still don't know exactly why they evolved. Brad Pitt has them, Paul Newman had them — but when it comes to the human population as a ...