While a dog’s eyes are generally less acute than our own, they actually see better in the dark (by about five or six times) than a human. This was largely useful in their predatory days—detecting motion in low light was a matter of survival! The trade off of good night vision is the inability to distinguish detail and color as accurately as a human.
All eyes are made up of a series of rods and cones. Rods help detect motion in dim light, while cones detect color and detail in good light. Therefore, a dog’s eyes have more rods than a human’s, but about one-tenth the amount of cones. So, count on Fido to fly down the path ahead of you in the dark, but don’t expect him to know if he’s chasing a squirrel or a chipmunk.