Cats are masterful predators, capable of spotting prey from meters away in the dead of night. But place a treat in front of them, and they’re basically blind.
What’s up with that? How can such good hunters be so lousy at seeing what’s right in front of them?
It turns out that their vision isn’t always amazing, since being able so see well at night comes with some drawbacks.
Cats are crepuscular, which means they’re most active at dawn and dusk. As a result, their eyes have evolved to see best when the light is low.
For one thing, their eyes are huge. They’re nearly as large as human eyes, even though their heads are less than half the
size of ours. Their slit-shaped pupils also have a greater range of size.
Human pupils can dilate to 15 times their smallest size; cats’ pupils can dilate by 135-fold,
and get even wider than human pupils to let in a lot more light. The parts of their eyes that let in and focus light
—their corneas and lenses— are also proportionally larger,
which ultimately means more light reaches the light-sensing tissue in the back, called the retina.
