Deer eyes have pupils that are wide, horizontal slits, as you can see in the image above. This shape allows them to let in more light than human pupils can, especially as they open wider in low-light conditions. It also is important in detecting movement across a wide, horizontal view where danger is most likely to appear. While this pupil shape helps them monitor a broader area, they sacrifice sharpness. Normal human eyesight is 20/20. Deer have a normal daylight eyesight of about 20/60, which means they see 3 times less clearly than humans!
They are best adapted to be “crepuscular,” active around dawn and dusk.
Deer sacrifice clarity and focus for the ability to detect danger in almost every direction at once.
it probably doesn't even see that fence :/