http://www.ck12.org Chapter 1. Human Biology
1.44 Human Vision
- Describe how humans see and explain why vision is important.
How have you used your vision today?
Maybe you were just doing some schoolwork. Or walking down the hallway. No matter what you were doing, you
were probably using your sense of sight. You may depend on your sense of sight so much that it’s hard to think of
anything you do without it, except sleep. Why is sight so important?
The Nature of Human Vision
Think about all the ways that students use their sense of sight during a typical school day. As soon as they open their
eyes in the morning, they might look at the clock to see what time it is. Then, they might look out the window to see
what the weather is like. They probably look in a mirror to comb their hair. In school, they use their eyes to read
the board, their textbooks, and the expressions on their friends’ faces. After school, they might keep their eye on the
ball while playing basketball (Figure1.82). Then, they might read their homework assignment and text messages
from their friends.
Sight, orvision, is the ability to see light. It depends on the eyes detecting light and forming images. It also depends
on the brain making sense of the images, so that we know what we are seeing. Human beings and other primates
depend on vision more than many other animals. It’s not surprising, then, that we have a better sense of vision than
many other animals. Not only can we normally see both distant and close-up objects clearly, but we can also see in
three dimensions and in color.