The anatomy of the eye.
The eye has many parts that must work together to produce clear vision: The cornea, a clear window at the front of the eye, covers the iris and the pupil. A clear lens, located behind the pupil, acts like a camera lens by focusing light onto the retina at the back of the eye. The optic nerve carries electrical signals from the retina to the brain where it is processed into our thoughts, as vision.
If any part along the way is not functioning properly, our vision will be affected.