A person with normal sight (emmetropia), without any type of visual correction, is able to see clearly at distance, because parallell rays are carried to focus right at the macula of the retina, when the eye is in a relaxed mode.
You need to upgrade your Flash Player
Upgrade here please.
Note how the lens gets thicker when reading (accommodation of the eye).
When testing visual acuity, one eye is tested at a time and subsequently both eyes together. Two eyes can usually see more sharply than one.
The results of the test is put down as numbers or fractions. The notation for full visual acuity is 1.0 or 20/20 (feet) or 6/6 (meters). One tenth visual acuity corresponds to 0.10 or 20/200 or 6/60.