Vision tests check many different functions of the eye. The
tests measure your ability to see details at near and far
distances, check for gaps or defects in your field of vision,
and evaluate your ability to see different colors. - Visual
acuity tests are the most common tests used to evaluate
eyesight. They measure the eye's ability to see details at near
and far distances. The tests usually involve reading letters or
looking at symbols of different sizes on an eye chart. Usually,
each eye is tested by itself. And then both eyes may be tested
together, with and without corrective lenses (if you wear them).
Several types of visual acuity tests may be used. - Refraction
is a test that measures the eyes' need for corrective lenses
(refractive error). It is usually done after a visual acuity
test. Refractive errors, such as nearsightedness or
farsightedness, occur when light rays entering the eye can't
focus exactly on the nerve layer (retina) at the back of the
eye. This causes blurred vision. Refraction is do