Six oculomotor muscles are attached to each of your eyeballs and
let you make various types of movements with your eyes. Some of
these movements are slow, such as when your eyes follow an
object passing in front of them. Others, called saccades, are
very rapid. One good example of saccades is the movements that
your eyes are making while you are reading this page. Your eyes
stop for a moment at one point in a sentence to analyze its
image, then jump ahead very quickly to the next point. As can be
seen in the cross-section here, the first structure through
which light passes into the eye is the conjunctivea thin,
transparent membrane that covers the front of the eye and then
folds over to line the inside of the eyelids. The cornea is
continuous with the white of the eye, or sclera, which forms the
hard outer wall of the eyeball. Three pairs of muscles are
inserted into the sclera. It is these ocular muscles that enable
the eyeball to move in its socket in the skull. Between the
sclera and the retina lies the c