The majority of focusing of light rays is accomplished by the
adjustments of focusing are provided by the crystalline
The additional focusing provided by the crystalline lens is one of the processes
n. Accommodation refers to the various adjustments made
by the eye to see better at different
The crystalline lens is kept in a flattened condition by the tension of the zonular
s. This tension is released by contraction of the
y muscle, resulting in
ing of the lens.
When both eyeballs move through an equal angle in the same direction, it is
called a con
e eye movement. When both eyeballs turn toward the midline to
focus upon a nearby object, the result is a con
t eye movement.
During a "searching" eye movement, the eyeballs do not focus on a particular
object until it is l
d. During a "following" eye movement, the eyeballs continually
x on an object.
Vestibular control of eye movements is necessary in order to compensate for
The sudden movement of an individual in response to an unexpected visual
stimulus is part of the
Changes in the size of the pupil with changes in the amount of light are produced
Automatic movement of the eyelids over the exterior surface of the eyeball is
The lacrimal fluid keeps the conjunctiva
ent. Also, with the blink reflex,
the lacrimal fluid w
s away foreign particles.
The secretion of the special oil glands of the upper and lower eyelids helps
fluid from escaping.
The auricle serves as a collector of airborne w
s. At the inner end of the
external auditory meatus, the waves act upon the