The Ciliary Muscle is located
in each eye in the human body.
It is one of three zones of the ciliary
body (which connects the choroid
with the iris).
Contraction and relaxation of the ciliary muscle alters
the curvature of the lens
The correct term for the adjustment of the shape of the lens to change
the focus of the eye is "accommodation".
This process may be described simply as the balance existing at any one
time between between two states:
Ciliary Muscle relaxed:
The suspensory ligaments attached to the ciliary body that hold the lens
in place are stretched, causing the lens to be relatively flat.
This enables the eye to focus on distant objects.
Ciliary Muscle contracted:
The tension on the suspensory ligaments attached to the ciliary body is
reduced allowing the lens to be relatively round.
This enables the eye to focus on close objects (near to the eye).
The subject of visual (also known as "physiological") optics
is a key component of many courses within the fields of both biology and
physics. It is also an essential consideration in the design of displays
and control units used in many applications from televisions and mobile
telephones to advanced aircraft. In the context of engineering "visual
optics" is one of several medical and psychological topics in the
important area of "Human Factors".