by Bobby Keith

Created on: May 26, 2007

Much like you would focus the lens of a camera on a object based on it's distance, the lens of our eye is able to focus on objects at different distances so that we can see them clearly. This process is known as "accommodation".

The ability of our lens to focus on objects at different distances is due to the elasticity of the lens.

There are fibers that are attached to the lens. These fibers are called the suspensory ligament. The suspensory ligament attaches the lens to another part of the eye known as the ciliary body.

When we view distant objects, the muscles in the ciliary body expand, causing increased tension on the suspensory ligament. This causes the lens to stretch and become thinner in the middle. The power of the lens decreases so that we can clearly see the distant object.

When we view near objects, the opposite takes place. The muscles in the ciliary body contract, releasing tension on the suspensory ligament. This squeezes the lens, causing it to become thicker in the middle, which in turn increases the power and allows us to see near objects clearly.

As we grow older, our ability to "accommodate" decreases. The reason for this is that the lens never stops growing.

As new cells develop around the outer edges of the lens, there is no way for the older cells to be absorbed or discarded, so they are compressed in the center of the lens. This causes the lens to lose some of its elasticity, and therefore we have trouble focusing on objects that are far away, as well as those that are near.

This condition is know as presbyopia.

Presbyopia usually becomes noticeable around age 40, but some people are affected earlier in life, and some later. If you live long enough, you will develop presbyopia.

Once you have been diagnosed with presbyopia, your eye doctor will probably prescribe a multi-focal lens to improve both distant and near vision. Many style of multi-focal lenses are available as lined bifocals, lined trifocals, and no-line progressive lenses. There are also contact lenses available to help presbyops (a person with presbyopia) see clearly.

This condition, as well as many others, can be diagnosed during a yearly, routine eye exam.

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