Overview of the Eye and How We See

A normal part of the aging process brings about the development of cataracts in many individuals. The word cataracts is derived from the Latin word for waterfall, and is so named due to the perception that one is looking through a waterfall when a cataracts is present. Cataracts cause normal eyesight to become progressively blurry and cloudy. The once transparent, clear lens of the eye begins to turn opaque and in some cases causes the patient to see halos around lights.

In a healthy eye, the lens brings light into the eye and helps to focus it onto the retina at the back of the eye. The lens is a clear, disk-like structure located behind the iris and the pupil. In order for an image or an object to be seen, the light reflected from the object is filtered through the lens of the eye which focuses the light onto the light-sensitive membrane of the retina. The light from the image activates the membrane of the retina and is transformed into nerve signals. The nerve signals travel along the optic nerve and are translated by the brain and the final picture of the object is "seen".

In order for the light to hit the retina and form a complete and clear picture in the brain, the lens must be transparent so that all of the light reflected from the image makes it to the retina. If the lens is clouded, only a portion of the image's light is received by the retina. In turn, the brain is not supplied with enough nerve signals to create a clear and sharp picture. Instead, the picture that the brain "sees" is blurry and cloudy. Additionally, when the lens is affected by a cataracts, the light coming through the lens tends to scatter, also decreasing the quantity of light finding its way to the retina.

The lens is composed of three layers. There is the capsule which is a thin, clear membrane. This capsule, or outer layer, protects and surrounds the soft material of the cortex; the middle layer. Inside of the cortex lies the center layer of the lens, the hard nucleus.