This excerpt taken from the EYE 8-K filed Jul 13, 2005.
Refractive Vision Disorders
The human eye functions much like a camera. It incorporates a lens system that focuses light (the cornea and the lens), a variable aperture system that regulates the amount of light passing through the eye (the iris), and film that records the image (the retina). In a properly functioning eye, entering light is refracted by the cornea and lens, causing the image to focus on the retina. The retina translates the image into an electrical signal, which is relayed to the optic nerve and then to the brain.
In a refractive vision disorder, the cornea is improperly curved and cannot properly focus (or refract) light passing through it onto the retina. As a result, the image is blurred. The three refractive vision disorders most commonly treated today are:
Currently, eyeglasses or contact lenses are most often used to correct these vision disorders.
In addition to these refractive vision disorders, eyeglasses are also required for reading by many individuals that are over 50 years of age to correct presbyopia. This condition results from an age-related loss of accommodation by the lens of the eye which results in an inability to focus at close range.
Other vision disorders, known as higher order aberrations, can also result in blurred vision. Higher order aberrations cannot currently be corrected with eyeglasses or contact lenses and, until recently, were not measurable. Recent technological advances enable treatment of these higher order aberrations with laser vision correction.