- Laser canes are electronic traveling devices prescribed by an ophthalmologist or optometrist. The laser cane requires specialized training from an orientation and mobility instructor, requiring from thirty to forty hours of instruction. The device is a long cane that sends out three thin beams of invisible infrared light which can detect objects within twenty feet at face level, waist level, and ground level. It can also detect changes in the terrain of the path, including drops down to five inches below the surface, as curbs and potholes. When the laser light hits an obstacle, it sets vibrating pins into motion and/or sends out an auditory signal. The signal is pitched according to the height of the obstacle. When the beam touches an obstacle at face level, the auditory signal is a high-pitched beep. When it hits a center or waist-high obstacle, the beep is pitched lower; and when it hits ground-level obstacles, the pitch is still lower.
LASIK (See Refractive Surgery.)
Lens of the eye is a transparent, elastic, semi-soft material about half the diameter of a dime which can change shape to focus on objects at different distances from the eye. It is suspended in place by threadlike fibers called the Zonule of Zinn, or simply zonules. The shape of the lens is automatically controlled by the ciliary muscle, a thin band of muscle that lines the wall of the eye and surrounds the lens like a headband. To focus on a close object, the ciliary muscle contracts, loosening the fibers’ tension on the lens and allowing it to bulge. This increases the optical power of the system. As the lens ages, it loses some of its elasticity and is not able to bulge as much. This is known as presbyopia (aging eyes) and is the reason people in their forties start leaning toward the need for reading glasses. The lens has the highest protein content of any organ in the body – 33% as compared to 18% of muscle. The reason for the transparency of the lens has to do with a unique physical and chemical orderly arrangement of the protein fibers.
Low-vision specialist is a technician with a knowledge of highly specialized optical lenses and devices that may restore reading, writing, and driving capabilities to those whose vision cannot be corrected with regular eye wear. Many of their clients have retinal problems, especially macular degeneration, which cannot be helped by other forms of treatment.
Lutein is a nutrient in the carotenoid family that is thought to reduce the risk of developing age-related macular degeneration. While most researchers and doctors agree that good nutrition is important to overall eye health, they cannot bring themselves to go so far as to say that lutein can prevent macular degeneration, preferring instead to rely on drugs. However, the National Eye Institute (NEI) in March 2000 issued a statement concerning the value of taking lutein supplements although they did say that possible benefits are yet uncertain because no scientific studies have presented definitive conclusions. Usually, there are far fewer dangers in taking nutritional supplements than there are in resorting to drugs to correct a problem. Foods rich in carotenoids include green, leafy vegetables, for example, as kale and cabbage.