Monday, June 2, 2008

Changes In Vision

Posted by Neill Abayon

Vision is the process in which light waves from an object being looked at are registered, interpreted and stored as an image by the brain. For this to happen, the light waves pass through the cornea, pupil and lens of the eye. The light waves are then projected onto the retina, which is located at the back of the eye. The optic nerve behind the retina picks up the signals from the nerve endings in the retina and relays them to parts of the brain that process the image and make it recognizable.

Various malfunctions in the process of vision may occur as a person ages. They may be caused by:

* Reduced muscle tone
* Decreased eye lubrication
* Any one of a number of eye disorders or diseases

Reduced muscle tone. The muscles that control movement of the eyes can malfunction with age. More commonly, the muscles that support the skin around the eye sockets and control the upper and lower eyelids may become too relaxed or weak and lose their firmness and elasticity. Over time, they become flaccid, causing the supporting connective tissue and skin around the eyes to droop and sag in ever-thickening folds.

This decrease in muscle tone and functioning can lead to a number of conditions in the aging eye, although these conditions are not always caused by aging. Most prominent among these conditions is blepharoptosis, or ptosis — a marked drooping of the upper eyelid. If left untreated, ptosis may impair vision and can lead to headaches and fatigue.

Decreased eye lubrication. The lacrimal gland in the eye produces protective tears with each blink. These tears keep the eye clean and lubricated. With age, the gland may start to malfunction, decreasing tear production. This can lead to burning, itchy eyes and other eye irritation.

A common problem that can develop as the eye ages is dry eye syndrome, in which the protective tear film that coats the eye dries too rapidly. And because tear production diminishes with age, replenishment of this tear film is insufficient.

Eye disorders or diseases. Vision problems may result when various structures in the eye deteriorate or become diseased. The pupil gets smaller — as much as a third of its size by age 60 according to one estimate — altering how (and how much) light passes through it.

Here are the eye disorders and diseases that most commonly occur with age:

* Age-related macular degeneration — This disease is the leading cause of blindness in people older than 50. Age-related macular degeneration is marked by damage to the macula area on the retina, an area that makes clearly defined, central vision possible.

* Glaucoma — Glaucoma is a leading cause of blindness in the United States. This disease is caused by an abnormal rise in pressure in the fluid-filled chambers of the eyes, damaging the optic nerve.

* Cataracts — Another byproduct of aging is the development of cataracts, a condition in which the normally clear lens of the eye becomes progressively clouded, ultimately blocking light from reaching the retina or scattering light and creating glare.

* Presbyopia — Almost everyone will develop this condition, typically starting around age 40. In presbyopia, the normally flexible lens of the eye becomes increasingly rigid and unable to focus on objects close-up.

* Night blindness — People with cataracts may suffer from night blindness, called nyctalopia by medical professionals. It may be hard for some people to distinguish certain colors, especially blue from green. Glare from excessive light scattering caused by cataract may lead to difficulty driving at night or difficulty navigating the way to the bathroom in the dark, etc.

To reduce your chances of developing any of these problems at a younger age, it is important that you have regular eye examinations beginning at age 40.

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