Why Aging May Cause Problems - How The Eye Works: Eye Care

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Why aging may cause problems

Just as hair turns gray and skin sags with age, the eyes, too, undergo a metamorphosis as you grow older. Although many of these changes are part of normal aging, some set the stage for more serious eye problems.

As eyes age, eyelid muscles weaken, and skin becomes thinner and more flaccid. This can cause the upper lid to droop or the lower lid to sag. Eyelashes and eyebrows may lose their lushness and thin out considerably.

Tear production also drops off, and the oily film that tears provide decreases as lubricating glands in the conjunctiva and lids fail. These changes may lead to a buildup of mucus, resulting in stickiness, or may make the cornea dry, causing irritation or an uncomfortable, gritty sensation in the eye.

The conjunctiva turns thinner and more fragile with age and takes on a yellowish tinge from an increase in elastic fibers. The white of your eye (sclera) also assumes a yellow hue from a collection of lipid, or fat, deposits. The exposed conjunctiva between the lids begins to degenerate, and the cornea may develop an opaque white ring around its edge.

With time, the crystalline lens hardens and loses its elasticity. This makes it more difficult to focus on near objects, a common condition called presbyopia. You may also find that your night vision grows poorer. These changes usually occur simultaneously in both eyes.

Aging may also cause the lens to darken, grow opaque, and in some cases thicken, causing nearsightedness. Clouding of the lens, which is called cataract, usually develops slowly over many years. It may go unnoticed until the cloudiness blocks the central line of sight and impairs vision (see "Cataract").

Over time, the anterior chamber in each eye may become shallower in some susceptible individuals — those who have small eyes and are farsighted, for example — raising the risk for blockage of the aqueous humor drainage system near the iris. This fluid backup may lead to increased pressure inside the eye that damages the optic nerve; this is called closed-angle glaucoma, which, if left untreated, can cause blindness. Another form of glaucoma, called open-angle glaucoma, occurs when pressure builds up in the eye because of a blockage within Schlemm's canal, deeper in the drainage pathway (see "Glaucoma").

The aging retina thins and may grow less sensitive because of cell loss, a decreased blood supply, or degeneration. Especially prone to deterioration is the macula; age-related macular degeneration is a serious disease that can steal a person's central vision (see "Age-related macular degeneration").

Although age-related changes affect everyone, significant racial disparities exist when it comes to the type of problem that may develop. In Americans older than 40, the leading cause of blindness in white people is age-related macular degeneration, while in black people it is cataract, and in Hispanic people it is glaucoma (see Figure 4). This probably results from a combination of factors such as genetics, dietary patterns, and access to medical care.

Figure 4: Cause of blindness by race The leading causes of blindness vary by race and ethnicity, as seen in the pie charts above. Source: The Eye Diseases Prevalence Research Group, "Causes and Prevalence of Visual Impairment Among Adults in the United States," Archives of Ophthalmology, April 2004. Adapted with permission of the Archives of Ophthalmology.

Last updated:	June 19, 2007