Eye Focus Problems

The focus of the eye is determined by the lens, a clear body the size and shape of an M&M candy just behind the iris and pupil of the eye. Several disorders affecting the lens or other parts of the eye can affect focus, and they can be congenital, or appear in youth or as part of aging.

Refraction Errors

• Three common refraction errors are myopia, hyperopia and presbyopia. In normal focusing (emmetropia, or 20/20 vision), the focus point is at the macula, in the center of the retina in the back of the eye. Myopia, or near-sightedness, happens when the focus point falls short of the macula. In hyperopia, or far-sightedness, the focus point stretches beyond the back of the eye, so that near objects are not in focus. Presbyopia normally occurs at or after age 40, in which focusing on near objects becomes more difficult. People with presbyopia usually require bifocals or reading glasses to see up close.

Cataracts

• Cataracts are caused when the lens becomes cloudy or develops opaque parts, which leads to blurry vision. Cataract comes from the Latin word for waterfall, because it appears a person with cataracts is looking through a waterfall. Cataracts affect about half of Americans over age 80. They can be corrected through surgery. Symptoms of cataracts include blurred vision, sensitivity to light, halos around lights, fading or yellowing of colors and double vision or multiple vision in one eye.

Glaucoma

• Glaucoma is caused by increased pressure of fluid inside the eye. This presses against the optic nerve and can cause tunnel vision or other blind spots in the eye. Early glaucoma is treated by medicine or surgery. The main symptom of glaucoma is the loss of side, or peripheral, vision.

Macular Degeneration

• Macular degeneration happens when the macula--in the center of your retina, marking the center of your visual field--deteriorates, leading to a blurry or blind spot in the center of your vision. Age-related macular degeneration is the most common cause of loss of vision in people over 60. While there is no cure for macular degeneration, detecting it early can help save some of your sight.

Floaters

• As people age, the jelly-like vitreous humor that makes up the bulk of the eyeball can become more liquid, causing accumulated debris to float around, sometimes into the field of vision. These "floaters" are generally harmless, and appear as moving spots, but too many or a combination with other symptoms can indicate other problems, such as a retinal tear or eye cancer.