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Glossary & Eye Anatomy
Common Vision Problems in Adults
Age-Related Macular Degeneration (AMD)
Age-Related Macular Degeneration (AMD) is a condition that affects the macula, a portion of the retina, and leads to loss of sharp central vision. AMD is the leading cause of legal blindness in America. Approximately 15 million Americans live with the disease and it is most common in older people ages 75-80.
Symptoms include gradual loss of the ability to see objects clearly; distorted vision; gradual loss of color vision; and dark or empty areas appearing in the center of vision.
Cataracts
A cataract is a clouding of all or part of the normally clear lens within the eye. It will eventually block and distort light entering the eye. More than 20.5 million Americans over age 40 are affected with this condition. Cataracts are usually found in people over age 55, but occasionally younger people can get then. Symptoms include cloudy or blurry distance vision; altered color perception; problems with glare; difficulty reading fine print; poor night vision and frequent changes in corrective lenses.
Diabetic Retinopathy
Diabetic retinopathy is a secondary complication of diabetes and is caused by changes in the blood vessels of the retina. Small blood vessels swell, leak and hemorrhage into the retina blurring vision and occasionally leading to blindness. When detected and treated in a timely fashion, significant vision loss can usually be avoided. Approximately 4.1 million Americans with diabetes have diabetic retinopathy. Anyone with diabetes, either type 1 or type 2, is at risk of developing this condition. At least yearly examinations are necessary for diabetics, as diabetic retinopathy has no symptoms.
Glaucoma
Glaucoma is a condition in which the optic nerve is gradually damaged because the pressure inside of the eye is too high. Between three and four million Americans have glaucoma; including an estimated 1.5 to two million people who do not even know that they have the disease. Those who are over 40, Hispanic, African American, have a family history of glaucoma, are very nearsighted or diabetic are at higher risk of developing the condition. The most common type of glaucoma develops gradually and painlessly, with no symptoms for an extended period of time. If untreated, loss of side vision will occur and may eventually lead to blindness.
Presbyopia
Presbyopia is a progressive condition that makes reading and doing close work, such as sewing, increasingly difficult as eyes age. For people in their 40's and early 50's, it's often the first sign of aging; by age 55, it affects everyone. Even those with perfect eyesight may find they can no longer read books and printed materials at normal distances.
Refractive Error
Refractive errors occur when there is a variance between the focusing strength of the eye and the length of the eyeball. When a refractive error is present, light entering the eye is not focused, which results in a blurry image. Refractive errors are the most common vision disorder and can be corrected by eyeglasses, contact lenses or refractive surgery. The four most common refractive errors are myopia (nearsightedness), hyperopia (farsightedness), astigmatism, and presbyopia.
Common Vision Problems in Children
Amblyopia
Amblyopia (or lazy eye) occurs when vision in one of the eyes is reduced because the eye and the brain are not working together properly. Amblyopia is the most common cause of visual impairment in childhood. It affects about 2% of adolescents. Amblyopia usually develops before the age of 6 and can persist for life if untreated. It causes more vision loss than trauma and all other ocular diseases.
Astigmatism
Astigmatism is a very common vision problem caused by an irregularly shaped cornea. Blurred vision at all distances is the most significant indicator of astigmatism and many people who have astigmatism also have myopia or hyperopia. It is often present at birth. Family history of the condition increases risk.
Strabismus
Strabismus is when eyes are turned in, turned out or not working as a team. It affects up to 5 percent of all children to some degree and can begin during infancy. Signs and symptoms include wandering eye, double vision, vision in only one eye and eyes that appear crossed.
Eye Anatomy
Conjunctiva
The thin, moist tissue that lines the inner surfaces of the eyelids to help protect the eye and keep it from drying out.
Cornea
The front surface of the eye. It covers iris, pupil, and anterior chamber and is responsible for 70% of the total focusing ability.
Iris
Behind the cornea is the iris, which contains the pupil. By controlling the amount of light entering the eye, the iris adjusts the size of the pupil.
Lens
Behind the pupil is the lens of the eye. The lens focuses light on the retina, which sends messages through the optic nerve to the brain.
Optic nerve
Is made up of over a million nerve fibers that transport visual messages from the retina to your brain.
Pupils
The pupil is contained within the iris. It gets larger or smaller depending on how much light is available. It controls how much light enters the eye by opening up in the darkness and closing in the light.
Retina
Located at the back of the eye, the retina receives images from the cornea and the lens and then sends those messages back to the brain.
*All content on this page has been approved by The Better Vision Institute – the medical advisory panel of The Vision Council.
