About vision: Vision conditions

MYOPIA (nearsightedness)

Nearsightedness is a vision condition in which near objects are seen clearly, but distant objects do not come into proper focus. Nearsightedness occurs if your eyeball is too long or the cornea has too much curvature, so the light entering your eye is not focused correctly.

Nearsightedness is a very common vision condition that affects nearly 30 percent of the U.S. population. Some evidence supports the theory that nearsightedness is hereditary. There is also growing evidence that nearsightedness may be caused by the stress of too much close vision work. It normally first occurs in school age children. Since the eye continues to grow during childhood, nearsightedness generally develops before age 20.

A sign of nearsightedness is difficulty seeing distant objects like a movie or TV screen or chalkboard. A comprehensive optometric examination will include testing for nearsightedness. Your optometrist can prescribe eyeglasses or contact lenses to optically correct nearsightedness by altering the way the light images enter your eyes. You may only need to wear them for certain activities, like watching TV or a movie or driving a car, or they may need to be worn for all activities.

Corneal refractive therapy (CRT) and Lasik refractive laser surgery are also possible treatments for nearsightedness. CRT is a non-invasive procedure that involves the wearing of a series of specially-designed rigid contact lenses to progressively reshape the curvature of the cornea over time.
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HYPEROPIA (farsightedness)

Farsightedness is a vision condition in which distant objects are usually seen clearly, but close ones do not come into proper focus. Farsightedness occurs if your eyeball is too short or the cornea has too little curvature, so light entering your eye is not focused correctly.

Common signs of farsightedness include difficulty in concentrating and maintaining a clear focus on near objects, eye strain, fatigue and/or headaches after close work, aching or burning eyes, irritability or nervousness after sustained concentration.

Common vision screenings, often done in schools, are generally ineffective in detecting farsightedness. A comprehensive optometric examination will include testing for farsightedness.

In mild cases of farsightedness, your eyes may be able to compensate without corrective lenses. In other cases, your optometrist can prescribe eyeglasses or contact lenses to optically correct farsightedness by altering the way the light enters your eyes.
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ASTIGMATISM

Astigmatism is a vision condition that occurs when the front surface of your eye, the cornea, is slightly irregular in shape. This irregular shape prevents light from focusing properly on the back of your eye, the retina. As a result, your vision may be blurred at all distances.

People with severe astigmatism will usually have blurred or distorted vision, while those with mild astigmatism may experience headaches, eye strain, fatigue or blurred vision at certain distances. Most people have some degree of astigmatism. A comprehensive optometric examination will include testing to diagnose astigmatism and determine the degree.

Almost all levels of astigmatism can be optically corrected with properly prescribed and fitted eyeglasses and/or contact lenses.

Corneal modification is also a treatment option for some patients.
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PRESBYOPIA

Presbyopia is a vision condition in which the crystalline lens of your eye loses its flexibility, which makes it difficult for you to focus on close objects.

Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-forties. Presbyopia is a natural part of the aging process of the eye. It is not a disease and it cannot be prevented.

Some signs of presbyopia include the tendency to hold reading materials at arm's length, blurred vision at normal reading distance and eye fatigue along with headaches when doing close work. A comprehensive optometric examination will include testing for presbyopia.

To help you compensate for presbyopia, your optometrist can prescribe reading glasses, bifocals, trifocals or contact lenses. Since presbyopia can complicate other common vision conditions like nearsightedness, farsightedness and astigmatism, your optometrist will determine the specific lenses to allow you to see clearly and comfortably. You may only need to wear your glasses for close work like reading, but you may find that wearing them all the time is more convenient and beneficial for your vision needs.

Since the effects of presbyopia continue to change the ability of the crystalline lens to focus properly, periodic changes in your eyewear may be necessary to maintain clear and comfortable vision.
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SPOTS OR FLOATERS

Spots (often called floaters) are small, semi-transparent or cloudy specks or particles within the vitreous, the clear, jelly-like fluid that fills the inside of your eyes. They appear as specks of various shapes and sizes, threadlike strands or cobwebs. Since they are within your eyes, they move as your eyes move and seem to dart away when you try to look at them directly.

Spots are often caused by small flecks of protein or other matter trapped during the formation of your eyes before birth. They can also result from deterioration of the vitreous fluid, due to aging; or from certain eye diseases or injuries.

Most spots are not harmful and rarely limit vision. But, spots can be indications of more serious problems, and you should see your optometrist for a comprehensive examination when you notice sudden changes or see increases in them.

By looking in your eyes with special instruments, your optometrist can examine the health of your eyes and determine if what you are seeing is harmless or the symptoms of a more serious problem that requires treatment.
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STRABISMUS (crossed eyes)

Crossed eyes occurs when one or both of your eyes turns in, out, up or down. Poor eye muscle control usually causes crossed eyes. This misalignment often first appears before age 21 months but may develop as late as age six. This is one reason why the American Optometric Association recommends a comprehensive optometric examination before six months and again at age three.

There is a common misconception that a child will outgrow crossed eyes. This is not true. In fact, the condition may get worse without treatment.

Treatment for crossed eyes may include single vision or bifocal eyeglasses, prisms, vision therapy, and in some cases, surgery. Vision therapy helps align your eyes and solves the underlying cause of crossed-eyes by teaching your two eyes to work together. Surgery alone may straighten your eyes, but unless your eye muscle control is improved, your eyes may not remain straight.

If detected and treated early, crossed eyes can often be corrected with excellent results.
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AMBLYOPIA (lazy eye)

Lazy eye is the loss or lack of development of central vision in one eye that is unrelated to any eye health problem and is not correctable with lenses. It can result from a failure to use both eyes together. Lazy eye is often associated with crossed-eyes or a large difference in the degree of nearsightedness or farsightedness between the two eyes. It usually develops before age six and it does not affect side vision.

Symptoms may include noticeably favoring one eye or a tendency to bump into objects on one side. Symptoms are not always obvious.

Treatment for lazy eye may include a combination of prescription lenses, prisms, vision therapy and eye patching. Vision therapy teaches the two eyes how to work together, which helps prevent lazy eye from reoccurring.

Early diagnosis increases the chance for a complete recovery. This is one reason why the American Optometric Association recommends that children have a comprehensive optometric examination by the age of six months and again at age three. Lazy eye will not go away on its own. If not diagnosed until the pre-teen, teen or adult years, treatment takes longer and is often less effective.
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EYE COORDINATION PROBLEMS

Eye coordination is the ability of both eyes to work together as a team. Each of your eyes sees a slightly different image and your brain, by a process called fusion, blends these two images into one three-dimensional picture. Good eye coordination keeps the eyes in proper alignment. Eye coordination is a skill that must be developed. Poor eye coordination results from a lack of adequate vision development or improperly developed eye muscle control. Although rare, an injury or disease can cause poor eye coordination.

Because the images seen by each eye must be virtually the same, a person usually compensates for poor eye muscle control by subconsciously exerting extra effort to maintain proper alignment of the eyes. In more severe cases, the muscles cannot adjust the eyes so that the same image is seen and double vision occurs. Since the brain will try to avoid seeing double, it eventually learns to ignore the image sent by one eye. This can result in amblyopia, a serious vision condition commonly known as lazy eye.

Some signs and symptoms that may indicate poor eye coordination include double vision, headaches, eye and body fatigue, irritability, dizziness and difficulty in reading and concentrating. Children may also display characteristics that may indicate poor eye coordination including covering one eye, skipping lines or losing their place while reading, poor sports performance, avoiding tasks that require close work and tiring easily.

Since poor eye coordination can be difficult to detect, periodic optometric examinations, beginning at age six months and again at age three years are recommended. A comprehensive examination by a doctor of optometry can determine the extent, if any, of poor eye coordination. Poor eye coordination is often successfully treated with eyeglasses and/or vision therapy. The success rate for achieving proper eye coordination is quite high. Sometimes, eye coordination will improve when other vision conditions like nearsightedness or farsightedness are corrected. In some cases, surgery may be necessary.
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COLOR VISION DEFICIENCY (color blindness)

Color vision deficiency means that your ability to distinguish some colors and shades is less than normal. It occurs when the color-sensitive cone cells in your eyes do not properly pick up or send the proper color signals to your brain. About eight percent of men and one percent of women are color deficient.

Red-green deficiency is by far the most common form and it results in the inability to distinguish certain shades of red and green. Those with a less common type have difficulty distinguishing blue and yellow. In very rare cases, color deficiency exists to an extent that no colors can be detected, only shades of black, white and grey.

Since many learning materials are color-coded, it is important to diagnose color vision deficiency early in life. This is why the American Optometric Association recommends a comprehensive optometric examination before a child begins school.

Color vision deficiency is usually inherited and cannot be cured, but those affected can often be taught to adapt to the inability to distinguish colors. In some cases, a special red tinted contact lens is used in one eye to aid persons with certain color deficiencies.
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20/20 VISION

20/20 vision is a term used to express normal visual acuity (the clarity or sharpness of vision) measured at a distance of 20 feet. If you have 20/20 vision, you can see clearly at 20 feet what should normally be seen at that distance. If you have 20/100 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 100 feet.

20/20 does not necessarily mean perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance. There are other important vision skills, including peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision that contribute to your overall visual ability.

Some people can see well at a distance, but are unable to bring nearer objects into focus. This condition can be caused by hyperopia (farsightedness) or presbyopia (loss of focusing ability). Others can see items that are close, but cannot see those far away. This condition may be caused by myopia (nearsightedness).

A comprehensive eye examination by a doctor of optometry can diagnose those causes, if any, that are affecting your ability to see well. In most cases, your optometrist can prescribe glasses, contact lenses or a vision therapy program that will help improve your vision. If the reduced vision is due to an eye disease, the use of ocular medication or other treatment may be used.
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