About Your Eyes and Vision
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About 80 percent of all babies are born farsighted — able to see objects clearly at a distance but less clearly close up. Some five percent are born nearsighted, or unable to see objects at a distance clearly.
Approximately 15 percent are born with nothing wrong with the refractive parts of the eye — the cornea and crystalline lens which bend light and focus it properly on the retina. Farsightedness usually decreases as a child ages, typically normalizing to a negligible value by the age of 7-8.
After a child grows and the incidence of farsightedness decreases, that of nearsightedness increases. Many school-age children and teens first discover they are nearsighted when they have difficulty reading the writing on the board at school. Nearsightedness usually occurs before age 25.
Vision skills for school
Your school-age child’s eyes are constantly in use in the classroom and at play. When his or her vision is not functioning properly, learning and participation in recreational activities can suffer.
Good vision involves many different skills working together to enable your child not only to see clearly but also to understand what he or she sees.
Those skills include:
Near Vision Ability to see clearly and comfortably at 13-16 inches, the distance at which school deskwork should be performed.
Distance Vision Ability to see clearly and comfortably at 10 feet or more.
Binocular Coordination Ability to use the two eyes together.
Eye Movement Skills Ability to aim the eyes accurately, and move them smoothly across a page and quickly and accurately from one object to another.
Peripheral Awareness Ability to be aware of things to the side while looking straight ahead.
Eye/Hand Coordination Ability to use the eyes and hands together.
If any of these or other vision skills is lacking or not functioning properly, your child’s eyes have to work harder. This can lead to blurred vision, headaches, fatigue and other eyestrain symptoms.
Why thorough vision examinations are important Don’t assume your child has good vision because he or she passed a school vision screening. A 20/20 score means only that your child can see at 20 feet what he or she should be able to see at that distance. It does not measure any of the other vision skills needed for learning.
Vision screenings are important but they should not be substituted for a thorough vision examination.
Things you can do There are things you can do to help ensure that your child’s vision is ready for school each year and to relieve the visual stress of schoolwork.
Be alert for symptoms that may indicate your child has a vision problem. Note if your child frequently:
- Loses his or her place while reading.
- Avoids close work.
- Holds reading material closer than normal.
- Tends to rub his or her eyes.
- Has headaches.
- Turns or tilts their head to use one eye only.
- Makes reversals when reading or writing.
- Uses a finger to maintain their place while reading.
- Omits or confuses small words when reading.
- Performs below potential.
- Closes one eye while reading.
Make sure your child’s homework area is evenly lighted and free from glare. Furniture should be the right size for proper posture. During periods of close concentration, have your child take periodic breaks. Rest breaks are also recommended when your child is using a computer or playing video games.
To make TV viewing easier on your child’s eyes:
- Be sure the room has overall soft lighting.
- Place the set to avoid glare and reflections.
- Watch from a distance at least five times the width of the screen.
Be sure your child’s hours away from school include time for exercise and creative play. Both can help keep his or her vision skills functioning properly.
Teach your child eye protection through these safety rules:
- Keep away from the targets of darts, bows-and-arrows, air guns and missile-throwing toys.
- Don’t shine laser pointers into anyone’s eyes. Teach them laser pointers are not toys.
- Don’t run with or throw sharp objects.
- Wear safety goggles when using chemistry sets, power tools and household and yard chemicals. (Note: Be certain your child is mature enough to handle these items safely, and provide proper supervision.)
Thorough vision care is important Because a change in vision can occur without you or your child realizing it, have your child’s eyes examined every year.
A thorough eye examination should include:
- A review of your child’s health and vision history.
- Tests for nearsightedness, farsightedness, astigmatism, color perception, lazy eye, crossed-eyes, eye coordination, depth perception and focusing ability.
- An eye health examination.
If your child’s eyes need help After assessing your child’s test results, glasses, contact lenses or vision therapy may be prescribed. He or she may also recommend preventive measures, such as mild prescription lenses to be worn only when doing schoolwork or watching television. These may help relieve stress on your child’s eyes.
Vision therapy is prescribed for conditions that cannot adequately be treated with glasses or contact lenses alone. By reinforcing or re-teaching vision skills, conditions such as poor eye coordination and movement, lazy eye and perceptual problems can be improved.
Your care and concern for your child’s vision can enrich his or her future while helping develop eye care habits for a lifetime of good vision.
Our ability to "see" starts when light reflects off an object at which we are looking and enters the eye. As it enters the eye, the light is unfocused. The first step in seeing is to focus the light rays onto the retina, which is the light sensitive layer found inside the eye. Once the light is focused, it stimulates cells to send millions of electrochemical impulses along the optic nerve to the brain. The portion of the brain at the back of the head interprets the impulses, enabling us to see the object.
Light, refraction and its importance. Light entering the eye is first bent, or refracted, by the cornea — the clear window on the outer front surface of the eyeball. The cornea provides most of the eye's optical power or light-bending ability.
After the light passes through the cornea, it is bent again — to a more finely adjusted focus — by the crystalline lens inside the eye. The lens focuses the light on the retina. This is achieved by the ciliary muscles in the eye changing the shape of the lens, bending or flattening it to focus the light rays on the retina.
This adjustment in the lens, known as accommodation, is necessary for bringing near and far objects into focus. The process of bending light to produce a focused image on the retina is called "refraction". Ideally, the light is "refracted," or redirected, in such a manner that the rays are focused into a precise image on the retina.
Most vision problems occur because of an error in how our eyes refract light. In nearsightedness (myopia), the light rays form an image in front of the retina. In farsightedness (hypermetropia), the rays focus behind the retina. In astigmatism, the curvature of the cornea is irregular, causing light rays to focus to more than one place so that a single clear image cannot be formed on the retina, resulting in blurred vision. As we age, we find reading or performing close-up activities more difficult. This condition is called presbyopia, and results from the crystalline lens being less flexible, and therefore less able to bend light.
Since changing the apparent refraction of the eye is relatively easy through the use of corrective spectacle or contact lenses, many of the conditions that contribute to unclear vision can be readily corrected.
How do we make sense of light? Sensory interpretation Even with the light focused on the retina, the process of seeing is not complete. For one thing, the image is inverted, or upside down. Light from the various "pieces" of the object being observed stimulate nerve endings — photoreceptors or cells sensitive to light — in the retina.
Rods and cones Two types of receptors — rods and cones — are present. Rods are mainly found in the peripheral retina and enable us to see in dim light and to detect peripheral motion. They are primarily responsible for night vision and visual orientation. Cones are principally found in the central retina and provide detailed vision for such tasks as reading or distinguishing distant objects. They also are necessary for color detection. These photoreceptors convert light to electrochemical impulses that are transmitted via the nerves to the brain.
Millions of impulses travel along the nerve fibers of the optic nerve at the back of the eye, eventually arriving at the visual cortex of the brain, located at the back of the head. Here, the electrochemical impulses are unscrambled and interpreted. The image is re-inverted so that we see the object the right way up. This "sensory" part of seeing is much more complex than the refractive part — and therefore is much more difficult to influence accurately.
What is 20/20 Vision? You may be pleased to hear that you have 20/20 vision and think you have perfect vision. But do you?
Not necessarily. 20/20 only indicates how sharp or clear your vision is at a distance. Overall vision also includes peripheral awareness or side vision, eye coordination, depth perception, focusing ability and color vision.
20/20 describes normal visual clarity or sharpness measured at a distance of 20 feet from an object. 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.
Is 25/25 vision better than 20/20? No. 25/25 means normal sharpness of vision, or visual acuity, at 25 feet just as 20/20 indicates normal vision at 20 feet.
Why do some people have less than 20/20? The ability to see objects clearly is affected by many factors. Eye conditions like nearsightedness, farsightedness, astigmatism or eye diseases influence visual acuity. Most people with vision slightly below 20/20 function very well, whereas some people who have better than 20/20 vision feel that their vision is not satisfactory. Everybody's visual expectations are different and satisfactory vision is far more complex than just being able to see 20/20.
If my vision is less than optimum, what can I do? A comprehensive eye examination will identify causes that may affect your ability to see well. We may be able to 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 needed. If necessary, referral will be undertaken if an eye disease is found which warrants further investigation.
Most changes in vision occur in the early and later years of life. Although some people may discover they have nearsightedness — or difficulty seeing at a distance — as late as their mid-20s, vision typically stabilizes during the late teen years. From then until around age 40, vision typically changes little, if at all.
Presbyopia – Age-related loss of close-up vision At about 40 years of age, seeing to read or do close work such as sewing may become difficult. This is known as “presbyopia.” Presbyopia, a name that comes from the Greek words for “old eye,” occurs because the crystalline lens, an essential component of the eye’s refractive, or light-bending structure, loses flexibility as it grows thicker with age. This lack of flexibility affects the ability to focus on close objects.
Generally, by around age 45, reading glasses may be required for nearby tasks. If near- or farsightedness is also present, a number of vision correction options will be evaluated to best meet your needs.
Spots and floaters People of every age may at times see spots and floaters, which appear to look like specks of material, cobwebs, thread-like strands or showers of brilliant crystals. During the middle years of life, they may become more frequent. These are optical defects that occur, as the vitreous, the jelly-like body in the main globe of the eye, becomes less jelly-like and more liquid as time goes by. This change is not always uniform, and so the mixture of jelly-like and liquid materials can affect the passage of light to the retina.
The result is seen as ‘floaters.’ Although spots and floaters are typically not of concern, they should be evaluated promptly. If you suddenly experience a large number of floaters, don’t delay in making an appointment. A sudden change may signify that something is wrong.
Glaucoma For adults, it is important to schedule regular eye examinations in order to detect and treat any occurrence of glaucoma in its earliest stages. Most types of glaucoma occur without the presence of any symptoms and can only be detected during a routine eye examination. Glaucoma occurs when fluid pressure inside the eye rises, cutting off the blood supply in the very small arteries carrying food and oxygen to the retina and causing loss of side vision or blindness if left untreated. It is a condition that can be arrested or slowed down but not reversed, so early detection is essential. Treatment often involves special eye drops or medicine, but, in some cases, surgery may be required. If detected early, chances that vision can be maintained are usually very good.
Retinal disorders Retinal disorders have a greater chance of developing in older adults, due to the aging process. These often impair central vision. Advances in eye and health care have made treatments more successful, with chances of maintaining good vision now better than ever. Conditions once considered sight threatening may now be successfully treated if diagnosed early.
Suggestions for better sight
- Be aware of your visual limitations and compensate for them.
- You may need more light for reading and other close tasks. Move the lamp closer to you and/or use a larger watt bulb. It is a fact that a 60 year old needs three times as much light as a 20 year old to see near work as easily.
- Side vision and reaction time may reduce with age. Keep this in mind while driving or walking near traffic.
- Limit night driving to well-lighted roads; keep headlights and windshields clean; and be visually aware of traffic.
- Be sure to keep glasses clean.
- Be sure to wear distance spectacles if they are prescribed for you. While you may feel that your distance vision is as good as it was when you were younger, very often this is not the case.
Although natural vision changes can’t be prevented, they need not mean giving up activities such as driving your car. By practicing good health habits and having regular eye examinations, you should be able to continue an active, productive and independent life.
Good vision is vital to reading well. And although vision may not be the only cause of reading difficulties, it is one that is sometimes overlooked.
Eight vision skills needed to read Reading requires the integration of eight different vision skills. Only one is checked by the typical school eye chart test. Quick eye examinations may cover only one or two. Since a comprehensive eye examination will cover the eight vision skills, it is a must for anyone having trouble reading. The eight skills include:
Visual acuity, or the ability to see objects clearly at a distance. Visual acuity is sometimes measured in a school vision screening. Normal visual acuity is referred to as 20/20 vision (or 6/6 vision in the metric system) — a measure of what can normally be seen at a distance of 20 feet, or six meters. If a problem is discovered in the screening, a thorough optometric examination should follow.
Visual fixation, or the ability to aim the eyes accurately. One type of fixation, called direct, has to do with the ability to focus on a stationary object or to read a line of print. The other type, called pursuit fixation, is the ability to follow a moving object with the eyes.
Accommodation, or the ability to adjust the focus of the eyes as the distance between the individual and the object changes. Children frequently use this skill in the classroom as they shift focus between books and blackboards.
Binocular fusion, or the brain’s ability to gather information received from each eye separately and form a single, unified image. Eyes must be precisely aligned or double vision (diplopia) may result. If it does, the brain often subconsciously suppresses or inhibits the vision in one eye to avoid confusion. That eye may then develop poorer visual acuity (amblyopia or lazy eye).
Stereopsis, a function of proper binocular fusion enhancing the perception of depth, or the relative distances of objects from the observer.
Convergence, or the ability to turn the two eyes toward each other to look at a close object. Any close work, such as deskwork, requires this vision skill. If convergence is poor then reading becomes uncomfortable after a relatively short period of time and double vision may result.
Field of vision, or the area over which vision is possible. It is important to be aware of objects on the periphery (left and right sides and up and down) as well as in the center of the field of vision.
Perception, the total process of receiving and recognizing visual stimuli. Form perception is the ability to organize and recognize visual images as specific shapes. A reader remembers the shapes of words, which are defined and recalled as reading skills are developed.
Treating reading-related vision problems When a vision problem is diagnosed, the practitioner will prescribe glasses or contact lenses, vision therapy or both. Vision therapy involves an individualized program of training procedures designed to help develop or sharpen vision skills and possibly develop the eye muscles involved in focusing.
Because reading problems usually have multiple causes, treatment must often be multidisciplinary. Educators, psychologists, optometrists and other professionals often must work together to meet each person’s needs. The optometrist’s role is to help overcome any vision problems interfering with the ability to read. This may require the use of corrective spectacles and/or the implementation of a variety of eye exercises. Once any vision problems are addressed, the student is better prepared to respond to special reading education efforts.
Eye care experts generally agree: Watching television will not harm your eyes or vision if the TV room is lit properly and if you follow a few viewing tips. In fact, there is usually less strain involved in TV viewing than in doing close work such as sewing or reading. But TV watching for long stretches of time can leave your eyes fatigued.
What are the best conditions for TV viewing? A normally lit room, suitable for general activities, is best. Excessively bright lighting tends to reduce contrast on the screen and “wash out” the picture. No lights should be placed where glare or reflections will be seen in or near the television screen. Strongly colored lighting should not be used and surroundings should be neutral in color.
Is it all right to watch television in a dark room? This situation is not ideal. When the room is totally dark, the contrast between the television screen and the surrounding area is too great for comfortable and efficient vision. When the room is softly illuminated, undesirable high contrast is kept to a minimum.
Is it better to adjust the television set to room lighting or room lighting to the set? Adapt the set’s brightness and contrast to room lighting — not room lighting to the set — after the room lights have been turned on.
Is it all right to wear sunglasses while watching television? Generally, no. Sunglasses may shut out too much light for good vision. If worn when not needed, they tend to make it difficult for the viewer to adapt promptly to normal light levels. If you are bothered by brightness, consult with an eye care practitioner about the possible need for lenses more appropriate to TV viewing.
Possible difficulties with TV viewing Children sometimes sit close to the set. Does this hurt their eyes? While close-up viewing is certainly not recommended, it is generally not harmful. It is best to watch television from a distance of at least five times the width of the picture. Picture details will appear sharper and better defined and the television lines and defects will be less apparent. If your child persists in watching television from a short distance, have his or her vision checked. Nearsighted (myopic) children like to sit close to the screen.
What does it mean if the eyes water or if there is other visual discomfort while watching television? It could indicate a problem that needs professional attention. Some viewers, especially those over 50 years old, may find relief with special glasses for television viewing. Discomfort could also indicate that the drainage passages which drain tears from the eyes into the nose are partially blocked and require examination.
What about color television for viewers with color vision deficiencies? Color deficiency (i.e. color blindness) is generally not a barrier to enjoying color television. However, viewers with color deficiencies may disagree with others as to the “proper” color adjustment. A color TV picture properly adjusted for most people may appear too green to a protanomalous (weak red) observer, or too red to a deuteranomalous (weak green) viewer. When the set is adjusted to “correct” its color, the resulting picture is usually unsatisfactorily tinted for other viewers. Viewers who are severely color deficient, the so-called “red blind” or “green blind,” will see little or no difference in widely different color mixtures, and will not be bothered by most color adjustments.
TV viewing tips:
- Make sure your television set is properly installed and the antenna properly adjusted.
- Place the set to avoid glare and reflections from lamps, windows and other bright sources.
- Adjust brightness and contrast controls to individual and/or viewer’s taste and comfort.
- Have the set at approximately eye level. Avoid having to look up or down at the picture.
- Avoid staring at the screen for lengthy periods. Briefly look away from the picture, around the room or out the window.
- Wear lenses prescribed for vision correction, if advised to do so by your eye care practitioner.
- View from a distance at least five times the width of the television screen.