Vision Conditions
- Visual Acuity1
- Myopia (Short-sightedness)2
- Hyperopia or Farsightedness3
- Presbyopia4
- Astigmatism5
- Amblyopia (Lazy Eye)6
- Strabismus / Squint / Cross Eyes7
- Spots / Floaters8
- Color Vision Deficiency9
- Eye Coordination 10
Visual
Acuity
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. (Under the metric system 20/20 is written as 6/6 where meters are used in place of 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 can diagnose those causes, if any, that are affecting your ability to see well. In most cases, your eye doctor 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.
Myopia (Short-sightedness)
Nearsightedness, or myopia, as it is medically termed, 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. 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. Because 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 eye examination will include testing for nearsightedness. Your eye doctor 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.
Refractive surgery or laser procedures are also possible treatments for nearsightedness as is orthokeratology.
Hyperopia or Farsightedness
Farsightedness, or hyperopia, as it is medically termed, 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 eye 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 eye doctor can prescribe eyeglasses or contact lenses to optically correct farsightedness by altering the way the light enters your eyes.
Presbyopia
Presyopia 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-40s. 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 eye examination will include testing for presbyopia.
To help you compensate for presbyopia, your eye doctor can prescribe reading glasses, bifocals, trifocals or contact lenses. Because presbyopia can complicate other common vision conditions like nearsightedness, farsightedness and astigmatism, your eye doctor 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.
Because 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.
Astigmatism
Astigmatism is a vision condition that causes blurred vision due either to the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye. An irregular shaped cornea or lens prevents light from focusing properly on the retina, the light sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance.
Astigmatism is a very common vision condition. Most people have some degree of astigmatism. Slight amounts of astigmatism usually don't affect vision and don't require treatment. However, larger amounts cause distorted or blurred vision, eye discomfort and headaches.
Astigmatism frequently occurs with other vision conditions like nearsightedness (myopia) and farsightedness (hyperopia). Together these vision conditions are referred to as refractive errors because they affect how the eyes bend or "refract" light.
The specific cause of astigmatism is unknown. It can be hereditary and is usually present from birth. It can change as a child grows and may decrease or worsen over time.
A comprehensive eye examination will include testing for astigmatism. Depending on the amount present, your eye doctor can provide eyeglasses or contact lenses that correct the astigmatism by altering the way light enters your eyes.
Laser eye surgery is also a possible treatment option for some types of astigmatism. It changes the shape of the cornea by removing a small amount of eye tissue. This is done using a highly focused laser beam on the surface of the eye.
Amblyopia (Lazy Eye)
Lazy eye, or amblyopia, 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 the age of 6, 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 it is recommended that children have a comprehensive eye examination by the age of 6 months and again at age 3. 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.
Strabismus / Squint / Cross
Eyes
Strabismus occurs when one or both of your eyes turns in, out, up or down, and is usually caused by poor eye muscle control. This misalignment often first appears before age 21 months but may develop as late as age 6. This is one reason why it is recommended that a comprehensive eye examination before 6months and again at age 3.
There is a common misconception that a child will outgrow strabismus. This is not true. In fact, the condition may get worse without treatment.
Treatment for strabismus 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 strabismus 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, strabismus can often be corrected with excellent results.
Spots /
Floaters
Spots (often called floaters) are small, semi-transparent or cloudy specks or particles within the vitreous, which is 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. Because 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 eye doctor for a comprehensive examination when you notice sudden changes or see increases in them.
By looking in your eyes with special instruments, your ophthalmologist can examine the health of your eyes and determine if what you are seeing is harmless or the symptom of a more serious problem that requires treatment.
Color Vision Deficiency
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.
Because many learning materials are color-coded, it is important to diagnose color vision deficiency early in life. This is why it is recommended that 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 people with certain color deficiencies.
Eye
Coordination
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. Because 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.
Because poor eye coordination can be difficult to detect, periodic eye examinations, beginning at age 6 months and again at age 3 years are recommended. A comprehensive examination by a ophthalmologist 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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