Education
Eye Diseases & Infections
Information provided by the American Optometric Association, 1/19/11

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.
Visual Acuity FAQs

Acanthamoeba
     Acanthamoeba is one of the most ubiquitous organisms in the environment, but rarely causes infections. When infection does occur, however, it can be extremely serious and vision threatening. Recently, there have been multiple reports of increasing incidence of Acanthamoeba keratitis. Co-infection with a bacterial keratitis is common both in the contact lens case and on the cornea, complicating prevention, diagnosis and treatment. The best defense against Acanthamoeba keratitis infection is proper contact lens hygiene. An additional risk factor includes the use of tap water in cleaning and disinfecting contact lenses.
     Symptoms include: (1) A red, (frequently) painful eye infection—especially if the discomfort does not improve with treatment. (2) Foreign body sensation, tearing, light sensitivity, and blurred vision. (3) Red, irritated eyes lasting for an unusually long period of time after removal of contact lenses.

Amblyopia (Lazy Eye)
     Amblyopia, or, 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 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. It is recommended that children have a comprehensive optometric examination by the age of 6 months and again at age 3. If not diagnosed until the pre-teen, teen or adult years, treatment takes longer and is often less effective.
Amblyopia FAQs

Anterior Uveitis
     Anterior uveitis is an inflammation of the middle layer of the eye, which includes the iris (colored part of the eye) and adjacent tissue, known as the ciliary body. If untreated, it can cause permanent damage and loss of vision from the development of glaucoma, cataract or retinal edema. It usually responds well to treatment; however, there may be a tendency for the condition to recur. Anterior uveitis can occur as a result of trauma to the eye, such as a blow or foreign body penetrating the eye. It can also be a complication of other eye disease, or it may be associated with general health problems such as rheumatoid arthritis, rubella and mumps. In most cases, there is no obvious underlying cause.
     Signs/symptoms may include a red, sore and inflamed eye, blurring of vision, sensitivity to light and a small pupil. Becuase the symptoms of anterior uveitis are similar to those of other eye diseases, your optometrist will carefully examine the inside of your eye, under bright light and high magnification, to determine the presence and severity of the condition. Your optometrist may also perform or arrange for other diagnostic tests to help pinpoint the cause. Treatment usually includes prescription eye drops, which dilate the pupils, in combination with anti-inflammatory drugs. Treatment usually takes several days, or up to several weeks, in some cases.
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Astigmatism
     Astigmatism, a very common vision condition, 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. 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.
     A comprehensive optometric examination will include testing for astigmatism. Depending on the amount present, your optometrist can provide eyeglasses or contact lenses that correct the astigmatism by altering the way light enters your eyes.
Astigmatism FAQs

Blepharitis
     Blepharitis is an inflammation of the eyelids causing red, irritated, itchy eyelids and the formation of dandruff-like scales on eyelashes. It is a common eye disorder caused by either bacterial or a skin condition such as dandruff of the scalp or acne rosacea. It affects people of all ages. Although uncomfortable, blepharitis is not contagious and generally does not cause any permanent damage to eyesight. Blepharitis is classified into two types:
          (1) Anterior blepharitis occurs at the outside front edge of the eyelid where the eyelashes are attached.
          (2) Posterior blepharitis affects the inner edge of the eyelid that comes in contact with the eyeball.
     Individuals with blepharitis may experience a gritty or burning sensation in their eyes, excessive tearing, itching, red and swollen eyelids, dry eyes, or crusting of the eyelids. For some people, blepharitis causes only minor irritation and itching. However, it can lead to more severe signs and symptoms such as blurring of vision, missing or misdirected eyelashes, and inflammation of other eye tissue, particularly the cornea. In many cases, good eyelid hygiene and a regular cleaning routine can control blepharitis. This includes frequent scalp and face washing, using warm compresses to soak the eyelids, and doing eyelid scrubs. In cases where a bacterial infection is the cause, various antibiotics and other medications may be prescribed along with eyelid hygiene.

Cataract
     A cataract is a cloudy or opaque area in the normally clear lens of the eye. Depending upon its size and location, it can interfere with normal vision. Most cataracts develop in people over age 55, but they occasionally occur in infants and young children. Usually cataracts develop in both eyes, but one may be worse than the other. Reasearchers have linked eye-friendly nutrients such as lutein/zeaxanthin, vitamin C, vitamin E, and zinc to reducing the risk of certain eye diseases, including cataracts. For more information on the importance of good nutrition and eye health, please see nutrition. 
     Signs and symptoms of a cataract may include: (1) Blurred, hazy, or vision (2) Reduced intensity of colors  (3) Increased sensitivity to glare from lights, particularly when driving at night (4) Increased difficulty seeing at night (5) Change in the eye's refractive error

Chalazion
     A chalazion is a slowly developing lump that forms due to blockage and swelling of an oil gland in the eyelid. It is more common in adults than children and occurs most frequently in persons 30 to 50 years of age. Initially, a chalazion may appear as a red, tender, swollen area of the eyelid. However, in a few days it changes to a painless, slow growing lump in the eyelid. A chalazion often starts out very small and is barely able to be seen, but it may grow to the size of a pea. Often times they may be confused with sties, which are also areas of swelling in the eyelid. A sty is an infection of an oil gland in the eyelid. It produces a red, swollen, painful lump on the edge or inside surface of the eyelid. Sties usually occur closer to the surface of the eyelid than do chalazia. A chalazion is generally not due to an infection, but results from a blockage of the oil gland itself. However, a chalazion may occur as an after-effect of a sty.
     Common signs or symptoms of a chalazion include: (1) Appearance of a painless bump or lump in the upper eyelid, or, less commonly, in the lower eyelid 
(2) Blurred vision, if the chalazion is large enough to press against the eyeball (3) Tearing
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Color Vision Deficiency
     Color vision deficiency is the inability to distinguish certain shades of color or in more severe cases, see colors at all. The term "color blindness" is also used to describe this visual condition, but very few people are completely color blind. Most people with color vision deficiency can see colors, but they have difficulty differentiating between: (1) particular shades of reds and greens (most common) or (2) blues and yellows (less common).  
     The severity of color vision deficiency can range from mild to severe depending on the cause. It will affect both eyes if it is inherited and usually just one if the cause for the deficiency is injury or illness. Color vision is possible due to photoreceptors in the retina of the eye known as cones. These cones have light sensitive pigments that enable us to recognize color. Found in the macula, the central portion of the retina, each cone is sensitive to either red, green or blue light, which the cones recognize based upon light wavelengths. Normally, the pigments inside the cones register differing colors and send that information through the optic nerve to the brain enabling you to distinguish countless shades of color. But if the cones lack one or more light sensitive pigments, you will be unable to see one or more of the three primary colors thereby causing a deficiency in your color perception.
     The most common form of color deficiency is red-green. This does not mean that people with this deficiency cannot see these colors at all; they simply have a harder time differentiating between them. The difficulty they have in correctly identifying them depends on how dark or light the colors are. Another form of color deficiency is blue-yellow. This is a rarer and more severe form of color vision loss than red-green since persons with blue-yellow deficiency frequently have red-green blindness too. In both cases, it is common for people with color vision deficiency to see neutral or gray areas where a particular color should appear.

Conjunctivitis
     Conjunctivitis is an inflammation or infection of the conjunctiva, the thin transparent layer of tissue that lines the inner surface of the eyelid and covers the white part of the eye. Conjunctivitis, often called “pink eye,” is a common eye disease, especially in children. It may affect one or both eyes. Some forms of conjunctivitis can be highly contagious and easily spread in schools and at home. While conjunctivitis is usually a minor eye infection, sometimes it can develop into a more serious problem. Conjunctivitis may be caused by a viral or bacterial infection. It can also occur due to an allergic reaction to irritants in the air like pollen and smoke, chlorine in swimming pools, and ingredients in cosmetics or other products that come in contact with the eyes. Sexually transmitted diseases like Chlamydia and gonorrhea are less common causes of conjunctivitis. 
     People with conjunctivitis may experience the following symptoms: (1) A gritty feeling in one or both eyes (2) Itching or burning sensation in one or both eyes 
(2) Excessive tearing (3) Discharge coming from one or both eyes (4) Swollen eyelids (5) Pink discoloration to the whites of one or both eyes (6) Increased sensitivity to light.

Diabetic Retinopathy
     Diabetic retinopathy is a condition occurring in persons with diabetes, which causes progressive damage to the retina, the light sensitive lining at the back of the eye. It is a serious sight-threatening complication of diabetes. Diabetic retinopathy is the result of damage to the tiny blood vessels that nourish the retina. They leak blood and other fluids that cause swelling of retinal tissue and clouding of vision. The condition usually affects both eyes. The longer a person has diabetes, the more likely they will develop diabetic retinopathy. If left untreated, diabetic retinopathy can cause blindness.
     Symptoms of diabetic retinopathy include: (1) Seeing spots or floaters in your field of vision (2) Blurred vision (3) Having a dark or empty spot in the center of your vision (4) Difficulty seeing well at night.
     Treatment of diabetic retinopathy varies depending on the extent of the disease. It may require laser surgery to seal leaking blood vessels or to discourage new leaky blood vessels from forming. Injections of medications into the eye may be needed to decrease inflammation or stop the formation of new blood vessels. In more advanced cases, a surgical procedure to remove and replace the gel-like fluid in the back of the eye, called the vitreous, may be needed. A retinal detachment, defined as a separation of the light-receiving lining in the back of the eye, resulting from diabetic retinopathy, may also require surgical repair.
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Dry Eye
     Dry eye is a condition in which there are insufficient tears to lubricate and nourish the eye. Tears are necessary for maintaining the health of the front surface of the eye and for providing clear vision. People with dry eyes either do not produce enough tears or have a poor quality of tears. Dry eye is a common and often chronic problem, particularly in older adults. With each blink of the eyelids, tears are spread across the front surface of the eye, known as the cornea. Tears provide lubrication, reduce the risk of eye infection, wash away foreign matter in the eye, and keep the surface of the eyes smooth and clear. Excess tears in the eyes flow into small drainage ducts, in the inner corners of the eyelids, which drain in the back of the nose. 
     The most common form of dry eyes is due to an inadequate amount of the water layer of tears. This condition, called keratoconjunctivitis sicca (KCS), is also referred to as dry eye syndrome. People with dry eyes may experience symptoms of irritated, gritty, scratchy, or burning eyes, a feeling of something in their eyes, excess watering, and blurred vision. Advanced dry eyes may damage the front surface of the eye and impair vision. 
     Treatments for dry eyes aim to restore or maintain the normal amount of tears in the eye to minimize dryness and related discomfort and to maintain eye health.

Glaucoma
     Glaucoma is a group of eye disorders leading to progressive damage to the optic nerve, and is characterized by loss of nerve tissue resulting in loss of vision. The optic nerve is a bundle of about one million individual nerve fibers and transmits the visual signals from the eye to the brain. The most common form of glaucoma, primary open-angle glaucoma, is associated with an increase in the fluid pressure inside the eye. This increase in pressure may cause progressive damage to the optic nerve and loss of nerve fibers. Vision loss may result. Advanced glaucoma may even cause blindness. Not everyone with high eye pressure will develop glaucoma, and many people with normal eye pressure will develop glaucoma. When the pressure inside an eye is too high for that particular optic nerve, whatever that pressure measurement may be, glaucoma will develop.
     The most common form of glaucoma, primary open-angle glaucoma, develops slowly and usually without any symptoms. Many people do not become aware they have the condition until significant vision loss has occurred. It initially affects peripheral or side vision, but can advance to central vision loss. If left untreated, glaucoma can lead to significant loss of vision in both eyes, and may even lead to blindness. A less common type of glaucoma, acute angle closure glaucoma, usually occurs abruptly due to a rapid increase of pressure in the eye. Its symptoms may include severe eye pain, nausea, redness in the eye, seeing colored rings around lights, and blurred vision. This condition is an ocular emergency, and medical attention should be sought immediately, as severe vision loss can occur quickly.
Glaucoma FAQs

Hyperopia (Farsightedness)
     Hyperopia, or 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. A comprehensive optometric examination will include testing for farsightedness.
     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. 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.
Hyperopia FAQs

Keratoconus
     Keratoconus is a vision disorder that occurs when the normally round cornea (the front part of the eye) becomes thin and irregular (cone) shaped. This abnormal shape prevents the light entering the eye from being focused correctly on the retina and causes distortion of vision.
     In its earliest stages, keratoconus causes slight blurring and distortion of vision and increased sensitivity to glare and light. These symptoms usually appear in the late teens or late 20s. Keratoconus may progress for 10-20 years and then slow in its progression. Each eye may be affected differently. As keratoconus progresses, the cornea bulges more and vision may become more distorted. In a small number of cases, the cornea will swell and cause a sudden and significant decrease in vision. The swelling occurs when the strain of the cornea's protruding cone-like shape causes a tiny crack to develop. The swelling may last for weeks or months as the crack heals and is gradually replaced by scar tissue. If this sudden swelling does occur, your doctor can prescribe eyedrops for temporary relief, but there are no medicines that can prevent the disorder from progressing.
     Eyeglasses or soft contact lenses may be used to correct the mild nearsightedness and astigmatism that is caused by the early stages for keratoconus. As the disorder progresses and cornea continues to thin and change shape, rigid gas permeable contact lenses can be prescribed to correct vision adequately. In most cases, this is adequate. The contact lenses must be carefully fitted, and frequent checkups and lens changes may be needed to achieve and maintain good vision.
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Monovision
Monovision is a treatment technique that is often prescribed for people age 40 and older who are affected by presbyopia. Presbyopia occurs when, as part of the natural aging process, the eye’s crystalline lens loses its ability to bring close objects into clear focus. Monovision means wearing a contact lens for near vision on one eye and, if needed, a lens for distance vision on the other eye. Alternative treatments for presbyopia include a combination of contact lenses and reading glasses, or your doctor may also prescribe bifocal contact lenses.

Myopia (Nearsightedness)
     Myopia, or nearsightedness (affecting nearly 30 percent of the U.S. population, is a vision condition in which close objects are seen clearly, but objects farther away appear blurred. Nearsightedness occurs if the eyeball is too long or the cornea, the clear front cover of the eye, has too much curvature. As a result, the light entering the eye isn’t focused correctly and distant objects look blurred.
     A common sign of nearsightedness is difficulty with the clarity of distant objects like a movie or TV screen or the chalkboard in school. A comprehensive optometric examination will include testing for nearsightedness. An optometrist can prescribe eyeglasses or contact lenses that correct nearsightedness by bending the visual images that enter the eyes, focusing the images correctly at the back of the eye. Depending on the amount of nearsightedness, you may only need to wear glasses or contact lenses for certain activities, like watching a movie or driving a car. Or, if you are very nearsighted, they may need to be worn all the time.
     Another option for treating nearsightedness is orthokeratology (ortho-k), also known as corneal refractive therapy. It is a non-surgical procedure that involves wearing a series of specially designed rigid contact lenses to gradually reshape the curvature of your cornea. The lenses place pressure on the cornea to flatten it. This changes how light entering the eye is focused.
Myopia FAQs

Nystagmus
     Nystagmus is a vision condition in which the eyes make repetitive, uncontrolled movements, often resulting in reduced vision. These involuntary eye movements can occur from side to side, up and down, or in a circular pattern. As a result, both eyes are unable to hold steady on objects being viewed. Nystagmus may be accompanied by unusual head positions and head nodding in an attempt to compensate for the condition.
     Nystagmus can be inherited and appear in early childhood or develop later in life due to an accident or illness. Generally, nystagmus is a symptom of some other underlying eye or medical problem. However, the exact cause is often unknown. Persons with nystagmus may experience reduced visual acuity. They may also have problems with depth perception that can affect their balance and coordination. Nystagmus can be aggravated by fatigue and stress.
     Most individuals with nystagmus can reduce the severity of their uncontrolled eye movements and improve vision by positioning their eyes to look to one side. This is called the "null point" where the least amount of nystagmus is evident. To accomplish this they may need to adopt a specific head posture to make the best use of their vision.

Ocular Hypertension
     Ocular hypertension is an increase in the pressure in your eyes that is above the range considered normal with no detectable changes in vision or damage to the structure of your eyes. The term is used to distinguish people with elevated pressure from those with glaucoma, a serious eye disease that causes damage to the optic nerve and vision loss.
     Ocular hypertension has no noticeable signs or symptoms. Your doctor of optometry can check the pressure in your eyes with an instrument called a tonometer and can examine the inner structures of your eyes to assess your overall eye health.
     Not all people with ocular hypertension will develop glaucoma. However, there is an increased risk of glaucoma among those with ocular hypertension, so regular comprehensive optometric examinations are essential to your overall eye health. There is no cure for ocular hypertension, however, careful monitoring and treatment, when indicated, can decrease the risk of damage to your eyes.
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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-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 optometric examination will include testing for presbyopia.
     To help you compensate for presbyopia, your optometrist can prescribe reading glasses, bifocals, trifocals or contact lenses. Because 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. 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.

Retinitis Pigmentosa
     Retinitis pigmentosa (RP) is a group of inherited diseases that damage the light-sensitive rods and cones located in the retina, the back part of our eyes. Rods, which provide side (peripheral) and night vision are affected more than the cones that provide color and clear central vision.
     Signs of RP usually appear during childhood or adolescence. The first sign is often night blindness followed by a slow loss of side vision. Over the years, the disease will cause further loss of side vision. As the disease develops, people with RP may often bump into chairs and other objects as side vision worsens and they only see in one direction - straight ahead. They see as if they are in a tunnel (thus the term tunnel vision).
     Currently, there is no cure for RP, but there is research that indicates that vitamin A and lutein may slow the rate at which the disease progresses. Your doctor of optometry can give you more specific information on nutritional supplements that may help you. Also, there are many new low vision aids, including telescopic and magnifying lenses, night vision scopes as well as other adaptive devices, that are available that help people maximize the vision that they have remaining. An optometrist, experienced in low vision rehabilitation, can provide these devices as well as advice about other training and assistance to help people remain independent and productive.

Retinoblastoma
     Retinoblastoma is the most common cancer involving the eye in young children. In the United States, this fast-growing cancer occurs in 1 in every 20,000 children, making it the tenth most common pediatric cancer. There are 2 forms of retinoblastoma—hereditary and sporadic. Although sporadic retinoblastoma occurs more frequently, families with a history of hereditary retinoblastoma should be assessed by your optometrist.

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 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 symptom of a more serious problem that requires treatment.
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Strabismus (Crossed Eyes)
     Strabismus, or crossed eyes, is a condition in which both eyes do not look at the same place at the same time. It occurs when an eye turns in, out, up or down and is usually caused by poor eye muscle control or a high amount of farsightedness. Strabismus usually develops in infants and young children, most often by age 3, but older children and adults can also develop the condition. There is a common misconception that a child with strabismus will outgrow the condition. However, this is not true. In fact, strabismus may get worse without treatment. Any child older than four months whose eyes do not appear to be straight all the time should be examined.
     There are six muscles attached to each eye that control how it moves. The muscles receive signals from the brain that direct their movements. Normally, the eyes work together so they both point at the same place. When problems develop with eye movement control, an eye may turn in, out, up or down. The eye turning may be evident all the time or may appear only at certain times such as when the person is tired, ill, or has done a lot of reading or close work. In some cases, the same eye may turn each time, while in other cases, the eyes may alternate turning.
     Maintaining proper eye alignment is important to avoid seeing double, for good depth perception, and to prevent the development of poor vision in the turned eye. When the eyes are misaligned, the brain receives two different images. At first, this may create double vision and confusion, but over time the brain will learn to ignore the image from the turned eye. If the eye turning becomes constant and is not treated, it can lead to permanent reduction of vision in one eye, a condition called amblyopia or lazy eye.

UV Protection 
     The sun’s primary danger is in the form of Ultraviolet (UV) radiation. UV radiation is a component of solar radiation, but it can also be given off by artificial sources like welding machines, tanning beds and lasers. Most are aware of the harm UV radiation can do to the skin, but many may not realize that exposure to UV radiation can harm the eyes or that other components of solar radiation can also affect vision. There are three types of UV radiation: UV-C is absorbed by the ozone layer and does not present any threat; UV-A and UV-B radiation can have adverse long- and short-term effects on the eyes and vision.
     If your eyes are exposed to excessive amounts of UV radiation over a short period of time, you are likely to experience an effect called photokeratitis. Like a “sunburn of the eye”, photokeratitis may be painful and include symptoms such as red eyes, a foreign body sensation or gritty feeling in the eyes, extreme sensitivity to light and excessive tearing. 
     Long-term exposure to UV radiation, however, can be more serious. Scientific studies and research have shown that exposure to small amounts of UV radiation over a period of many years increases the chance of developing a cataract and may cause damage to the retina, a nerve-rich lining of the eye that is used for seeing. Additionally, chronic exposure to shorter wavelength visible light (i.e. blue and violet light) may also be harmful to the retina. The longer the eyes are exposed to solar radiation, the greater the risk of developing later in life such conditions as cataracts or macular degeneration. Since it is not clear how much exposure to solar radiation will cause damage, we recommend wearing quality sunglasses that offer UV protection and wearing a hat or cap with a wide brim whenever you spend time outdoors. Also, certain contact lenses can provide additional UV protection.
     To provide adequate protection for your eyes, sunglasses should: (1) block out 99 to 100 percent of both UV-A and UV-B radiation. (2) screen out 75 to 90 percent of visible light. (3) be perfectly matched in color and free of distortion and imperfection; and (4) have lenses that are gray for proper color recognition.
UV Radiation Checklist
If you can answer “yes” to one or more of the following questions, you could be at higher risk for harm to the eyes from UV radiation and should strongly consider asking your optometrist for a recommended pair of sunglasses
(1) Do you spend a great deal of time outdoors?
(2) Do you spend time skiing, mountain climbing or at the beach?
(3) Do you use a sunlamp or tanning parlor?
(4) Do you live in the mountains or the United States Sunbelt?
(5) Are you a welder, medical technologist or do you work in the graphic arts or in the manufacture of electronic circuit boards?
(6) Do you take prescription or over-the-counter drugs that can increase your sensitivity to UV radiation (check with your optometrist, pharmacist, or physician)?
(7) Have you had cataract surgery in one or both eyes? 
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Information provided by the American Optometric Association, 1/19/11
General Eye Information
Contact Lenses
Vision Conditions