Retinitis Pigmentosa

On August 4th, 2010, posted in: Eye & Vision Problems by

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).

Fortunately, most cases of retinitis pigmentosa take a long time to develop and vision loss is gradual. It may take many years for loss of vision to be severe.

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.

Becuase it is an inherited disease, research into genetics may one day provide a prevention or cure for those who have RP.

American Optometric Association, 8/4/10

read more

Retinoblastoma

On August 4th, 2010, posted in: Eye & Vision Problems by

Every parent dreads to hear the word “cancer,” but cancer has a high prevalence in the United States. Early detection of cancer can greatly reduce the severity of the illness and increase life expectancy.

Optometrists diagnose, refer, and comanage cancers that involve the eye area. The most common cancer involving the eye in young children is retinoblastoma. 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.

Adapted from Hoppe E, Frankel R. Optometrists as key providers in the prevention and early detection of malignancies. Optometry (2006) 77, 397-404

American Optometric Association, 8/4/10

read more

Spots and Floaters

On August 4th, 2010, posted in: Eye & Vision Problems by

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.

American Optometric Association, 8/4/10

read more

    Crossed eyes, or strabismus as it is medically termed, 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.

    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.

    Some babies’ eyes may appear to be misaligned, but are actually both aiming at the same object. This is a condition called pseudostrabismus or false strabismus. The appearance of crossed eyes may be due to extra skin that covers the inner corner of the eyes, or a wide bridge of the nose. Usually, this will change as the child’s face begins to grow.

    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.

    Strabismus is classified by the direction the eye turns:

    • Inward turning is called esotropia
    • Outward turning is called exotropia
    • Upward turning is called hypertropia
    • Downward turning is called hypotropia.

    Other classifications of strabismus include:

    • The frequency with which it occurs – either constant or intermittent
    • Whether it always involves the same eye – unilateral
    • If the turning eye is sometimes the right eye and other times the left eye – alternating.

    Treatment for strabismus may include eyeglasses, prisms, vision therapy, or eye muscle surgery. If detected and treated early, strabismus can often be corrected with excellent results.

    [back to top]


    What causes strabismus?

    Strabismus can be caused by problems with the eye muscles, the nerves that transmit information to the muscles, or the control center in the brain that directs eye movements. It can also develop due to other general health conditions or eye injuries.

    Risk factors for developing strabismus include:

    • Family history – individuals with parents or siblings who have strabismus are more likely to develop it.
    • Refractive error – people who have a significant amount of uncorrected farsightedness (hyperopia) may develop strabismus because of the additional amount of eye focusing required to keep objects clear.
    • Medical conditions – people with conditions such as Down syndrome and cerebral palsy or who have suffered a stroke or head injury are at a higher risk for developing strabismus.

    Although there are many types of strabismus that can develop in children or adults, the two most common forms are accommodative esotropia and intermittent exotropia.

    Accommodative esotropia often occurs because of uncorrected farsightedness (hyperopia). Because the eye’s focusing system is linked to the system that controls where the eyes point, the extra focusing effort needed to keep images clear in farsightedness may cause the eyes to turn inward. Signs and symptoms of accommodative esotropia may include seeing double, closing or covering one eye when doing close work, and tilting or turning of the head.

    Intermittent exotropia may develop due to an inability to coordinate both eyes together. The eyes may have a tendency to point beyond the object being viewed. People with intermittent exotropia may experience headaches, difficulty reading, and eye strain. They also may have a tendency to close one eye when viewing at distance or in bright sunlight.

    [back to top]


    How is strabismus diagnosed?

    Strabismus is diagnosed through a comprehensive eye exam. Testing for strabismus, with special emphasis on how the eyes focus and move, may include:

    • Patient History – A patient history is obtained to determine any symptoms the patient is experiencing or the parent is observing, and to note the presence of any general health problems, medications taken, or environmental factors that may be contributing to the symptoms.

    • Visual Acuity – Visual acuity measurements are taken to assess the extent to which vision may be affected. As part of the testing, you will be asked to read letters on distance and near reading charts. This test measures visual acuity, which is written as a fraction such as 20/40. When testing distance vision, the top number is the standard distance at which testing is done, twenty feet. The bottom number is the smallest letter size you were able to read at the twenty foot distance. A person with 20/40 visual acuity would have to get within 20 feet of a letter that should be seen at forty feet in order to see it clearly. “Normal” distance visual acuity is 20/20.
    • Refraction – A refraction is conducted to determine the appropriate lens power needed to compensate for any refractive error (nearsightedness, farsightedness, or astigmatism). Using an instrument called a phoropter, your optometrist places a series of lenses in front of your eyes and measures how they focus light using a hand held lighted instrument called a retinoscope. Or the doctor may choose to use an automated instrument that automatically evaluates the refractive power of the eye. The power is then refined by the patient’s responses to determine the lenses that allow the clearest vision.
    • Alignment and Focusing Testing – How well your eyes focus, move and work together needs to be assessed. In order to obtain a clear, single image of what is being viewed, the eyes must effectively change focus, move and work in unison. This testing will look for problems that keep your eyes from focusing effectively or make it difficult to use both eyes together.
    • Examination of eye health – The structures of the eye are observed to rule out any eye disease that may be contributing to strabismus. The health of the external and internal parts of the eye will be assessed using various testing procedures.

    This testing may be done without the use of eye drops to determine how the eyes respond under normal seeing conditions. In some cases, such as for patients who can’t respond verbally or when some of the eyes focusing power may be hidden, eye drops may be used. They temporarily keep the eyes from changing focus while testing is done.

    Using the information obtained from these tests, along with results of other tests, your optometrist can determine if you have strabismus. Once testing is complete, your optometrist can discuss options for treatment.

    [back to top]


    How is strabismus treated?

    People with strabismus have several treatment options available to improve eye alignment and coordination. They include:

    • eyeglasses or contact lenses
    • prism lenses
    • vision therapy
    • eye muscle surgery

    Eyeglasses or contact lenses may be prescribed for patients with uncorrected farsightedness. This may be the only treatment needed for some patients with accommodative esotropia. Once the farsightedness is corrected, the eyes require less focusing effort and may remain straight.

    Prism lenses are special lenses that have a prescription for prism power in them. The prisms alter the light entering the eye and assist in reducing the amount of turning the eye has to do to look at objects. Sometimes the prisms are able to fully compensate for and eliminate the eye turning.

    Vision therapy is a structured program of visual activities prescribed to improve eye coordination and eye focusing abilities. Vision therapy trains the eyes and brain to work together more effectively. These eye exercises help remediate deficiencies in eye movement, eye focusing and eye teaming and reinforce the eye-brain connection. Treatment may include office-based as well as home training procedures.

    Eye muscle surgery can change the length or position of the muscles around the eye in an attempt to better align the eyes. Eye muscle surgery may be able to physically align the eyes so they appear straight. Often a program of vision therapy may also be needed to develop a functional improvement in eye coordination and to keep the eyes from reverting back to their previous condition of misalignment.

    American Optometric Association, 8/4/10

    read more

    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.

    Visual Acuity FAQs

    Q.

    What does 20/20 vision mean?

    A.

    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.

    Q.

    Does 20/20 mean perfect vision?

    A.

    No. 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 vision ability.

    Q.

    Is 15/15 vision better than 20/20 Vision?

    A.

    No. 15/15 vision means normal sharpness of vision at 15 feet just as 20/20 indicates normal acuity at 20 feet. For consistency, optometrists in the United States use 20 feet as the standard to express sharpness of vision.

    Other countries express visual acuity in their own way. In England, for example, optometrists express visual acuity in meters (6/6 is considered normal).

    Q.

    Why do some people have less than 20/20 vision?

    A.

    Visual acuity is affected by many factors. Less than optimum clarity may result from vision conditions like nearsightedness, farsightedness or astigmatism or from eye diseases.

    Q.

    Will clarity of vision vary with distance?

    A.

    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).

    Q.

    If my vision is less than 20/20, what can I do?

    A.

    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.

    American Optometric Association, 8/4/10

    read more