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Learn About Eye Conditions
Nearsightedness. People who are myopic can see better up close than they can far away. The higher your prescription the closer you have to hold something to see it clearly. If the prescription is very high, even viewing up close is difficult.
Nearsightedness is caused by the shape of the eye. Nearsighted eyes are generally longer from front to back or the front curvature of the eye is more curved than normal.
Much research is being done to investigate methods of slowing myopia progression. Some success has been achieved with multifocal contact lenses. If a child exhibits myopia at a very young age, or has significant increases in prescription every year, multifocal contact lenses may be a treatment option, especially if the child's parents are highly nearsighted.
Farsightedness. In general, farsighted eyes see better at far distance than at closer distances. Some may be able to compensate for a low amount of hyperopia to see clearly by increasing the amount their eyes focus. To do this, they must use the near focusing system of the eye, normally only used for close-range tasks, to assist distance vision. As a result, this places an even greater focusing effort on close-range vision. The ability to focus becomes more difficult with age causing farsighted adults to gradually see less clearly at all distances. Even at a young age, the eyes are doing extra work to compensate, so headaches, intermittent blur at near, and eyestrain can result.
Farsightedness is caused by the shape of the eye. Farsighted eyes are generally shorter from front to back or the front curvature of the eye is flatter than normal.
Farsightedness is most commonly corrected with eyeglasses or contact lenses, sometimes just for reading, other times for full-time wear. If adults require different prescriptions for distance and near, multifocal contact lenses are available. Less commonly, refractive surgery such as LASIK, is an option, but outcomes are slightly less reliable than with nearsighted eyes.
85-90% of all eyeglass prescriptions contain some correction for astigmatism. Astigmatism causes blurred and distorted vision, as well as eyestrain, headaches and sensitivity to light. Astigmatism occurs when the front surface of the eye has more than one curvature, rather than a perfectly round shape. With astigmatism, the shape of the cornea is asymmetrical, or somewhat "egg" shaped, rather than uniformly round like a ball. As a result, an astigmatic eye requires a two-power lens prescription. The first glasses prescription for a moderate to large amount of astigmatism may take a few weeks to get used to. Toric contact lenses can also be prescribed.
Presbyopia is a normal decline in close-range focusing ability of our eyes with time. The average person requires a different prescription for distance and near around the age of 42. As the close-range focusing continues to decrease, the near prescription will need to be increased. These gradual increases will occur until around the age of 60.
Floaters are caused by a common age-related change in the eyes called vitreous degeneration. The vitreous is a transparent gel that fills the eye. Vitreous degeneration can cause multiple small floaters or a sudden onset of a single large floater.
Flashes of light may also occur as the changing vitreous tugs on the retina (the photosensitive layers of tissue in the eye that transmits what is seen to the brain.) Some degree of vitreous degeneration is natural and expected. However, there is possible risk of retinal tear or detachment if the changing vitreous pulls too hard on the retina. If you experience a noticeable change in visual floaters, notice your vision is distorted or part is missing, or have a sudden increase in the frequency or duration of light flashes, you should see an eye care professional immediately.
Without an associated retinal tear or detachment, floaters on their own are harmless, but can be very annoying. , They are often more noticeable when outdoors, looking at the sky, or a white wall. Any surgery to remove them is very invasive, so is very rarely done. The floaters may settle and move out of sight with time.
Cataract is a clouding of the eye’s lens, which rests behind the pupil and the iris (the colored part of the eye). In most cases, cataract is a result of aging and UV exposure. However, cataract can also occur at birth or due to trauma. Treatment for the removal of cataract is widely available. Today, lens implants can correct for refractive error. This is often done so glasses are not needed for distance viewing, but reading glasses are still necessary. However, there are newer implants that correct for both distance and near vision with varying success.
Amblyopia, also referred to as “lazy eye,” is the most common cause of vision impairment in children. The eye itself looks normal and is not affected by disease, but is not being used normally because the brain is favoring the other eye. Even with the proper corrective lenses, the visual acuity of the amplyopic or lazy eye is reduced at both distance and near. Accuracy of eye movements, focusing strength, and contrast sensitivity of the amblyopic eye is also decreased, and depth perception is often reduced. Usually just one eye is affected, however in some cases when there is very high refractive error in both eyes, both eyes can be affected.
An eye that turns in or out can become amblyopic. Other causes of amblyopia include large amounts of uncorrected optical errors, or more farsightedness, nearsightedness, or astigmatism in one eye than the other.
It is estimated that 2-4% of the population has amblyopia. Early diagnosis of amblyopia is imperative. Proper treatment for lazy eye includes vision therapy, patching the eye, and on occassional prism correction in glasses. The lazy eye must be taught the necessary skills to develop its visual functioning.
Although it is commonly believed that amblyopia must be treated prior to age 10, recent evidence demonstrates that there is no age limit for improving sight and function as long as no active disease is occurring. However, the earlier this problem is treated, the better the chances are of developing optimum vision.
Strabismus is an imbalance in the positioning and lack of coordination between the two eyes. An eye can turn in (esotropia) or turn out (exotropia). As a result, the eyes look in different directions. They do not focus together on a single point and depth perception is reduced. An eye turn can cause double vision because the eyes are pointed in different directions, but usually the brain suppresses, or "turns off" the deviating eye to eliminate double vision. Now, only one eye is being used to see and the turned eye becomes amblyopic or a "lazy" and does not see as well. (See Amblyopia).
Strabismus can be caused by muscle problems, difficulty using both eyes together comfortably, anatomical abnormalities, and trauma. Children who have relatives with an eye turn are more likely to have one as well. The eye turn can present shortly after birth, or develop during childhood.
Symptoms can include double vision, blurry vision, fatigue, headaches, and difficuly reading or maintaining attention on a task.
The treatment for strabismus varies depending upon the degree of the eye turn. Frequently, glasses or contact lenses may also be needed to help align the eyes comfortably. Vision therapy, a prescribed, individualized treatment program can treat some cases of strabismus successfully. Specialized computer programs and optical devices, including therapeutic lenses, prisms, filters, and 3-D anaglyphs are used during therapy to improve efficiency, endurance, and automaticity of visual skills, to keep the eyes comfortably aligned. If the eye turn is large, surgery may also be recommended as an adjunct to vision therapy in order to best manage the eye turn.
Glaucoma is a group of diseases that damage the eye's optic nerve and results in vision loss and blindness. If visual symptoms are noticed by the patient, significant irreversible damage and visual loss has already occurred. Regular eye exams are very important to detect glaucoma early before significant damage has already occurred. With early treatment, you can often protect your eyes against serious vision loss or blindness.
Glaucoma has been most closely associated with high fluid pressure inside the eyes that presses on the optic nerve, damaging it. However, recent findings now show that glaucoma can occur with normal eye pressure. Many individual factors are involved. As the optic nerve is damaged, peripheral vision is lost. If not treated, and damage progresses and becomes more severe, central vision can also be affected.
Diabetic retinopathy (DR) is the leading cause of blindness among working-aged adults in the United States ages 20–74. An estimated 4.1 million Americans have retinopathy and nearly 900,000 Americans have progressed to vision-threatening retinopathy.
Diabetes damages blood vessels in the body, including those in the eyes. When damaged the blood vessls leak, and become blocked, depriving the retina of blood and oxygen. In response new, abnormal blood vessels grow (proliferative diabetic retinopathy) which is the most advanced stage. Diabetic retinopathy usually affects both eyes.
The longer someone has diabetes, the greater their risk for developing diabetic retinopathy. Poor blood sugar control, high blood pressure, and lipid abnormalities greatly increase this risk. High fluctuation in blood sugar is even more of a risk; for example, if blood sugar is very low one day, then very high, then very low again. A blood test measuring your A1C is a good indication of your blood sugar control over a period of time.
Regular eye exams, early diagnosis of DR and timely treatment reduce the risk of vision loss.
Age-Related Macular Degeneration (ARMD)
An eye disorder associated with aging that affects central vision and the ability to see fine details. Macular degeneration can be called "dry" or "wet" depending on whether or not abnormal blood vessels in the eye are leaking.
Dry macular degeneration is more common, and accounts for 70-90% of cases. It progresses more slowly than the wet form, and vision loss is usually not as severe. Dry macular degeneration is characterized by drusen, small yellow deposits under the retina. Drusen are typical of the aging process, however if there are many, or if they are large, the risk of developing advanced dry ARMD or wet ARMD is increased. If large or numerous drusen are present, high doses of antioxidant vitamins may be recommended in an attempt to slow progression.
A study by the National Eye Institute involving more than 3,600 people, found that supplementation with vitamins C and E, beta-carotene and zinc reduced risk of progressing to advanced ARMD. If you smoke, high doses of beta carotene should be avoided because it has been associated with a higher risk of developing cancer in smokers. Talk with your doctor. Too much of any vitamin or mineral may affect the body's ability to absorb other important nutrients.
Dry macular degeneration can progress to the wet form. Abnormal blood vessels grow behind the macula, the area of the retina responsible for central, detailed vision. These abnormal blood vessels leak producing the "wet" form of macular degeneration. The bleeding and scarring caused by leakage cause rapid vision loss. An early symptom of wet ARMD is that straight lines appear wavy.
Monthly injections into the eye are used to treat wet macular degeneration. Overall, about a third of patients receiving injections experience vision improvement.
It is estimated that 1.8 million Americans 40 years and older are affected by ARMD and 7.3 million are at substantial risk of developing ARMD.
This is a condition in which the front surface of the eye (cornea) thins and bulges outward into a cone shape. This process typically starts during puberty and through early adulthood and may continue to progress into middle age. The symptoms include blurred vision, ghosting of images, glare, and sensitivity to light. Eyes with keratoconus are best treated with special contact lenses. Advanced cases may eventually require a corneal transplant.