Myopia; Shortsightedness; Refractive error - nearsightedness
Nearsightedness is when light entering the eye is focused incorrectly. This makes distant objects appear blurred. Nearsightedness is a type of refractive error of the eye.
If you are nearsighted, you have trouble seeing things that are far away.
People are able to see because the front part of the eye bends (refracts) light and focuses it on the retina. This is the back surface of the eye.
Nearsightedness occurs when there is a mismatch between the focusing power of the eye and the length of the eye. Light rays are focused in front of the retina, rather than directly on it. As a result, what you see is blurry. Most of the eye's focusing power comes from the cornea.
Nearsightedness affects males and females equally. People who have a family history of nearsightedness are more likely to develop it. Most eyes with nearsightedness are healthy. However, but a small number of people with severe nearsightedness develop a form of retinal degeneration.
A nearsighted person sees close-up objects clearly, but objects in the distance are blurred. Squinting will tend to make far away objects seem clearer.
Nearsightedness is often first noticed in school-aged children or teenagers. Children often cannot read the blackboard, but they can easily read a book.
Nearsightedness gets worse during the growth years. People who are nearsighted need to change glasses or contact lenses often. Nearsightedness most often stops progressing as a person stops growing in his or her early twenties.
Other symptoms may include:
Exams and Tests
A nearsighted person can easily read the Jaeger eye chart (the chart for near reading), but has trouble reading the Snellen eye chart (the chart for distance).
A general eye exam, or standard ophthalmic exam may include:
- Eye pressure measurement (tonometry)
- Refraction test, to determine the correct prescription for glasses
- Retinal examination
- Slit-lamp exam of the structures at the front of the eyes
- Test of color vision, to look for possible color blindness
- Tests of the muscles that move the eyes
- Visual acuity, both at a distance (Snellen), and close up (Jaeger)
Wearing eyeglasses or contact lenses can help shift the focus of the light image directly onto the retina. This will produce a clearer image.
The most common surgery to correct myopia is LASIK. An excimer laser is used to reshape (flatten) the cornea, shifting the focus.
Early diagnosis of nearsightedness is important. A child can suffer socially and educationally by not being able to see well at a distance.
Complications may include:
- Corneal ulcers and infections may occur in people who use contact lenses.
- Rarely, complications of laser vision correction may occur. These can be serious.
- People with myopia, in rare cases, develop retinal detachments or retinal degeneration.
When to Contact a Medical Professional
Call your health care provider if your child shows these signs, which may indicate a vision problem:
- Having difficulty reading the blackboard in school or signs on a wall
- Holding books very close when reading
- Sitting close to the television
Call your eye doctor if you or your child is nearsighted and experiences signs of a possible retinal tear or detachment, including:
- Flashing lights
- Floating spots
- Sudden loss of any part of the field of vision
It has been generally believed that there is no way to prevent nearsightedness. Reading and watching television do not cause nearsightedness. In the past, dilating eye drops were proposed as a treatment to slow the development of nearsightedness in children, but those early studies were inconclusive. However, there is recent information that certain dilating eyedrops used in certain children at just the right time, may decrease the total amount of nearsightedness that they will develop.
The use of glasses or contact lenses does not affect the normal progression of myopia -- they simply focus the light so the nearsighted person can see distant objects clearly. However, it is important to not prescribe glasses or contact lenses that are too strong. Hard contact lenses will sometimes hide the progression of nearsightedness, but vision will still get worse "under" the contact lens.
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