Myopia

Definition

Myopia is a vision disorder, not a disease.

Myopia is most often due to a too long eye, the image of a distant object is formed therefore in front of the retina.

 

 

Symptoms

 If you have myopia, you have trouble seeing things far away, but you can see nearby things clearly. This is why myopia is commonly called nearsightedness.

If you can see well enough to read what’s on your laptop or in a book, but you struggle to see what’s on the television or a movie screen, you may be nearsighted.

Sometimes people with undiagnosed myopia will have headaches and eyestrain from struggling to clearly see things in the distance.

Source : National Eye Institute

 

Frequency

Nearsightedness, or myopia, is the most common refractive error of the eye, and it has become more prevalent in recent years.

In fact, a recent study by the National Eye Institute (NEI) shows the prevalence of myopia grew from 25 percent of the U.S. population (ages 12 to 54) in 1971-1972 to a whopping 41.6 percent in 1999-2004.

Though the exact cause for this increase in nearsightedness among Americans is unknown, many eye doctors feel it has something to do with eye fatigue from computer use and other extended near vision tasks, coupled with a genetic predisposition for myopia.

Source :  All About Vision

 

Causes

Myopia occurs when the eyeball is too long, relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.

Nearsightedness also can be caused by the cornea and/or lens being too curved for the length of the eyeball. In some cases, myopia is due to a combination of these factors.

Myopia typically begins in childhood and you may have a higher risk if your parents are nearsighted. In most cases, nearsightedness stabilizes in early adulthood but sometimes it continues to progress with age.

Source : All About Vision 

 

Evolution

In most cases, nearsightedness is simply a minor inconvenience and poses little or no risk to the health of the eye. But sometimes myopia can be so progressive and severe it is considered a degenerative condition.

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Degenerative myopia (also called malignant or pathological myopia) is a relatively rare condition that is believed to be hereditary and usually begins in early childhood. About 2 percent of Americans are afflicted, and degenerative myopia is a leading cause of legal blindness.

In malignant myopia, the elongation of the eyeball can occur rapidly, leading to a quick and severe progression of myopia and loss of vision. People with the condition have a significantly increased risk of retinal detachment and other degenerative changes in the back of the eye, including bleeding in the eye from abnormal blood vessel growth (neovascularization).

Degenerative myopia also may increase the risk of cataracts.

Surgical treatment for complications of degenerative myopia includes a combination drug and laser procedure called photodynamic therapy that also is used for the treatment of macular degeneration.

Source : All About Vision 

Diagnosis

An eye care professional can diagnose myopia during an eye exam, which usually begins with a visual acuity test. This test uses a standardized chart or card with rows of letters that decrease in size from top to bottom. Covering one eye, you will be asked to read out loud the smallest line of letters that you can see. When done, you will test the other eye. If the vision test shows that you are nearsighted, your doctor will use a retinoscope to shine light into your eyes and observe the reflection off the retina to determine the amount of refractive error you have.

Source : National Eye Institute

 

Treatment

Glasses, contact lenses, or refractive surgery can correct myopia.

With myopia, your prescription for glasses or contact lens is a negative number, such as -3.00. The higher the number, the stronger your lenses will be.

  • Refractive surgery can reduce or even eliminate your dependence on glasses or contact lenses. The most common procedures for myopia are performed with a laser, including:
  • Photorefractive keratectomy. Also called PRK, a laser is used to remove a layer of corneal tissue, which flattens the cornea and allows light rays to focus closer to or even on the retina.
  • Laser-assisted in situ keratomileusis. Commonly called LASIK, a laser is used to cut a flap through the top of the cornea, a laser removes some corneal tissue, then the flap is dropped back into place. LASIK is the most common surgery used to correct nearsightedness.
  • Corneal rings. Plastic corneal rings, called Intacs, are implanted into the eye to alter the shape of the cornea. One advantage of the rings is that they may be left in place permanently, may be removed in case of a problem, or adjusted should a prescription change be necessary.

Source : Medicinenet

 

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