Overview and prevention for myopia

What is myopia?
Nearsightedness or myopia, occurs when light entering the eye focuses in front of the retina instead of directly on it.  This is caused by a cornea that is steeper, or an eye that is longer, than a normal eye.  Nearsighted people typically see well up close, but have difficulty seeing far away. This problem is big in Taiwan and often discovered in school-age children who report having trouble seeing the chalkboard.  Near-sightedness usually becomes progressively worse through adolescence and stabilizes in early adulthood.  It is an inherited problem.
Signs and Symptoms

• Blurry distance vision
• Vision seems clearer when squinting

Cause of myopia
Myopia was once thought to be genetic -- inherited from your parents -- but it's now clear that idea was only partially correct. Countless modern studies indicate with little doubt that nearsightedness is the result of doing more near-work than our eyes were made for, and people are susceptible in degrees that vary with their heredity. That is to say, some people are more prone to nearsightedness than others, but the cause  is the strain of excess near-work. Consequently, there's every reason to believe that nearsightedness can be prevented by good vision habits.
Prevention of myopia

• Read books and use computers at the furthest possible distance -- most people get much too close.  Consider reading at 20" (50cm) a minimum distance for adults.  (Nowadays I wear plus lenses and work at 70cm from my computer)
• Do not wear full-strength prescription minus-lens glasses (the type given to nearsighted people) when doing near work.  These glasses make close things appear even closer -- wearing them for close work is the worst thing you can do.  Normal and mildly nearsighted people can read fine without glasses, and if you are already too nearsighted to read at a reasonable distance, consider the "plus lens" idea in the next section.
• It's also good to look out into the distance several times an hour.  This is not just idle advice -- it's a very helpful technique that can really make a difference.  Far-focusing allows your eyes' focusing muscles (the ciliaries) to relax & helps relieve the strain of nearwork. Far-focusing is especially useful to do before bedtime. It forces the ciliaries to relax, helping to prevent ciliary spasm (a common condition in which these muscles never fully relax). Just a glance at a eyechart and focusing for that far-away distance is all it takes.

Treatment of myopia

Nearsightedness may be corrected with glasses, contact lenses or refractive surgery. Depending on your vision problem, you may need to wear your glasses or contact lenses all the time, or only when you need distance vision, like driving, seeing a chalkboard or watching a movie. 
Refractive surgery can reduce or even eliminate your need for glasses or contacts. The most common procedures are performed with an excimer laser. In photorefractive keratectomy (PRK) andlaser-assisted in situ keratomileusis (LASIK) , the laser removes a layer of corneal tissue, which flattens the cornea and allows light rays to focus closer to or even on the retina. Then there's orthokeratology, a non-surgical procedure where you wear special contact lenses in the night that slowly reshape the cornea over time to correct your myopia. When the lenses are removed in the day-time, the cornea temporarily retains the new shape, so you can see clearly without the lenses.

Besides, there is good evidence from several RCTs that pharmacological intervention with antimuscarinic agents like atropine and pirenzepine is both effective and safe in retarding the progression of childhood myopia over 1-2 year period.

Strabismus and amblyopia

Strabismus, more commonly known as crossed-eyes, is a vision condition in which a person can not align both eyes simultaneously under normal conditions. One or both of the eyes may turn in, out, up or down. An eye turn may be constant (when the eye turns all of the time) or intermittent (turning only some of the time, such as, under stressful situations or when ill). Whether constant or intermittent, strabismus always requires appropriate evaluation and treatment. It is estimated that up to 5 percent of all children have some type or degree of strabismus. Children with strabismus may initially have double vision. This occurs because of the misalignment of the two eyes in relation to one another. In an attempt to avoid double vision, the brain will eventually disregard the image of one eye (called suppression).

Amblyopia.is the medical term used when the vision in one of the eyes is reduced because the eye and the brain are not working together properly. The brain and the eye work together to produce vision. Light enters the eye and is changed into nerve signals that travel along the optic nerve to the brain. The eye itself looks normal, but it is not being used normally because the brain is favoring the other eye. This condition is also sometimes called lazy eye.

Amblyopia may be caused by any condition that affects normal visual development or use of the eyes. Amblyopia can be caused by strabismus, an imbalance in the positioning of the two eyes. Strabismus can cause the eyes to cross in (esotropia) or turn out (exotropia). Sometimes amblyopia is caused when one eye is more nearsighted, farsighted, or astigmatic than the other eye. Occasionally, amblyopia is caused by other eye conditions such as cataract.

Amblyopia treatment is most effective when done early in the child's life, usually before age 7. Treating amblyopia involves making the child use the eye with the reduced vision (weaker eye). Currently, there are two ways used to do this:

Atropine
A drop of a drug called atropine is placed in the stronger eye once a day to temporarily blur the vision so that the child will prefer to use the eye with amblyopia. Treatment with atropine also stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.

Patching
An opaque, adhesive patch is worn over the stronger eye for weeks to months. This therapy forces the child to use the eye with amblyopia. Patching stimulates vision in the weaker eye and helps the part of the brain that manages vision develop more completely.