Amblyopia (Lazy Eye)

Amblyopia, also known as lazy eye, is a vision development disorder in which an eye fails to achieve normal visual acuity, even with prescriptioneyeglasses or contact lenses.

Amblyopia begins during infancy and early childhood. In most cases, only one eye is affected. But in some cases, reduced visual acuity can occur in both eyes.

Particularly if lazy eye is detected early in life and promptly treated, reduced vision can be avoided. But if left untreated, lazy eye can cause severe visual disability in the affected eye, including legal blindness.

It's estimated that about 2 to 3 percent of the U.S. population has some degree of amblyopia.

Amblyopia Signs and Symptoms

Because amblyopia typically is a problem of infant vision development, symptoms of the condition can be difficult to discern. However, a common cause of amblyopia is strabismus. So if you notice your baby or young child has crossed eyes or some other apparent eye misalignment, schedule an appointment for a children's eye exam immediately — preferably with an optometrist or ophthalmologist who specializes in children's vision.

Another clue that your child may have amblyopia is if he or she cries or fusses when you cover one eye. You can try this simple screening test at home by simply covering and uncovering your child's eyes (one eye at a time) when he or she is performing a visual task, such as watching television.

If your child is not bothered when one eye is covered, but objects when the other eye is, this may suggest that the eye you have covered is the "good" eye, and that the uncovered eye is amblyopic, causing blurred vision.

But a simple screening test is no substitute for a comprehensive eye exam. Have your child's eyes examined as recommended to make sure he or she has normal vision in both eyes and that the eyes function together properly as a team.

What Causes Amblyopia?

There are three types of amblyopia, based on the underlying cause:

• Strabismic amblyopia. Strabismus is the most common cause of amblyopia. To avoid double vision caused by poorly aligned eyes, the brain ignores the visual input from the misaligned eye, leading to amblyopia in that eye (the "lazy eye"). This type of amblyopia is called strabismic amblyopia.
• Refractive amplyopia. Sometimes, amblyopia is caused by unequal refractive errors in the two eyes, despite perfect eye alignment. For example, one eye may have significant uncorrected nearsightedness or farsightedness, while the other eye does not. Or one eye may have significant astigmatism and the other eye does not.
   
  In such cases, the brain relies on the eye that has less uncorrected refractive error and "tunes out" the blurred vision from the other eye, causing amblyopia in that eye from disuse. This type of amblyopia is called refractive amblyopia (or anisometropic amblyopia).
• Deprivation amblyopia. This is lazy eye caused by something that obstructs light from entering and being focused in a baby's eye, such as a congenital cataract. Prompt treatment of congenital cataracts is necessary to allow normal visual development to occur.

Amblyopia Treatment

In some cases of refractive amblyopia, normal vision can be achieved simply by fully correcting the refractive errors in both eyes with glasses or contact lenses. Usually, however, at least some patching of the "good" eye is needed to force the brain to pay attention to the visual input from the amblyopic eye and enable normal vision development to occur in that eye.

Treatment of strabismic amblyopia often involves strabismus surgery to straighten the eyes, followed by eye patching and often some form ofvision therapy (also called orthoptics) to help both eyes work together equally as a team.

Patching may be required for several hours each day or even all day long and may continue for weeks or months.

If you have a lot of trouble with your child taking the patch off, you might consider a specially designed prosthetic contact lens that prevents light from entering the good eye but does not affect your child's appearance.

Though prosthetic contact lensesare more costly than a simple eye patch and require a contact lens exam and fitting, they can work wonders in difficult cases of amblyopia treatment when compliance with eye patching is poor.

In some children, atropine eye drops have been used to treat amblyopia instead of an eye patch. One drop is placed in your child's good eye each day (your eye doctor will instruct you). Atropine blurs vision in the good eye, which forces your child to use the eye with amblyopia more, to strengthen it. One advantage of using atropine eye drops is that it doesn't require your constant vigilance to make sure your child wears the patch.

In one large study of 419 children younger than 7 years of age with amblyopia ranging from 20/40 to 20/100 prior to treatment, atropine therapy produced comparable results to eye patching (though improvement in visual acuity in the amblyopic eye was slightly greater in the patching group). As a result, some previously skeptical eye care practitioners are using atropine as their first choice for amblyopia treatment over patching.

However, atropine does have side effects that should be considered: light sensitivity (because the eye is constantly dilated), flushing and possible paralysis of the ciliary muscleafter long-term atropine use, which could affect the eye's accommodation, or ability to change focus.

Help for Older Children and Adults With Lazy Eye

For years, experts believed that if amblyopia treatment was not initiated very early in life, no improvement in visual acuity was possible. The critical period for intervention was said to be around age 8.

But it now appears that older children and even adults with long-stranding lazy eye can benefit from amblyopia treatment using computer programs that stimulate neural changes leading to improvements in visual acuity and contrast sensitivity.

One such program — called RevitalVision — has produced improved vision in older children with lazy eye and adults with long-standing amblyopia. The treatment generally consists of 40 training sessions of 40 minutes each, conducted over a period of several weeks.

In one clinical study of 44 amblyopic children and adults ranging in age from 9 to 54 years, 70.5 percent of the participants had a visual acuity improvement of 2 or more lines on a standardized eye chart after a full regimen of RevitalVision training sessions.

Currently, RevitalVision is the only FDA-approved computerized treatment for amblyopia. The program is approved for individuals age 9 and older with best corrected vision of 20/100 or better and little or no strabismus.

Other computer programs to treat lazy eye also are available and in use by eye doctors who specialize in children's vision and vision therapy.

Early Detection and Treatment is Important

Though modern amblyopia treatments might improve vision in older children and adults, most experts agree that early detection and treatment of lazy eye is preferred for normal visual development and the best visual outcomes from amblyopia treatment.

Amblyopia will not go away on its own, and untreated lazy eye can lead to permanent visual problems. If later in life your child's stronger eye develops disease or is injured, he or she will depend on the poor vision of the amblyopic eye, so it is best to treat amblyopia early on.

In some cases, uncorrected refractive errors and amblyopia in young children can lead to behaviors that seem to indicate developmental or other disorders when the problem is purely visual.

Myopia Control

Myopia, or nearsightedness, is a big problem for many children. This difficulty with distance vision interferes with many daily activities, including learning at school. And as they grow, many children experience progressive myopia, which means the problem gets worse over time.

Can anything slow or stop the progression of myopia? Eye doctors and other researchers have studied this question for some time. Here's the scoop on the various strategies they have tried:

Using Rigid Contact Lenses

Over the years, several studies seemed to indicate that myopia could be controlled by wearing rigid gas permeable or RGP contact lenses. (Now more eye care practitioners are calling them GP contact lenses.) The idea was that the rigid contact lens would act as a splint to fortify the front of the eye without affecting the overall corneal shape. The lens would reduce myopic progression, as compared with wearing eyeglasses or soft contact lenses.

Are bookworms more likely to be nearsighted than other people? It's one of the many ideas that scientists have explored in their efforts to slow or stop the progression of myopia in children.

This idea was controversial, and some eye care practitioners scoffed. Since many of the studies were flawed because of inadequate controls of important variables, incomplete follow-up and poor selection of study participants, their results were inconclusive.

Finally, the Contact Lens and Myopia Progression (CLAMP) study published its findings in 2004. The CLAMP study, funded by the National Eye Institute, followed myopia progression in more than a hundred children aged 8 to 11 over a three-year period. Some wore rigid GP contact lenses, while others wore soft lenses. The researchers measured the participants' visual acuity as well as the physical growth of their eyes. In myopic people, the eyeball grows longer than normally, with a steeper cornea; this longer axial length is what causes the blurred distance vision.

The GP lens wearers did show less myopia progression, but it was only temporary. Their eyes continued to grow as long as the eyes of the soft lens wearers, and since the GP lenses were not able to slow or stop the growth, they could not provide permanent myopia reduction. A clinical trial conducted in Singapore reached a similar conclusion.

One difficulty in proving that wearing GP lenses definitely retards myopia lies in not knowing how nearsighted someone would be without such treatment. It's not an exact science: practitioners can't say that your child would have progressed to a prescription of -8.50 diopters if he hadn't worn GP lenses to control myopia. On the other hand, myopia does seem to run in families, and if most of the family members are very myopic, it's not unreasonable to suppose your child will eventually become very myopic as well.

Soft Contact Lenses Do Not Increase Myopia Progression, Says Study

Will wearing soft contact lenses make your child more nearsighted?

Over the years, eye care practitioners have disagreed about this. Some eye doctors believe nearsighted kids may become more myopic if they wear soft contacts rather than wearing eyeglasses, and they have called this phenomenon "myopic creep."

But a study presented at the 2008 annual meeting of the Association for Research in Vision and Ophthalmology says it isn't so.

Researchers studied the progression of myopia among 484 nearsighted children ages 8 to 11. Roughly half of the children were assigned to wear soft contact lenses, and the other half wore eyeglasses.

At the end of the three-year study period, no significant difference in myopic progression, increase in eye length or increase in corneal curvature was found between the two groups.

The researchers concluded that nearsighted children who wear soft contact lenses have no greater risk of "myopic creep" than nearsighted kids who wear eyeglass.

Undercorrecting Myopia

Some eye doctors have tried undercorrecting nearsightedness, in hopes of reducing near focusing strain that has been suggested as a cause of progressive myopia. A recent study failed to support this idea, finding no statistically significant difference between those who received full correction and those who received undercorrection. Two other studies found that undercorrecting nearsightedness actually increased the rate of its progression.

Another study, the Correction of Myopia Evaluation Trial (COMET), has been testing the idea of using eyeglasses with bifocal lenses or progressive lenses to reduce the eye focusing needed for sustained near vision. So far it has found that progressive lenses, compared with regular single vision lenses, did slow myopia progression in children by a small, statistically significant amount during the first year. But the effect wasn't significant in the next two years.

Undercorrecting myopia is therefore not a proven strategy for slowing the progression of nearsightedness in children. It also has the disadvantage of causing blurred distance vision if the treatment is performed with single vision lenses.

Atropine and Pirenzepine Drug Therapies

Several studies have shown that atropine eye drops can reduce myopia progression by temporarily paralyzing the focusing muscle inside the eye. (Atropine also causes the pupil to dilate widely.) One such study is the Atropine in the Treatment of Myopia (ATOM) study, which tested 400 children aged 6 to 12 over a two-year period.

So why isn't atropine a standard treatment for myopia? The focusing paralysis and pupil dilation caused by atropine cause light sensitivity and reduce children's ability to perform well at school and during sports. Plus, a constantly dilated pupil looks odd, a problem for kids because they tend to want to fit in, not stand out from the crowd.

Pirenzepine gel has also shown potential as a drug therapy for slowing myopia progression, but it is not FDA-approved, and, like atropine, it has unwanted side effects.

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