Strabismus

Strabismus and anisomtreopia are the most common causes of amblyopia.

Amblyopia (Lazy eye)

What is it?
Practice makes perfect. Young eyes need practice in order for mature vision to develop in the brain. For this to happen, a clear image of the world needs to land on the retina and be transmitted to the visual cortex of the brain.

Amblyopia is the loss of vision caused when a clear image of the world is not available on the retina during key periods of development. The visual cortex of the brain develops dramatically in babies and young children. It continues to develop throughout the first decade of life.

Anything that interferes with a normal image on the retina during this time can lead to amblyopia – a loss of vision that continues even if no problem remains in the eye.

Who gets it?
Amblyopia might occur in strabismus, when one eye deviates to the side and isn’t used as much. It might occur if there is unequal vision in the two eyes from astigmatism, or if one eye is more nearsighted or farsighted than the other. It might occur if there is a cataract blocking vision in one eye, or if there has been an injury.

Whatever the cause, if the “lazy” eye relaxes, the vision in that eye gets worse, and a destructive cycle begins. The initial difference between the eyes does not have to be dramatic.

Amblyopia can also occur if there is a severe blurring of vision in both eyes, as in severe nearsightedness or farsightedness.

Amblyopia only begins during the first ten years of life. It is more likely, and often more serious, the younger the child is when the retina is not receiving a clear image.

What are the symptoms?
Most amblyopia is discovered during routine eye screening – without any symptoms having been noticed. The symptom of amblyopia is decreased visual acuity, but this is not usually found unless the child has her vision checked.

An eye that deviates, cloudiness in one eye, or any signs or symptoms of nearsightedness, farsightedness, or astigmatism might suggest that amblyopia is developing as a result.

Is it contagious?
No

How long does it last?
If normal vision is not restored to the eye by about age 6, some degree of vision loss will probably be permanent. Usually a lazy eye should be diagnosed by age 3 in order to restore normal vision to that eye by age 6.

How is it diagnosed?
A March 2002 policy statement by the American Academy of Pediatrics (AAP) recommends that all babies have vision screening (including screening for strabismus and amblyopia) at the earliest possible age, and at regular intervals throughout childhood. Rather than relying on informal or subjective assessments of vision, the policy discusses photoscreening, a new test that can make checking vision easier and more accurate for even very young babies. A specially equipped camera takes their picture and a computer or a person analyzes the eye data obtained. Ask your pediatrician about having your baby screened.

If there are abnormal results on vision screening, or any reason to suspect amblyopia, the child should have a complete eye exam as soon as possible.

How is it treated?
The key to treating amblyopia is starting early. The first order of business is to identify and plan to treat the underlying cause of the amblyopia if it is still present.

It is also important to temporarily block vision in the better eye so that the child will use and exercise the “lazy” eye. This process may go on for weeks or months or even years.

Eye patches have long been a standard treatment for amblyopia. But children and parents alike sometimes have a tough time following through. Even if the child is initially enthusiastic about looking like a pirate, the patch ordeal can soon get old. It did in my house.

I was pleased to see a study published in the March 2002 issue of Archives of Ophthalmology that tested children with amblyopia at 47 different clinical sites. Half received patching (6 hours a day for 6 months); the other half were treated with blurring eye drops in the good eye (one drop of atropine a day for 6 months).

Treatment was successful (at least 3 lines of vision improvement, or vision brought to at least 20/30) in 79 percent of the patched kids and 74 percent of those receiving drops. Atropine drops appear to be a great treatment choice for some families.

How can it be prevented?
Amblyopia can be prevented by the early detection and treatment of strabismus, astigmatism, cataracts, and other vision problems.

Amblyopia, also known as "lazy eye," is a condition characterized by diminished vision in one eye. It is not correctable by eyeglasses or contact lenses and is not usually triggered by an eye disease.Instead, amblyopia can develop when:

* the extraocular muscles fail to align the eyes properly and the part of the brain that controls vision "favors" one eye over the other;
* an eye with a significant refractive error in one eye goes uncorrected for a period of time; or
* there is a large difference in the refractive power, and one eye is favored.

All babies are born with poor eyesight that normally improves as they grow. In amblyopia, one eye becomes stronger. If the weaker eye is untreated, eyesight will progressively worsen.

Incidence and Prevalence
Amblyopia is the most common cause of visual impairment restricted to one eye in children and young to middle-aged adults. About 5% of children in the United States have amblyopia.

Types
The two most common types of amblyopia are strabismic and anisometropic. In strabismic amblyopia, strabismus is present and the eyes are not aligned properly resulting in one eye being used less than the other. The nonpreferred eye is not adequately stimulated and the visual brain cells do not develop normally. With anisometropic amblyopia, the eyes have different refractive powers. For example, one eye may be nearsighted and the other farsighted. It may be difficult for the brain to balance the difference and it favors the stronger eye.

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Risk Factors

Anything that interferes with equal development of vision in both eyes between birth and about 6 years can result in amblyopia. Strabismus and anisomtreopia are the most common causes of amblyopia. Other risk factors include congenital cataracts, something that blocks the cornea or lens and a droopy eyelid that obstructs the field of vision in one eye.

Signs and Symptoms

Amblyopia may not produce symptoms that are obvious to a parent or the affected child. Amblyopia caused by an undetected refractive error may go unnoticed for years, due to the fact that one of the eyes is functioning normally. As a result, many children remain unaware of vision problems, especially before they begin school. The condition is often diagnosed during the first eye examination at a later age, when improvement in vision to its fullest potential may no longer be possible.

Sometimes, though, a child may squint or close one eye, which indicates a visual problem. A child old enough to verbalize may complain of headaches or eyestrain. In strabismic amblyopia, the crossed eye is an obvious sign.