Amblyopia

Amblyopia is an eye condition that develops during childhood in which the vision in one eye is weaker than in the other. It occurs even if the child seems to have no other ocular (eye) problems. Because amblyopia can have serious, permanent effects on your child, it is important that he or she have regular vision tests.

What causes amblyopia?

The most common cause of amblyopia is a major difference in the focusing powers of the two eyes. For example, large differences between the two eyes in astigmatism (irregular shape of the eye) or farsightedness can cause amblyopia. The brain will favor seeing out of the eye that provides a clearer and sharper image and will neglect the other image, which can cause the vision in the weaker eye to get worse.

Another cause of amblyopia is a misalignment (poor positioning) of the eyes (strabismus); for instance, if the eyes are crossed or drift apart. If this happens, the brain tends to favor using the eye that is more frequently aligned (positioned) and ignore the other eye, which leads to a decline in vision.

Other causes of amblyopia arise from anything that is blocking the visual axis (line of vision) of an eye. For example, a cataract (a clouding of the lens), intraocular tumor, or an injury that causes bleeding into the eye or scarring of the front surface (cornea) of the eye may blur the visual axis and lead the brain to favor the stronger eye.

Amblyopia can also develop in both eyes if both images are blurry due to any cause. Cloudy vision in both eyes can interfere with the visual stimulation to the brain, which can lead to a permanent weakening in eyesight.

How is amblyopia diagnosed?

Your child’s pediatrician or the vision program at school will check three features of your child’s eye health:

• Do your child’s eyes let light all the way through?
• Do both eyes see equally well?
• Are the eyes moving properly? Are they aligned?

If there seems to be a problem (something blocking the light, unequal vision, or concern with movement), the pediatrician or school nurse might recommend a visit to an eye specialist such as a pediatric ophthalmologist.

The eye specialist will:

• Examine your child’s vision and eye alignment and movement;
• Check the health by looking at the front and back of the eye; and,
• Measure how well each eye focuses.

Sometimes problems can be found before the child develops amblyopia. In most children with amblyopia, however, the vision has already started to get worse by the time they visit the doctor.

How is amblyopia treated?

There are several types of treatment for amblyopia. Treatment should be started as soon as possible after the diagnosis, while the child is still young and the connections between the brain and the eye are still developing.

Treatment works best in children under 6 years old, and maybe up to around 10 years old. Different treatment will be recommended based on the cause of your child’s amblyopia. Some of the most common treatments include the following:

• Glasses: Glasses are often the first treatment for children who have amblyopia from unequal prescriptions or certain types of eye crossing. The child should wear the glasses at all times during the day, except he or she is bathing or sleeping.
• Patching: The most common treatment for amblyopia is to force the brain to start using the “bad” eye by putting a patch over the “good” eye for a few hours every day. This will force the brain to use the image from the lazy eye, eventually making the weaker eye stronger. Although at first the child will have a hard time seeing with the weaker eye while wearing the patch, the vision will eventually improve. Sometimes this can take several months to years. After the doctor decides that the vision has improved as much as possible, the patch will not be needed.
• Eye drops: In cases of mild amblyopia, the doctor might recommend using an eye drop called atropine in the “good” eye instead of a patch. Atropine blurs near vision (up close), but may have a smaller effect at distance vision, as well. Like a patch, atropine drops force the weaker eye to do most of the work, making it stronger in the process.
• Surgery: Surgery is recommended in a few situations. One of the most common is if glasses alone do not help control the crossing or drifting of eyes. Another common reason to have surgery is if there is something blocking the visual axis in the eye, such as a cataract.

Your doctor will discuss with you what treatment is most appropriate for your child.

What is the outlook for children with amblyopia?

When eye problems like those described above are found and managed early, most children regain normal vision in the amblyopic eye. However, amblyopia in older children is more difficult to treat. In some cases, if the amblyopia is severe before treatment is started, vision may not completely improve.

If too much vision is lost in the eye with amblyopia, it might be impossible to get it all back, but treatment should be continued until no more improvement can be made.

It is very important to follow your doctor’s advice about treatment. It can be challenging to convince a child to wear an eye patch every day. With the use of atropine as another method of treatment, more and more children with amblyopia can be successfully treated.

When should children have eye examinations?

Amblyopia often starts before there is any obvious sign that something is wrong. This is why babies and young children need to have their eyes checked at regularly scheduled appointments with the doctor.

The American Academy of Ophthalmology recommends that children have eye examinations at the following times:

• Before the child is 3 months old
• Between the ages of 6 months and 1 year
• At 3 years of age
• At 5 years of age

If you are concerned that your child may be suffering from or developing “lazy eye,” have him or her examined right away. Children whose family members have amblyopia are at a higher risk for developing it themselves.