Colloquially known as lazy eye, amblyopia is a childhood vision disorder where one of a child’s eyes doesn’t develop normally. If detected and treated early in life, reduced vision can be avoided. But if amblyopia is left untreated, the brain can begin to ignore the signals from the affected eye, which could lead to permanent vision damage, even blindness in that eye.
Dr. Thom treats amblyopia in our Fargo office.
What is amblyopia?
Amblyopia begins during infancy or early childhood. It typically affects just one of the eyes, with that eye trailing the other eye in the development of normal visual acuity. This may even be the case with prescription eyeglasses or contact lenses. Amblyopia commonly starts when one eye has much better focus than the other. Sometimes, one eye is more farsighted or has a higher degree of astigmatism than the other.
What causes amblyopia?
There are three types of amblyopia, categorized by their cause.
- Strabismic amblyopia — When the eyes are poorly aligned, the brain ignores the information it receives from the misaligned eye, leading to reduced development in that eye, the “lazy” eye.
- Refractive amblyopia — In this type, the eyes are aligned properly, but there are unequal refractive errors between the two eyes. For instance, one eye can have a significant degree of near or farsightedness, or astigmatism, and the other eye doesn’t. The brain uses the input from the better eye and blocks out the blurred vision from the other eye. This leads to amblyopia because the eye isn’t used.
- Deprivation amblyopia — This is a congenital condition, where something is obstructing the light from entering and being focused in a baby’s eye. This is often due to a congenital cataract, which needs to be removed for the eye to develop normally.
What are the signs or symptoms a child has amblyopia?
Because amblyopia is a condition that usually affects infants, noticing symptoms or signs isn’t always easy to do. Strabismus, however, is a common cause of amblyopia, so if you notice your child’s eyes are crossed or otherwise improperly aligned, Dr. Thom needs to see your child immediately.
A screening test can show signs. Cover one of your child’s eyes while he or she is watching television or doing another visual task. If the child cries, begins to fuss, or otherwise objects, this is a sign you are covering the “good” eye, and the other eye has amblyopia and is being ignored by the brain.
A comprehensive infant eye exam is the best way to spot the condition.
How common is amblyopia?
Amblyopia affects between 2-3 percent of U.S. children. It is the most common cause of visual impairment among children
Who is more likely to get amblyopia?
It usually occurs before age 8. If the parents had amblyopia as children, there is an increased risk of it being present in their children. Otherwise, infants born prematurely or at low birth weight are at a greater risk for developing amblyopia.
What does a child with amblyopia see?
Normally, the images each eye sends to the brain are identical. With lazy eye, the two images differ, either in quality (with refractive error differences) or in content (with misaligned eyes). Because the images are different, the brain needs to choose the input to process and create the image of what is being seen. It takes one eye’s input and rejects the other, leading to deterioration in the ignored eye.
Can lazy eye develop over time?
No, amblyopia is caused when one eye is either misaligned, has dramatically different refractive errors than the other eye, or is having light blocked by a cataract. This causes the brain to ignore the input it receives from one eye, and this causes the ignored eye to cease to develop normally.
However, when a child has normal vision, the brain immediately uses both eyes in tandem, so they develop as a pair. The first 7-10 years features rapid development of the eyes in children, and this development will be in both eyes, precluding a lazy eye from developing over time where one eye is being ignored.
What are the limitations someone faces with amblyopia?
Amblyopia that has been left untreated eventually stabilizes and the ignored eye is virtually unused. If this has been allowed to progress untreated, the condition is now very difficult to treat. If adults have amblyopia, they are limited in the occupational and leisure activities they can participate in because of their lack of depth perception — they are basically seeing with just one eye.
When a child has lazy eye, you may notice that he or she favors one eye for vision. He or she may have the tendency to bump into objects on one side of their body.
Can amblyopia be corrected?
Dr. Thom treats amblyopia by basically forcing the child’s brain to start using the weak eye. He’ll first check the degree of refractive error in the lazy eye, as most kids with amblyopia need glasses to help their eyes focus. If a cataract is blocking the light, he will perform surgery to remove it.
In some cases, correcting the refractive error in the lazy eye is all that is needed, but in most cases the use of a patch is necessary. A patch is placed over the strong eye. The child will probably not like wearing the patch, as his or her vision will be much poorer, but it’s important they wear the patch. The vision will improve as the lazy eye works, but this can take a period of weeks or even months.
In some children, getting them to wear the patch is difficult. In these cases, Dr. Thom may use a specially designed prosthetic contact lens that prevents light from entering the good eye, forcing the lazy eye to take over the vision load.
Dr. Thom keeps tabs on the child’s vision as it improves. When it is back to normal, the patch won’t need to be worn all the time, although when the child goes back to using both eyes he or she may lose some vision in the former lazy eye, which would then call for wearing the patch again.
If the cause is strabismus, Dr. Thom may need to perform strabismus surgery to straighten the eyes, followed by eye patching or other therapy to then get the eyes to cooperate and work together.
In mild cases, Dr. Thom may use an atropine eye drop that blurs the vision in the strong eye. This makes the weak eye take over, without the need for wearing a patch.
What is the long-term outlook for treatment of amblyopia?
With early diagnosis and treatment, most children regain vision in the formerly unused eye. That’s why the American Optometric Association recommends that all children have their first eye exam at 6 months of age, another exam at age 3, and a third exam prior to entering school. This ensures the vision is developing normally. If signs of amblyopia show up, they can be treated effectively the earlier they are diagnosed.