Amblyopia (Lazy Eye)
Also known as “lazy eye,” amblyopia (am-blee-O-pea) occurs when vision in one eye (or both eyes) is impaired because the eye and brain are not working together. Often the eye itself looks normal, but the eye is not being used normally because the brain is favoring the other eye. In children, amblyopia is the most common cause of visual impairment. Two to three out of every hundred children suffer from amblyopia. If left untreated, the condition will continue into adulthood and lead to visual impairment.
The effects of this condition can range from mild to severe. There are three types of amblyopia:
- Amblyopia secondary to Strabismus: Strabismus is the medical term used to describe eyes that are misaligned. Children’s’ brains are neuroplastic, which means they can easily adapt and eliminate problems such as double vision by suppressing images from one eye. But the plastic response to the brain results in amblyopia. Typically this form of amblyopia is treated with eyeglasses, or by placing an eye patch over the dominant eye to force the weak eye to communicate with the brain.
- Refractive or anisometropic amblyopia: A refractive error between the two eyes (anisometropia) may result in refractive amblyopia. The dominant eye is typically the one that provides the brain with the clearest image. When the image from the other eye is blurry, it results in an abnormal development of one half of the visual system. Amblyopia is often associated with a combination of strabismus and anisometropia.
- Form-deprivation and occlusion amblyopia: Form-deprivation amblyopia is seen in people with eye problems such as cataracts. Like other conditions that create opacity (non-transparency or non-translucency) of the ocular media, cataracts prevent normal visual input from reaching the eye, which results in disrupted development. In this form, if it is not treated during the early stages, amblyopia can persist after the cause of the opacity is removed. In occlusion amblyopia, the visual axis may be blocked due to a hemangioma (a benign tumor) or some other obstruction.
Symptoms of Amblyopia
Amblyopia can be mild or severe. In some mild cases, the person may not know they have the condition until they get older. This is because vision in the good eye is often strong enough to compensate for the bad eye, allowing for normal vision. Symptoms of severe amblyopia may include:
- Poor depth perception
- Eyes that turn in or out
- Eyes that obviously do not work together
- Low sensitivity to contrast
- Low sensitivity to motion
If you suspect amblyopia in yourself, your child, or someone you know, contact your eye doctor or healthcare provider to set an appointment.
What Causes Amblyopia?
In most cases, amblyopia is the result of an undeveloped nerve pathway from one eye to the brain during childhood. An affected eye sends blurry images (or sometimes wrong images) to the brain. This confuses the brain and may encourage it to ignore images from the weaker eye. The most common cause of amblyopia is strabismus. Typically, there is a family history of the condition, but not all cases of amblyopia are due to strabismus. Additional causes may include:
Unlike other eye conditions, amblyopia typically can be diagnosed without special tests. This condition is easily diagnosed with a complete eye examination. Your eye doctor may ask you questions about the severity of your symptoms, your medical history, and your family history in order to make a correct diagnosis.
Treating amblyopia typically involves treating the cause of the condition first. For example, if cataracts are present the cataracts will be treated. If eyeglasses are needed for farsightedness or astigmatism, they are prescribed. It is common for an eye patch to be placed over the normal eye to force the brain to communicate with the weaker eye. Occasionally, instead of an eye patch, eye drops are used to blur the vision of the dominant eye. The eye drops used to blur the good eye are called Atropine, and they are quite safe for monitored chronic use. Children will often refuse patching or Atropine treatment, but the parent must insist and take charge so that vision and normal depth perception can be restored. In cases in which one eye is good but vision is not expected to recover fully, scratch- and shatter-resistant glasses with protective polycarbonate lenses are prescribed. These cases are mostly seen in children.
In most cases, children under the age of five who receive adequate treatment usually recover almost completely, although depth perception may be a problem throughout the child’s life. Delayed treatment inevitably results in permanent vision damage. If the condition is not treated before the age of 10, partial recovery of vision is the best that can be expected.
Complications of Amblyopia
If not treated in a timely manner, complications of amblyopia can include:
- Permanent vision loss in the amblyopic eye
- Problems with eye muscles which may require surgery
- Possible complications if eye surgery is needed
Like many eye conditions, amblyopia can sometimes be prevented by recognizing the symptoms and beginning treatment during the early stages of the condition. If a child starts to develop the need for glasses and this is recognized early and treated, then anisometropic amblyopia won’t develop. Similarly, if a child is developing an occlusion, such as from a hemangioma, then by treating the occlusion when it threatens the visual axis one can prevent amblyopia. All children should have an eye exam between the ages of three and five. Most eye-care professionals use special techniques when dealing with young patients who are unable to communicate.
Resources for Amblyopia Sufferers
Questions to Ask Your Doctor
- How severe is my child’s amblyopia?
- Which treatment options would best help my child?
- In addition to the common ones, which symptoms should I watch for?
- What are the chances my other children will develop this condition?
- Which type of amblyopia does my child have?
- Which kinds of tests can we expect during the diagnosis?
- What are the side effects of the available treatment options?
- Which lifestyle changes should I make?
Did you know: Prevent Blindness America says that only 21 percent of American children have their vision screened before kindergarten, with only 14 percent receiving a comprehensive eye exam?
- J. Weizer, MD; J Stein, MD, MS “Reader’s Digest Guide to Eye Care” (Quantum Publishing, 2009) 24, 75-76
- J. Lavine, MD “The Eye Care Sourcebook” (Contemporary Books, 2001) 109, 111-112
- J. DiGirolamo “The Big Book of Family Eye Care” (Basic Health Publications, 2011) 102-104
- American Optometric Association, Amblyopia (Lazy Eye) http://www.aoa.org/x4699.xml