Amblyopia (Lazy Eye)
What is amblyopia (lazy eye)?
Amblyopia (pronounced am·blee·OH·pee·uh) is poor vision in an otherwise healthy eye. When an untreated eye problem interferes with the vision in a young child’s normal eye, the brain begins relying more on the fellow eye that still sees well. As the brain depends more on the eye with the stronger vision, the eye with the poorer vision gets weaker.
Conditions like strabismus (crooked eyes), congenital cataract, and severe refractive errors can all lead to amblyopia in the affected eye. Many eye conditions which cause amblyopia can be inherited. Successful treatment of the poorer-seeing eye is the first step in reversing amblyopia.
Amblyopia, sometimes called “lazy eye,” usually develops in the early years of life, typically by age 7. In children, it is the most common cause of vision loss, but early treatment is effective. Generally, it affects one eye, although in rare cases, it can affect both eyes.
A “wandering” eye is probably the first thing most people associate with having amblyopia, but it is not always present. Symptoms can be subtle—such as head tilting—which can make the condition hard to notice at first.
Vision screening as part of regular well-child visits help doctors make an early diagnosis of amblyopia or other vision issues that could lead to it.Treating amblyopia as soon as possible helps avoid lifelong vision problems, and treating it in childhood is more effective than in adulthood.
What are the different types of amblyopia (lazy eye)?
Types of amblyopia are classified by the eye exam findings and the underlying cause of the condition. Different types can occur singly or at the same time.
The types of of amblyopia are:
Strabismic. This is the most commonly diagnosed form of amblyopia with one eye veering off inward, outward, up or down. When the eyes are not aligned they cannot transmit a single visual image to the brain. The brain chooses which eye to use and ignores the fellow eye. Strabismus is a treatable condition that can be present at birth or develop later in life. It also can be triggered as the result of an accident or a neurologic problem.
Refractive. This is poor vision caused by an untreated refractive error such as nearsightedness, farsightedness or astigmatism which is far worse in one eye compared to the fellow eye. Refractive errors can be corrected with glasses or contacts. However, if these vision issues are left untreated, refractive amblyopia can develop.
- Deprivation. This is the rarest form of amblyopia and develops when a condition, such as congenital cataracts or a drooping eyelid, blocks light rays from entering the eye.
What are the symptoms of amblyopia (lazy eye)?
The principal symptom of amblyopia is decreased vision. Infants and young children are unaware there is a problem and don’t complain. The eye can look perfectly normal even if amblyopia is present.
The most common signs are efforts made to see more clearly, such as:
Shutting one eye
- Moving closer to objects
Children with amblyopia may also experience bumping into things frequently (poor depth perception) or notice a significant difference in vision quality in one eye compared to the other.
Because symptoms of amblyopia may be unnoticeable, doctors recommend vision screening beginning at a young age, at least once between the ages of 3 and 5, if not earlier.
What does amblyopia (lazy eye) look like?
The most commonly diagnosed type of amblyopia is the result of strabismus, when one eye veers up, down, inward or outward.
This misalignment changes the quality of the image that is transmitted to the brain, causing it to rely on the vision coming from the stronger eye.
After addressing issues causing amblyopia, treatment to retrain the brain includes wearing an eye patch over the stronger eye, forcing the brain to rely on the weaker eye until vision improves. These can include an adhesive patch applied to the skin around the eye or a cloth covering that can go over glasses.
What causes amblyopia (lazy eye)?
Amblyopia occurs in infants and young children when one eye sees better than the other. The brain cannot tolerate two separate images, one clear and one blurry. Nor will it tolerate marked double vision. In both situations the brain decides which eye to use and which eye to ignore. Vision in the “ignored” eye will progressively decline and will not improve until the underlying problem is corrected. To summarize, amblyopia is a condition caused as a consequence of a different underlying vision problem, such as:
Strabismus (crooked eyes) which prevents the two eyes from forming a clear, single image
Physical obstruction like a drooping eyelid or a congenital cataract
Significant refractive error, affecting one eye more compared to the other, which can cause blurry vision in the affected eye
What are the risk factors for amblyopia (lazy eye)?
Some factors may increase a child’s risk of amblyopia. Not everyone with risk factors will develop the condition.
Risk factors for amblyopia include:
Family history of amblyopia or other eye conditions, such as childhood cataracts
Smaller than average size at birth
- Developmental disabilities
Reducing the risk of amblyopia (lazy eye)
While it is not possible to definitively prevent amblyopia from developing, keeping up with routine eye exams can lead to early detection and treatment, which can avoid or reduce long-term vision loss. A doctor can explain your individual risk factors and advise on recommended timing for vision screenings.
How do doctors diagnose amblyopia (lazy eye)?
Eye exams, either as part of regular well-child visits or with an eye specialist, detect amblyopia. Testing methods depend on age and developmental stage. For example, children who are not verbal require testing techniques that can assess their ability to stare fixedly at something or to follow moving objects. Children who are verbal can be tested by asking them to read letters on a chart or identify images.
Vision exams also may include:
Dilation, administering eye drops to make the pupils larger for easier examination of the inner eye
Ophthalmoscope, a hand-held light that allows doctors to view the internal structure of the eye to check for physical issues, such as cataracts
Refraction, measuring the amount of refractive error (nearsightedness, farsightedness, astigmatism)
Snellen chart, the easily recognizable chart with rows of letters, numbers, or familiar images at diminishing sizes that eye doctors use to test vision. Your provider often will have you cover one eye and then the other to assess the strength of each eye individually.
What are the treatments for amblyopia (lazy eye)?
After identifying the underlying vision conditions causing amblyopia, such as strabismus, refractive error, or cataracts, the first line of treatment will be to address those. Doctors may recommend contacts to treat nearsightedness or farsightedness, or surgery to repair cataracts.
Once the causative conditions are addressed, the brain will need to be retrained to once again rely on both eyes instead of favoring the stronger eye. Typical treatments to do this include:
Wearing an eye patch. The stronger eye is covered by an eye patch, most often an adhesive type, which forces the brain to use the weaker eye. Instead of an adhesive patch directly on the skin, cloth or semi-transparent stickers can be used over eyeglasses. More traditional “pirate” patches are not recommended, as they fit loosely and do not completely block vision.
- Atropine eye drops. These are used once a day to temporarily blur vision, forcing the brain to use the non-blurry eye.
The length of these treatments will depend on the depth of amblyopia and how quickly vision improves. Patients often see results within a few weeks, but for long-term success and to prevent recurrence of amblyopia, treatment may have to last several months to a couple of years.
Patients may also participate in activity-based therapies, such as drawing or playing computer games, although these have not been proven to improve treatment.
Children ages 7 to 17 respond to treatment, but starting treatment before the age of 7 allows for the best results. Adults do not respond as well to amblyopia treatment. Interestingly though, if an adult with amblyopia goes blind in their good eye (such as, due to trauma, tumor), the amblyopic eye will often regain good vision even after decades of poor sight.
Once treatment is completed, regular eye exams are important to maintain eye health. Amblyopia can return, and if it does, treatment will need to begin again.
What are the potential complications of amblyopia (lazy eye)?
Amblyopia does not go away on its own. If untreated, it can lead to vision loss.
In children with amblyopia, complications can also include:
Difficulty in school
- Limited ability to participate in activities due to poor hand-eye coordination