The term “lazy eye” is common, even sort of folksy, but this description for a misaligned eye or crossed eye does not adequately convey how severe amblyopia can be if left untreated.
Even though anyone can develop a lazy eye in adulthood, the condition is most often seen in children. So, for the purposes of this discussion, we will focus our attention on amblyopia in infants and children.
Considering amblyopia’s impact on visual acuity and quality of life early on, it is important to recognize and address the condition as soon as possible to preserve as much eyesight as possible.
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What is a lazy eye?
A lazy eye, or amblyopia, develops over time. In young children, the difference in vision from one eye to the other physically changes the nerve pathways between the retina and the brain.
Eventually, the brain begins to compensate for weak vision or refractive error in one eye by favoring the stronger eye and ignoring confusing signals from the weaker eye.
Lazy eye may or may not even be noticeable to others, but this disturbance in how the eyes and brain coordinate to receive and process visual input can further diminish vision in the weaker eye and cause difficulty with 3D vision. Binocular vision is vital to depth perception, which helps us safely navigate the world around us.
Between 2 and 5 percent of people will develop a lazy eye, with the greatest proportion of those cases occurring in children. Amblyopia is one of the most common reasons parents schedule a visit for their child with an ophthalmologist.
Who is at risk for a lazy eye?
Although a lazy eye can develop at any age, the condition is most prevalent in children still developing neurological pathways from sensory input.
Not all amblyopia is the same, but there are a number of situations that are known to be risk factors for the condition, including:
- a family history of amblyopia
- low birth weight
- premature birth
- developmental disabilities
Amblyopia cannot be ruled out in adults either. It’s essential to receive regular eye examinations to ensure your eyes are working properly – and symmetrically.
There are different types of amblyopia
How lazy eye is diagnosed and treated depends on what type of amblyopia an individual has.
- Strabismic Amblyopia. Strabismic amblyopia, or strabismus, is caused by misaligned eyes. You may notice one of your child’s eyes points slightly to one side or the other, or further up or down than the other. This misalignment will gradually force the brain to shut off signals from the weaker eye and take input only from the stronger eye, further diminishing vision in the affected eye.
- Deprivation Amblyopia. Sometimes, one eye simply sees better than the other right from the start, such as with childhood cataracts. If deprivation amblyopia is not caught early, the brain will “rewire” to compensate, and the child may never recover normal vision.
- Refractive Amblyopia. A refractive error in one eye, or an unequal degree of refractive error, causes a type of lazy eye called refractive amblyopia. As with deprivation amblyopia, the brain learns to ignore poor visual input from the weak eye in favor of visual input from the stronger eye. Refractive amblyopia can be difficult to recognize: A child may see well enough out of the good eye that they don’t perceive that they have a “bad eye.” The eye may appear perfectly normal, and the child may not experience much blurriness.
- Anisometropic Amblyopia. Anisometropic amblyopia, also known as anisometropia, occurs when each eye requires a different refractive correction. One eye may be myopic, while the other is hyperopic. Perhaps one eye is astigmatic, but the other is not. As with other amblyopia types, the brain will favor the stronger eye or the eye that requires less correction, and the weaker eye will become even weaker.
What are some lazy eye symptoms?
Obvious misalignment of the eyes is an easily recognizable symptom of a lazy eye. However, it won’t always be easy to spot a suspected case of lazy eye, particularly in young children who cannot recognize or express visual problems. Some other less obvious symptoms of lazy eye might include:
- Shutting or coving an eye
- Tilting the head to focus
- Difficulty focusing on a person or object
- Trouble determining distance of an object (depth perception)
- Eyes that do not seem to work together
- Abnormal results of vision screening tests
Sometimes you may notice none of these symptoms in your child. Very young children may simply be irritable from headaches, or they may fall down a lot due to visual disturbances you may not be aware of.
Every child should receive eye exams at 6 months, 3 years, and annually after that. If you notice any of the amblyopia symptoms – or you have a family history – schedule an exam immediately with your child’s pediatrician and an ophthalmologist, even if an annual exam is not due.
Complications of not treating a lazy eye can be severe, including permanent vision loss. This loss of vision can create other difficulties for your child, including trouble learning, clumsiness, and discomfort.
It is not uncommon for a newborn to occasionally exhibit crossed eyes. This is most often due to his still-developing muscles and ligaments. Normally, this will stop as the child can focus on objects, people, and his surroundings.
Often, a lazy eye is diagnosed when crossed eyes or a wandering eye appears a little later, at around age 1 or 2. An eye doctor will test for amblyopia by covering one eye to see how the child responds or if he can “track” an object with the uncovered eye.
Is it possible to fix a lazy eye?
Yes, a lazy eye can be treated, but treatment must begin as early as possible to achieve children’s best visual outcomes. Treatment options depend on the root cause of amblyopia and may include:
- Surgery. Strabismic amblyopia may require eye muscle surgery to correct the misalignment of the eyes. If a cataract is the cause, surgery to remove the cataract must be the first step in treatment.
- Eye patches have been used to correct many cases of lazy eye successfully. With this treatment, the stronger eye is covered. This forces the brain to begin again, accepting input from the weak eye. This type of visual training can take many weeks or months to complete.
- A Bangerter filter works in a similar fashion to an eye patch but is worn over the eyeglass lens to blur the dominant eye. This forces the formation of better pathways between the weaker eye and the brain.
- Corrective eyeglasses may be used to address refractive errors that have led to a lazy eye.
- Atropine eye drops are used in some cases to blur the strong eye long enough to allow the weaker eye to strengthen.
Technology and treatment for lazy eyes are constantly evolving, so correction of the condition may differ from the approaches listed here. However, one thing that will probably never change is the importance of early detection and treatment of a lazy eye for the best visual results.