Amblyopia, commonly known as “lazy eye,” affects approximately 2 to 3 out of every 100 children. Vision in one of the eyes is reduced because the eye and the brain are not working together correctly. One of amblyopia’s most common precursors is strabismus — otherwise known as “crossed eyes” or “turned eye” — in which an individual’s eyes do not line up in the same direction when focusing on an object.
What is Amblyopia?
Amblyopia (“lazy eye”), is decreased vision in one or both eyes due to abnormal vision development in infancy or childhood, causing the brain not to receive normal stimulation from one or both eyes. The eye itself may look normal, but it is not being used normally because the brain is favoring the other eye. The reason it is often called “lazy eye” is because one eye is not being used as much as the other eye.
Without early detection and correction, a child faces a permanent loss of vision in the affected eye.
Treatments are generally most successful when they are done early in life, due to the plasticity of a child’s visual system. At a young age, vision connections from the eyes to the brain are still developing and can, therefore, be corrected. As a child ages, the connections are solidified and cannot be changed. Consequently, all children in the region must be screened by a trained professional using a medical screening model.
Long-term Consequences of Untreated Amblyopia:
- Permanent vision loss, including loss of depth perception and peripheral vision, may occur in the affected eye if not treated properly.
- Increased risk of permanent damage to the unaffected eye due to higher usage and exposure.
Causes and Risk Factors:
- Refractive errors like nearsightedness, farsightedness, and astigmatism. Treatment with prescription eyeglasses or contact lenses can correct these issues.
- Strabismus (a turned or crossed eye), can cause the affected eye to not work like the straight eye. An eye can drift vertically, or to either side.
- Children with born congenital cataract are at higher risk for amblyopia. A cataract can cause cloudiness in the lens of an eye, which will cause images to look blurry. This is rarer in babies and children, but still possible.
It can be challenging to spot a child with amblyopia. Depth perception can be an issue. You may also notice your child squinting more, shutting one eye, or tilting their head. Regular (at least annual) vision screenings for young children (ages 1–5) are essential for early detection and treatment.
Unless treated in early childhood, amblyopia usually persists into adulthood and will continue to worsen in the affected eye. It is the most common cause of monocular (one- eye) visual impairment among children and young and middle-aged adults. The good news is that early treatment works well and usually prevents long-term vision problems.
If there is an underlying condition, doctors may recommend:
- Glasses or contacts (for kids with refractive error)
- Surgery (for kids with cataract)
Then, the doctor will want to “re-train” the brain to use the weaker eye. Like with exercise, the more the eye is used, the stronger it gets. These treatments include:
- Wearing an eye patch on the stronger eye. This forces your child to use the weaker eye. The length of time child needs to wear the eye patch can vary, and this can be a stressful time for some children. You must be a positive support for your child in helping them comply with the doctor’s instructions.
- Applying special eye drops in the stronger eye. These eye drops (atropine) temporarily blur a child’s near vision in the stronger eye, forcing the brain to use the weaker eye.
Both of these options can be effective, and treatment length may range from a few weeks to many months. Working with your pediatric ophthalmologist is best to decide which is best for your circumstance.
What is Strabismus?
Strabismus is the medical term used when the two eyes do not look in the same direction at the same time. Also called “crossed eyes” or “turned eye,” the condition occurs in approximately 2 to 4% of the population.
There are three common types of strabismus:
- Crossed eyes (Esotropia). A child may be born with this condition, or they may develop it within a few months of birth or around two years of age.
- Walleye, or divergent eyes (Exotropia). A child may be born with this condition, or it may develop later.
- Vertical strabismus. The eyes are out of alignment vertically.
Long-term Consequences of Untreated Strabismus:
- Reduction of vision (amblyopia) in the turned eye. Reduced vision may occur in one eye, especially under certain circumstances, such as late treatment.
- Defective binocular vision. The eyes must be straight for the brain to be able to combine what the two eyes see into a single image. This enables accurate vision and stereopsis (3-D vision), which is used to judge depth.
Causes and Risk Factors:
- Family history. Most commonly, a tendency to have some type of strabismus is inherited.
- Farsightedness. Sometimes, the condition is due to the eyes being far-sighted and requiring corrective eyeglasses.
- Muscle abnormality. The muscles in the eyes may not be working correctly, which can cause strabismus.
- Another eye problem. Very rarely, strabismus may be secondary to a severe abnormality inside the eye, such as a cataract or tumor.
It can be challenging to spot a child with strabismus. The most common symptom a parent may notice is the misalignment of one or both of their child’s eyes. The child likely does not realize that one or both of their eyes are misaligned. You may notice your child bumping into things more than usual because depth perception can be an issue. You may also see your child squinting more, shutting one eye, or tilting their head. Regular (at least annual) vision screenings for young children (ages 1–5) are essential for early detection and treatment.
Treatment aims to restore functional vision in each eye individually, as well as good binocular vision—the earlier the treatment, the better the chances of positive outcomes for the child. If treatment is delayed, vision may not be restored. This permanent vision loss can be prevented with early detection and treatment. Do not delay if your child has strabismus. Seek professional advice from your family doctor.
Treatment usually includes:
- Patching. Patching the eye that is always straight to bring the vision up to normal in the turned eye.
- Prescription eyeglasses. Eyeglasses may be used, particularly for eyes that are out of focus.
- Eye drops. Special eye drops (phospholine iodide) may also help straighten the eyes.
- Surgery. Surgery on the eye muscles is sometimes necessary.
Mitigating the Effects of Strabismus and Amblyopia
Amblyopia and strabismus can both lead to irreversible vision loss in children. The best way to prevent this is through early detection and treatment of these diseases. The American Academy of Ophthalmology and the American Association for Pediatric Ophthalmology and Strabismus offer age-specific recommendations for childhood eye screening:
- Newborn: An ophthalmologist, pediatrician, family doctor, or another trained health professional should examine a newborn baby’s eyes.
- Infant: A second screening for eye health should be done by an ophthalmologist, pediatrician, family doctor, or another trained health professional at a well-child exam between six months and the first birthday.
- Preschool-Age:Between the ages of 3 and 3½, a child’s vision and eye alignment should be assessed by a pediatrician, family doctor, ophthalmologist, optometrist, or person trained in vision assessment of preschool children.
- Visual acuity should be tested as soon as the child is old enough to cooperate with an eye exam using an eye chart.
- School-age: Upon entering school, or whenever a problem is suspected, children’s eyes should be screened for visual acuity and alignment by a pediatrician, family doctor, ophthalmologist, optometrist, orthoptist or person trained in vision assessment of school-aged children, such as a school nurse.
However, if you or your child notices problems with his or her vision, visit an eye doctor immediately.