Commonly known as “lazy eye,” is a condition where one eye has reduced vision because it didn’t develop properly in early childhood. It usually occurs due to abnormal visual experience early in life, such as strabismus (misaligned eyes), a significant difference in refractive errors between the eyes (anisometropia), or deprivation of vision due to factors like congenital cataracts. The brain relies more on the stronger eye, leading to decreased vision in the weaker eye. Early detection and treatment are crucial, typically through glasses, eye patches, or vision therapy. If left untreated, amblyopia can lead to permanent vision problems. Regular eye exams for children can help catch and treat amblyopia early.
Symptoms
Signs and symptoms of lazy eye include: An eye that wanders inward or outward, Eyes that appear to not work together, Poor depth perception, Squinting or shutting an eye, Head tilting and Abnormal results of vision screening tests.
When to see a doctor
See your child’s doctor if you notice his or her eye wandering after the first few weeks of life. A vision check is especially important if there’s a family history of crossed eyes, childhood cataracts or other eye conditions. For all children, a complete eye exam is recommended between ages 3 and 5.
Causes
Lazy eye develops because of abnormal visual experience early in life that changes the nerve pathways between a thin layer of tissue (retina) at the back of the eye and the brain. The weaker eye receives fewer visual signals. Eventually, the eyes’ ability to work together decreases, and the brain suppresses or ignores input from the weaker eye. Anything that blurs a child’s vision or causes the eyes to cross or turn out can result in lazy eye.
Common causes of the condition include:
- Muscle imbalance (strabismus amblyopia).
- The most common cause of lazy eye is an imbalance in the muscles that position the eyes. This imbalance can cause the eyes to cross in or turn out, and prevents them from working together.
- Difference in sharpness of vision between the eyes (refractive amblyopia).
- A significant difference between the prescriptions in each eye – often due to farsightedness but sometimes to nearsightedness or an uneven surface curve of the eye (astigmatism) – can result in lazy eye. Glasses or contact lenses are typically used to correct these refractive problems. In some children, lazy eye is caused by a combination of strabismus and refractive problems.
- Deprivation.
- A problem with one eye – such as a cloudy area in the lens (cataract) – can prohibit clear vision in that eye. Deprivation amblyopia in infancy requires urgent treatment to prevent permanent vision loss. It’s often the most severe type of amblyopia.
Risk factors
Factors associated with an increased risk of lazy eye include: Premature birth, Small size at birth, Family history of lazy eye, Developmental disabilities.
Diagnosis
Your doctor will conduct an eye exam, checking for eye health, a wandering eye, a difference in vision between the eyes or poor vision in both eyes. Eye drops are generally used to dilate the eyes. The eye drops cause blurred vision that lasts for several hours or a day. The method used to test vision depends on your child’s age and stage of development:
- Preverbal children.
- A lighted magnifying device can be used to detect cataracts. Other tests can assess an infant’s or toddler’s ability to fix his or her gaze and to follow a moving object.
- Children age 3 and older.
- Tests using pictures or letters can assess the child’s vision. Each eye is covered in turn to test the other.
Treatment
It’s important to start treatment for lazy eye as soon as possible in childhood, when the complicated connections between the eye and the brain are forming. The best results occur when treatment starts before age 7, although half of children between the ages of 7 and 17 respond to treatment. Treatment options depend on the cause of lazy eye and on how much the condition is affecting your child’s vision.
Your doctor might recommend:
Corrective eyewear. Glasses or contact lenses can correct problems such as nearsightedness, farsightedness or astigmatism that result in lazy eye.
Eye patches. To stimulate the weaker eye, your child wears an eye patch over the eye with better vision for two to six or more hours a day. In rare cases, wearing an eye patch too long can cause amblyopia to develop in the patched eye. However it’s usually reversible.
Bangerter filter. This special filter is placed on the eyeglass lens of the stronger eye. The filter blurs the stronger eye and, like an eye patch, works to stimulate the weaker eye.
Eyedrops. An eyedrop of a medication called atropine (Isopto Atropine) can temporarily blur vision in the stronger eye. Usually prescribed for use on weekends or daily, use of the drops encourages your child to use the weaker eye, and offers an alternative to a patch. Side effects include sensitivity to light and eye irritation.
Surgery. Your child might need surgery if he or she has droopy eyelids or cataracts that cause deprivation amblyopia. If your child’s eyes continue to cross or wander apart with the appropriate glasses, your doctor might recommend surgical repair to straighten the eyes, in addition to other lazy eye treatments.
Activity-based treatments – such as drawing, doing puzzles or playing computer games – are available. The effectiveness of adding these activities to other therapies hasn’t been proved. Research into new treatments is ongoing.
For most children with lazy eye, proper treatment improves vision within weeks to months. Treatment might last from six months to two years.
It’s important for your child to be monitored for recurrence of lazy eye – which can happen in up to 25 percent of children with the condition. If lazy eye recurs, treatment will need to start again.