Strabismus
Lazy eye (amblyopia) is reduced vision in one eye caused by abnormal visual development early in life. The weaker — or lazy — eye often wanders inward or outward.
Amblyopia generally develops from birth up to age 7 years. It is the leading cause of decreased vision among children. Rarely, lazy eye affects both eyes.
Early diagnosis and treatment can help prevent long-term problems with your child’s vision. The eye with poorer vision can usually be corrected with glasses or contact lenses, or patching therapy.
What are the symptoms of Strabismus or Lazy-eye?
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
- Abnormal results of vision screening tests
Sometimes lazy eye is not evident without an eye exam.
What are the 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.
Other conditions associated with strabismus include:
- Uncorrected refractive errors
- Poor vision in one eye
- Cerebral palsy
- Down syndrome (20-60% of these patients are affected)
- Hydrocephalus (a congenital disease that results in a buildup of fluid in the brain)
- Brain tumors
- Stroke (the leading cause of strabismus in adults)
- Head injuries, which can damage the area of the brain responsible for control of eye movement, the nerves that control eye movement, and the eye muscles
- Neurological (nervous system) problems
Graves’ disease (overproduction of thyroid hormone)
Risk factors that could cause Cataract:
Factors associated with an increased risk of lazy eye include:
- Premature birth
- Small size at birth
- Family history of lazy eye
- Developmental disabilities
What are the treatment of Strabismus?
Treatment options include the following:
- Eyeglasses or contact lenses: Used in patients with uncorrected refractive errors. With corrective lenses, the eyes will need less focusing effort and may remain straight.
- Prism lenses: Special lenses that can bend light entering the eye and help reduce the amount of turning the eye must do to look at objects.
- Orthoptics (eye exercises): May work on some types of strabismus, especially convergence insufficiency (a form of exotropia).
- Medications: Eye drops or ointments. Also, injections of botulinum toxin type A (such as Botox) can weaken an overactive eye muscle. These treatments may be used with, or in place of, surgery, depending on the patient’s situation.
- Patching: To treat amblyopia (lazy eye), if the patient has it at the same time as strabismus. The improvement of vision may also improve control of eye misalignment.
- Eye muscle surgery: Surgery changes the length or position of eye muscles so that the eyes are aligned correctly. This is performed under general anesthesia with dissolvable stitches. Sometimes adults are offered adjustable strabismus surgery, where the eye muscle positions are adjusted after surgery.
When to see an ophthalmologist?
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.
