What Is It?
Lazy eye, also called amblyopia, is an eye problem that can occur in growing children. In the typical child with lazy eye, the right and left eyes have significantly different qualities of vision, so that the visual images produced by one eye are weak or distorted compared with the images produced by the other eye. Because the weak eye sends poorly focused images to the brain, the brain learns to depend on the stronger eye for its visual information. If this situation is not corrected, the brain eventually chooses to accept images from the stronger eye alone and ignores images from the weak one. In other words, the weak eye doesn’t learn to see.
The brain’s choice usually is made early in childhood when the brain’s visual pathways are still developing. This critical period begins at birth and probably ends sometime between the ages of 6 and 9. If lazy eye is not diagnosed and treated within this critical period, the brain may choose to ignore the weak eye permanently, causing a lifelong loss of vision on that side.
Lazy eye has several underlying causes, including:
- Crossed eyes (strabismus) — Children with crossed eyes often have double vision (diplopia) when they use both eyes at the same time. To prevent this, a child may consistently focus with one eye more than the other.
- Problems related to severe nearsightedness or farsightedness — When a child suffers from nearsightedness, in which distant objects look blurry, or farsightedness, in which nearby objects look blurry, the problem may not affect both eyes equally. For example, one eye may have perfectly normal vision, while the other is blurred; or both eyes may be blurred, but one is worse than the other. In either situation, the brain gradually will learn to ignore visual images from the eye that has poorer vision.
- Structural problems — Sometimes, a growing child’s vision is blocked by a structural problem of the eye or eyelid. Common examples include a congenital cataract (an opaque area that develops inside the lens of the eye before birth), a scar on the cornea or congenital ptosis (a drooping eyelid that is present at birth).
Currently in the United States, lazy eye affects an estimated 1 percent to 2 percent of the population. In rare cases, the problem is bilateral. In other words, the brain ignores both eyes because both are producing blurry images. This can produce permanent blindness in both eyes.
Lazy eye usually does not cause any symptoms. Sometimes parents suspect vision problems because a child squints, looks cross-eyed, or holds his or her head in awkward positions to see things. In many cases, the problem is detected by a routine vision-screening exam, either before or after a child starts school. Results of the screening exam will show that the child’s vision is much better in one eye than the other.
If the results of a screening exam suggest that your child has lazy eye, your primary-care doctor will refer you to an ophthalmologist, a physician who specializes in eye disorders. The ophthalmologist will confirm the diagnosis by performing a thorough eye examination, including separate tests of visual acuity (how well the eye sees) for each eye. As part of the diagnostic process, the ophthalmologist also will inspect your child’s eyes for structural abnormalities, check eye alignment to rule out crossed eyes, and assess movement of the eye muscles.
Lazy eye begins early in childhood and should be treated as soon as possible. Without proper treatment, the condition can produce profound loss of vision that lasts a lifetime.
To prevent permanent loss of vision in a weak eye, the underlying causes of lazy eye must be identified and treated as early as possible during childhood. Make sure your newborn receives a thorough eye exam within the first few days after delivery. This exam will rule out any obvious abnormalities involving the structure of your child’s eyes or eyelids. As your child grows, your doctor should check your child’s eyes as a part of every “well-child” visit. Your child also should have more formal visual-acuity testing, using pictures, letters or numbers, beginning no later than age 3, and at regular intervals thereafter.
Treatment of lazy eye has two goals:
- Produce a clear visual image in both eyes — Depending on the cause of your child’s lazy eye, this can be done with prescription eyeglasses to correct severe focusing problems; surgery and eye muscle exercises to realign crossed eyes; and surgery to correct any structural problem of the eye or eyelid that is blocking normal vision.
- Strengthen the weak eye — Several treatment options are available. In the most common approach, your child will wear a patch over the stronger eye for a certain number of hours each day. In many cases, your doctor first will recommend that the patch be worn for the entire day. This daily patching typically will continue for at least six months, and your child’s progress will be monitored with frequent eye exams. Once your child’s vision has normalized, occasional patching may be necessary until about age 10. As an alternative to patching, some doctors use an opaque contact lens. Others prescribe atropine eye drops (Atropine-Care and other brand names) to blur vision temporarily in the stronger eye.
When To Call A Professional
Make an appointment to see your pediatrician or ophthalmologist if your child:
- Appears cross-eyed
- Holds his or her head in an abnormal position while looking at something in the distance — tilts the chin up, looks down his or her nose, faces one eye forward or uses some other unusual posture to compensate for a vision problem
- Persistently squints — Squinting temporarily corrects blurred vision, so it can be a sign that your child’s eyes are not focusing properly.
- Consistently covers or closes one eye — Crossed eyes cannot work together without causing double vision, so if your child has crossed eyes he or she may eliminate the problem by blocking the vision in one eye.
Also, make an appointment if your child’s school notifies you that your child’s vision exam was abnormal.
The prognosis is good if the condition is treated early. Proper treatment during early childhood usually produces near-normal vision in the affected eye.
Traditionally, doctors have offered a poor prognosis when older patients are treated for lazy eye. Many believed that the cut-off age for successful therapy was age 12, or even sooner, according to some specialists. However, new evidence suggests that the prognosis for lazy eye may be improved with prompt, appropriate treatment regardless of the age at which it is diagnosed. There have been well-documented cases in which teen-agers and even middle-aged adults with lazy eye have recovered vision in the weak eye.
by Sharon M. Smith, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.