Brian G. Mohney, M.D., a pediatric ophthalmologist at Mayo Clinic Children's Center in Rochester, Minnesota, answers questions about Mayo Clinic's approach to treating children with strabismus.
How common is strabismus?
Strabismus is relatively common. Between 2 and 4 percent of kids have esotropia, and 1 to 1.5 percent have exotropia. Almost 1 out of 20 kids has strabismus.
When should children be referred to a pediatric ophthalmologist?
Uncorrected strabismus can have far-reaching effects, including loss of vision and stereoacuity, and adverse effects on psychosocial development and gainful employment.
Esotropia, in general, is most urgent in terms of requiring immediate attention to manage any vision loss or adverse effects on stereoacuity.
Exotropia is generally a more intermittent and slowly progressive disorder, allowing for observation over time.
However, a child with any form of strabismus should be seen as soon as possible by an eye specialist to rule out vision loss or a visually dangerous or unexpected cause of the deviation.
Sometimes esotropia isn't present from birth. A child's eyes might be fine up to age 3 or 4 years but then suddenly start to cross. If we catch that crossing early and straighten the eyes with surgery within three to six months, the 3D vision starts to work again. If a child lacks the potential for developing normal 3D vision, the eyes are prone to drifting again. Amblyopia or poor vision due to strabismus — esotropia or exotropia — that isn't corrected before age 9 will result in a permanent loss of vision.
How can you determine when esotropia began in an infant or child?
Oftentimes the parents aren't aware of when it started. They might think it's been there months when it's actually been there years, or vice versa. We often ask parents to bring in pictures of the child so that we can determine the onset.
How is strabismus treated at Mayo Clinic Children's Center?
For 99 percent of our patients, an office visit alone is enough for us to diagnose their eye conditions and provide a treatment plan. Each child undergoes a careful history and clinical evaluation.
Exotropia, depending on the severity, can be simply observed or may require treatment such as glasses, part-time patching or even eye muscle surgery. Children with esotropia are generally treated at the time of their first office examination with glasses and patching for those who have amblyopia. Esotropia that does not respond to glasses will require surgery, usually within several months, to preserve stereopsis.
If we treat the child with glasses, we have a follow-up visit about six weeks afterward. We can usually determine by then if the glasses will be sufficient or if the child will need surgery. Seven out of 8 kids will successfully respond with one surgery. In more-complicated cases, 2 out of 3 will straighten with one surgery; the remaining third will need a second surgery and sometimes more.
What signs and symptoms of other eye disorders should physicians look for when considering referrals?
If one of a child's pupils is a different color than the other — either lighter or darker — the child might have a cataract or retinoblastoma. Such children should be referred for evaluation within a week.
About 11 percent of newborns have a blocked tear duct. The vast majority of these blockages will resolve on their own. For those that don't, we used to wait until the child was a year old before treatment. But we recently studied 2,000 of these kids and found that the rate of spontaneous resolution drops after age 9 months. We're now advocating treatment at age 8 or 9 months since there's no real reason to wait.