People who see second lines of print while they're working at their computer or see a car heading down their lane while they're driving may be suffering from strabismus, says Martha Howard, MD, a surgeon at the Yale Medicine Pediatric Ophthalmology & Strabismus Program. "It can be very frightening,” says Dr. Howard.

Strabismus is a condition in which the eyes are not aligned. It affects people’s ability to function and can even cause them to lose their independence. Fortunately, in many situations, it’s also very treatable. Yale Medicine offers an array of strabismus specialists who have a deep knowledge of conditions, treatment and procedures.

An adult with strabismus will experience double vision. The onset can be sudden or gradual, says Dr. Howard. The distortion may occur only sometimes or in specific circumstances.

Strabismus may be intermittent at first and then become constant. “It may only happen when you look in a particular direction,” says Dr. Howard. “For some people, it may occur only when they are looking to one side."

Many times, the appearance will be obvious to outside observers. “But sometimes only family members or friends will notice that the eyes are not aligned,” Dr. Howard says.

Children with strabismus don’t see the second image because their brains suppress it. Adult brains don’t have that ability.

An estimated 4 percent of adults in the United States will experience strabismus in their lifetimes. The condition can be further described by the direction of the misalignment.

• Esotropia, the eyes cross inward
• Exotropia, one or both of the eyes look outward
• Hypertropia, one eye moves up out of alignment
• Hypotropia, one eye moves down out of alignment

Some adults with strabismus were born with the condition. It may have first appeared when they were children, but corrected itself as they matured. The risk of adult strabismus increases with age, so the condition can reappear when a person gets older.

“Unfortunately, as we age, our eye muscles do not function as well as they did in the past,” says Dr. Howard. “We call that decompensation.”

Such other health problems as circulation or neurological problems can lead to strabismus. Mini-strokes, diabetes and hypertension can impair the circulation to the muscle or to the nerves that control them. “Damage to different cranial nerves can cause strabismus and double vision,” Dr. Howard says.

Strabismus can occur in people with a history of thyroid disease, even if the thyroid blood levels are in control. Tumors in the brain stem or in the eye can cause strabismus as can trauma.

Diagnosing strabismus starts with a simple test: covering and uncovering each eye.

“When either eye is covered, the double vision resolves,” says Dr. Howard. “That’s a distinguishing feature. If you cover an eye and the double vision remains, that’s not strabismus.”

The ophthalmologist will perform a complete exam and check a patient’s ocular motility, which describes how well the eyes move in various directions. The physician will also measure the misalignment with prisms. “From that information, we can identify what kind of strabismus the patient has,” she says.

“In some situations, the double vision will resolve with time,” says Dr. Howard.

In some patients, strabismus can be improved by placing prisms in their glasses. In other cases, one eye must be covered with an opaque film over one lens of a person's glasses to eliminate the second image.

Surgery can play a significant role in improving the symptoms of strabismus. When necessary, surgery is usually performed with local anesthesia in an outpatient setting. However, general anesthesia is possible as well.

“I often use adjustable sutures,” says Dr. Howard. This allows post-surgery fine-tuning with topical (eye drop) anesthetics.

We have the only program for strabismus in southern New England located within an academic medical center. We are experts in diagnosing and treating strabismus disorders in adults. Our ophthalmologists understand the available options to improve symptoms of strabismus, including surgery if prisms become unwieldy.