Cross-Eyed: What It Means and When to Worry

What being cross-eyed means

To see a single, clear image, both eyes must point at the same spot. Six muscles around each eye, controlled by three cranial nerves, move the eyes together with great precision. When the balance fails, one eye turns. Turning in is esotropia (cross-eyed). Turning out is exotropia (wall-eyed). Turning up or down is hypertropia or hypotropia. All are types of strabismus.

The crossing may be:

• constant or intermittent, for example only when tired or ill
• in one eye always, or alternating between the eyes
• present only when looking near or only when looking far

Cross-eyed babies: what is normal

Newborns' eyes often wander or cross briefly because the visual system is still developing. By about 4 months, the eyes should be straight most of the time. See a doctor if crossing is constant, or continues after 4 months.

Many babies look cross-eyed but are not. A wide, flat nose bridge and skin folds at the inner corners of the eyes hide some of the white of the eye, making the eyes look turned in. This is called pseudostrabismus. A doctor can check with a light reflection test: if the light reflects from the same spot in both pupils, the eyes are straight. It disappears as the face grows.

Causes in children

Accommodative esotropia

The most common type in children, usually starting between ages 2 and 4. Farsighted children (hyperopia) have to focus hard to see clearly. That focusing effort is linked with a reflex that turns the eyes inward. Glasses that correct the farsightedness often straighten the eyes completely.

Infantile (congenital) esotropia

A large, constant inward turn that appears in the first 6 months. Glasses do not usually fix it, and eye muscle surgery is often needed, typically in the first 1 to 2 years of life.

Other causes in children

• Poor vision in one eye, for example from cataract or a retinal problem, letting the eye drift. Rarely this is retinoblastoma, an eye cancer of young children that can show as a white pupil in photos.
• Neurological conditions, including cerebral palsy, Down syndrome, hydrocephalus and prematurity.
• Sixth nerve palsy after viral illness or, rarely, from raised pressure in the head.
• Family history: strabismus runs in families.

Causes of sudden crossed eyes in adults

In adults, a new inward turn usually causes double vision, because the brain has already learned to use both eyes together. Causes include:

• Sixth cranial nerve palsy: the eye cannot turn outward, so it drifts inward. Common causes are diabetes and high blood pressure affecting the nerve's blood supply. It often recovers within 3 to 6 months. Other causes include raised brain pressure, tumors, infections and head injury.
• Stroke affecting the brainstem.
• Thyroid eye disease: swollen eye muscles, often with bulging eyes, in people with Graves' disease.
• Myasthenia gravis: double vision and droopy eyelids that worsen through the day.
• Decompensated childhood strabismus: a childhood turn that was controlled for years can break down with age.
• Divergence insufficiency: in older adults, double vision only at distance, for example when driving.

Why crossed eyes in childhood need treatment

A young child's brain learns to ignore the image from the turned eye to avoid double vision. Over time that eye's vision fails to develop normally, causing amblyopia (lazy eye). Children also lose depth perception (3D vision). Amblyopia responds best to treatment before age 7 to 8. That is why early eye exams matter.

How it is diagnosed

An eye doctor (pediatric ophthalmologist or optometrist) will:

• check vision in each eye
• shine a light to compare reflections in both pupils
• perform a cover test, covering one eye at a time to see if the other moves to fix on a target
• measure the angle of turn with prisms
• check eye movements in all directions
• use eye drops to relax focusing and measure farsightedness accurately
• examine the inside of the eye

Adults with sudden crossing may need blood tests (glucose, thyroid function, myasthenia antibodies) and a brain MRI.

Treatment

• Glasses: correct farsightedness and often fully fix accommodative esotropia. Bifocals help children who cross more when looking near.
• Treating lazy eye: patching the stronger eye for some hours a day, or atropine drops to blur it, so the brain uses the weaker eye.
• Eye muscle surgery: loosens or tightens eye muscles to straighten the eyes. It is usually a day procedure.
• Prism lenses: in adults, prisms in glasses can join double images.
• Botulinum toxin injections: weaken an overacting muscle, used in some children and adults.
• Treating the cause: controlling diabetes, thyroid disease or myasthenia gravis.

Eye exercises alone do not correct esotropia, though specific exercises help some other problems, such as convergence insufficiency.

Frequently asked questions

Is it normal for a baby to be cross-eyed?

Brief, occasional crossing is normal in the first 3 to 4 months while vision develops. Constant crossing at any age, or crossing that continues after 4 months, needs an eye exam. Many babies only look cross-eyed because of a wide nose bridge, which a doctor can check.

Can being cross-eyed be fixed?

Yes, in most cases. Glasses fix many childhood cases caused by farsightedness. Others need eye muscle surgery. Lazy eye is treated with patching or drops. Adults can also have successful surgery or prism glasses at any age.

What causes sudden crossed eyes in an adult?

Common causes are a sixth nerve palsy from diabetes or high blood pressure, thyroid eye disease and myasthenia gravis. Stroke, head injury, tumors and raised pressure in the brain are less common but serious. Any sudden crossing with double vision needs prompt medical assessment.

Will my child outgrow crossed eyes?

True strabismus does not go away by itself after infancy, and waiting risks lazy eye. Pseudostrabismus, where the eyes only look crossed because of facial shape, does fade as the nose bridge develops. An eye exam tells the two apart.

Can looking cross-eyed on purpose damage your eyes?

No. Crossing your eyes on purpose briefly is harmless, and the eyes do not get stuck. The old warning is a myth. Strabismus comes from problems with eye focusing, muscles or nerves.