Strabismus, Misaligned Eyes

Esotropia

Esotropia is in-turning or crossing of one or both eyes. It can occur at any age, be intermittent or constant, and be present with only distance or near fixation, or both. The crossing may be predominantly with one eye or alternate between both eyes.

Esotropia can be a normal phenomenon in infants up to approximately four months of age. Usually, the crossing is of a small magnitude and intermittent and improves steadily with time. Any crossing noted after four months, or a large, constant crossing noted before then, needs to be evaluated by a pediatric ophthalmologist.

There are many different types of esotropia, and treatment varies accordingly. Esotropia may be classified by the age of onset (infantile vs acquired), whether it responds to glasses (accommodative vs non-accomodative), or whether it is secondary to an underlying systemic process (e.g. hyperthyroidism, neurologic conditions such as cerebral palsy or hydrocephalus). Other isolated ocular conditions can also result in esotropia, such as poor vision in one eye.

The result of esotropia is potential loss of depth perception (3-D vision), and in children, loss of vision in one eye (amblyopia). Other problems that may occur are double vision, eye strain, and an undesirable cosmetic appearance.

The primary principles of treatment are to improve vision and re-align the eyes. The most common modalities used include glasses (possibly with a bifocal), patching if amblyopia is present, and eye muscle surgery. Your doctor will discuss with you which one or more of these various options are right for your child.

Accomodative Esotropia

Accommodative esotropia, or refractive esotropia, is one of the most common forms of esotropia (crossed eye), which is a type of strabismus, or eye misalignment. It refers to eye crossing that is caused by the focusing efforts of the eyes as they try to see clearly. Patients with refractive esotropia are typically farsighted (hyperopic). This means that the eyes must work harder to see clearly, particularly when the object of regard is up close. This focusing effort is called accommodation. The closer an object is to the eye, the greater the amount of accommodation that is required. A side effect of the accommodative effort can be excess convergence or crossing of the eyes.

If a child’s eyes cross at an early age, then vision will not develop normally. Vision can be permanently reduced in one eye if it is not “used” properly during childhood (this is called amblyopia), and fine depth perception may never develop. If crossing of the eyes is diagnosed and treated early, then vision development can proceed normally. Crossing of the eyes is never normal (except for occasional crossing in the first three months of life), and any child suspected of having crossed eyes should be examined by a pediatric ophthalmologist.

Initial treatment for accommodative esotropia usually involves the prescription of eyeglasses or contact lenses to correct the patient’s refractive error (hyperopia). By letting the eyeglasses do the work, the eyes can relax their focusing or accommodative effort. In turn, this will reduce the convergence or crossing stimulus and the eyes will straighten as they relax. Glasses or contacts which are used to treat accommodative esotropia should be worn full time.

Even after a child has been successfully wearing glasses to treat accommodative esotropia, it is still normal for the eyes to continue crossing without the glasses. In fact, the crossing may be even more noticeable than it was before the child started wearing glasses. The important thing is whether the eyes are straight and controlled with the glasses on. If the eyes are not straight with glasses on, then vision with two eyes will not develop normally. Your pediatric ophthalmologist is the best person to judge this and will give you feedback at follow-up examinations. These follow-up examinations are important not only to monitor the eye crossing, but also to check for associated problems such as amblyopia (decreased vision in one or both eyes which is common in this type of strabismus).

In some cases, children will have particularly excessive amounts of eye crossing (esotropia) at near, such as while reading. This may occur even when wearing the correct glasses to correct their farsightedness (hyperopia) and they may have perfectly straight eyes when looking at distant objects. These children may benefit from making the lower, reading area of the eyeglasses “extra strong” in the form of a bifocal lens.

Children can outgrow accommodative esotropia. This usually happens during the grade school and adolescent years as a child becomes less farsighted. It is difficult to predict early in childhood whether or not any given child will outgrow their need for glasses.

Exotropia

Exotropia is the condition, sometimes called wall-eyed, where an eye will drift outward or to the side.

The outward drifting of exotropia can be seen in the first few months of life. If it is only present some of the time or intermittently it will often go away by the time the child reaches 1 year of age. If the divergent drifting continues past a year of age, it will not resolve and be present the rest of the child’s life. If the drift seen in the first year of life is constant, where one or the other eye is always looking to the side and not straight, this is true infantile exotropia and it will not go away and usually requires eye muscle surgery to correct.

The most frequently seen type of exotropia or outward drifting of the eyes is called intermittent exotropia. Intermittent exotropia usually starts to be seen after the age of 2 to 3 years but can be seen at any age. Parents will note that the drifting is seen more often when the child is tired or sick. People with intermittent exotropia will often be noted to close one eye, especially when they are outside in the sunlight.

The treatment of intermittent exotropia depends on how often the drifting or misalignment is seen. If the eyes are straight most of the time and the vision is developing equal in the two eyes, then the patient is just observed with an examination every few months. If the drifting is seen a significant part of the time and especially every day, then part time patching may be prescribed for a few weeks or months to see if this will help the child control or reduce the frequency of the drifting . Patching is also done if the vision seems to be developing better in one eye than the other and amblyopia or poor vision in one eye is present.

If the eyes are seen to be misaligned a significant part of the time every day, especially after some patching therapy, then surgery is indicated. The goal is to have the two eyes straight and looking at the same object so that the child can have binocular or 3-D vision. Not only are straight eyes necessary for binocular vision to be seen, but straight eyes are also required for the visual part of the brain to be stimulated to develop the ability to have binocular vision.

Exercises can be helpful in a certain kind of exotropia called convergence insufficiency. This type of exotropia is mostly seen in older children and adults, where the divergent drifting is present when the patient is looking up close such as when reading. Exercises do not have any lasting treatment effect on the other, most common types of intermittent exotropia.

Vertical Misalignment or Strabismus

Hypertropia refers to an eye that is higher than its fellow eye.  Hypotropia is the opposite, referring to one eye being lower than its fellow eye.  The causes of vertical strabismus are numerous, and include nerve weaknesses (such as fourth nerve palsy), tight muscles (such as Graves’ disease or Brown’s syndrome), and traumatic cases (orbital fractures with muscle entrapment).  In addition, there is a special type of vertical strabismus in which one or both eyes tend to float upwards, called a dissociated vertical deviation.

Some forms of vertical strabismus are present since birth and others are acquired.  They may be isolated or secondary to a neurologic or systemic condition and may require further investigations such as blood tests or neuro-imaging.

Vertical misalignments may result in double vision, a face turn or chin-up/down position, difficulty focusing, eye strain, and an undesirable cosmetic appearance.  If an eye is low or hypotropic, sometimes the upper eyelid can rest in a lower position as well, causing the appearance of a droopy eye.

Treatment depends on the cause and extent of the misalignment.  Not all cases require treatment right away but may simply need to be monitored.  Some younger patients will require patching if there lazy vision in one eye, or amblyopia.  Others may require surgery to re-establish the normal alignment of the eyes.  If the strabismus is small enough, prism glasses may help to eliminate double vision.

Dissociated vertical deviation (DVD) is often associated with a prior history of strabismus or poor vision in one eye.  It usually does not develop until 2-3 years of age, though can occur at any time.  In some individuals, it is present only when they are tired, but in others, it occurs more frequently throughout the day.  DVD can be minimized with glasses or patching, but may require surgical treatment also.

Children’s Eye Care provides this information for general educational purposes only. It should not be construed as personal medical advice. Information published on this website is not intended to replace, supplant, or augment a consultation with an eye care professional. Children’s Eye Care disclaims any and all liability for injury or other damages that could result from use of the information obtained from this site.