Accommodative Esotropia

This article is reprinted with the permission of Dr. Kenneth W. Wright, Medical Director of the Wright Foundation for Pediatric Ophthalmology & Strabismus. Check out his website for information on over 20 pediatric eye disease and conditions.
Accommodative Esotropia

Normal Binocular Vision

Normally, both eyes are aligned on the same visual target and the images from each eye are merged in the brain to form a single three-dimensional image, or binocular vision. The brain’s process of merging or “fusing” images from each eye into one image is called binocular fusion. The perception of three-dimensional depth is called stereoscopic vision. Stereoscopic vision is the highest level of binocular vision and requires intricate processing of information from both eyes. Binocular vision develops during early infancy, and proper alignment during this time is necessary for normal binocular development to occur.

Accommodative Esotropia

Esotropia means one eye is turned in towards the nose, or crossed eyes. Patients with esotropia have one eye aligned on the visual target, but the other eye is turned in towards the nose. When the eyes are crossed only one eye is aligned with the target and the child is forced to use only one eye for vision. Accommodative esotropia is a type of esotropia caused by significant farsightedness (hypermetropia). Most think that farsighted people can see well only in the distance. In children, this is not true. Children have the ability to focus great amounts, so most children can see well for distance and near even without glasses. Focusing (medically termed accommodation) is the process of increasing the lens power of the eye to see clearly. Linked to focusing is the natural reflex of convergence (eyes move in). As one focuses on an approaching near object, the eyes move in to stay on target. This process of focusing and convergence used for near vision is termed the near reflex. Accommodative esotropia occurs because the farsighted child has to over focus to see clearly. When eyes over focus, the natural reflex is for the eyes to cross. You can experience this by trying to see the tip of your nose. When you look at the tip of your nose you have to over focus and consequently your eyes cross. Since more focusing is needed to see near objects, the crossing tends to be greater when looking at close objects.

Accommodative Esotropia eye turns
Right eye turns in because patient is farsighted and not wearing glasses.
Accommodative Esotropia corrected
Eyes are in excellent alignment after prescribing glasses.
 
 
 
 
 
 
 
 
The onset of accommodative esotropia is most commonly seen between the ages of 2 and 4; however, even infants can have crossed eyes. This situation is usually first noticed when the child is tired, sick, or looking at an object very near to their face. Some children cross when they are tired and this is because they cannot sustain the effort to keep the eyes straight. The crossing is usually intermittent at first, but can quickly become constant. There may be a parent or a close relative with the same problem; however, in many cases there is no family history of crossed eyes.

During the examination, three important determinations are necessary. The first determination is to make sure the vision is normal in each eye. This is done by assessing the visual behavior of the preverbal child, or simply having the verbal child read the eye chart. Secondly, the amount of crossing is evaluated. This is measured using prisms while the child is viewing an object. Thirdly, the need for glasses is measured, and this requires drops to dilate the pupil and relax the child’s focusing. These drops take approximately 20 to 30 minutes to work and will blur vision for 1 to 3 hours, but the pupil may stay large for much longer. After the eyes have been dilated, the eyeglass prescription is calculated using a special light (retinoscope) along with lenses. Determining the proper lens power in young children is difficult and may require repeat exams and changes in the eyeglass lenses.

Effects of Esotropia on Visual Development

Esotropia occurring in young children and infants results in the immature brain turning off the information from the deviated eye. This mechanism of turning off visual areas of the brain connected to the deviated eye is called “suppression.” Thus, patients with esotropia use one eye at a time (monocular vision) and do not have binocular fusion or stereoscopic vision. Suppression disrupts normal binocular visual development and if not treated early, causes permanent loss of binocular vision and stereoscopic vision. Early treatment of esotropia is critical to stimulate binocular development.

How Do Patients with Esotropia See?

If the esotropia is acquired in late childhood (after 7 to 9 years of age) or in adulthood, it will cause double vision. Esotropia occurring in infants and young children, however, does not cause double vision, as the young, immature brain has the ability to suppress the information from the deviated eye. The child uses one eye at a time to see and avoids double vision. The fact that the eyes are crossed disrupts normal binocular visual development and often causes permanent loss of binocular vision and stereoscopic vision. Early treatment of esotropia is critical in order to stimulate binocular development.

Treatment of Accommodative Esotropia

Glasses

The goal of treatment is to align the eyes, stimulating them to work together to establish binocular vision and stereoscopic vision. Children and infants who are significantly farsighted are best treated with glasses. If the glasses align the eyes, then surgery is not necessary, and the treatment is to continue with the glasses. The full, hypermetropic (farsighted) prescription is usually given via eyeglasses, and most parents are surprised at how well these children adjust to the glasses. When properly worn, most children adapt to the glasses like “fish to water.” The glasses not only straighten the eyes, but also relax the child’s vision, as they no longer have to over focus. In patients with accommodative esotropia, glasses must be worn full-time. Older children over 4 to 5 years may have blurred distance vision when they first put on their glasses. This is because they had a strong habit of over-focusing and continue to do so even when wearing the glasses. Over several days, most children will relax their over-focusing and enjoy the comfort the glasses afford. In those children who do not adapt to the glasses, drops can be used to relax focusing, or a reduced prescription power can be given. In most cases, however, the best treatment is to give the full power. The eyes usually straighten within a few days to a few weeks after wearing the glasses. If the eyes are still crossing with the glasses and the child is not using the eyes together after several weeks, then eye muscle surgery is usually required. Occasionally, an initial response to glasses is that the eyes “break down” and cross for distance and near. In this situation, surgery in addition to the glasses may be required.

Bifocal Glasses

In certain children, glasses will align the eyes for distance viewing, but the eyes will still cross for near work. These patients can be helped with bifocal glasses. A bifocal is a small powerful lens placed in the lower part of the eyeglass lens. This more powerful lens will further relax near focusing to straighten the eyes for near work. Chin-up posturing for near work indicates that the child is using the bifocals correctly and is viewing through the bifocal lens for near work.

Amblyopia

Some children with crossed eyes have a strong fixation preference for one eye (dominant eye) and constantly have one eye turned in. Constant use of only one eye can lead to vision loss of the deviated, or non-dominant, eye. Poor vision occurs as visual areas in the brain connect with the dominant eye and are then subsequently suppressed. If left untreated, the deviated eye will progressively lose vision over time. This poor vision caused by brain suppression is called amblyopia. Amblyopia occurs only in young children when the visual areas are immature and still developing. Children who have a difference in the strength of the glasses in one eye as compared to the other have an increased risk of developing amblyopia in the more farsighted eye. Approximately 20 to 40% of patients with esotropia will also have amblyopia of the non-preferred eye.

Patching

If amblyopia is present, patching of the good eye is indicated to promote visual stimulation of the amblyopic eye and improve vision. Patching does not straighten the eyes and is not indicated if vision is equal. Another way to promote stimulation of the amblyopic eye is to blur the vision of the “good eye.” This can be done by placing a blurring lens over the good eye, or by administering drops to blur the good eye. In most cases, patching the good eye with an adhesive patch is the most practical treatment. Patching is continued until vision improves in the weaker eye, usually taking a few weeks to several months. In the vast majority of patients, vision can be improved if the parents and child are compliant with the treatment.

10/8/15

Dr. Kenneth WrightKenneth W. Wright, MD
Medical Director, Wright Foundation for Pediatric Ophthalmology & Strabismus
Clinical Professor of Ophthalmology, USC Keck School of Medicine

Common Pediatric Eye Diseases

8/21/14

In the third of this series, Buddy Russell, from the Emory University Eye Center, provides a great overview of common pediatric eye diseases.

Some Conditions Frequently Seen in Pediatrics

A basic understanding of some of the conditions that may be present in pediatric patients is important to not only know what they are but also understand well enough to explain to the parent or caregiver. The following is intended to be an overview of some of those conditions and not a complete explanation.Girl with eye chart-common pediatric eye diseases

  1. Nystagmus – Nystagmus is a vision condition in which the eyes make repetitive, uncontrolled movements, often resulting in reduced vision. These involuntary eye movements can occur from side to side, up and down, or in a circular pattern. As a result, both eyes are unable to hold steady on objects being viewed. Unusual head positions and head nodding in an attempt to compensate for the condition may accompany nystagmus. Most individuals with nystagmus can reduce the severity of their uncontrolled eye movements and improve vision by positioning their eyes to look to one side. This is called the “null point” where the least amount of nystagmus is evident. To accomplish this they may need to adopt a specific head posture to make the best use of their vision. The direction of nystagmus is defined by the direction of its quick phase (e.g. a right-beating nystagmus is characterized by a rightward-moving quick phase, and a left-beating nystagmus by a leftward-moving quick phase). The oscillations may occur in the vertical, horizontal or torsional planes, or in any combination. The resulting nystagmus is often named as a gross description of the movement, e.g. downbeat nystagmus, upbeat nystagmus, seesaw nystagmus, periodic alternating nystagmus. Having nystagmus affects both vision and self-concept. Most people with nystagmus have some sort of vision limitations because the eyes continually sweep over what they are viewing, making it impossible to obtain a clear image. If a refractive error is found, contact lenses may be the most effective way of obtaining best-corrected vision.
  2. Strabismus – Strabismus is any misalignment of the eyes. It is estimated that 4% of the U.S. population has strabismus. Strabismus is most commonly described by the direction of the eye misalignment. Common types of strabismus are esotropia (turn in), exotropia (turn out), hypotropia (turn down), and hypertropia (turn up). Eye misalignment can cause amblyopia in children. When the eyes are oriented in different directions, the brain receives two different visual images. The brain will ignore the image from the misaligned eye to avoid double vision, resulting in poor vision development of that eye. Also, an eye that sees poorly tends to be misaligned. The goal of strabismus treatment is to improve eye alignment, which allows for better work together (binocular vision). Treatment may involve eyeglasses, contact lenses, eye exercises, prism, and / or eye muscle surgery.
  3. Amblyopia – Amblyopia, sometimes called a “lazy eye,” occurs when one or both eyes do not develop normal vision during early childhood. Babies are not born with 20/20 vision in each eye but must develop it between birth and 6-9 years of age by using each eye regularly with an identical focused image falling on the retina of each eye. If this does not occur in one or both eyes, vision will not develop properly. Instead, vision will be reduced and the affected eye(s) are said to be amblyopic. This common condition, affecting up to 4% of all children, should be diagnosed and treated during infancy or early childhood to obtain optimum three-dimensional vision and to prevent permanent vision loss. What causes amblyopia?
      • Misaligned eyes (strabismus)
        Misaligned eyes are the most common cause of amblyopia. When both eyes are not aimed in exactly the same direction, the developing brain “turns off” the image from the misaligned eye to avoid double vision and the child uses only the better eye — the dominant eye. If this persists for a period even as short as a few weeks, the eye will not connect properly to the visual cortex of the brain and amblyopia will result.
      • Unequal refractive error (anisometropia)
        Unequal refractive error is an eye condition in which each eye has a different refractive error and therefore both eyes cannot be in focus at the same time. Amblyopia occurs when one eye (usually the eye with the greater refractive error) is out of focus because it is more nearsighted, farsighted or astigmatic than the other. Again, the brain “turns off” the image from the less focused eye and this eye will not develop normal vision. Because the eyes often look normal, this can be the most difficult type of amblyopia to detect and requires careful vision screening of acuity measurements at an early age. Treatment with glasses or contact lenses to correct the refractive error of both eyes, sometimes with part-time patching of the better seeing eye, is necessary in early childhood to correct the problem.
      • Obstruction of or cloudiness (deprivation)
        Obstruction of or cloudiness in the normally clear eye tissues may also lead to amblyopia. Any disorder that prevents a clear image from being focused can block the formation of a clear image on the retina and lead to the development of amblyopia in a child. This often results in the most severe form of amblyopia. Examples of disorders that can interfere with getting a clear image on the retina are a cataract or cloudy lens inside the eye, a cloudy and or irregular shaped cornea, or a droopy upper eyelid (ptosis) or eyelid tumor.It is not easy to recognize amblyopia. A child may not be aware of having one normal eye and one with reduced vision. Unless the child has a misaligned eye or other obvious external abnormality, there is often no way for parents to tell that something is wrong. In addition, it is difficult to measure vision in very young children at an age in which treatment is most effective.To treat amblyopia, a child and their caregiver must be encouraged to use the weaker eye. This is usually accomplished by patching the stronger eye. This covering of the stronger eye with an adhesive patch, an cclude contact lens or temporary surgery often proves to be a frustrating and difficult therapy. Patching will often continue for weeks, months, or even years in order to restore normal or near normal vision and maintain the improvement in the amblyopic eye. Occasionally, blurring the vision in the good eye with eye drops or lenses to force the child to use the amblyopic eye treats amblyopia. In some cases, cataract surgery or glaucoma surgery might be necessary to treat form deprivation amblyopia. Patching may be required after surgery to improve vision, and glasses or contact lenses may be required to restore appropriate focusing.Surprising results from a nationwide clinical trial in 2005 show that many children age seven through 17 with amblyopia may benefit from treatments that are more commonly used on younger children.
        Treatment improved the vision of many of the 507 older children with amblyopia studied at 49 eye centers. Previously, eye care professionals often thought that treating amblyopia in older children would be of little benefit. The study results, funded by the National Eye Institute (NEI), appear in the April issue of Archives of Ophthalmology.
  4. Congenital Cataract – A congenital cataract, or clouding of the crystalline lens is present in 2-3 per 10,000 live births of children. The presence of a visually significant cataract in a child is considered an urgent disorder. The resultant form deprivation of vision requires immediate surgery to remove the obstruction, prompt optical correction and amblyopia therapy in unilateral cases. Until the 1970s, it was generally believed that there was no means of restoring the vision in an eye with a unilateral congenital cataract. However, subsequent studies demonstrated that excellent visual results could be obtained with early surgical treatment coupled with optical correction with a contact lens and patching therapy of the fellow eye. However, treatment results continue to be poor in some infants with unilateral congenital cataracts due to a delay in treatment or poor compliance with contact lens wear or patching therapy of the fellow eye. The Infant Aphakia Treatment Study (IATS) was designed to compare the visual outcomes in children 1 to 6 months of age with a unilateral congenital cataract randomized to optical aphakic correction with contact lenses or an intraocular lens (IOL). Children randomized to IOL treatment had their residual refractive error corrected with spectacles. Children randomized to no IOL had their aphakia treated with a contact lens. In previous publications we have shown that the visual results are comparable for these two treatments at 1 year of age, but significantly more of the infants randomized to IOL implantation required additional intraocular surgeries.
  5. Accommodative Esotropia – Accommodative esotropia refers to a crossing of the eyes caused by farsightedness. Accommodative esotropia is a type of strabismus. Children who are farsighted easily and automatically focus on objects at distance and near through accommodation. As a result, a child who is farsighted usually does not have blurred vision. However, in some children who are farsighted, this accommodative effort is associated with a reflex crossing of the eyes. Accommodative esotropia can begin anywhere from 4 months to 6 years of age. The usual age of onset is between 2 and 3 years of age.Full-time use of the appropriate hyperopic glasses prescription or contact lenses will often control the esotropia. When wearing the correction, the child will not need to accommodate and hence the associated eye-crossing reflex will disappear. However, after removing the prescribed correction, the crossing will reappear, perhaps even more than before the child began wearing the correction. Sometimes the correction will only cause the crossing to disappear when the child views a distant object. However, when gazing at near objects, crossing may persist despite the use of the correction. In these circumstances, a bifocal lens is often prescribed to permit the child to have straight eyes at all viewing distances. One potential advantage of contact lenses compared to spectacles when correcting hyperopic powers is the decrease in accommodative demand. The increased effort to converge the eyes with spectacles requires one to over come the resultant base out prism when viewing a near object.

 

Buddy Russell - pediatric contact lensesBuddy Russell, FCLSA, COMT
Associate, Specialty Contact Lens Service
Emory University Eye Center