or Crossed Eyes
Strabismus is a misalignment of the eyes. It includes in-turned eyes, called Esotropia, out-turned eyes, called Exotropia and other eye muscle disorders. Because strabismus is treated so often by pediatric ophthalmologists, many pediatric ophthalmologists including Dr. Furlan also treat adults with strabismus. When strabismus occurs in an adult for the first time, it can lead to double vision, or diplopia. Sometimes children are successfully treated for strabismus only to redevelop strabismus later in life. This may be secondary to the inability of a person to use both eyes together, called binocular vision, or other unknown causes. People who have one eye that does not see well when fully corrected with glasses, called Amblyopia, may develop strabismus with time. Most often, the poorer seeing eye drifts outward. In adults who suddenly develop strabismus we must be concerned about vascular insults to a nerve that controls the movement of one or more eye muscles. This is most often seen in adults with a history of diabetes or high blood pressure.
Types of Strabismus
This form of esotropia, or crossed eyes is also known as infantile esotropia. It usually develops before the child is six months old and is characterized by a large eye turn. Unlike Accommodative esotropia, glasses will not correct the eye turn. Amblyopia is common in children with congenital esotropia and should be treated early. Once the child’s vision is equalized, treatment can be recommended for the eye turn. Eye muscle surgery is the treatment for patients with infantile esotropia. The surgery is usually performed on both eyes, although it may also be done on one eye. The goal of treatment in infantile esotropia is to straighten the eyes so that the child can learn to use them together and develop “binocular vision. The ability to use both eyes together will help to keep them aligned. Studies have shown that early surgical alignment improves the chances of developing binocular vision. Therefore, many pediatric ophthalmologists recommend surgery when the angle of crossing is stable and the vision in each eye is good.
Many children with congenital esotropia develop other eye muscle disorders. This occurs even when their eyes have been successfully made straight with surgery. Recurrent esotropia following surgery for congenital esotropia occurs frequently and often can be treated with glasses and not require further surgery. This is a different type of esotropia than the original infantile crossing. Many patients develop vertical strabismus which can occur months to years after the original surgery. Treatment may require further surgery.
As you can see, infantile esotropia is a complex disorder. Although surgery is required to treat it, it is only the start of the process. These children must be carefully followed for other problems during the visually immature period of their life.
Most children are farsighted. In children, this means that they have the potential to see well at both distance and at near. However, they have to “focus” or accommodate to do so. This is usually not a problem as children have a large “focusing” ability. A reflex exists that makes the eyes want to cross when we try to focus. This normal reflex allows our eyes to maintain alignment when we focus to read material close to us, i.e. our eyes must both turn in a little to work together at near. However, if a child is very farsighted, their eyes will cross when they focus to see well. In this case, they must make a subconscious decision to see well or cross their eyes. The treatment for this type of strabismus is eyeglasses. The child is given glasses to correct their farsightedness. Because they no longer have to focus to see well, they will no longer cross their eyes. Amblyopia is very common in this setting. If Amblyopia is present, in addition to eyeglasses, treatment for the Amblyopia may be required as well. Many children lose some of their farsightedness as they get older and will outgrow their glasses. This is dependent on the initial level of farsightedness and the growth curve of the eye. It is very individualized and therefore it is hard to predict who will outgrow their need for glasses.
Intermittent Exotropia is a type of strabismus where one, or both, eyes turn outward intermittently. It usually begins in the 2-3 year age group. It is first seen infrequently when the child is sick or tired and only when they are looking into the distance. For this reason, in its early stages, it may not be seen in a pediatrician’s office, when the child is examined only up close and is well rested. It generally progresses in frequency and duration with the eye turn occurring earlier in the day and the deviating eye staying out for longer periods of time. Often, the child closes one eye to eliminate the double vision that it may cause. This is especially noticeable in sunlight. As the disorder progresses, the eyes will also start to turn out when looking at close objects as well, i.e. reading. If not treated, the eye may turn out constantly and binocular vision could be lost. Amblyopia can occur in intermittent exotropia but is uncommon.