If you haven't read my post on the basics of strabismus yet, please make your way over there first before reading this post. That will give you some background information about strabismus, including an explanation of the medical terms you will see below.
What is congenital esotropia?
Congenital esotropia, also known as infantile esotropia, is when a child begins to have crossing in of the eyes at an early age, typically within the first 6 months of life. This type of strabismus is one of the most common we see in the pediatric ophthalmology world.
Congenital esotropia can be associated with the following:
- Children with congenital esotropia usually only have a small amount of farsightedness (generally less than +2.50 sphere of hyperopia for my fellow eye docs), meaning that glasses alone are not likely to fix the eye turning.
- Children with congenital esotropia often learn how to cross fixate. Since the eyes are turned inward, instead of working to uncross the eyes to see, a child may use each eye to look at the opposite side of the world. In other words, a child may use the right eye to look at the left side of his/her world since the eye is already turned towards the left side of the world and vice versa. Children who cross fixate often are using each eye for a similar amount of time and are less likely to develop amblyopia.
- Children with congenital esotropia tend to have a large amount of constant eye crossing.
- Many children with congenital esotropia also develop some kind of vertical misalignment of the eyes. During the eye exam we specifically look for any upward drifting of the eyes. The eye doctor will determine if the vertical misalignment is due to a phenomenon called dissociated vertical deviation or from an overacting inferior oblique muscle (more on the eye muscles below).
- Children with congenital esotropia may also have a small rhythmic horizontal shaking of the eyes when one eye is covered. This is called latent nystagmus.
Picture A shows an example of cross fixation: The right eye looks at left side of the world and the left eye looks at the right side of the world. Picture B shows an example of a vertical misalignment of the eyes that we commonly see with congenital esotropia. In this example, the right eye spontaneously drifts up without any associated movement in the other eye. This is an example of a dissociated vertical deviation of the right eye. Picture C shows an example of the right eye shaking horizontally when the left eye is covered. This is an example of latent nystagmus.
What causes congenital esotropia?
We don't really know. Some believe that the parts of the brain needed to use both eyes together did not develop fully, causing the eye misalignment. Others think it's really a problem with the tightness of the different eye muscles. It's complicated. We do know that it is associated with certain conditions such as prematurity.
Should I be worried about it?
Any child with constant crossing in of the eyes should have a formal eye evaluation to figure out the cause of the crossing. We need to rule out structural eye issues, brain issues, and to make sure there is not an unknown need for a glasses prescription that could be causing the crossing.
How do you treat it?
As I mentioned above, most kids with congenital esotropia do NOT have a high glasses prescription or amblyopia, so glasses and patching usually do not play a role in fixing this particular type of eye crossing. I would say that the majority of pediatric eye doctors would recommend surgery as first line treatment.
By surgically aligning the eyes, this gives a child's brain the opportunity to develop binocular vision (depth perception). Past studies have found that there is a better visual prognosis for the child if the surgery is done by age 2. Some even argue that doing surgery at a younger age, as early as 3 to 5 months of age, provides an even higher chance of success.
Before I start talking about what is involved in surgical correction, let's do a quick anatomy lesson and take a look at a picture of the eye and the muscles around the eye:
Here is a picture of an eye with the 6 muscles that sit along the outside of the eye. These muscles are called extraocular muscles. The muscle that pulls the eye towards the nose is called the medial rectus muscle. The muscle that pulls the eye out and away from the nose is the lateral rectus muscle (this is the muscle that Eye Dogtor Julie is standing next to). The muscle that pulls the eye up is the superior rectus muscle, and the muscle that pulls the eye down is the inferior rectus muscle. There are also two muscles called the superior and inferior oblique muscles that primarily help rotate the eye in or out. The oblique muscles are more complicated than this and also help pull the eyes up or down or even in or out depending on the direction you are looking at. If the inferior oblique muscles are overacting, when a person looks left or right, this can cause one of the eyes to swing upward relative to the other eye and cause a vertical misalignment.
I drew Eye Dogtor Julie pulling on the lateral rectus muscle here to help show how when this muscle contracts, it pulls the eye out and away from the nose. You can imagine pulling on each muscle to figure out how that muscle will move the eye.
Back to talking about surgery. How do you fix crossed eyes? You can either weaken the inner muscles (medial rectus muscles) that pull the eyes in towards the nose or strengthen the outer muscles (lateral rectus muscles) that pull the eyes away from the nose. For congenital esotropia, most strabismus surgeons prefer to do symmetric surgery on both eyes rather than work on one eye. The most common surgery to correct congenital esotropia is to move the medial rectus muscles further back on the eyes so that the muscles cannot pull the eyes in as strongly. This procedure to weaken a muscle is called a recession. If you weaken the medial rectus muscles on both eyes, the surgery is called a bilateral medial rectus recession. If you choose instead to strengthen the lateral rectus muscles to pull the eyes out more, you can either do a resection or plication of these muscles. Both of these procedures work by shortening the muscle overall so that it has a stronger pull. If you do a procedure to strengthen the lateral rectus muscles of both eyes, this surgery is called a bilateral lateral rectus resection or plication.
If the amount of crossing is really large, some surgeons may do a combination of 3 or even 4 muscles (both sets of inner and outer muscles) at one time to correct this. Sometimes a child may have to undergo more than one surgery with various combinations of the procedures described above to fix the eye crossing. If there is any upward drifting of the eyes, the eye surgeon may also need to work on muscles other than the medial and lateral rectus muscles to correct the vertical misalignment.
The treatment options I presented above are based on my training and experience. What is challenging about discussing this topic of congenital esotropia is that each child's case is different, and thus, each pediatric eye doctor may approach the problem of uncrossing the eyes differently. The above information is for educational purposes only and does NOT constitute medical advice. If you have concerns that your child has congenital esotropia, please reach out to your primary care provider for a referral to see a pediatric ophthalmologist for a formal evaluation.