Esotropia (Inward Eye Turn)

Strabismus, or eye-turns are an interesting phenomenon that can occur at any stage of life. Just as interesting, either eye can turn and it can turn in any direction; up, down, in or out. In today's blog we are going to discuss esotropia; an inward eye turn. This a condition with many varieties that responds to a number of treatments

Eye turns vary in size, frequency, direction and cause. As you can imagine, managing strabismus is quite complex. There are several factors that must be evaluated in order for the doctor to make clinical decisions about the case. The majority of eye doctors do not manage strabismus cases. We often see patients with eye turns and our doctors are the first to have identified it (even though the patient has gone to eye exams every year). How can this happen? Very few eye doctors have specialty training in strabismus and not all doctors test for it. Working with a doctor who is residency-trained in binocular vision, or having your child see a doctor who is residency-trained in pediatric eye care, will ensure that the specific type of strabismus is identified and the proper treatment is initiated (no not all eye turns require surgery).

Today we are going to focus on esotropia, or an inward eye turn. There are several types of esotropia, each of which has its own unique characteristics and treatment.
 

Types of Esotropia:

• Accommodative Esotropia: An accommodative esotropia is an inward eye turn that results from excessive focusing. This occurs because the eye focusing and eye teaming systems are linked within the brain. Engaging one's eye focusing causes the eyes to cross. Too much eye focusing can cause the eyes to cross too much and an esotropia results.
  
  An accommodative esotropia is associated with a hyperopic (far-sighted) prescription, which requires excessive focusing when uncorrected. The term far-sighted doesn't actually mean that a person can see far but not close. Farsightedness gets its name from the fact that light rays are focused on the far side of the retina. Someone who is far-sighted may have the ability to see clearly at all distances or they may see blurry at all distances – it all depends on whether or not they can focus their eyes enough to make things clear. This excessive focusing not only makes things blurry, but can also cause an eye to turn in – accommodative esotropia.
  
  Accommodative esotropias generally develop around the ages of 2-3 years of age. The most appropriate treatment for an accommodative esotropia is a pair of glasses determined with a cycloplegic (dilated) examination with a residency-trained pediatric eye-care provider.

• Infantile Esotropia: An infantile esotropia is an in-ward eye turn that occurs within the first year of life. Causes of an infantile esotropia are still unknown but it is believed to be related to sensory or oculomotor difficulties. An infant may be at a higher risk if they were born premature, if there is a family history of an eye-turn, or if they have a significant health problem such as a seizure disorder.
  
  These individuals are unable to use their eyes together as a team and may alternate which eye they are fixating with (one looks straight ahead while the other turns in). This means they may be unable to appreciate 3D vision. They may also have a vertical misalignment of their eyes when one eye is covered, this is called a dissociated vertical deviation. Surgical correction may be indicated for a cosmetic alignment.

• Sensory esotropia: A sensory esotropia is an in-ward eye-turn associated with something depriving the macula (center of best vision) of visual stimuli. If the macula cannot obtain a clear image the eye may deviate to allow an off-macula point to be used for improved visual clarity.

  Some examples could be a cataract (yes, children can have cataracts), corneal scarring, and other types of pathologies. A sensory esotropia is most common in children under the age of five. Treatment should include addressing the causative factor and may require surgical intervention.

• Acute esotropia: An acute esotropia is an in-ward eye turn that occurs in an individual who previously had normal binocular vision. Generally this will occur with adults or school-aged children. The individual will notice double vision that comes on suddenly. In any cases of sudden double vision it is imperative to have a thorough examination with a residency-trained neuro-optometrist or neuro-ophthalmologist as soon as possible. Sudden onset double vision can be a sign of a life threatening condition.

When evaluating an esotropia it is important to have a comprehensive assessment with the residency-trained eye-care providers to ensure the most appropriate diagnosis and treatment. Some types of esotropia require intervention with glasses or contacts, others require prism correction (incorporated into glasses), others require vision therapy, and some require surgery. Many types of strabismus benefit most from a combined treatment approach. Strabismus results in both mechanical (the physical misalignment of the eyes) and sensory (the ability of the brain to use both eyes together in an aligned manner) barriers. If a treatment does not consider both the sensory and mechanical barriers to binocular (two-eyed) vision, the treatment may not deliver the results you expect. For example, many kids will go through multiple strabismus surgeries because 'the first one didn't work'. Even after multiple surgeries, the eye turn may be reduced to a size that is too small to be easily noticed, but it is still present. Why do these patients get marginal cosmetic improvement but no functional improvement? Because surgery does not necessarily address the sensory barriers to using both eyes together. This is why many patients incorporate vision therapy into their treatment – to remove the sensory barriers to using both eyes together, allowing for a true functional benefit.

Why do orthopedic surgeons prescribe physical therapy? Functional improvement. Why do some people do physical therapy to avoid surgery? Not all conditions require surgery. These same principles hold true for the eyes. This is why a variety of treatment options will be discussed by a binocular vision specialist. This ensures that your goals will be met with treatment. Are you interested in a cosmetic fix, a functional improvement or both? These types of discussions should be had with the eye doctor managing your esotropia.