Chapter 3: What Causes Strabismus?

A Patient & Parent Guide to Strabismus Surgery
George R. Beauchamp, M.D.

There are many medical conditions that are associated with strabismus, and a few of these associations are mentioned in this communication.  In general, however, it can be said that the ―causes fall into the following categories: hereditary influences, neurological problems, selected medical conditions, and by far the largest category, unknown.  The prevalence of strabismus in the general population is about 4 %.  Please remember, not all strabismus requires treatment and a minority of strabismus requires surgery.

Hereditary Influences

Certain genetic syndromes—Down’s Syndrome being the most common—have a high incidence of strabismus.  In some of these conditions, it may be so characteristic as to be expected in most cases.  When there is a family history of strabismus (without a known genetic syndrome), with or without amblyopia, the prevalence in existing and subsequent family members can be as high as 25%. Please note two aspects about this number: the overall chances are actually against a child having strabismus if parents have it; and importantly, statistics only have meaning for populations and not individuals.  And the hereditary patterns of strabismus are quite variable.  In some families and for certain conditions, only a few are affected; sometimes called sporadic or recessive with low genetic expression (penetrance).  In others, many family members are affected; and the pattern is more dominant, and/or with higher penetrance of genetic expression.

Neurological Problems

Neurological problems encompass a diverse group of conditions that includes developmental problems and delays such as prematurity, cerebral palsy, and head trauma. Depending on the condition, the incidence of strabismus may be as high as 50% of cases.  Please be sure to share with your doctor any concerns you may have about your child’s or your condition that may relate to neurological and developmental issues.  Please make particular note of any instances of head trauma or fractures of head and face bones, even if in the distant past.  There are many medical conditions that may affect the alignment of the eyes.  Examples include:

• thyroid disease (also called Grave’s disease),
• myasthenia gravis,
• circulatory problems (including stroke)
• and diabetes.

Again, please share all you know about your medical condition and its treatment, including any allergies you have.  Please include allergies to foods, medicines and other substances, such as latex.  Please make special note of any problems with anesthesia experienced by you ore related family members.

Unknown

Finally, strabismus is, in most cases, unrelated to any of the above.  It just happens to some and not others. Therefore, most of the time, there is no known cause or association with other medical conditions.  While the prevalence is low—less than 4 per cent—the population is large, making this by far the largest category.

Read Chapter 4: What are the Signs and Symptoms of Strabismus?