Strabismus is the medical term for eye misalignment, found in up to 5% of infants, children, and adults. You may have heard terms such as “wall eye”, “crossed eyes,” “lazy eyes,” or “squint” used to refer to this health condition that can impair a person’s vision, self-esteem, and quality of life.
The causes of strabismus are, basically, neurological or neuromuscular. The congenital (aka infantile) form, with onset before six months of age, is highly heritable. Twin studies have identified concordance rates of 73%–82% among monozygotic (identical) twins and 35%–47% among dizygotic (non-identical) twins. Another examination revealed that out of 7,100 strabismic individuals, 30% had a close relative also affected.
Even if treated during early childhood, the deviation can reappear in some form later in life. Moreover, strabismus may be acquired in adulthood from physical trauma, tumours, strokes, visual impairments, and thyroid eye disease, for example. It can manifest on its own or as part of a complex syndrome or disease such as cerebral palsy and Down syndrome (20%–60% of those with Down syndrome have a form of strabismus).
Strabismus and lower quality of life
Over the last few decades, several studies have used various instruments to conclude that eye misalignment is associated with lower health-related quality of life (HRQoL). This refers to an individual’s assessment of how their health affects their ability to live a satisfying, fulfilled life across different areas. Strabismic individuals have been shown to experience “significantly more psychosocial distress” compared to the non-affected. In addition to impacting a person’s self-esteem and self-image, the condition can lead to functional impairments and social and emotional issues, such as:
- Double vision (aka diplopia)
- Amblyopia: the loss or lack of clear vision in one or both eyes
- Lack of binocular and stereoscopic vision, and depth perception
- Needing to close or cover one eye
- Eye strain and discomfort
- Difficulties reading
- Social prejudice, negative attitudes, and rejection
- Reduced employment opportunities
- Mental health conditions (discussed later)
Results from a 2014 article suggest that most strabismic people with double vision often feel stressed and worried about their eyes. Even in the absence of diplopia, strabismus is a leading cause of amblyopia (aka “lazy eye”), with which it can be confused because they co-occur frequently.
Another unfortunate reality is that strabismus often affects infants and toddlers during the critical development period for binocularity and stereopsis (stereoscopic vision). The most crucial part of this window is around three to 18 months of age, but it continues up to three years old. Because their brains receive conflicting, confusing input from their mismatched eyes, they suppress one of them, rather than learning to fuse the two images to create three-dimensional representations, as in regularly sighted people.
If this happens, a strabismic person will typically have a dominant eye that they favour, and will fixate (or focus) through one eye at a time. We can see how this leads to a weakening of the other eye, contributing to amblyopia. And, unfortunately, once the critical window has passed the person is unlikely to ever develop stereopsis. (Although, there have been reports to the contrary, such as Susan R. Barry’s Fixing My Gaze.)
Strabismus and mental illnesses
Research has underscored that living with strabismus raises the odds for a range of mental health conditions. For example, a 2012 study published in Ophthalmology (the journal of the American Academy of Ophthalmology) revealed that 33% of individuals with congenital esotropia – esotropia referring to an inwardly deviating eye – had a mental illness by early adulthood, compared to 16% of the control group. Their odds were elevated 2.6 times.
Other studies have found similar results. This investigation highlighted that 41% of those with childhood strabismus, specifically esotropia or exotropia (inward or outward turn, respectively), had a mental health disorder by the time they reached adulthood. Exotropia increased the risk by 3.1 times relative to controls. And intermittent exotropia – an outward eye deviation that occurs sometimes, rather than all the time – was associated with worse mental health, more comorbid mental illnesses, and greater hospitalisations and suicidal ideation.
More recent research has corroborated the link between strabismus and psychological disorders. A 2022 article from JAMA Ophthalmology examined data from a database of over 12 million children under age 19 to investigate the prevalence of four mental illness groups in strabismic individuals. It discovered that each of the three strabismus varieties examined, esotropia, exotropia, and hypertropia (upward deviation), heightened the likelihood of developing anxiety disorder, depressive disorder, schizophrenia, and bipolar disorder.
Overall, the association between strabismus and mental illnesses exemplifies how physical health conditions and impairments often contribute to psychosocial issues and poorer quality of life.
Monique Moate is a writer, editor, wife, cat mum, and night owl who enjoys writing about a wide range of topics. She cares about mental health awareness and destigmatisation.