Visual Dysfunction in Patients with Autism
Autism is a neurodevelopmental disability characterized by:
- Impaired social interaction and communication – Delayed language development, lack of spoken language, poor understanding of the abstract meaning of words or words with special or temporal meanings such as “here” and “there”.
- Impairments in nonverbal communication – Limited eye contact, reduced facial expression and limited expressive gestures, poor processing of non-literal and pragmatic elements of speech.
MRI studies of autistic patients have found abnormalities in many locations of the brain including the cerebellum, brain stem, hippocampus, amygdala, the limbic system, and frontal cortex. This can make the individual either severely over-sensitive, under-sensitive, or both to outside sensory stimuli. The nervous system of autistic patients process sensory information in a different way. They may be overwhelmed by abundance or lack of sensory information that their nervous system receives and exhibit abnormal behaviors in an attempt to either reduce or increase amount of input.
Our internal “brain maps” give us a sense of our bodies and involve the regions of the brain that deal with the senses and movement. MRI images of autistic persons show scrambled brain maps – information connections for sensory functions still exist, but are located in the wrong parts of the brain. Autistic brains have been found to be larger than average with a higher amount of cells and extra connections between neurons. This excess circuitry is believed to cause problems in sensory function. This change in neurology means that no two autistic people are alike. Although they may share common behaviors, these behaviors will appear in all combinations and vary in intensity in all patients.
Visual impairment is characteristically under-diagnosed in people with complex needs. The signs can be difficult to delineate and many patients are not evaluated with a comprehensive ocular and visual examination contributing to this under-diagnosis. Undetected visual impairments are likely to impact behavior of individuals with autism and negatively impact quality of life, stress levels, and receptiveness to new information.
An estimated 1 in 5 preschoolers have a vision problem and 1 in 4 school age children wear corrective lenses in the U.S. Early diagnosis and treatment are essential to optimize children’s eye health and vision, and to prevent future vision loss. Left undiagnosed, vision problems can lead to issues with a child’s normal development, school performance, social interactions, self-esteem, level of education, and social interactions. Children with disabilities are reported to have significantly more eye and vision problems which may be related to increased severity of the disability.
In 2017 Review Journal of Autism and Developmental Disorders published “Autism and Visual Impairment: a Review of the Literature” by Maggie Butchart et al. The review looked into seven studies which examined children age 1 to 18 years old. Autism was found predominantly in the male population with 70-86% of the subjects being male. Refractive Error was found in 22-44% with a higher prevalence in astigmatism and anisometropia, strabismus was found in 8.6-41% and amblyopia in 11-16%. Since all the qualifying studies included young patients the incidence of age-related visual impairments remains to be established in the adult autistic population.
A 2009 study published in Vision Research called “Vision in Autism Spectrum Disorders” by David Simmons et al. looked into visual impairment in autism. They noted that children with autism spectrum disorders can have either or both hyper and hypo visual sensory dysfunction. Signs and symptoms of hyper visual sensory dysfunction include focusing on tiny pieces of dust/particles, dislike of the dark, dislike bright lights and flashing light, photosensitivity and covering or closing eyes from bright lights, looking down most of the time. Symptoms of hypo visual sensory dysfunction include being attracted to light, staring, looking intensely at objects or people, moving fingers or objects in front of the eyes, fascination with reflections and/or brightly colored objects, running hands around the edges of objects.
In general, these children have an increased level of internal noise in visual processing pathways. They are less influenced by prior knowledge in visual judgements and consequently visual processing may be less ‘top-down’ dominated – they have a difficulty with going from the general to the specific (big picture to tiny details). They also mis-judge interpersonal distance during social interaction and have difficulties with tasks such as ball-catching. Deficit in spatial attention and lower levels of attentional engagement is also found meaning they have difficulty attending to people particularly the eye regions of the face. There are mild impairments in the recognition of basic emotions from faces and mislabeling the approachability and trustworthiness of faces.
Children with autism also show a deficit in visual perception including visual form processing, visual completion, visual closure, motion processing, visuomotor control, and oculomotor function and saccades. There is a profound link between verbal ability and perceptual discrimination.
There were no deficits found in contrast sensitivity, color vision, or the ability to discriminate facial expressions. Superior visual search and attention and figure ground recognition was found in these patients.
Just like in any pediatric examination, optometrists work to diagnose problems in and optimize vision, binocularity, accommodation, oculomotor function, and visual perceptual deficits. Where indicated, refractive or vision therapy can help decrease the negative impact and stress that these deficits have on their quality of life and activities of daily living.
The following are wonderful resources for more information on vision problems as related to Autism:
- AOA Evidence-based Clinical Practice Guideline Comprehensive Pediatric Eye and Vision Examination
- AOA.org (American Optometric Association)
- OEP.org (Optometric Education Program)
- COVD.org (College of Optometrists in Vision Development)
- ASHA.org (American Speech-Language-Hearing Association)