Signs and Symptoms


The signs of visual stress are things that you might observe in a student, client, patient or family member.  Individuals may not realize they are doing these things when asked or may believe that the discomfort or distortions they experience are normal and experienced by everyone so will not readily report them.  When investigating for visual stress, observation is an important part of diagnosing the condition.

Common signs include:

  • Wearing brimmed hats or sunglasses inside 

  • Turning off or dim the lights inside and keep the blinds closed 

  • Sitting in dark places to read, study or work. 

  • Dimming computer screens and avoid working on them for extended periods. 

  • Difficulty reading without using a finger 

  • Difficulty writing neatly and well-spaced 

  • Skipping words or lines when reading aloud 

  • Appearing very uncomfortable when reading or doing homework: squint, rub eyes, angle their head to read, constantly change position, or shake their head like they are trying clear it. 

  • Easily distracted by the smallest things 

  • Frustrated, fidgety and restless when reading or doing homework 

  • Trouble with their vision prescriptions even if they are adjusted 

  • Not tolerating UV, blue blocker, or antireflective coatings on glasses (these are filters) 

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While these could be signs that visual stress is present, it is important to investigate other possible causes. In their book Vision and Reading Difficulties, Dr’s Wilkins, Evans and Allen cautioned people to make assumptions that it is visual stress because there are many factors to consider. It could be an undiagnosed refractive error, a problem with binocular vision, or a perceptual problem (visual stress).  It could also be a combination of all three, and thus all three should be corrected. 


No matter the apparent cause of the problem, anyone who has difficulty reading should have a full vision investigation by an eye care professional who specializes in vision and learning.  This assessment can occur in conjunction with a visual stress assessment as visual stress may still be present even after vision correction. 


In 2017, a Delphi study was conducted to improve the diagnostic criteria for visual stress.  Published in the Journal of Optometry, the study identified practical guidelines for diagnosing the condition (Evans, Allen, Wilkins J Optom. 2017 Jul - Sep;10(3):161-168. doi: 10.1016/j.optom.2016.08.002. Epub 2016 Nov 24).

Key indicators
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The following indicators were identified as diagnostic criteria for visual stress in a 2017 Delphi study

  • Sensitivity to patterns leading to an abnormally high score on the Pattern Glare Test

  • Perceptual distortions such as illusions and movement in text

  • Sensitivity to light, glare and flicker

  • Voluntary use of an overlay or other filter types, for a prolonged period, including avoidance of reading without the filter

  • Improved performance of 15% or more with the filter on the Wilkins Rate of Reading test

  • Family history of migraine, epilepsy, learning difficulties, and visual stress 

Key symptoms
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Physical discomfort:

  • Headache  

  • Sensation of heat at the back of the head 

  • Eye pain and strain 

  • Visual fatigue 

  • Cognitive fatigue 

  • Nausea from movement 

  • Discomfort ​ ​​

Visual perceptual difficulties:
Teacher and Young Student
  • Perceived excessive luminosity  

  • Visual sensory overload 

  • Illusions of shape, motion and colour 

  • Blurring and double vision 

  • Reading and tracking difficulties 

  • Depth perception difficulties 

  • Anxiety 

Many symptoms are related:

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If perceptual distortions are experienced in patterns, a high contrast patterned carpet may appear distorted or moving, leading to nausea and dizziness.  


If flickering is perceived on smooth surfaces, then it will likely be difficult to concentrate in a classroom filled with laminated and shiny surfaces such as desks and whiteboards. 

Identifying Distortions


As part of our assessments at Opticalm, we evaluate our clients’ perceptual distortions. After describing what they experience when viewing text and patterned images, we use a set of illustrated distortions to help them to further describe what they perceive.  Many clients are surprised we have images illustrating what they personally experience, especially since, until now, no one believed them.  These images are very useful in helping people convey to their teachers, employers and families, their challenges and the importance of accommodating for them.  

Over the past 35 years, multiple research papers have consistently reported the following perceptual distortions: intermittent blurring; duplication; jumping; switching; and fading of the visual image.


Static Sample Distortions 


Below are static sample distortions that people commonly report. You can also see the animated version of these and other images.


Animated sample distortions are not available on our mobile website.

WARNING: These images can cause discomfort and trigger seizures in patients with photosensitive epilepsy.