What is Visual Stress?
Visual stress is a common condition of the visual cortex which is often experienced by people with dyslexia, but is a separate and distinct condition. Apparent movement and distortion of text, headaches and sore eyes are common symptoms of visual stress. Coloured overlays have been shown to improve reading experience for about 20% of the population. Visual stress has some common misnomers, particularly "Scotopic sensitivity" (which suggests that it is a condition of the retina and not the visual cortex), and "visual dyslexia", which confuses the cognitive processing (dylexia) with visual processing (visual stress). Visual stress will create extra difficulties for a dyslexic person by making words hard to decipher, but once a reading ruler or overlay has made them visually clearer they still need to be decoded, and that is where dyslexia causes its problems..
Because visual stress is perceptual, rather than optical, in nature, it is not corrected by prescription glasses, and it cannot be detected by standard visual, educational or medical tests.
How do you know if you have Visual Stress?
Symptoms of Visual Stress vary , but can include headaches and migraines (especially when working at the computer), eyestrain, and words or letters appearing to "jump" or move on the page. People who have Visual Stress see the page differently because of distortions of the print or white background.
In general, somebody with Visual Stress may
- Experience difficulty looking at a computer screen
- Be unusually sensitive to bright lights, especially flourescent lighting.
- Have difficulty judging heights or distances, which sometimes causes problems with stairs and/or escalators.
- Find driving at night particularly stressful, sometimes experiencing a fragmentation of reflected light.
- Develop headaches and migraines when reading.
Some, or all, or the following can be noted while reading. Sufferers may:
- Fatigue quickly when working with text
- Experience problems copying from the board
- Skip words or lines when reading
- Seem to experience increased difficulty after an initial period of about 10 minutes
- Keep moving their head or body position, or moving closer to or further away from the page
- Read slowly and haltingly and have difficulty absorbing information
- Track with the finger
- Yawn while reading.
- Frequently rub their eyes
Visual Stress typically causes the following distortions of print, although not all of the following will necessarily be experienced by one person:
- The print appears to jump or otherwise move on the page - sometimes appearing to move off the page altogether.
- Swirling effects appear in the text.
- Whole lines of text may appear to move.
- Shimmering colours may appear on the page.
- White "rivers" may seem to run down the page, where the white background, as opposed to the black text, has become the dominant image perceived.
- Letters may double, reverse, fade or blur. Basically the image of the letters and words is unstable against the white background, and this instability can be experienced in a number of ways.
Does Visual Stress go away?
Generally, no; although there are cases reported where the contrary has been the case. Sensitivity does seem to change though, especially in a changed response to coloured filters. Somebody who has found a particular colour most beneficial may find that this preference changes and a different tint will be more helpful.
What can be done?
People with Visual Stress can read with much greater ease if they cover a print with a specially treated coloured overlay. Screening can help to identify which colour is most beneficial. Crossbow Education supply convenient Reading Rulers and the larger A4 size Coloured Overlays in ten colours that have been carefully selected to cover the full spectrum in different combinations.
Crossbow also supply the Visual Stress Assessment Pack for thorough screening of individual colour preferences. For any optical difficulties, it is important that an optometrist is also consulted to ensure that there are no underlying medical or ophthalmic conditions. Some optometrists prescribe coloured lenses, and have specialist equipment to test for colour preference. It is often found that lenses of a different colour from the overlays are needed. A list of specialist optometrists and Irlen centres can be found here.