Intro to visual stressors

Getting headaches looking at screens?  While everyone is different, there are four primary factors that could be contributing to this.

  1. Brightness
  2. Color
  3. Flicker
  4. Visual Gymnastics

Brightness acts as a multiplier of symptoms caused by color, flicker, and sometimes general light sensitivity.  The brighter a bulb or display the more effect harsh color and flicker will have.  In search of relief from symptoms we recommend exploring a reduced brightness to the absolute minimum necessary to make out what’s on the screen.  From that low brightness you may increase brightness as your tolerance improves.

Be aware that some devices flicker at all brightness levels, but many devices utilize harsh high frequency flicker only at lower brightness levels.  Find out if you device flickers by finding it on or by leaving a request for us.

Color is more complicated than you might expect and requires a brief explanation.  Firstly, there is no such thing as white light.  Light might appear white, but it’s actually a composite of many colors.  Sunlight contains mostly equal amounts of all colors, with somewhat less amounts of violet and blue (fun fact: those colors are deflected by gasses in the atmosphere by what is known as Rayleigh scattering, resulting in blue sky).  Because of the relatively equal amounts of all colors, sunlight is the least problematic for those most sensitive, as long as it’s not too bright.

Where problems arise is that many LEDs do not produce light that includes equal amounts of all colors.  Instead, the LEDs often output high intensities of very narrow bands of  color, the most problematic of which is blue light.  Put together, these bands may appear white but they are far more likely to result in elevated symptoms for those most sensitive.

Flicker is simply a rapid variation in light output.  Obvious flicker may be observed from a fireplace, or a lit candle, where subtle variation in the brightness of the flames are easily observed.  The more common and less obvious flicker is light that flickers at such a high frequency it does not appear to flicker at all, but can still contribute to problems including headaches.  These invisible visual stressors are almost everywhere.

The effects of flicker went largely unnoticed until the late 1970s and 1980s with the introduction of magnetically ballasted fluorescent office lighting.  Not only were the color characteristics poor, but the magnetically ballasted fluorescent bulbs flickered according to local A/C switching rates, ie. an aggravatingly low 50 or 60 Hz.  Complaints of headaches and other neurological problems followed together with loss of productivity.

These days flicker has improved but significant problems still exist in many products containing LEDs.  In the case of LED light bulbs, invisible flicker is almost always the result of cost-cutting measures.  In other cases such as smartphones, tablets or computer screens, flicker is sometimes used in clever ways to achieve better color accuracy at low brightness levels.  Unfortunately, many manufacturers design products that flicker at relatively low frequencies that are more likely to contribute to symptoms of those most sensitive.

Visual gymnastics your eyes and brain perform to use computers and other devices generally goes unnoticed until your capacity to do so is diminished.  Perhaps you’re watching a show involving scenes of gunfire resulting in a flashing screen, or even something as simple as scrolling webpages.  Depending on your impairments the type of visual stimulus you’re exposed to may contribute to your symptoms.  If your symptoms worsen, consider not only the type of light you’re exposed to but also the type of visual stimulus.

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