Flicker Rate Video Overview

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Verify Screen Refresh Rate

• Regulation 1194.21(k) states
  "Software shall not use flashing or blinking text, objects, or other elements having a flash or blink frequency greater than 2 Hz or lower than 55 Hz."

Note: both slides include the title 1194.21(k) Screen Flicker and a Department of Veterans Affairs logo.

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This next regulation is very important because it actually has medical implications if you get this wrong.

You need to verify the screen refresh rate if you have content that refreshes on the screen. If your content happens to refresh within two Hertz and 55 Hertz range, the UI could cause seizures.

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Screen Flicker

• Design your application to not require blinking or quickly refreshing elements
• Remove flashing content that refreshes between 2 and 55 times per second
• Practical test: is it slow enough to be noticed? Is it faster than twice a second?

--[Narrator]--

Most likely your application currently does not use blinking or quickly refreshing elements. However if it does, it's probably best to try to design your application to not require them.

If you do have that content, and you need it there for a certain purpose, a practical test to verify whether or not it's within dangerous levels is to check is it slow enough to be noticed? Is it faster than twice a second? If either of these two questions you had to answer True, you should either remove the content or adjust the refresh rate within the code to an acceptable value.

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