A TikTok account known for clever brain teasers and tricky optical illusions has posted a video that few people can figure out.

It’s an eye-catching optical illusion that will have you questioning what you see.

The TikTok is a classic “what number do you see?” test.

Digits are placed against backgrounds with almost no contrast — only people with extremely sensitive color perception can detect all five from the video.

The video is an example of the Ishihara test, a red-green color blindness evaluator that dates back to 1917.

In a more medical setting, the colored images from the TikTok would be called “pseudoisochromatic plates”.

In a full Ishihara test examination, patients would look at up to 38 different plates, though ophthalmologists can normally determine if someone has color blindness after a couple of examples.

The plates have different functions and some can only be seen by people that are red-green colorblind.

Color blindness can be the product of deficiencies or a lacking of color reading cones in the eyeball, located in the retina.

Dogs only have two of the three cones needed to see the full spectrum of color.

One in 12 men experiences a form of colorblindness, compared to one in 200 women.

The disparity is because color blindness men need only one parent to be a carrier of the color blindness gene, and women need both parents to be carriers.

Remember, TikTok is not a doctor’s office!

If you have difficulty seeing the numbers in the video, you can ask your doctor for an official exam.