I have bad eyes and need glasses. However I have noticed when it is dark, I am able to see contrasting colours a lot better in the corner of my eyes, than in the center, e.g a mark on my wall I can't see if I look directly at it, but I can see it at the corner of my eyes.

I have also noticed that the light in my kettle appeared to flash on and off in the corner of my eyes, but when I look directly at it, it doesn't blink at all.

Slow motion imagery on my phone shows the light IS indeed blinking.

So what specifically about human eyes allow for these effects? If it was simply blurry then I would just account that to lack of focus of light. But surely the refresh rate of my eyes (to see flashing) is constant?

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    $\begingroup$ While I understand what you are asking, I think you are asking three questions at once. Can you plase clarify what is the main question being asked? Peripheral vision, the cases you experience, or the refresh rate of your eye? Also, I wish there would be clearer grammar and statement. I am having a tough time understanding your third sentence. $\endgroup$
    – cc12amu
    Commented Apr 30, 2022 at 18:06
  • $\begingroup$ Does your kettle use LED by any chance? If so, those certainly blink on AC power, basically lots of on-off as the waveform passes through. Why the eye see it as steady is something for you to research. $\endgroup$
    – bob1
    Commented May 1, 2022 at 21:16
  • $\begingroup$ I would say the main question is about what causes the effect in my kettle, and the specific relation as to why I can only notice it when looking at it through the corner of my eye. $\endgroup$ Commented May 1, 2022 at 21:18
  • $\begingroup$ Yes the kettle is an LED, i know WHY it blinks. But not as to why the difference in my perception of it varies with the location on my eye. $\endgroup$ Commented May 1, 2022 at 21:20

1 Answer 1


I think we can agree that the faraway star we see mostly twinkles, or pulses when seen by our naked eye. Since you stated that the kettle LED is also blinking, both are the same cases.

You are experiencing what is called averted vision. Our eyes have 2 different cells that can sense light: cones and rods. Cones are adept in seeing colors and mostly concentrated on an angle centre to the eye (the fovea). The rods, however, are contrast sensing and more concentrated around the the periphery of the fovea.

Cones are simply great in distinguishing color, while the rods are great in detecting brightness. This affects what you are seeing in dim or dark locations: since there is not enough brightness to be sensed by your fovea, the cones can't distinguish really good. The rods around the fovea, however, are doing just fine. This is the reason you can see details while "tailing" using your eye. In fact, amateur (and ancient) astronomers observe faint stars by using their peripheral vision.

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    $\begingroup$ stars twinkle because of the atmospheric turbulence which gives the same effect as a haze mirage on a hot road. $\endgroup$ Commented Jun 1, 2022 at 7:30

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