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?