This is a very cool optical effect
Whichever dot you focus on looks purple while the others look blue
As someone whose eyes have been "settling" from cataract surgery followed by a superficial keratectomy in one eye, and has noticed my vision changing daily at various focal points, this is fascinating
@kims
Usually these images with black and white dots and the likes work for me.
This one doesn't, I don't see the blue dots this time.
Mar 1, 2026, 10:32 PM@kims All purple all the time for me. But I’m used to my eyes being weird.
@kims It’s a very striking effect. Very cool.
@kims Not sure about the blue, they all look purple to me, however the one I’m focused on is just a tad darker, and it is pretty fast too, almost instantaneous as far as I can tell, which looks like chasing the dark spot around! :blobcatgiggle2:
They all appear blue to me. But I may have cataracts.
@kims So it works if my glasses are on. And it's really weird!
.... if I take my glasses off to get a closer look, it stops.
@kims
I see the entire row I focus on as purple.
Scale of the display probably has an effect, i.e. phone vs monitor.
This is cool because I'm colorblind enough to struggle with distinguishing purple and blue, and all the dots look reliably the same color.
Mar 4, 2026, 12:27 AMthis is wild!
@kims Interesting. I’m red/green colorblind and initially wasn’t seeing the effect, but then I looked at the paper and saw that it’s a distance-dependent illusion, best seen at 30cm (about 12in). At that distance I DO see it faintly
Funny you mention cateract surgery. I had one eye done a bit over 3 months ago. The fixed eye makes everything look "cooler" (more blue white) than the unaltered eye (which has a much less severe cateract that "yellows" things a bit)
The illusion works as described on the organic unmodified eye with mild cataract, but no effect at all in the fixed eye.
Wild.
They are all blue in the fixed eye, and all purple in the unmodified eye, but the focused dot is a darker purple.
@kims
Huh. I get darker purple for the dot I focus on and the others are a lighter purple.
The background does look like a shade is blue to me.
Mar 4, 2026, 4:42 AM@kims I don't see blue dots, but if I quickly scroll the page up or down, I briefly see shadows of the dots.
@kims Not to me.