Only the orange square “jumps”

[Nancy T]

This is a trivial question only to satisfy my curiosity, so please don’t feel obligated to answer.

I have a “Summer Reading” T-shirt from the library that has four 2 x 2-inch solid colored blocks across the front, each containing a letter cut into it:

R   E   A   D

The square containing the R is green, E is yellow, A is orange, and D is blue. The background (and thus also the letter cut-outs) is light gray, and the squares are all separated from each other.

The funny thing is that whenever I’m wearing this T-shirt and reading while looking down--thus with the colored blocks in my lower “peripheral” vision--the orange square, or more likely perhaps just the gray arms of the “A”, quickly and repeatedly “jumps” side to side. (This seems unrelated to the problem I posted about earlier, namely vertical ghosting that comes on after a few minutes of reading while looking down.)

The “jumping” effect seems similar (in its type and speed of movement) to the fast, on-and-off flashing of white Lifesaver-like circles that I see--in my left eye only--when I move my eyes back and forth after turning out the light. (These flashing circles have been occurring for several years, and I assume they are the harmless entoptic phenomena often mentioned here.)

Any idea why only the orange square (or the gray A inside it) would jump? It is the square most directly below my left eye, but both my eyes are healthy. Is there something about orange on a gray background that would cause this?

I recently experimented with covering each eye, and it turns out that the jumping only happens when both eyes are open, not when one eye or the other is covered. I am 50 with a little myopia and presbyopia, if that makes any difference.

[Nancy T]

Thank you. I guess it must be some strange optical illusion.

[John C Hagan III, MD, FACS, FAAO]

Sorry, I've pondered and do not think that I can offer an explanation for the things you are describing.

JCH III MD