a small proportion of people have this, i have it mildly as well. my opthamologist at the time said it wasnt common and he only knew a teen that had it. its mostly because of the part of yuor brain thats active. its a wierd neurological thing. i suspect mines was due to diphenhydramine at the time, plus i had undaignosed spinal issue which would cause neurological/neuropathy in my limbs. i think the DPH made it more pronounced, as bringing it from the background.

its something having do with your lingual gyrus that is hyperactive(correlation)