So I went to the eyedoc for fitting a pair of RGP lenses.
during the process I had to try several curvatures for best fitting.
The weird thing is that for a badly fitting lens, particularly one that is not curved enough, you can feel its edge scraping against the underlid.
I was able to perfectly tell that the edge was round shaped and kinda sharp.
Weirdly I’m pretty sure I nevel had any kind of experience where the underside of my lid was stimulated like that so how come my brain is able to represent a complex shape like an arc, feel its motion direction and speed? I was expecting a more generic feeling of “something irritating there” but is a tactile surface almost as accurate as the tip of my finger even though it had no data to learn from?
I myself have mild astigmatism (up to 100 degree during my young ages, then self-healed to 50) so no glass correction (in addition to my -300 myopia) is needed. But my son has more serious (400) astigmatism, we tried to have him wearing RGP at around age 11 or so, but he ultimately refused it at all after a short period of trying, citing it way too uncomfortable.
I guess his cornea grows much irregular from the perfect round shape, maybe similar with you? I further guess that one’s brain has been trained to sense normality from underlid during its baby ages, as it moves eyes in early days. That way no matter how irregular the “self” is, it’ll feel “normal”; or otherwise some (even small) changes would feel rather irritating.
Maybe the brain is continuously actively detecting “normalities”, but the sense is just ignored by “conciousness” somehow.
I will argue that the tactile sensors under the lid simply map into the master map in the brain. That map places the sensation in the eye, the specific eye, and then uses learned data from the formation of the map to allow the perception of the shape and texture of the object to the limit of the resolution of the sensor array.
This is far more interesting than the fingertip example.