> It was a different kind of stroke, affecting a different part of my brain, essentially related to vision. I was half blind, but I only realized something was "strange" when I saw myself in the mirror: I had only one eye. My brain knew I should have two: I was half blind.
There's something going on here beyond just loss of raw visual input. If you lose an eyeball, or hold your eye closed, and look in the mirror, your one good eye will still show you that you have two eyes (or, as the case may be, sockets / sets of eyelids). Perceiving yourself as having one has to involve a loss of brain function, not just a loss of eye function.
There's a similar phenomenon called contralateral neglect (or one of various other names), where after brain damage to one hemisphere of their brain, a person tends to ignore things on the opposite side. The effect is sometimes in retinal coordinates (e.g. only scan objects in one half of the field of view), sometimes in object coordinates (e.g. eat only one half of a plate of food), and sometimes in egocentric coordinates (e.g. not shave one half of their face).
This seems to be similar, but different condition. Contralateral neglect is a problem of attention: they can see the things they ignore, they just won't spontaneously pay attention to them. This is a problem of perception, where they tried to pay attention to their eye, but perceived it as not being there.
I don't have an easy explanation for how this effect occurs.
My eyes were just fine: it's the brain that was the cause here. When it occurs, I can close one eye then the other and still not see in half of my FoV.
Part of my brain was not irrigated and did not function properly...
There was nothing in /var/logs: I couldn't perceive that I was half blind. syslogd crashed :-)
Is this always one half of your field of view? Or is it one half of certain objects (e.g. your face)?
If it's the first, then it sounds like damage to one visual pathway. The visual input from each eye is divided into left and right fields, and they're processed independently. Here's a good illustration:
After the optic chiasma, the two pathways diverge. Damage any time after there, such as to the occipital lobe of one hemisphere, could result in blindness to one half of the field of view.
It've talked about the face because I did not perceive that half my field of view was missing, but when looking at myself in the mirror, I saw one eye was missing... But it really was half of my field of view.
There's something going on here beyond just loss of raw visual input. If you lose an eyeball, or hold your eye closed, and look in the mirror, your one good eye will still show you that you have two eyes (or, as the case may be, sockets / sets of eyelids). Perceiving yourself as having one has to involve a loss of brain function, not just a loss of eye function.