PrematureApotheosis comments on I have apperceptive agnosia. Ask me stuff.: "It's a specific form of blindness. I'm not a neurologist, so my explanation no doubt leaves something to be desired, but the gist of it is that my eyes work fine (including dilating in reaction to light, tracking movement, even making eye contact with faces and face-shaped objects), my optic nerve works fine, and the visual part of my brain works fine... but the visual part of my brain does not communicate correctly with the part of my brain which IDENTIFIES what it is seeing (think colour recognition, symbol recognition, shape identification, light-and-dark detection, etc.). Most of the time, this occurs at one of two variable levels of 'intensity,' either an 'interrupted signal' which looks extremely similar to 'snow' on an old CRT-style television- basically just white noise crackling- or 'no signal' which looks like eigengrau, a flat dark grey that is close to black but not quite black proper.
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