An interesting and thought provoking story about perception is contained in the book Fixing My Gaze: a scientist's journey into seeing in three dimensions written by Susan Barry (2009), a formerly stereoblind professor of neurobiology. "Stereo Sue" (as she was dubbed by Oliver Sacks) tells of Susan Barry learning in a college course at age 20 that she was "stereoblind", meaning that she could not see the world in 3 dimensions. Though she knew that she had misaligned eyes (strabismus), she did not know that she wasn’t seeing the way others were seeing.
Most people use the different viewing perspectives of the two eyes to see in 3D (stereopsis). The eyes provide the input and the brain interprets it. For many with strabismus, because the data from each eye is contradictory, the brain suppresses the information from one eye and relies on other cues to gauge depth and distance. They become stereoblind.
I have a keen interest in perception not only as it relates to vision, but in a broader sense as it relates to one experiencing and understanding their socio-emotional life. The book talks about the clinical and emotional experiences of gaining stereopsis via vision therapy decades later after discovering the truth. Susan Barry's experience with vision therapy was a lot like the experience people have with psycho-therapy: Her symptom (stereoblindness) was a solution or adaptation to some other problem (strabismus).
What Stero Sue lacked was what many individuals with psychological problems lack: 'perspective', or the ability to use input from two different -- and yet aligned, (viewing) perspectives in order to give a sense of depth to their world. Prior to therapy Sue, and others, get by utilizing only part of the experience available to them and can't even imagine in what way it could be so much more.