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Herrmann and Pötzl describe a pathologico-anatomic observation which they call "optic allesthesia" (imaginary local signs within the visual space —things which are seen occasionally, under the influence of central changes, not in their actual place). Patients have the right conception as to space, form and size, but see things actually in a different place. Beyer made observations on himself during an attack of migrainous scotoma, and a similar experience has been described by Ernst Freund. Optic allesthesia was compared with other optic disturbances of optic motor and agnostic nature, and the entire work of investigation done in the Vienna Clinic of Julius Wagner-Jauregg.
The optic picture is transferred so that things left or right, above or below, are exchanged within the visual space. This has been recognized as a counter (contrasting) phase of tactile allesthesia. In order to differentiate optic from tactile allesthesia and to establish a name based
Die optische Allesthesie. Studien zur Psychopathologie der Raum-bildung.. Arch NeurPsych. 1930;23(3):613-614. doi:10.1001/archneurpsyc.1930.02220090208022