In devising an instrument for the study of subjective visual sensations an attempt is here made to accomplish two objects: to settle some disputed questions concerning the nature of such sensations, and 2, to furnish a practical means for the autodiagnosis of disturbances or defects in the field of projection.
It is well, however, at the beginning of this paper to understand that Zehender's definition of subjective visual sensations is the accepted one. His definition is at variance with the definitions given in the Century, Standard and Foster's medical dictionaries, but it is nevertheless the most rational. For the production of subjective visual sensations—"Gesichtsempfindungen" —Zehender's definition requires the presence in the interior of the eye of real corporeal bodies.
Subjective visual sensations, therefore, differ from objective visual sensations in the fact that the latter owe their origin to corporeal things outside of the eye; they differ from hallucinations, "visions," and
STILLSON H. THE SUBJECTOSCOPE.OR SOME SUBJECTIVE VISUAL SENSATIONS.. JAMA. 1899;XXXIII(2):71-75. doi:10.1001/jama.1899.92450540013002c