Line of Sight
Historical document, translated for reference. It reflects medical knowledge of the 1920s–30s and is not medical advice.
Summary
The line of sight connects a fixed object with the center of rotation of the eye. It does not coincide with the visual line but is positioned slightly inward from it, though they are often considered the same due to the small angle between them.
Encyclopedia entry (1928–1936)
Line of sight, a line connecting the fixed object with the center of rotation of the eye. Since this center is located on the visual axis, and therefore inside the visual line connecting the fixed object with the yellow spot, the line of sight does not coincide with the visual line and is located somewhat inside the latter. These lines converge on the fixed object at a very small angle, which explains the circumstance that in most cases the line of sight and the visual line are identified. According to Hering, the maximum angular displacement of the line of sight from its position in the primary position of the eyes is expressed in degrees: Inward Outward Upward Downward Left eye.... 44°, 59° These values show significant individual deviations.
These values show significant individual deviations.
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“Line of Sight.” Soviet Medical Encyclopedia. English translation of Bolshaya Meditsinskaya Entsiklopediya, 1st ed. (Moscow, 1928–1936), ed. N. A. Semashko. https://sovietmedicalencyclopedia.pages.dev/article/line-of-sight/