In the physics inherited from Aristotle an eye beam generated in the eye was thought to be responsible for the sense of sight. The eye-beam darted by the imagined basilisk, for instance, was the agent of its lethal power, given the technical term extramission.
The exaggerated eyes of fourth-century Roman emperors like Constantine the Great (illustration) reflect this character. The concept found expression in poetry into the 17th century, most famously in John Donne's poem "The Extasie." Later in the century Newtonian optics and increased understanding of the structure of the eye rendered the old concept invalid, but it was revived as an aspect of monstrous superhuman capabilities in popular culture of the 20th century.
Shakespeare's "Venus and Adonis", read in the light of contemporary conceptions of vision, founds a rhetoric of like kindnesses and loving mutuality is predicates loving mutuality upon a conceit of visual reciprocation achieved in the exchange of eyebeams.
Hear now and help, and lift no violent hand,
But favourable and fair as thine eye's beam,Hidden and shown in heaven".
The unheard music hidden in the shrubbery
And the unseen eyebeam crossed, for the roses
Had the look of flowers that are looked at.
- L. Safran, "What Constantine saw: reflections on the Capitoline Colossus, visuality and early Christian studies" Millennium 3' (2006:43-73), noted in Paul Stephenson, Constantine, Roman Emperor, Christian Victor, 2010: notes 333.
- B.S. Eastwood, "Mediaeval Empiricism: The Case of Grosseteste's Optics" Speculum: A Journal of Mediaeval Studies, 1968.
- Eric Langley , "'And Died to Kiss his Shadow': The Narcissistic Gaze in Shakespeare's Venus and Adonis", Forum for Modern Language Studies 44.1 (2008:12-26
- Quoted in K. R. Howe, "The Dating of Edward Tregear's 'Te Whetu Plains', and an Unpublished Companion Poem" Journal of New Zealand Literature 5 (1987:55-60) p. 58.