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Illustration from "On the mechanism of the eye" by English physicist Thomas Young, 1801

English physician and physicist Thomas Young (1773-1829) was elected a fellow of the Royal Society in 1794 and published a number of articles in Philosophical Transactions, including “On the mechanism of the eye” (1801) which included the first description of astigmatism.

  • Young provided this explanation for Plate V (above):
  • Fig. 17. Vertical section of my right eye, seen from without; twice the natural size.
  • Fig. 18. Horizontal section, seen from above.
  • Fig. 19. Front view of my left eye when the pupil is contracted; of the natural size.
  • Fig. 20. The same view when the pupil is dilated.
  • Fig. 21. Outline of the eye and its straight muscles when at rest.
  • Fig. 22. Change of figure which would be the consequence of the action of those muscles upon the eye, and upon the adipose substance behind it.
  • Fig. 23. Scale of the small optometer.
  • Fig. 24. Appearance of four images of a line seen by my eye when its focus is shortest.
  • Fig. 25. Outline of the lens when relaxed: from a comparison of M. Petit's measures with the phenomena of my own eye, and on the supposition that it is found in a relaxed state after death.
  • Fig. 26. Outline of the lens sufficiently changed to produce the shortest focal distance.
  • Fig. 27. Apparatus for ascertaining the focal length of the lens in water.