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Extraocular Muscles and their Effect on the Shape of the Eye
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The following works, two centuries old, provide evidence that
accommodation of the eye to different distances is a result of the
extraocular muscles
changing the shape of the cornea or of the eye as a whole.
They are reprinted from Philosophical Transactions of the Royal
Society of London, 1794-1802. Conspicuously absent from this collection
is the work by Thomas Young, whose theory that was the lens and the lens
only changes in shape during accommodation. He published two articles in
defense of his theory, one in 1794, and another (his most famous and
widely cited), in 1801. Young's theory is the only one that prevails
today in "scientific" circles, with the exception that Young thought the
lens to contain muscles, and now the ciliary muscles are said to be
responsible for controlling the lens's shape, as was proposed by
Hermann von Helmholtz in the 1840s.
- Mr. Pierce Smith. "Observations on the Structure of
the Eyes of Birds." And mammals for that matter. The author examines
the interface between the recti muscles and cornea in birds and
quadrupeds. Considerations about the human eye are also given.
Illustrated. (Published 1795)
- David Hosack, MD. "Observations on Vision."
An argument that the extraocular muscles are responsible for
accommodation in humans. Illustrated. (Published 1794)
- Everard Home, Esq.: The Croonian Lectures on Muscular Motion.
- 1794 Croonian Lecture.
Anatomical and experimental evidence that the cornea changes during
the eye's adjustment to different distances; extraocular muscles
must be involved. Illustrated. (Published 1795)
- 1795 Croonian Lecture.
Further evidence for corneal change during accommodation. Theory expanded
to include movement of lens and elongation of eye via ciliary and
extraocular muscles Illustrated. (Published 1796)
- 1801 Croonian Lecture.
Demonstration of accommodation in various lensless eyes. (Published 1802)
While most have abandoned the theory that the cornea is a dynamic part of
the eye, a few 20th century experiments support the idea that the cornea
changes more rapidly than is usually assumed.
In 1931 Optometrist J.W. Parker wrote an article on instant
Changes in
Corneal Astigmatism evidently produced by the extraocular muscles.
See also the bibliography,
The Incredible Changing Cornea.
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