Choroidal stress and emmetropization.

Abstract Human eyes of all ages were partly denuded by removing sclera behind, in front of, or about the equator. Inflation of the eyes, up to 14 mm of Hg, was followed by axial elongation rather than the radial expansion expected. Markers proved that the elongation was the result of ciliary muscle stretch; the strain of the choroid behind the equator was so slight that tracings of the posterior segment before and after loading could be superimposed. The axial expansion of the choroid supports a crucial point in a theory of emmetropization and demonstrates the potential significance of ciliary muscle tone on choroidal tension and scleral stretch.