The curvature of the eye lens is proven by the following facts: When the eye lens is extracted in operations for cataract, it takes about a plus 10 diopter spherical lens, in glasses, to replace it for clear distant vision. It takes about 3.00d. more for reading at 13 inches. It taks a lens of more than 100.00d. for hyper-sighted eyes. It takes a weaker lens for near-sighted eyes. A cataract lens is, ordinarily, a plus 10.00d. spherical lens.
Should the eyes grow bigger, if the growth is natural and symmetrical, it would make no difference for the focus. A larger sphere or a larger eye has less curvature. It would focus on the retina just the same as the one inch eye. Should the eye be smaller it would also make no difference. A smaller sphere or a smaller eye has more curvature to focus nearer.
It is claimed by many authorities that the far-sighted or hyper-sighted eyes are smaller eyes and near-sighted eyes are those whih grow bigger. This is a fanciful assumption. The midgets are not all hyper-sighted and the giants are not all nearsighted. The small birds cannot see farther than the eagle -- the eagle, surely, is not near-sighted.
The natural size and the natural growth of the eyes should have little
to do with being hyper-sighted and becoming near-sighted. It is the
unnatural use and the subsequent unnatural growth which can, and does,
make our eyes poor-sighted, near-sighted and astigmatic.
The optical curvature of our eyes and of lenses are relative curvatures; it is similar to relative humidity.
Contents | Lesson 12 | Lesson 14