Abstract :
The human eye has gone along through countless years, with little change in what was demanded from it. It worked through the daytime, for the most part looking at rather large objects, and when it became dark it generally ceased to function. Now, within just a few years this has all changed. The use of the eye for fine work, for reading and for fine manufacturing operations, has been very greatly increased and then in addition, we are demanding that it do much of its work under artificial light which, furthermore, in many cases is far from good.
