What is the use of the aqueous humor and the vitreous humor?
Light, when refracted through the lens, becomes separated into its component colors--red, yellow, green, blue, and violet; and the greater the magnifying power of the lens, and the brighter the object viewed, the greater the dispersion of the rays.

So that if the crystalline lens of the eye alone were used, we should see every white object bluish in the middle, and yellowish and reddish at the edges; or, in vulgar language, we should see starlight.
This difficulty perplexed Sir Isaac Newton all his life, and he never discovered the mode of making a refracting telescope which would obviate it.

But M.Dolland, an optician, reflecting that the very same difficulty must have presented itself to the Maker of the eye, determined to ascertain how he had obviated it.

He found that the Maker of the eye had a knowledge of the fact that different substances have different powers of refracting or bending the rays of light which pass through them, and that liquids have generally a different power of refraction from solids.

For instance, if you put a straight stick in water, the part under water will seem bent at a considerable angle, while if you put the stick through a little hole in a pane of glass it will not seem so much bent.