How do glasses help the eyes?
Some of us need glasses to get a clear picture of the distant scenery, Others need glasses to read a page of print. But this does not mean that the eyes are sick or damaged. They just need a little help to do their work better. The lenses in a pair of glasses do what the eyes would do for themselves if they could.
All day long, your eyes are busy taking colored, three dimensional movies. They work much like a camera, though they are far better than the best man made camera. Each eye is a round ball. The cornea is that bulge on the front of the eye ball and the lens is a tAndow pane of transparent tissue behind it. The cornea and lens work together to cast pictures on the retina, which is a kind of movie screen inside the back of the eyeball.
The scenery outdoors, a room and even a page of print are very large pictures. These large pictures must be telescoped down in perfect detail to tiny, tiny pictures. The tiny copies must fall exactly on the retina. The outside picture reaches the eye on beams of light and they must be tapered at just the correct angles.
This job is done by the lens and the cornea. When viewing a close object, the lens squeezes up and becomes thicker, When gazing at the distant scenery, the lens relaxes and become thinner, This adjusts the tapering angles of the light so that pictures from near and far focus exactly on the retina.
Nearsighted people see close objects clearly, but distance objects are blurred. This is because the light is tapered to form a picture just in front of the retina. Glasses with concave lenses cause the light rays to fan out a little before they reach the eye,
The eye can taper these rays to form a picture farther back where it focuses directly on the retina.
Farsighted people see the distant hills but the printed page is blurred, The light rays taper to form a picture too far back, behind the retina. Glasses with convex lenses taper the light rays a little before they reach the eye. With this extra help, the eye can 'Lend them to focus the picture farther forward, exactly on the retina.
Other sight problems call for different types of eye glasses. The expert to consult in all cases is an oculist. He is a doctor qualified to test the eyes and order the right glasses. The optician is the man who makes the glasses and frames and carried out the orders of the oculist.