266 THE HUMAN BODY 



eyes should be rested for several months. Short-sighted persons 

 are apt to have, or acquire, peculiarities of appearance : their eyes 

 are often prominent, indicative of the abnormal length of the eye- 

 ball. They also get a habit of "screwing" up the eyelids, probably 

 an indication of an effort to compress the eyeball from before back 

 so that distant objects may be better seen. They often stoop, too, 

 from the necessity of getting their eyes near objects they want to 

 see. The acquirement of such habits may be usually prevented 

 by the use of proper glasses. On the other hand, "it is said that 

 myopia even induces peculiarities of character, and that myopes 

 are usually unsuspicious and easily pleased; being unable to ob- 

 serve many little matters in the demeanor or expression of those 

 with whom they converse, which, being noticed by those of quicker 

 sight, might induce feelings of distrust or annoyance." 



In old age the lens loses some of its elasticity and becomes more 

 rigid. This leads to the long-sightedness of old people, known as 

 presbyopia. The stiffer lens does not become as convex as it did 

 in early life, when the ciliary muscle contracts and the suspensory 

 ligament is relaxed. In order to adapt the eye to see near objects 

 distinctly, therefore, convex glasses are required. 



In all forms of defective vision too strong glasses will injure 

 the eyes irreparably, increasing the defects they are intended to 

 relieve. Skilled advice should therefore be invariably obtained 

 in their selection, except perhaps in the long-sightedness of old 

 age, when the sufferer may tolerably safely select for himself any 

 glasses that allow him to read easily a book about 30 centimeters 

 (12 inches) from the eye. As age advances stronger lenses must 

 usually be obtained. 



