526 THE HUMAN BODY. 



such eyes; but young children frequently also possess them, 

 and if so should at once be provided with spectacles. 



Short-sighted eyes appear to be much more common now 

 than formerly, especially in those given to literary pursuits. 

 Myopia is rare among those who cannot read or who live 

 mainly out of doors. It is not so apt to lead to permanent 

 injury of the eye as is the opposite condition, but the effort 

 to see distinctly objects a little distant is apt to produce head- 

 aches and other symptoms of nervous exhaustion. If the 

 myopia become gradually worse the 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 eyeball. 

 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 ob- 

 jects 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 observe many little matters in 

 the demeanor or expression of those with whom they con- 

 verse, 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 con- 

 tracts and the suspensory ligament is relaxed. A special 

 effort of accommodation is therefore needed in order to adapt 

 the eye to see near objects distinctly; and convex glasses are 

 required. 



In all forms of deficient accommodation 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. 



Optical Defects of the Eye. The eye, though it answers 



