386 PHYSIOLOGY AND HEALTH. 



901. Far-sightedness is a defect of age, when the eye loses 

 the power of adapting its focus to near objects. The lena 

 loses its convexity in some degree, and the rays are not con- 

 centrated upon the retina. This evil is obviated by the use 

 of convex glasses, which give the rays the proper refraction, 

 throw the image upon the retina, and enable the eye to see 

 near objects distinctly, 



902. The eye suffers with the rest of the body. The sight 

 is best in vigorous health, and is impaired by many diseases. 

 Some disorders of the eye have their origin solely in dis- 

 orders in distant organs. A troublesome affection, called 

 muscce volitantes, or flying flies, is sometimes caused by in- 

 digestion merely. The dyspeptic then sees flies or motes, or 



little clouds, that seem to be flying before his eyes. These 

 are owing to the state of the retina, which is frequently caused 

 by the state of the digestive organs ; and when the stomach 

 is restored to health, -the flying flies are gone. 



903. The eye wants the utmost cleanliness for its health. 

 It should, therefore, be bathed and kept free from dust and 

 other matters. It is benefited by the bath as well as the 

 skin. It is well to dip the face every morning, with the eyes 

 open, in cold and clear water, and then to move the lids and 

 thus wash the surface. This should be done daily, and 

 oftener when exposed to dust or other offensive matters. 



904. The eye needs fresh and pure air. Those who live 

 in the foul air of crowded dwellings and shops, or in the 

 smoke of some rooms, often have disordered vision. 



905. The eye is made for, and should be accustomed to, the 

 light. Those who work in dark shops, or live in dark streets 

 or houses, or in parlors closely darkened with curtains and 

 blinds, and women who wear veils to shut out the free light 

 of day, have comparatively weakened vision. 



906. The eyes need light for vision, and suffer or lose their 

 power in some degree when required to labor in insufficient 

 light. Thus they are injured when used for reading, sewing, 

 or examining any minute objects by twilight or moonlight, or 

 in any insufficient light, by day or night. All imperfectly 



