EYESTRAIN 263 



C. Test for Astigmatism 



Method: Use the clock dial disk at 20 feet. If some lines are blacker 

 than others, then astigmatism is present. If headaches or other symp- 

 toms are present, then you should consult an oculist and have glasses 

 fitted to correct this trouble. 



Eyestrain. Eyestrain frequently results from attempts 

 to overcome defects of the eye, and also by putting the 

 eyes to too severe use, thus taxing the blood vessels of the 

 eye, and the nerves, which in turn affect the nerves of 

 the head and stomach. The following are some of the 

 things which we often call upon the eye to do : 



1. Change focus for different words in the line. This is 

 because they vary in their distance from the eye, and only 

 in two places are the eyes equally distant from the words 

 being read. 



2. Insufficient light. The illumination of the object is 

 of extreme importance as the light fades at close of day. 

 For then the white paper of a printed page becomes darker 

 and darker, until finally it reflects very little more light to 

 the eye than the printed letters ; consequently the letters 

 no longer stand out, and we have great eyestrain. 



3. The wrong position produces glare. One of the 

 most frequent errors around the home table is that boys 

 and girls frequently face the light rather than allow it to 

 come over the shoulder, or from above. Overhead light- 

 ing systems are far better than any light which throws a 

 glare on the paper. Reading in an unsteady or flickering 

 light, particularly on moving trains, is extremely bad for 

 the eye. 



4. Too much light in the field of vision is as bad as too 

 little light. For most purposes the student lamp, in- 

 candescent electric light, and Welsbach gas light of mod- 



