THE EYES 253 



We remember that a normal eye does not need to use 

 its accommodation muscles when looking at distant 

 objects, but only in reading, writing, and other close 

 work, requiring extra focusing power. However, a 

 farsighted eye must exert itself to focus the rays of 

 light at all distances, and so there is no rest for the 

 muscles except during sleep. Of course the remedy 

 for farsightedness is convex glasses, just the oppo- 

 site of the concave lenses that are used for near- 

 sightedness. How convex the glasses should be made 

 depends upon how faulty the formation of the eye 

 may be. That is a matter for the oculist to deter- 

 mine. 



A common defect usually 

 due to unequal curvature of 

 the cornea is called by the 

 long name astigmatism. Usu- 

 ally this condition dates from 

 birth, though it may not be 

 troublesome enough to attract 

 attention until the eyes are Tes t for Astigmatism. The Lines 



put tO Considerable USe in should appear of Equal Black- 

 ness. 



reading, study, or similar oc- 

 cupations. This defect in the form of the eyeball 

 causes inability to see horizontal and vertical lines 

 equally well. On the eye-test card, there are dia- 

 grams having lines of equal blackness radiating from 

 a center. If, when this test card is at a distance of 

 about twenty feet, any of these lines appear less 



