Chap, xxix.] ANOMALIES OF REFRACTION. 389 



that case, indistinct vision would result. The accom- 

 modation is called into play even for parallel rays, and 

 the image is thus focussed. But as the object is 

 brought nearer and nearer, the accommodation is more 

 and more called into play. As a result, the power of 

 accommodation fails before the object reaches the near 

 point of distinct vision for the normal eye. The 

 punctum proximum is, therefore, farther from the 

 eye than usual, and an object is held farther from the 

 eye than usual, hence the phrase long sight. It may 

 be that the focus for parallel rays falls so far behind 

 the retina that the utmost convexity of the lens, the 

 utmost effort of accommodation, will not bring it suffi- 

 ciently forwards to coincide with the retina. It will 

 be therefore impossible to get a distinct image with 

 parallel rays at all; and, thus, distant objects cannot 

 be properly seen. On the other hand, if the hypermr- 

 tropia be slight, a small amount of accommodation will 

 correct it, and the person may consequently be unaware 

 of the defect. But the accommodation is never at 

 rest, and hence a feeling of strain and fatigue of the 

 eyes may in time arise. The myopic eye, with its 

 shorter focal distance is able to see objects distinctly 

 when held nearer to the eye than usual, the punctum 

 proximum is nearer, and hence the phrase short sight. 

 In myopia, because the focus for parallel rays is in 

 front of the retina, they cannot be focussed on the 

 retina, and it is only as the object comes nearer that 

 the focal point passes backwards, and at last coincides 

 with the retina. The punctum remotum for a short- 

 sighted eye is, therefore, not infinity, but at a finite 

 distance. 



The cause of both conditions appears to be not a 

 difference in the refractive power of the media, but, 

 according to Bonders, a difference in the position of the 

 retina. In other words, the optic axis is in the one 

 case shorter, and in the other case longer than usual. 



