THE SENSE OF SIGHT 697 



very much hypertrophied, thus reinforcing the meridional fibers. In 

 myopia, on -the contrary, where the accommodative effort is at^a mini- 

 mum, the entire muscles possesses less than its average size and 

 development. 



According to Tscherning, a different explanation of the action of the 

 ciliary muscle must be given. Thus, when it contracts, the antero-internal 

 angle, that portion in close relation with the suspensory ligament, recedes 

 and exerts on the ligament a pressure which in turn exerts a traction on the 

 peripheral portions of the anterior surface of the lens, which produces the 

 deformation observed. At the same time the postero-external portion of 

 the muscle exerts traction on the chorioid, thus sustaining the vitreous 

 and indirectly the lens. 



The reason for the flattening of the periphery of the lens from zonular 

 compression and the sharpening of the central convexity is to be found in 

 the fact that the convexity of the more solid central portion, the nucleus, 

 is greater than that of the lens itself. Hence it is easily understood why a 

 zonular traction would give rise to peripheral flattening. 



There is, however, one point which seems difficult to harmonize wit. 

 Tscherning's view; that is, the fact that during accommodation the lens 

 appears to be slightly tremulous, thus showing relaxation, and not increased 

 tension, of the suspensory ligament. 



Range of Accommodation. It has been stated that rays of light 

 coming from a luminous point situated at any distance beyond 65 meters 

 are so nearly parallel that no accommodative effort is required for thei: 

 focalization. So long as the luminous point remains between infinity and 

 6s meters, the eye, directed toward it, remains completely relaxed. The 

 point at which the object can be distinctly seen without accommodation 

 is termed the far point or the punctum remotum. This for the normal eye 

 at ^distance of^ meters or beyond. 1 If the luminous point ^aduaUy 

 approaches the eye from a point 65 meters distant, the accommodative 

 power comes into play and gradually increases until it attains its maximum 

 The nearest point up to which the eye is able to form distinct images of 

 Sctelslffl its near point or puncture proximum This near point in a 

 healthy boy of twelve years will lie at a point situated 7 cm. from the eye 

 while t^e same point lies 20 cm. distant in a man of forty years Of ol > ects 

 which lie nearer than the punctum proximum the eye **& 



images. The distance between the punctum remotum and the 

 mum is termed the range of accommodation. 







: l the refracting power of which is such as to enable it to produce the 



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