ACCOMMODATION 



221 



at the corneo-sclerotic junction, when its radial fibres contract 

 they drag the ciliary processes, with the adherent hyaloid mem- 

 brane, forward, simultaneously the circular fibres by their con- 

 traction constrict the circle round which the suspensory ligament 

 is attached. The result is to relax the ligament and lens capsule, 

 and the elasticity of the lens comes into play. The maximum 

 alteration in radial curvature, which affects the anterior surface 

 almost exclusively, is from 10 mm. resting to 6 mm. fully accom- 



Cornea 



Sinus venosus 



Conjunctiva 



Retina 



FIG. 50. Section of anterior part of eyeball, showing structures concerned in 

 accommodation. (After Merkel and Kallius.) 



modated. The normal adult is thus enabled to see objects dis- 

 tinctly to within 10 or 15 cms. distance. (Note. This is the 

 theory of accommodation at present almost universally accepted.) 



The Abnormal Eye. 



In the normal or emmetropic eye, parallel rays, which in 

 practice are those coming from a distance greater than 6 metres, 

 are focused in the resting state. Within 6 metres accommodation 

 begins, and it increases as the object approaches, reaching its 

 maximum at about 10 or 15 cms. This is called the near point 

 of vision, and the point at which accommodation begins is called 

 the far point. 



