86 The Eye 



after a long and enfeebling illness, such as scarlet fever, and then, for 

 the first time, it may be discovered that the person is hyperinetropic. 



Myopic eye : axis too long ; parallel rays, a, a, brought to focus at b before reaching retina, 

 and eventually giving blurred image at b', b 1 ; concave glass needed. (DixoN.) 



With advancing age the power of accommodation naturally dimi- 

 nishes, whilst, at the same time, the lens grows flatter, so that the 



Hypermetropic eye : axis too short ; parallel rays, a, , tending to a focus at b, form circles 

 of dispersion on retina at b', b', but are brought to proper focus by the convex glass. 



(DlXON.) 



old man (Trpfo-fivs) is almost sure to be hypermetropic. "But, as the 

 loss of accommodation in his case is the result of age, and nojt of a con- 

 genital defect, it is called presbyopia. 



Reference is made elsewhere (p. 58) to the fact that contraction 

 of the ciliary muscle is constantly associated with that of the internal 

 rectus both muscles being supplied by the third nerve and so it 

 comes about that the hypermetropic child who triumphs over the 

 defective depth of his eye-ball by a course of ciliary athletics is apt 

 to develop a convergent squint. It would, indeed, be a grave error to 

 perform tenotomy in such a case ; the child should be treated by convex 

 lenses. 



In due course the myopic man finds such difficulty in securing bin- 

 ocular vision of near objects that he gets into the habit of using one 

 eye at a time. 



Mr. Juler ' gives an excellent account of the anatomy of near- 

 sightedness myopia (/uvco, cfose, o>^, eye from the habit which myopic 

 people have of partly ' closing the eyes ' for distant vision), the defect 

 in which the eye-ball is too long, rays of light being brought to a focus 

 before the proper time. The defect usually comes on in childhood, 

 and is due to deficient strength in the ocular tunics, especially when 

 the child is busied with fine work, and in a bad light; he attempts to 

 obtain larger retinal images by keeping his head close down to 



1 Ophthalmic Science and Practice, 1884, p. 333. 



