1916] on Eyesight and the War 697 



One word before I leave this important subject, which takes us 

 back to the question of wearing glasses in the Army. The glasses 

 must be worn alirays. You can quite understand that if you wear 

 glasses at one time and not at another, the muscle being probabl^" 

 in a state of spasm does not yield to the glass, and you do not get 

 the result you want. The important result is that, in young people, 

 by wearing the correction, the error tends to disappear. 



I think you would like to know how in every department at the 

 King George Hospital the soldier is considered. Everything is 

 up-to-date, and whether in the X-ray department, or the dental 

 rooms or the operating theatre, you will find the " last word " in 

 appliances and instruments. In my own department— the eye 

 department — the greatest care is taken in testing the sight. The 

 very best possible glasses, supplied by Messrs. Hamblin, are supphed 

 to the patients, and Messrs. Hamblin generously charge us for this 

 work less than cost price. Moreover, the fitting of the glasses is 

 not left to chance, for properly qualified opticians attend at the 

 hospital and take the most careful measurements. These opticians 

 measure and fit every glass, so that the patients get the fullest value. 

 We have heard so much during the War of mistakes and aljuses 

 that I think it is only fair, and certainly it is most pleasing, to 

 be able to concentrate our attention for a short time on a different 

 picture. 



So far we have been reviewing the effects of the War on com- 

 batants ; we now turn to the effects on those of us who are disqualified 

 by age to take an active part. 



We have been considering defects of the eyes due to their shape, 

 and we have seen how prevalent these defects are, yet some eyes 

 (it is true, very few) are normal. Now, there is a defect that attacks 

 all eyes if the individual lives long enough, viz. presbyopia, or old 

 sight. 



It may not be manifest, and the individual may be unconscious 

 of it ; bat nevertheless, as we shall see, no eye after about the age 

 of forty-five escapes it. It is a senile change, and is, as Bonders 

 observed, no more a disease than is grey hair. 



At the beginning of life the crystalline lens, which by focussing 

 rays of light on the retina gives us our distinct vision, is nothing 

 more than a little bag of semi-fiuid jelly. By making this lens 

 thicker or thinner we can focus for near or distant objects. This 

 work is done by the ciliary muscle, and chiefly by that portion of the 

 muscle which surrounds the lens pressing on it in the form of a 

 sphincter. The old theory (Helmholtz's) of the mechanism of 

 accommodation was that the lens at rest was compressed by its capsule, 

 and that when the ciliary muscle acted it pulled on this capsule and 

 released it, thereby allowing the lens to assume a more convex form. 

 The new theory, advanced by Tscherning, and supported entirely by 

 clinical proof, is that the lens at rest is unacted upon, but that when 



