;54 



NATURE 



[August 31, 1916 



accompanying table, where, out of 5000 eyes, 4303 were 

 found by me to be astigmatic : — 



1. Same refiac- j'rtEmmeliopia(see Pies- 

 l lion in boih I byopia below) ... 9 



eyes. -[ b Hypermetropia ... ^3 



(657) L Myopia 22 



\d Astigmatism 



j tlypermetropic 438 



\ Myopic ... 113 



\^Mixed ... \2. 



2. Refraction different ni llie two eyes 

 (Anisonieiropia) ... ... ... 1843 



2500 individuals 

 whose sight 

 aftercorrection 

 was normal and<[ 

 who had no 

 dise.ise of the 

 eyes. 



2500 



5000 eyes (as above) 



5000 



Of the 2500 individuals 961 were presbyopic, and only 9 of 

 these were emmetropic. 



(2) Low Anisometropia. — When the difference be- 

 tween the two eyes is small, impulses can pass from 

 the brain to one ciliary muscle to correct this defect. 

 In the above table, out of 2500 individuals, no fewer 

 than 1843 had "odd" vision. 



(3) Want of Balance between the External Muscles. 

 — When small in amount impulses caii pass to one 

 muscle to preserve the balance and so avoid diplopia. 



In all these instances of eyestrain this extra work 

 means an enormous unnecessary waste of nerve energy 

 going on all the waking hours, and it becomes im- 

 perative to stop this waste in all cases where a large 

 amount of nerve energy has already been lost, which 

 occurs from the effects of high explosives on our 

 soldiers. 



At the time of the explosion the "wind pressure" 

 is so great that I have recorded a case ^ where, with- 

 out being hit by any foreign body, an eye was com- 

 pletely destroyed through detachment of the retina 

 by wind pressure. This wind pressure is followed by 

 a high vacuum, which may be so great that in one 

 case I saw at the King George Hospital the eye had 

 been evulsed. Such etfects show how the soldier's 

 nervous system can suffer. Nerve energy is lost — as 

 after a bad railway collision — "virtue" is knocked 

 out, and it becomes imperative to conserve all the 

 ■energy that is left, and we must therefore remove the 

 eyestrain if it is present. At the King George Hos- 

 pital oift- resident ophthalmic medical officer. Dr. 

 Harwood, is keenly alive to the ill-effects of eyestrain, 

 and almost miraculous have been some of the cures 

 by simply putting the invalid into glasses. The neur- 

 asthenia following head injuries can often be cured 

 in the same way, and we had one very marked case 

 as an example of this. The man, aged thirty-eight, 

 was hit on the head while lying in his dug-out at 

 Gallipoli by a wet sand-bag falling 8 ft. He was not 

 rendered unconscious, but could not stand or walk. 

 After about six weeks he was admitted into the King 

 George Hospital. His symptoms all the time had 

 been inability to stand or walk, constant headache 

 and giddiness, inability to read or even look at the 

 light, with rather sluggish memory and mental facul- 

 ties — no treatment had succeeded. Dr. Harwood put 

 the eyes under atropine, when there was an imme- 

 diate improvement. He was given glasses correcting 

 0-25 astigmatism in one eye and 037 in the other. 

 Within a few hours of getting the glasses he was 

 reading, and within a week he could stand and walk, 

 and his headache and giddiness had disappeared. 



2 Medicnl Press and Circular, December 29, 1915. 



In many cases where wounds had remained sluggish, 

 the nerve energy required for the healing processes 

 being used up by eyestrain, a suitable pair of glasses 

 immediately proved a remedy. 



When there is a want of muscle equilibrium the 

 correction of the astigmatism generally removes it, 

 and in bad cases of head injuries, when testing the 

 patient was impossible. Dr. Harwood has obtained 

 excellent results by simply bandaging up one eye. 

 The testing has to be very carefully done, always 

 under a cycloplegic, and the ophthalmometer is a most 

 invaluable instrument for estimating the astigmatism, 

 even 012 D. being recorded. 



(The ophthalmometer and its working were here 

 explained.) 



(3) Presbyopia. 



We have been reviewing the effects of the war on 

 combatants ; we now turn to the effects produced on 

 those of us who are disqualified by age to take an 

 active part. 



We have been considering defects of the eyes due 



-1« iS ?J 1? 30 -SS" 



NO. 2444, VOL. 97] 



Fig. I. — Variation of accommodative power with age. 1200 cases. 



to their shape, and have seen how prevalent these 

 defects are; yet some eyes (it is true very few) are 

 normal. Now there is a defect that attacks aU eyes 

 if the individual lives long enough, viz. presbyopia, or 

 old sight. It may not be manifest, and the individual 

 may be quite unconscious of it, but nevertheless no 

 eve', after about the age of forty-five, escapes it. It 

 is a senile change, and is, as Donders observed, no 

 more a disease than is grey hair. 



At the beginning of life the crystalline lens is 

 nothing more than a little bag of semi-fluid jelly._ By 

 making the lens thicker we can focus for near objects. 

 This is done by the ciliary muscle, and chiefly by that 

 portion of the muscle which surrounds the lens and 

 acts like a sphincter. Tscherning's theory of the 

 accommodation which states that the lens is squeezed 



