VISION. 



n-65 



sec in trees, landscapes, the exterior of houses, 

 &c. As a general rule glasses are not ad- 

 missible for young persons, for if worn there 

 is scarcely any hope ( f amendment ; but it is 

 sometimes necessary to allow them during 

 music lessons, in which case they should be 

 of the lowest power that enables the child to 

 see the notes, and their use should be re- 

 stricted to that pursuit. 



Myopic persons, generally, should remove 

 objects they are regarding as far from them 

 as possible, and should avoid small type, 

 minute writing, and microscopical inves- 

 tigations. The use of a high desk is very 

 important, not merely as tending to prevent 

 oculo-cerebral congestion, but also pain in 

 the chest, which is often caused by stooping ; 

 and as a general rule, all near-sighted persons, 

 of whatever age, should exercise the eyes, 

 when in the open air, by endeavouring to 

 make out distant objects. 



There is a simple plan which persons who 

 write or read much should adopt as being 

 highly serviceable in preserving the powers of 

 their vision. It is that of raising their eyes 

 from their work at short intervals, and fixing 

 them upon the cornice of the ceiling at the 

 further end of the room, and if there be a 

 pattern, making it out. This exercises the 

 eyes at the focus for distant objects; and, 

 simple as it is, is of great use in preventing 

 nearsight. 



There is a form of myopia of which we 

 have seen several examples, and which is 

 deserving of attention. It occurs in young 

 persons, and leads to unmerited punish- 

 ment. The youth does not hold his book so 

 near the eyes as to attract attention, and reads 

 fluently at perhaps eight or ten inches ; but he 

 cannot see objects distinctly at twenty feet. 

 Such young persons have been brought to us 

 under the impression that they were " sham- 

 ming;" but careful investigation convinced us 

 that such was not the case. Great responsi- 

 bility attaches to the advice given in a case of 

 this description, as on it depends much of the 

 comfort of the individual during life. He 

 should by no means be allowed glasses, as 

 they would most assuredly confirm the mis- 

 chief. His books should be of large type ; he 

 should frequently rest his eyes when study- 

 ing ; should be much in the open air ; and 

 the eyes should be often bathed with cold 

 spring water. 



Presbyopia (irpcaSvs, old ; &\</, the eye) is that 

 condition of vision in which objects are not 

 distinctly perceived unless they are at some 

 distance from the eye. Although not neces- 

 sarily confined to advanced years, it is one of 

 the changes which warn the individual that 

 the prime of life is past, as it usually com- 

 mences about the age of forty. 



To a person in whom presbyopia is com- 

 mencing, distant objects appear as clear and 

 sharply defined as ever ; but reading, writing, 

 and working, especially by candlelight, be- 

 come irksome and distressing. The eyes feel 

 strained, and there is uneasiness over the 

 brow sometimes amounting to headach ; the 



page of a book appears misty, the type con- 

 fused at the ordinary reading distance, and a 

 strong light is indispensable. The person 

 therefore draws the candle to him, and holds 

 the book close to it nearly at arm's length, 

 throwing his head back to increase the dis- 

 tance. 



These symptoms are the result of changes 

 in the eye which cause the converging rays of 

 light to be brought to a focus beyond the 

 retina, upon which a confused and imperfect 

 image is consequently depicted. They may be 

 the result either of flattening of the cornea or 

 the crystalline lens, diminution in the density 

 of the humors, or diminished curvature of the 

 retina. Absence of the crystalline lens pro- 

 duces the same effect in an extreme degree. 



The explanation of the feelings of dis- 

 comfort, and other presbyopic symptoms, is 

 simply this the object being removed to a 

 greater distance than is natural, the visual 

 angle is reduced in size, the picture on the 

 retina diminished, and the quantity of light 

 becomes less: hence the retina, with its some- 

 what impaired sensibility is unable to appre- 

 ciate the object without effort, and a con- 

 siderable increase of light. 



The necessity for this increased quantity of 

 light is a frequent cause of amblyopia super- 

 vening upon presbyopia, for a very large 

 number of work-people pursue their avoca- 

 tions in densely crowded and ill lighted rooms, 

 and they are obliged to struggle on despite of 

 their failing sight. Dr. Sichel states that one 

 of the causes which renders amblyopia in 

 connection with presbyopia so common in the 

 conciergeries of Paris is, that the majority of 

 persons are tailors and shoemakers, who 

 almost without exception inhabit confined 

 rooms called loges, into which light and air can 

 scarcely penetrate. Presbyopia may be con- 

 genital, and it is frequently excited in persons 

 under thirty, by the injurious habit of wearing 

 convex glasses, miscalled "preservers." Among 

 the lower and even the middle classes the 

 belief is general that if from any cause the 

 sight is weakened, such glasses are beneficial, 

 an impression most fallacious. It however 

 answers the purpose of some advertising op- 

 ticians to encourage the idea, regardless of 

 the consequences to their victims. 



M. Desmarres states* that country people 

 are almost all attacked with presbyopia at an 

 earlv age, because their sight is much exer- 

 cised on distant objects, and very little on 

 near objects, whereas the dwellers in towns 

 are attacked later in life. It may be so in 

 France, but is certainly not the case in Eng- 

 land. The same writer affirms that this im- 

 perfection in sight is rife in countries win re 

 the light is very bright. 



The first indications of presbyopia are 

 always perceived in the evening, and it is im- 

 portant that they should be distinctly borne 

 in mind. During the day, persons past the 

 meridian of life, accustomed to read, write, or 

 work can do so without inconvenience, but as 



* Traite des Maladies des Yeux, p. 809. 



