1461 



VISION. 



France were rejected on the score of short 

 sight. 



Oculo-cerebral congestion may give rise 

 to myopia ; a case alluded to by Smith was 

 probably of this nature, that of a person 

 who suddenly became myopic on coining out 

 of a cold bath. And Revielle-Parise men- 

 tions an officer who was similarly attacked 

 at the end of a troublesome ague. Local con- 

 gestion is said to produce the same effect. 

 Desmarres relates a remarkable instance of a 

 lady excessively presbyopic, who became near- 

 sighted during a severe attack of conjunc- 

 tivitis, the former condition of vision returning 

 after the attack had subsided. Mr. Tyrrell also 

 mentions a lady who .had long suffered from 

 granular lids, which were eventually cured, 

 but she afterwards required the aid of concave 

 glasses, from the cornea having become un- 

 usually convex during the continuance of 

 the chronic disease. In each of these cases, 

 there may have been some change, either 

 in the quantity or quality of the aqueous 

 humour, or in the consistence of the cornea. 



Itis very common to meet with eyes differing 

 in their focal length, and in such cases one 

 usually falls into disuse ; it is also occasion- 

 ally found that one eye will be myopic and 

 the other presbyopic, a condition of vision 

 embarrassing to the patient and the sur- 

 geon ; but the nature of which may easily be 

 ascertained by careful trial with glasses. D . 

 Serre, in a memoir on the application of 

 phosphenes, or the luminous spectra excited by 

 compression of the eye *, states that these as- 

 ' sist in the diagnosis of myopia. He says that 

 in such cases the nasal and orbital phos- 

 phenes appear equal to the temporal in con- 

 stancy, brilliancy, and sometimes in size ; bnt 

 he cautions us against concluding that the re- 

 tinae of myopes are more sensitive than those 

 of persons having normal vision, ascribing the 

 above appearances to the greater prominence 

 of the eyes, which facilitates compression, and 

 admits of its application to the deeper parts of 

 the eye. These results he adds, are at com- 

 plete variance with the opinion of M. Steeber 

 of Strasburg, who thinks that the proximal 

 cause of myopia may sometimes be a peculiar 

 alteration of the retina admitting of a compli- 

 cation of myopia with amblyopia, or com- 

 mencing amuurosis ; for that if the retina be 

 essentially affected, the orbital, and sometimes 

 the nasal phospheues are scarcely appreciable, 

 or they may be entirely wanting. Dr. Serre 

 further asserts that which is certainly con- 

 trary to received opinions, and (we may 

 add), to our own experience, that when the 

 foci of two myopic eyes differ, the retina of 

 the eye with the shortest focus being that 

 least used, is absolutely stronger and more 

 active than the retina of the other eye. 



Myopia may be symptomatic of hydro - 

 phthalmia, and of conical cornea, In the former 

 case it will be accompanied with enlargement, 

 and symptoms indicating some inflammation 

 of the eye. In the latter, the change of form 



* Annales d'Oculistique, torn. xxiv. p. 161. 



in the cornea will be apparent on close exa- 

 mination.* Instances have also come under 

 our notice of congenital cataract having been 

 mistaken for myoj.ia. *j" In such cases the 

 patients have dull vision, and are unable to 

 see small objects distinctly even with the 

 aid of glasses. On careful examination a 

 greyish hue may be detected in the pupils ; 

 and if these be dilated by atropine, the 

 nature of the case is at once displayed by 

 the semi-opaque or slightly turbid lenses be- 

 coming visible. 



The progress of myopia depends very much 

 upon the line of conduct pursued by the indi- 

 vidual. If that be judicious from the com- 

 mencement, the defect may not increase, or if 

 acquired, may diminish ; but its march is too 

 often as follows : A person who is occupied 

 for months together in reading small type (for 

 example), finds that he discerns distant objects 

 less and less distinctly, and at once jumps to 

 the conclusion that spectacles are required ; 

 he goes to an optician, tries a pair, sees 

 better, purchases them, and proceeds with 

 his labour. After a time he finds that these 

 glasses do not afford the same amount of 

 assistance they did at first ; they are care- 

 fully wiped, but still are not satisfactory, and 

 therefore a pair of a higher power arj 

 purchased; with these he sees sharply at 

 first, though they do diminish a little ; but 

 they in time are laid aside, and the individual 

 goes on and on, until the whole scale has been 

 run through, and he is half blinded for the 

 remainder of his life. In the progress of such 

 a case other symptoms often develop them- 

 selves ; not only is the sight rapidly shortened, 

 but it is weakened; the eyes ache, and are 

 speedily fatigued by application ; there is op- 

 pression about the brow, and often faeadach; 

 he is teased with muscae volitantes, and the 

 sight is obscured from time to time by a mist. 



The case now assumes the character of 

 impaired vision from overwork, and unless 

 judicious treatment be adopted, amaurosis 

 may be the result. 



It is important to know that near sight 

 may be acquired in childhood by the common 

 practice that children have, of approaching 

 their eyes very close to any object on which 

 their attention may be engaged. When learn- 

 ing to read or write, or draw, they almost 

 invariably hold their faces sideways, nearly 

 touching the slate or paper. This should at all 

 times be discouraged. In like manner infants 

 should not have very small toys given them, 

 or such as require to be looked at closely, for 

 not only may they be rendered short-sighted, 

 but strabismus may be caused, for as the visual 

 axes naturally converge when objects are held 

 very near the eyes, the frequent repetition of 

 this may occasion a squint. For the same 

 reason there is sound judgment in printing 

 children's books in good bold type, and it is 

 well to encourage young people to observe 

 distant objects, and to describe what they 



* See Practical Remarks on Near Sight, pp. 47. 50, 

 { London Journal of Medicine, vol. i. p. 507. 



