MULTIPLE VISION WITH ONE EYE. 277 



double vision will be the consequence. In almost all cases, however, 

 of distortion of the eyeballs, the image falls upon a part of one retina, 

 which is more sensible than the portion of the other on which it falls; 

 the consequence will be, that the mind will acquire the habit of attend- 

 ing to the impression on one eye only; and the other may be so neg- 

 lected, that it will assume a position to interfere as little as possible 

 with the vision of its fellow: so that, although at first, in squinting, 

 there may be a double impression, vision is ultimately single. Buffon, 1 

 who was of this opinion, affirms, that he examined the eyes of many 

 squinters, and found that they were of unequal power ; the weaker, in 

 all cases, having turned away from its direction, and generally towards 

 the nose, in order that fewer rays might reach it, and consequently 

 vision be less interfered with. Yet it is always found, if the sound 

 eye be closed, that the other resumes its proper direction; a fact which 

 disproves the idea of De La Hire 2 and others that the cause of strabis- 

 mus or squinting is a difference of sensibility in the corresponding 

 points of the retinae, and that the discordance in the movements of 

 the organs occurs in order that the images may still fall upon points 

 of the retinae that are equally sensible. According to this view, both 

 eyes must of course act. 



The fact of the diverted eye resuming its proper direction when the 

 sound one is closed is of practical application. Many of the cases of 

 squinting that occur in infancy have been caused by irregular action 

 in the muscles of the eyeball ; so that certain of them, from accident 

 or imitation, having been used more frequently than others, the due 

 equilibrium has not been maintained; double vision has resulted; and 

 the affected eye has gradually attained its full obliquity. In these 

 cases, we can, at times, remedy the defect, by placing a bright or con- 

 spicuous object in such a position as to exercise the enfeebled muscles ; 

 or, we can compel the whole labour of vision to be effected by one eye, 

 and that the affected one, which, under the stimulus, will be correctly 

 executed, and, by perseverance, the inequality may be obviated. 

 These, indeed, are the only cases in which we can expect to afford 

 relief ; for if the defect be in the interior of the eye, in a radical want 

 of correspondence between the retinae, or in inequality of the foci, it is 

 irremediable. 



It would appear, then, that in confirmed squinting, one eye is mainly, 

 if not solely used, and vision is single, and that the inclination of one 

 eye inwards may be so great as to deprive it of function, or so slight as 

 to allow the organ to receive rays from the same object as its fellow, 

 and although on different parts of the retina, yet they may become asso- 

 ciated; but, in either case, it would seem, that they, who squint habitu- 

 ally, neglect the impressions on the distorted eye, and see with but one. 



It has been remarked, that the eyeball of the imperfect eye is drawn 

 towards the nose, in order that as few rays as possible may penetrate 

 the organ, and the vision of the sound eye be less liable to confusion. 

 Sir Everard Home 3 conceives, that it takes this direction in consequence 



1 Mem. de 1' Academic, 1743, p. 231. 



* Ibid., torn. ix. 530; Jurin, in Essay appended to Smith's Optics, 178-194. 



3 Philos. Transact., 1797, and Lectures on Comparative Anatomy, iii. 238, Lond., 1823. 



