The Theory Breaks Down 255
Further study of the subject has only added to its dif ficulty, while at the same time it has tended to relieve the schools of much of the responsibility formerly attributed to them for the production of myopia. As the "American Encyclopedia of Ophthalmology" points out, "the theory that myopia is due to close work aggravated by town life and badly lighted rooms is gradually giving ground before statistics."1
In an investigation in London, for instance, in which the schools were carefully selected to reveal any differ ences that might arise from the various influences, hy gienic, social and racial, to which the children were sub jected, the proportion of myopia in the best lighted building of the group was actually found to be higher than in the one where the lighting conditions were worst, although the higher degrees of myopia were more nu merous in the latter than in the former. It has also been found that there is just as much myopia in schools where little near work is done as in those in which the demand upon the accommodative power of the eye is greater.2 It is only a minority of children, moreover, that become myopic; yet all are subject to practically the same influ ences, and even in the same child one eye may become myopic while the other remains normal. On the theory that shortsight results from any external influence to which the eye is exposed, it is impossible to account for the fact that under the same conditions of life the eyes of different individuals and the two eyes of the same individual behave differently.
Owing to the difficulty of reconciling these facts on the basis of the earlier theories, there is now a growing
1 American Encyclopedia and Dictionary of Ophthalmology, edited by Wood, 1913-1919, vol. xi, p. 8271. 2Lawson: Brit. Med. Jour., June 18, 1898.