Binocular vision in light adaptation and dark adaptation in normal subjects and coal-miners.

PART II. COAL-MINERS HAVING established the behaviour of the normal subject when tested on the synoptophore under specified conditions of light adaptation and dark adaptation (Campbell and others, 1951), we have used the same methods to examine a large number of coal-miners (some 09htAdapted employed on the coal-face, and '60A some certified as suffering from / \ coal-miners' nystagmus). /# ' In our former observations (Campbell and others, 1948), the number of subjects available ~20 ./ \\ was too small for a detailed comparison, but it was obvious (a) Xc:< "(b) that normal coal-miners have ol . . . .remarkably high levels of stereo-^o Dark-Adopted scopic vision and adduction. < ,' , They tend to adopt an abnormal z A Coolminers /A \ fixation in the dark since they Normel subjects / habitually look upwards, and, X1 \/ in addition, the corneal reflexes 20 \"> I \,/are high. We have now recorded the (C) /(d)as s (C) \4 / (d ) = results as simply as possible, and *C . cr+Id. 0* + e,,.+5J , <have, therefore, omitted the Unoccommodoted Accommodoted actual synoptophore readings. Fio. 7.-Fusion angles in normal subjects Additional information is in(a) and s b), and coal-miners (c) and (d), in light adaptation and dark adaptation. cluded as to the effect of age, and the degree of accommodation for half-distance, since both these factors enter into the miner's normal working life.