Eyesight, and how to care for it / edited by George Black.

Date:
[1888]
Catalogue details

Licence: Public Domain Mark

Credit: Eyesight, and how to care for it / edited by George Black. Source: Wellcome Collection.

    119/168 (page 115)
    bright a light in reading, there is much more danger of the opposite extreme, and it is only necessary, in this direction, to avoid a dazzling or an irritating glare. It is not often that daylight indoors is too bright to read by — the direct rays of the sun being, of course, avoided — but too little light is a real and very common grievance. The distinctness of an ob- ject depends upon the amount of light reflected from its surface as well as upon its size; and to diminish the light by which it is seen is, so far as the eye is concerned, the same thing as to diminish its size. An increase in the size of the retinal image is at once required, to compensate for its dulness; to gain this increase, the object is brought closer to the eye, and the converging and focusing power is put upon the strain. Much injury is done by reading in twilight, and by reading or working in badly-lighted rooms. Good artificial light is much to be preferred to in- sufficient daylight. The direction in which the light comes is by no means a matter to be disregarded. All light that does not come from the page, in reading, can only be a source of annoyance, by irritating the retina, if it is direct, or by confusing the image of the print with the images of other objects, if it is reflected. The irritating effect of direct light, even in distant vision, is shown by the pulpit-lights in church or the foot-lights in a theatre; and the confusion caused by