In reading we wish light from the printed page. Hence we should avoid light entering the eye from any other source at this time. While reading, then, do not face a window, another light, a mirror, or white wall, if it can be avoided. In a room, white walls are likely to injure the eyes. Choose a dark colour for a covering for a reading table. Sewing against the background of a white apron has worked serious mischief. Direct sunshine near the book or on the table is likely to do harm.
Preferably have the light from behind and above. Many authors say “from the left” or “over the left shoulder.” In writing with the usual slant of the letters this may be desirable. But vertical writing is now strongly advocated, as it enables one to sit erect, and have the light from above and equally to the two eyes. Having stronger light for one eye than for the other is bad. Sitting under and a little forward of a hanging lamp will give the light equally to the two eyes and send no light direct into the face. In reading by daylight avoid cross-lights as much as possible. The incandescent electric light has an advantage in being readily lighted without matches, and in giving out little heat, thus making it valuable for house-lighting; but owing to its irregular illumination (due to the shadow cast by the wire or filament), it is not well suited for study or other near work. For this purpose an Argand gas or kerosene burner is much to be preferred, since it throws a soft, uniform, and agreeable light upon the work.
Reading out-of-doors is likely to injure the eyes, especially when lying down. To try to read while lying in a hammock is bad in many ways. Too much light directly enters the eye, and often too little falls upon the printed page.
Do not hold the book or work nearer the eyes than is necessary. So far as possible avoid continuous reading in large or heavy books by artificial light. Such books being hard to hold, the elbows gradually settle down against the sides of the body, and thus, without thinking about it, the book is held too close to the eyes, or at a bad angle, or the body assumes a bad position.
Frequently rest the eyes by looking up and away from the work, especially at some distant object. One may rest the eyes while thinking over each page or paragraph, and thus really gain time instead of losing it.
Have light that is strong enough. Remember that the law of the intensity of light as affected by distance is that at twice the distance from the source of light the light is only one-fourth as strong. Reading just before sunset is risky. One is tempted to go on, not noticing the gradual diminution of light.
Save the easiest reading for the evening. Newspapers, as a rule, have neither good print nor good paper. If the eyes have much work to do, finish this kind of reading by daylight if possible, and by artificial light read books, which usually have better type and better paper.
In all ways endeavour to favour the eyes by doing the most difficult reading by daylight, and saving the better print and the books that are easier to hold for work by artificial light. Writing is usually much more trying to the eyes than reading. By carefully planning his work the student may economize eyesight, and it is desirable that persons blessed with good eyes should be careful, as well as those who have a natural weakness in the eyes; for it often results that those inheriting weak organs, by taking proper care, may outlast and do more and better work than those naturally stronger, but who through carelessness injure organs by improper use or wrong use.
Reading before breakfast by artificial light is usually bad.
Many eyes are ruined during convalescence. At this time the whole system is often weak, including the eyes. Still, there is a strong temptation to read, perhaps to while away the time, perhaps to make up for lost time in school work. This is a time when a friend may show his friendship by reading aloud to the convalescent.