Artificial Light

For comfortable use of the eyes in artificial light, the source of light should be steady (no flicker), uniform, non-glaring, and of adequate intensity. Intensity of illumination is measured in terms of foot-candles by photoelectric instruments called light meters. A foot-candle is the amount of light projected at

 a distance 1 foot from the flame of a standard candle.

The critical distance for seeing is the dis­tance between the light source and the ob­served object. Where close work such as read­ing, writing, or sewing is to be done, the light falling on the book or paper or threads should be of an intensity of about 15 or 30 foot candles, or more.

The major source of light on the printed page or other close work should come from behind. Direct glare of light into the eyes should always be avoided. Lamps should be well shaded, and bulbs should be frosted. It is better to work in a room that is reasonably well lighted throughout than to depend on "pinpoint" lighting on the work itself. In this respect modern, indirect lighting is an advan­tage. Position while reading-for example, reading in bed - makes little difference pro­vided that the proper conditions of illumina­tion are maintained. The book should be about 14 inches in front of the eyes.

You are the best judge of the amount of light you need to read or do other work. If there is not enough light, you will start to squint and frown and become uncomfortable. If there is too much light and glare, you will begin blinking and turn away from the light source.

Glare requires eye muscles to make con­stant and extensive readjustments, resulting in eyestrain and in an extreme case, under special conditions, "snow blindness." Use of tinted. glasses, optically correct, can be a help in avoiding undue glare. Too many people, however, wear sunglasses solely for costume effect.

When to Wear Sunglasses

You can buy sunglasses for anywhere from 25 cents to $2750 (diamond-studded frames) a pair. For a good acceptable pair of sunglasses you will have to pay anywhere from about $6 to $20. An "acceptable" pair of sunglasses transmits from about 15% to 30% of visible light (i.e. it cuts out from about 70% to 80%) and also offers adequate protection against infrared and ultraviolet rays of the sun. Neu­tral colors-gray, green, and tan, in that order - are preferable.

Sunglasses should be worn for the purpose for which they are primarily manufactured: to protect your eyes from discomforting expo­sure to the sun's rays. They should not be worn for night driving - that is, to protect the driver from the glare of oncoming headlights.

Fashion has made dark glasses a more popular item of feminine beauty accessories than is physiologically warranted. Too many young women, perhaps, have gotten into the habit of concealing the natural beauty of the eyes and distorting the natural and appealing contours of their faces by hiding themselves behind dark glasses when this is not really necessary. One observer has said of light-tint sunglasses (those that transmit more than 30% of visible light): They are a cosmetic, a decoration-a palliative for neurotics."