Light

The retina is, stimulated by light, shocked by shadow, The fovea is interested only in light and hunts light all around this shadow, through thin places, through openings and crevices, in angles and around curves. The brighter the light the better it can shine through and the more vividly the object observed throws the shadow. Therefore, a good light is necessary. As Aldous Huxley states: "In insects and fishes; birds and beasts and men, eyes have been developed with the express purpose of responding to light waves. Light is their element; and when they are deprived of light, either wholly or in part they lose their power and even develop serious diseases." The mind, a shadow interpreter, is soothed by light if it is unbroken by shadow since no interpretation is called for; hence, sun-bathing rests and relaxes tense minds.. The mind is interested only in the shadow to be analysed. The stronger the light, the sharper the contrast between the light and the shadow falling on the retina to stimulate the light-finder and quicken the shadow-interpreter. Therefore, good light is essential to good eyesight. We all know this: that we see well on a clear day, dimly on a dark night.

Homes are heavily curtained and shrubbery-shrouded. Business offices, banks, libraries, where accurate vision is a necessity, are notorious for their dim cathedral lighting. Many lawyers have told me that their eye troubles started in law school, poring over the tomes in dimly lighted libraries. Many school children do their homework beneath a low-power light in the ceiling giving no attention to how or whether it strikes the page. People read in living-rooms at home by floor lamps which throw row their brightness against the ceiling, not down on the grey print of the newspaper where the eye needs the light. Dim light slows down the shift of even normal eyes, consequently tiring them more quickly. If use .of good eyes under these conditions is prolonged, both mental and visual strain will result. Red Indians did their close work beading, feather trimming, arrow shaping, pottery decoration in the daytime with sunshine to aid. After sundown, the braves sat about the camp-fires smoking while the squaws chewed leather, never attempting close eye work without good light.

In our civilisation, we often require our keenest vision at night or in rooms never visited by sunshine. Fortunately, science has given us electric light to compensate but few avail themselves of light bulbs sufficiently powerful to approximate dim daylight, let alone sunshine.

Dr. Matthew Luckiesh, director of the Lighting Research Laboratory for the General Electric Company in Cleveland, writes in his excellent book, Light, Vision and Seeing, human eyes and human beings, operating as human seeing-machines, are products of Nature, and best adapted to Nature's brightness-levels.

The proper function and objective of artificial light is to compete with daylight, not with darkness. In a study conducted for General Electric, he declares, "Your eyes are best fitted to use the sun's energy for seeing." And again, "Nature invites us to work and play under 500, 1000, and 10,000 foot-candles of illumination." Within a modem factory he found the best lighting near the sills of large: to be but, foot-candles of illumination- a sunny day; ten feet from the window, only 20 foot-candles; and on the far, wall but one or two foot-candles. Think what that light for an eight-hour day of precision work would be in cloudy weather. No wonder the eyes of the working public are strained.

A study made by a photometer compared the visual, effects of different lights on the printed page. Sun. shine reflected from a white printed card at noon on a clear day registered 1300 foot-candles; in the outdoor shadow the reflection was reduced to 130 foot-candles. Indoors, a 150-watt reflector spot bulb registered on the card the same as outdoors in the shade on a sunny day, 130 foot-candles. But a 60 watt bulb, which is more than many eye workers are afforded, .at the same distance registered only two foot-candles, reflected from the same card. The indirect lamp containing a 300-watt bulb threw from the ceiling down onto the card only one-half foot-candle, despite its power. The fluorescent light registered one-fourth to two foot-candles.

When so few school children and students are afforded anything distantly approximating daylight for their heavy study work, it is no wonder that glasses are so generally prescribed for those attempting an education. Adequate lighting would greatly reduce this eyestrain and prevent deterioration of sight. The blame is generally put on "too much reading.

Good light is necessary for keen thinking while one reads or studies. The mental strain which results from trying to read poorly lighted print slows down the learning process, for the mind can only assimilate knowledge when it is relaxed.

The eye works by contrast; in print, contrast of light and dark, straight lines and curved, tall lines and short. If the illumination is too weak to throw the print up in bold contrast to the white background, which in dim light seems not white but grey, the mind must struggle to make it out. Sun on the printed page makes the white background very white and the print very black. Poor artificial light reduces this contrast to the minimum. Worse yet, if the light is so constructed that it does away with shadow, which the fluorescent lights seem to do, it also does away with the sharp contrast between the black print and the white page. Just as it whitens the shadows fluorescent light seems to lighten the print to the point where the mind must struggle to interpret, a frequent cause of eyestrain and brain fag.

One draughtsman with excellent vision did drawing during the war in a blacked-out defence plant, working all day under shadow less lighting. He came to me completely thwarted. "My eyes, simply close on me at the drawing board," he explained. "I am so drowsy in my car driving home after work that I have to pull up to the kerb and doze for a few minutes to avoid sleeping at the wheel." The lad was leading a regular life, took aplenty of sleep. at night, felt rested in -the morning and liked his work. But as soon as he bent over his drawing board again, extreme drowsiness assailed him. Enquiry into his working light disclosed that it was the type of light which killed all contrast by eliminating shadow. At my suggestion, he procured a strong, bright desk light, had no further trouble and, once more, enjoyed comfortable use of his good vision.

Photophobia, as the doctors call it, is fear of light. When sun or headlights hurt the eyes, it is just that: fear induced by the shock of sudden light. This fear tightens muscles, nerves and blood vessels; then the eye, thus tensed, cannot handle the light, and pain or discomfort results.

Eyes need light to do their seeing. They are organs of light. The weaker the eyes, the more light they require. But all eyes, good and bad, resent glare on the page or on objects to be regarded. One of the most prevalent and continuous conditions of glare in our present civilisation is the glare on the school black boards where students must interpret accurately. It may be here that children's eyes first start straining and the habits of sinful seeing are formed habits which can easily blight their young lives and carry the damage over into adult years. As a rule, blackboard work is a mental strain under all conditions. In the place, it generally consists of handwriting, notoriously poor since the Spencerian system went out of vogue. Secondly, what the instructor puts on the board in poor handwriting is always something of importance to the. student; therefore, the mental strain is increased. But most disastrously, there is generally but one time each day for each seat in the classroom writing when the light strikes the ting correctly on a clean blackboard. All the other positions present a glare though which the student must peer and strain. Add to these difficulties the usual shale of soft chalk dust, each particle of which catches and diffuses the light, and most of the students in any classroom are straining to see and interpret misty and mysterious -hieroglyphics merging into a shining greyish surface. Is it any wonder that eyestrain begins early and increases as the work intensifies in quantity and quality, in amount and importance during, the student's progression from the classroom to the lecture hall? Some improvement in, or substitute for, blackboards should be found.

Eyes need light in which to do their work exceptionally good light, if we are making artificial demands of them: long hours at the close point or overtime for accurate vision. Parents should carefully plan their children's study life and put sufficient light where it is needed. A 150-watt bulb in a bridge lamp placed about four feet back at the left side and at an angle to prevent glare on the page, should be furnished. The same amount of light should be arranged for office workers- Bridge lamps with strong bulbs for home and bedtime reading should be the rule, not the exception; thus, the steady decrease of visual acuity, would be halted. The general health of the population As better; if eyes were properly used and treated humanely vision too would be improved. Eyes like to work, but resent strain. Incorrect or inadequate lighting is one of the greatest causes of strain.

Eyes hate sudden shock. It always takes a bit of doing to accustom eyes to varying degrees and types of light. During the war boys returning from long service in the Aleutians found ordinary United States daylight tremendously brilliant. London eyes, used to mists and fogs, find New York, daylight too bright. Eyes used to sunshine at sea level, dulled, by ocean mist, must accustom themselves to the brilliance of mountain sun. in the higher altitudes. If the eyes are given their lessons in sunning, these shocks can readily be modified and any type of natural light made acceptable to the eye without, resentment or discomfort.