Adaptability of Eye to Light
The eye has a great range of adaptability to the intensity of light. This is evidenced by the fact that the eye is readily adapted to the intensity of the bright sunlight or to the soft rays of the moon. In both instances there is no disturbance in vision, even though the intensity of illumination at midday when the light is brightest is almost a million times greater than the illumination from the full moon on a clear night. This adaptation takes place so perfectly and so independent of the educated mind that we give little thought to the great difference in intensity of light.
It must be remembered, however, that although this adaptation takes place so perfectly and without any apparent difficulty, it requires an expenditure of Innate force to accomplish this action. If the change takes place too rapidly from a soft light to an intense light, without sufficient time for adaptative action to take place, the delicate structure of the eye will be damaged by the violent light vibrations. The change from the soft rays of the moonlight to the intense illumination from the bright sun takes place gradually. First, the night; next, the gray dawn of morning; and then comes the sun, whose rays are softened as they pass through a maximum amount of atmosphere near the horizon, and as the sun approaches the dome of the arc, the rays become more intense, since they pass through less of the earth’s atmosphere. Then the process is reversed as the intense light from the sun gives way to the softer rays from the moon.
This gives Innate plenty of time to bring about the adaptative processes so necessary to adjust the eye to these extremes, time being a very important factor in all the processes of the body.
Thus it is appreciated that the subject of lighting is important from a hygienic standpoint, since improper lighting necessitates an unnecessary expenditure of energy and causes impaired health.