As we age , natural physical changes of the human eye decreases our visual abilities including our capacity to read.
Research initiated and supported by Holtkotter at the University of Colorado to study and develop the scientific basis of lighting for the aging eye and to research how good lighting can mitigate the effects of the natural physical changes we are all subjected to as time passes.
The cornea becomes more opaque , the lens absorbs more light, and the pupil diameter diminishes, resulting in a reduction in retinal illuminance. Increased fat deposits in the cornea and lens lead to an increase in light scattering inside the eye in which recognizable objects become more difficult to see. The lens yellows and absorbs a higher amount of blue wavelengths. Weaker ciliary muscles and an increased hardening of the lens decrease our ability to focus and to adjust to different light levels easily.
The decrease in retinal illuminance requires a light level of more than 100 foot-candles for optimal reading performance. The 75-Watt or 100-Watt Halogen light bulb by Osram, as well as the shape and construction of the inside of the reflector, allow for a light level in excess of 100 foot-candles. A matte glass diffuser and a reflector that focuses the light only on the reading material will reduce glare and scattering. Adjustable dimming controls and the adjustability of the physical reflector location allow the light levels to be set at the optimal position, reducing the need for the eye to adjust to different light levels.
This study has resulted in the series of table, chair-side and floor reading lamps below.