Seeing, reading, light conditions

Seeing, Reading, Light Conditions

Today, there are many advancements that are created to make our life easier. However, not all the improvements of our modern world are good for our health. Since the invention of the printing press we are used to reading the printed word on paper. But this is now changing and reading happens increasingly on computer screens, be it at the office, in school or at home. When we read on the screen we are looking into an active light source, which hits our retina. We also want to see the letters clearly, so the light is being focussed to the Fovea centralis (point of sharpest vision) by the eye lens like with a burning glass. When we compare our seeing habits with those of our forefathers, we find that much has changed, but not to the advantage of our eyesight!

When we read on paper the color of the light will is altered. This is because only a part of the light is being reflected by the paper. A few decades ago, the used paper was generally unbleached, and the slight tint acted as filter which reduced the excess blue parts of the artificial light automatically. Today, even reading from paper is very strenuous for the eyes, because the commonly used bleached paper increases the proportion of visible blue parts through optical brighteners.

Why are blue wavelengths so important to the reading process? A basic explanation of light optics is worth mentioning here. The eye is partly build like a camera and works with a lens and optic elements like the vitreous body. Every optical element disperses the light´s rays in a typical manner and shows effects such as those that can be observed in a prism. The wavelengths of light are refracted and the white light is split in its component colors, when the long-wave red light is less strongly refracted than the shortwave blue light. This difference in the behavior of the refraction of different colors can be observed in all types of lenses as color distortion, called chromatic aberration by opticians. The blue part of light is most affected, because it creates the color edges that make seeing sharply more difficult. In sport, where keen eyesight is necessary, glasses that filter out the high blue parts of light are already widely used. Golfers, pilots, skiers and target shooters like to use this method to enhance their performance.

However, it is not only for the benefit of visual acuity if less blue light hits the retina. Over the last years, medical research has recognized two more processes that are triggered by blue light. Firstly, shortwave light influences our biological clock and creates bodily activation up to the point of systemic hormonal stress. On the other hand it has been recognized that blue light leads to a stronger oxygen radical formation in the tissue of the organism. While short-wave blue light causes stress on a cellular level, long-wave red and infrared light can counteract this cellular stress and support regeneration of the tissue.

In nature, the composition of sunlight and fire automatically balances the effect in the tissues, because the long-waves are present. The spectral composition of fire light contains very little blue, but also in the sunlight, where blue light is present, it is balanced by a much larger proportion of long-wave red light, which supports regeneration.

These eye-friendly properties of the light are only found in natural light sources, in which light and heat radiation socialize, like sunlight and fire. Even the light-bulb can be counted to the natural light sources, because its light follows the rules of natural spectral distribution.

A different case altogether are the modern discharge lamps and LEDs (light-emitting diodes). These light sources contain a high proportion of blue wavelengths, which are not compensated by long-wave red wavelengths. Neither regular energy saving light-bulbs nor white LEDs produce notable amounts of red or infrared rays, thus the effect of the tissue regeneration through long-wave radiation does not apply. The physiological balance of these new light sources with their synthetic spectrum is therefore doubly negative, because they produce more cell stress through the high amount of blue light, and allow less cell regeneration through the missing long-wave radiation and heat.

This is especially unfortunate in the retina, because at the point of visual acuity the blood circulation is less than optimal for the cells; in order to see clearly, there can be no blood vessels across this area, even though the nutrient and oxygen supply is especially high. The eyes mainly depend on diffusion for providing nutrients and to removing the metabolic waste products. Red heat radiation improves all metabolic processes, including the blood circulation. Therefore, red wavelengths have a very positive effect on the retina.

If one works in poor quality artificial light, which is missing the long-wave spectrum, the only possibility left to reduce the negative effects on the retina is by filtering out the short blue wavelengths. This can be done by wearing yellow glasses with special filter properties, which are optimzed to the spectral distribution of the artificial light.

Lastly, we shall look at the influence of shortwave light on the hormonal system. For over ten years, science has known the process that is responsible for the hormonal effect caused by blue light. In the retina, in addition to the photoreceptor cells, there is another group of cells, the so-called ganglion cells. Some of them are sensitive to blue light, even without participating in the visual process. If those cells are activated through blue light they send signals to our biological clock and to the hormonal control centers of the organism. This makes the body adapt to the environmental conditions and synchronizes its inner clock to the rhythms of nature. Through bright, bluish light at the wrong time, the biological clock shifts. Especially at night our body is more susceptible to such light induced disturbances. When those disturbances are occur increasingly or even on a regular basis, this can have detrimental consequences to our health.

All of the above leads to the conclusion, that we need to deal with our modern light sources very sensibly and with caution. In most situations, from a light biologist´s point of view, it is advisable to filter out the blue components of the light. When working on a computer during office hours and in the evening in general, the reduction of blue light exposure is sensible and necessary, especially when certain light-related diseases or symptoms are already present. These include headaches, concentration difficulties, exhaustion or sleep disturbances.

As most people have no influence to the kind of lightening at work, filtered eyewear are often the only possibility to escape the damage from aggressive synthetic light. Especially when worrking on a screen, but also in the home environment, these glasses can provide excellent preventive health benefits.

PRiSMA bluelightprotect glasses have been on the market for years with thousands of satisfied users. This is the result of a successful collaboration between the light biologist Alexander Wunsch and Innovative Eyewear – the leading German manufacturer of colored therapy glasses. Through the fusion of light biological competence with modern production technics, PRiSMA bluelightprotect glasses – a high quality product for modern healthcare – have been developed, enabling thousands of people to enjoy better and healthier living and working conditions.

Contact:

Alexander Wunsch, physician and photo-biologist, Heidelberg, GERMANY wunschart@mac.com