Short-wave light in the invisible spectrum (UV light) is known to damage the eyes. It is not without reason that all sunglasses must offer full UV protection. Visible short-wave light in the blue range is similarly high in energy, but penetrates much further in the eye. While UV light is absorbed in the vitreous body and therefore “only” endangers the ocular surface and lens, blue light hits the retina directly.
Acute retinal damage from bright (blue) light sources is very well researched and documented.
Chronic damage, however, is difficult to detect by this route. Because even though the known mechanisms suggest that decades of blue light exposure lead to damage such as macular degeneration, there is no experimental design that could conclusively prove this. Neither cell cultures nor laboratory animals can replicate these time frames. An observational study of humans is also difficult to conduct, because who can say with certainty what cumulative blue light levels they have been exposed to over the course of their lifetime?
So researchers have to do detective work in this area and rely on circumstantial evidence.
One promising approach is to study neurotransmitters that act as markers of cell damage. These are messenger substances that are released in the body to initiate repair processes, for example. These are measurable even before visible damage.
In addition, modern medicine offers the opportunity to observe a “natural” experimental setup. After cataract surgery, patients are fitted with artificial lenses (intraocular lenses = IOL). Due to the numerous indications of the importance of blue light protection for retinal health, lenses that partially filter out the blue range have been increasingly used in this area in recent years. However, comprehensive studies did not find any clinically relevant difference here. This may be due to the fact that only a small part of the blue light is filtered out, but also because the patients are usually older. Those who have already accumulated several decades worth of blue light damage show no health benefits after only a few years of limited protection.
With these limited possibilities to design studies on long-term effects, it often comes down to circumstantial evidence. The individual steps of disease development and the underlying mechanisms can often be demonstrated in isolated experiments on cell cultures. This body of evidence then coalesces into an overall theory of the risk of accumulated blue light exposure that is widely accepted among experts.
This 2014 study may represent a milestone in the research on blue light damage. It shows that the protein neuroglobin, which exerts a protective function for neurons, can act as a biomarker for cell damage in the retina. An increased concentration of this substance can be detected even before damage to the retina occurs.
This meta-analysis evaluates the results of 51 different studies conducted worldwide on the relationship between blue-filtering IOLs and retinal health. IOL is short for intra-ocular lenses, which are artificial eye lenses used after cataract surgery.
This 2020 review summarizes the results of nearly 90 individual studies, focusing on the proven effects of blue light on eye health, as well as ways to prevent and treat blue light damage. It is available as freely accessible full text (in English)
The abbreviation AMD stands for age-related macular degeneration. This condition is often associated with chronic blue light exposure, and patients are commonly prescribed blue light protective eyewear to slow the progression of the disease. But how exactly is blue light related to AMD?
Short-wave radiation has a high energy potential and can thus lead to the formation of oxygen free radicals when it hits tissue. These lead to oxidative processes that can damage and even destroy cells.
At the site of most acute vision, the “yellow spot” (macula lutea), there is natural protection by the body’s own pigments (e.g. lutein and zeaxanthin), which absorb short-wave light. However, the concentration of these pigments decreases with age; this allows the blue light to exert its oxidative effect more strongly. This can lead to macular degeneration, the so-called “age blindness”, in which the vision at the point of sharpest focus diminishes and slowly disappears completely. At 50%, macular degeneration is the most common cause of acquired blindness.
Bildschirmbrillen mit Blaulichtfilter, die für das Arbeiten am PC empfohlen werden, würden angeblich keinen großen Mehrwert bieten. So lautet das Ergebnis einer Übersichtsstudie der Cochrane-Vereinigung,
Die PRiSMA® BluelightProtect LiTE95 Filtergläser sind mit einer Blaulichtfilterrate von echten 95% im Bereich von 400 bis 500 Nm als der UNIVERSAL-Filter zu bezeichnen. Er