Based on these promising results, a team from University College London designed a pilot study in humans involving 24 healthy participants aged between 28 and 72 years. They were given a “red light shower” with special flashlights emitting a wavelength of 670nm. The test subjects were instructed to hold the red light source in their eye for three minutes a day over a period of two weeks. The light was focused on the retinal area. Before and after the two-week red light therapy, various tests were carried out to assess visual function. The older participants (over 40 years of age) showed a significant improvement in contrast sensitivity. This improvement was particularly noticeable in the middle and lower contrast range.
In order to validate the results of the first pilot study and to investigate further aspects of red light therapy, the same team conducted a follow-up study. In particular, the aim was to investigate whether and for how long a single application with a lower dose of light would have an effect and whether the timing of the treatment was relevant. This follow-up study worked with participants between the ages of 34 and 70, in whom greater effects were to be expected than in younger subjects. The participants were again provided with LED flashlights with a wavelength of 670 nanometers (nm), which, however, emitted significantly weaker light. The participants were divided into two groups: One group received the red light therapy in the morning (between 8 and 9 am), the other group in the early afternoon (between 12 and 1 pm).
Before and after the 3-minute irradiation, various tests were carried out to assess visual function. This included tests to determine contrast sensitivity and color vision. In addition, the tests were also repeated seven days after the red light application to assess the duration of the effects. The participants who received the red light therapy in the morning showed significant improvements in contrast sensitivity and color vision compared to the control group and the group that received the therapy in the afternoon. The improvements in visual function remained measurable seven days after application, indicating that the effects of red light therapy are persistent and do not disappear immediately after discontinuation of treatment.
These studies suggest that red light treatment could be a simple, safe, and cost-effective at-home intervention for preserving vision in old age. Further studies should include larger groups of subjects and focus on fine-tuning the parameters to maximize the efficacy of this therapy. It remains exciting to see how this research will develop in the coming years.