Among all the different types of cancer treatments, photodynamic therapy, where light is used to destroy cancer cells, may cause one of the strangest side effects: patients begin to see better in the dark.
Researchers have finally figured out how this strange phenomenon arises. It turned out that rhodopsin, the photosensitive retinal protein in our eyes, interacts with another photosensitive compound called “chlorin E6” – the most important component of this type of cancer therapy.
The influence of the visible spectrum of light radiation leads to the fact that the retina is separated from the rhodopsin, which generates an electrical signal read by the brain – this is how we recognize the world around us. There is not much light around at night, however, as it turned out, the same mechanism can be triggered by another combination of light and chemical signals. If you introduce chlorin to a person, and then expose the retina to infrared light, the retina will react in the same way as in daylight.
“This explains the increase in visual acuity at night. However, we were not exactly sure how rhodopsin and its active retinal group interacted with chlorine. It was this mechanism that we managed to find out using molecular modeling, ” explained chemist Antonio Monari of the University of Lorraine in France.
Since chlorine E6 absorbs infrared radiation, it interacts with oxygen in the tissues of the eye, turning it into a highly reactive form of the so-called “Singlet” oxygen. By destroying cancer cells, singlet oxygen can also react with the retina and stimulate an increase in night vision, as the simulation showed at the molecular level.
Now that scientists know the chemistry underlying this strange side effect, they can reduce the likelihood of these symptoms in patients undergoing photodynamic therapy. Now it became clear to the doctors why the patients complained about the mysterious “silhouettes and strange shapes” in the dark.
In the future, this chemical reaction can even be used to treat certain types of blindness or hypersensitivity to light. Note that doctors strongly do not recommend trying to use chlorin E6 to provide superhuman night vision.
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