I remember reading somewhere that it is analogous to closing your eyes under the sun, as your eyelids only allow some wavelengths of sunlight. Not sure if that's accurate.
[1] "Measuring and predicting eyelid spectral transmittance" Journal of Biomedical Optics, Vol. 16, Issue 6, 067011 (June 2011) https://doi.org/10.1117/1.3593151
Bright enough to warm the body, but not thermally stress the cells.
And yeah, closing your eyelids would block UV light from getting in and cross linking proteins and causing cataracts, while still allowing for NIR light to get in and speed up the mitochondria.
Analogous for sure