>...excess light at times of the day when the Sun don't shine messes up our evolutionary psycho-biology, causing issues with sleep.
That is folk wisdom in the IT field. At best, it is blue light, but there aren't enough long term studies to conclusively say this. BMJ Open Ophthalmology published a study in 2018 that said blue light could be a factor in eye tiredness, but it also stated dry eyes due to lack of blinking for long periods a more serious cause of eye strain. It also noted very small fonts, low contrast, and medical conditions like uncorrected astigmatism and presbyopia as factors.
Human eyes don't have good night vision, we see best in daylight.
Black text on a white background is best, since the color properties and light are best suited for the human eye. That’s because white reflects every wavelength in the color spectrum. Because of the reflection, our irises don’t need to open as wide to absorb the white light. That leaves our irises in a neutral position and allows us to see with better clarity. This is especially true when white light is contrasted against black, which absorbs wavelengths instead of reflecting them.
Light text on a dark background makes the eye work harder and open wider, since it needs to absorb more light. When this happens, the light letters can bleed into the dark background and cause halation, which makes the text blurry. Our eyes focus better when the iris is narrow.
Additionally, most people are born with some form of astigmatism, a misshaped cornea that blurs vision. For people that have the worst forms of astigmatism, light text on dark backgrounds aggravates the condition. When looking at a light display, the iris closes more, decreasing the effect of the deformed cornea. When using a dark display the iris opens to receive more light and the deformation of the cornea makes halation worse.
On the flip side, dark mode helps with floaters, tiny fibers or spots that appear in a person's vision. These are caused by changes to the fluid in the eye which cause shadows to be cast on the retina. Floaters distort vision in light mode. This condition tends to increase with age.
Also, people with light sensitivity might be better served by a dark background.
Both light and dark mode should be offered for accessibility reasons.
That is folk wisdom in the IT field. At best, it is blue light, but there aren't enough long term studies to conclusively say this. BMJ Open Ophthalmology published a study in 2018 that said blue light could be a factor in eye tiredness, but it also stated dry eyes due to lack of blinking for long periods a more serious cause of eye strain. It also noted very small fonts, low contrast, and medical conditions like uncorrected astigmatism and presbyopia as factors.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6020759/
Human eyes don't have good night vision, we see best in daylight.
Black text on a white background is best, since the color properties and light are best suited for the human eye. That’s because white reflects every wavelength in the color spectrum. Because of the reflection, our irises don’t need to open as wide to absorb the white light. That leaves our irises in a neutral position and allows us to see with better clarity. This is especially true when white light is contrasted against black, which absorbs wavelengths instead of reflecting them.
Light text on a dark background makes the eye work harder and open wider, since it needs to absorb more light. When this happens, the light letters can bleed into the dark background and cause halation, which makes the text blurry. Our eyes focus better when the iris is narrow.
Additionally, most people are born with some form of astigmatism, a misshaped cornea that blurs vision. For people that have the worst forms of astigmatism, light text on dark backgrounds aggravates the condition. When looking at a light display, the iris closes more, decreasing the effect of the deformed cornea. When using a dark display the iris opens to receive more light and the deformation of the cornea makes halation worse.
On the flip side, dark mode helps with floaters, tiny fibers or spots that appear in a person's vision. These are caused by changes to the fluid in the eye which cause shadows to be cast on the retina. Floaters distort vision in light mode. This condition tends to increase with age.
Also, people with light sensitivity might be better served by a dark background.
Both light and dark mode should be offered for accessibility reasons.