Visual activities illuminated by natural light are advised, especially during growth period.
The optimal artificial illumination of a paper document comes out of an incandescent 75 W bulb or an equivalent LED or low consuming bulb, positioned at 75 cm of the document, at the left side of a right-handed reader, at the right side of a left-handed reader.
During reading and writing, position the paper document at 40 cm (twice your handbreadth) of your nose.
While looking to the television screen, position your seat at 3.5 folds the diagonal of the TV screen. The room illumination should be moderate to strong. Looking to the television in the dark is not harmful but tiresome for the eyes.
During work on a computer screen, the distance between your eyes and the screen should be twice the diagonal of the screen. The centre of the screen should be at the level of your shoulders. The screen should be at 75% illumination and contrast, mat, without any light reflection. Ideally, the main colour of the screen should be as similar as possible to that of the after-ground of the space you look to while you work.
If paper and screen documents are to be frequently and simultaneously consulted, place the paper documents vertically on a document holder, at 40 cm of your nose and choose colours of the screen font and after ground similar to those of the paper document.
If you work intensively on a computer screen, do not forget to regularly blink.