Screen brightness has an effect on Saccades https://www.sciencedirect.com/topics/medicine-and-dentistry/saccadic-eye-movement. Saccades can easily be defined as rapid shifts in the gaze, that aligns the line of sight (between the two eyes) on the desired object on the screen. They are rapid eye movements that enable us to scan a visual scene.

These eye movements depict how the nervous system relates to the repertoire system. In short, the screen brightness of your computer, tablet or phones has an effect on your brain. The brighter the screen the less the pupils of your eyes dilate, and reduce the ambient light that enters your eyes: probably why most people prefer to turn their brightness all the way up. Saccades move slower in a dim screen than on a bright screen. Because saccades move faster on a brighter screenhttps://www.ncbi.nlm.nih.gov/pubmed/29111439, you are able to see more details.

However, it is not advisable to use a very bright screen–be moderate. A very bright screen might cause headaches: though not to everyone.The light intensity might trigger migraines, especially for people with neurological deficits https://www.theraspecs.com/blog/computer-screens-headaches-migraines-and-concussions/.

The goal is to let in as much light into your eyes as possible, to see the detail you need to see. So while working at your monitor, the light comes in through both ambient and monitor sources. If the monitor light is low, and ambient light relatively high, ambient light will burn your peripheral nerves, as eyes dilate to see the monitor (the low light intensity of the monitor causes your pupils to dilate). The effect is that the dilated pupils will allow more light to get into your eyes from the ambient light source. The best situation is low ambient light matching low screen brightness; if you increase the ambient temperature, you better increase screen brightness.

At low light, the pupils dilate and allows more light to enter the eyes. But that does not mean you will see more details. Saccades allow you to see more details, and they are very low at a low light intensity. Therefore, the best situation is to have a balance between the ambient light and the screen brightness.