Poor screen management causes unnecessary strains on the eyes, which can often lead to headaches and, in some cases, migraines. Migraines often cause nausea and vomiting.
As we know from earlier, you are entitled to a free eye test voucher, but you have a responsibility to adjust your monitor to ensure that it has sufficient light and that the settings are adequate for the user.
Any problems regularly experienced with eyes should immediately be highlighted with an optician or a medical professional.