An apparatus comprising means for: determining that a user is reading text on at least one display; controlling an amount of light entering at least one eye of the user while the user is reading the text on the at least one display to enable at least one electrooculography, EOG, measurement to be determined; receiving EOG information from at least one user head worn EOG sensor comprised in a user head worn device while the user is reading the text on the at least one display; determining, based, at least in part on the received EOG information, at least one EOG measurement; determining, based, at least in part, on the determined at least one EOG measurement, light adaptivity information of the at least one eye of the user; and performing at least one action based, at least in part, on the determined light adaptivity information.