A longitudinal survey in two different phases with an interval of 4 ye
ars (including more than 23 000 employees) has been carried out to stu
dy whether the time spent using VDU (daily hours and years of work) ca
n change the refractive state. With reference to the whole sample incl
uding all refractions, there was no significant difference in the refr
active state in employees who spent varying daily hours or years worki
ng at VDU. Furthermore, there were no significant changes in the refra
ctive states of emmetropic, hypermetropic and myopic subjects, with re
gard to the time spent working at VDU. The data have shown that a high
exposure to VDU work (more than 6 h per day or more than 6 years spen
t working at a VDU) is not responsible for inducing or worsening refra
ctive error.