In the UK regarding VDU's what the HSE give out are only 'Guide Lines'. They do however recomend frequent short breaks, so I have a timer at work set for 30 minutes and when the alarm goes, get up, put stuff in the post, all the little jobs we usually save to amke a more worthwhile task.
For me doing the little job frequently is worthwhile
Looking at a computer screen, reading a book or anything needing concentration makes our blink rate go down do our eye dry up. this leads to lenses becoming uncomfortable and if we do nothing about it we have a major bad eye day preventing us wear lenses for a few days or even worse a trip to the eye unit!
A dry lens will certainly not help the cornea as it moves on the cornea as there is not that lubricating layer of tears so damage could occur.