tax + duty implications of importing goods from UK + US ?

Hi,
I am going to buy Contact Lenses + solution online,
either from a US website or one from the UK, there's not much difference in price. I have used the US one in the past + didn't have to pay anything to Customs although the parcels were small enough.
Are there any tax and duty implications of importing goods through the post from UK
or is it just liable from countries outside of the European Union ?

Sorry if this has been answered before I have searched previous posts and revenue.ie but it's too early in the morning from my brain to figure it out.
Some info I found....
[broken link removed]
[broken link removed]

Got car parts worth €155 from UK last week and only had to pay UK VAT no duty. Saved €120 on the equivalent Irish price. ( and they were OWM parts too )
Got contact lenses from yourlenses.ie which while advertised as an Irish site in Euro the goods actually come from Sweden. Am assuming that Irish VAT was charged on those but way cheaper than in the shops. No duty there either. The US is the main problem with VAT and duty payable on goods. The Revenue Customs department should be able to clarify if you're not certain.

the EU has a common trade area so you won't pay customs on any goods that you bring into Ireland from anywhere in the EU, whereas customs may have to be paid on goods imported from outside the EU (eg the US)
As far as I remember (but I'm open to correction), if you are buying goods from another EU country for personal use then you just pay the VAT in that country, so again you wouldn't have any additional charges when bringing the contact lenses in from the UK

thanks dudes!