If you have sufficient PRSI contributions you can get a free eye test and free basic glasses or a €42 contribution to more expensive frames.
https://www.welfare.ie/en/Pages/Treatment-Benefit1.aspx
Sorry to resurrect an old thread - this page mentions that you can get the €42 contribution for spectacles and certainly that's the case when you order in Ireland. Does anyone know if it's possible to claim this expense if I order prescription glasses on the internet, rather than in-store in Ireland. Thanks