http://www.ewtn.com/library/liturgy/zlitur440.htm
'Ordo benedictionis coniugum intra Missam, occasione data anniversarii Matrimonii adhibendus.' This appendix recommends that on the main anniversaries of marriage, e.g., 25th, 50th, or 60th, a special remembrance of the sacrament may be held within Mass. This includes inviting the couple to renew before God their commitment to live a holy married life. The 'renewal' then includes the exchange of a formula between the couple: 'Blessed are you, Lord, for by your goodness I took N. as my wife/husband.' And then both together pray a prayer of renewal. A blessing of the rings may also follow. And following the Our Father, there is a special blessing which the priest bestows. Thus, it would seem that the universal Church has indeed proposed such a renewal of commitment to married life, though the terms 'renewal of vows' — as you pointed out — is avoided."