1) Pseudo-exfoliation syndrome (PE syndrome) is a condition with worldwide distribution. 2) Marked geographical variations have been demonstrated. 3) Environmental factors may be of etiological significance for the development of PE syndrome. 4) The PE syndrome's ability to promote glaucoma may vary from one area to another. 5) There seems to be a trend towards lower debut age of PE syndrome at lower latitudes. 6) More prevalence studies from different parts of the world are needed. A standardized set-up of such works would facilitate comparison of the results, and so some guidelines have been proposed.