**3. Epidemiology**

Dry eye disease affects from 5 to 50% of population; this discrepancy is probably observed due to the absence of a consensus on the diagnosis of dry eye and the lack of standardization in its classification [13]. It is more frequently in women [14], probably because of the hormone effects in the ocular surface and eye glands [4].

It is more common in Asia and Europe, with only one study showing the prevalence in South of Equator [4], and it seems to be also more frequent in older people, possibly because of the aging alterations in the lids, glands, ocular surface, and adnexal tissue [15].
