Epithelial xerosis of the conjunctiva is caused by
Epithelial xerosis:  It occurs due to hypovitaminosis -A. 
Epithelial xerosis may be seen in association with night blindness or as a part and parcel of the xerophthalmia (the term which is applied to all ocular manifestations of vitamin A deficiency which ranges from night blindness to keratomalacia
Trachoma
Xerophthalmia
Diphtheria
Pemphigus