Arlt's line are usually seen in:

Cicatricial trachoma linear scars may be seen in the sulcus subtarsalis, these are called Arlt'slines. Since its caused by Chlamydia trachomatis the antibiotic of choice is azithromycin. Ref: A.K KHURANA (2005), Chapter 4, "Disease of The Conjunctiva", In the book, "Opthalmology", 3rd Edition, Newdelhi, Page 90