A 52-year-old woman from a rural village in Odisha presents with a 10-year history of progressive eye irritation and vision loss. On examination, she has bilateral upper eyelid entropion with inturned eyelashes, corneal pannus formation, and dense corneal scarring. Visual acuity is counting fingers in both eyes. She recalls having recurrent eye infections with purulent discharge during childhood and adolescence. What is the most likely stage of trachoma, and what is the primary cause of vision loss in this patient?