This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Conjunctiva, Subject name: Ophthalmology
[{'content': 'Cause of blindness in trachoma - \nSelect and explain. \nA. Scarring, B. pannus, C. Chronic dacrocystitis, D. Entropion', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The later structural changes of trachoma are referred to as "cicatricial trachoma". Rubbing of eye lashes of scarred eye lids against the cornea leads to corneal opacities and scarring and then to blindness. Ref: Parson\'s 22nd/e p.172-174 & 21st/e p.172-174; Khurana 7th/e p.67 & 4th/e p.62-64', 'role': 'assistant'}]