This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, 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: Ans. is \'a\' i.e., Scarring The later structural changes of trachoma are referred to as "cicatricial trachoma". These include scarring in the eyelid (tarsal conjunctiva) that leads to distoion of the eyelid with buckling of the lid (tarsus) so that eye lashes rub on the eye (trichiasis). Rubbing of eye lashes of scarred eye lids against the cornea leads to corneal opacities and scarring and then to blindness. Thus actual cause of blindness is corneal opacity and scarring, which may be secondary to eyelid scarring.', 'role': 'assistant'}]