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
Cause of blindness in trachoma - 
Select and explain. 
A. Scarring, B. pannus, C. Chronic dacrocystitis, D. Entropion
A: Scarring
Answer: A: Scarring 
Explanation: 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