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': 'Which among the following is the earliest sign of vitamin-A deficiency in developing countries? \nSelect and explain. \nA. Conjunctival xerosis, B. Nyctalopia, C. Retinopathy, D. Pain', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Night blindness is the earliest symptom. Dryness of the conjunctiva (xerosis) and the development of small white patches on the conjunctiva (Bitot spots) are early signs. Ulceration and necrosis of the cornea (keratomalacia), perforation, endophthalmitis, and blindness are late manifestations. Xerosis and hyperkeratinization of the skin and loss of taste may also occur. Ref: Baron R.B. (2013). Chapter 29. Nutritional Disorders. In M.A. Papadakis, S.J. McPhee, M.W. Rabow (Eds), CURRENT Medical Diagnosis & Treatment 2013.', 'role': 'assistant'}]