This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy, Development and clinical examination, Subject name: Ophthalmology
[{'content': '"Fleischer ring" is a distinct feature of \nSelect and explain. \nA. Keratoconus, B. Pterygium, C. Congenital ocular melanosis, D. Congenital epithelial Melanosis', 'role': 'user'}, {'content': "Answer: B \nExplanation: A condition in which the clear tissue on the front of the eye (cornea) bulges outward. Visual: astigmatism, blurred vision, distoed vision, double vision, inability to see in dim light, nearsightedness, sensitivity to light, or vision loss Also common: a rim of discolouration around the front of the eye (fleischer ring) Picture show Keratoconus, a non circular, non-centered oval caused by a bulging cornea. Very common in Keratoconus, it is best viewed under cobalt blue light, that's why the sclera looks blue. Reference: Ganong&;s review of medical physiology 25edition page 132", 'role': 'assistant'}]