This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Diseases of Cornea, Subject name: Ophthalmology
[{'content': "Diagnose:- \nSelect and explain. \nA. Keratoconus, B. Wilson's disease, C. Glaucoma, D. Williams syndrome", 'role': 'user'}, {'content': "Answer: B \nExplanation: Wilson's disease Kayser - Fleischer rings (KF rings) are dark rings that appear to encircle the iris of the eye. Itoccurs due to copper deposition in Descemet's membrane of cornea. In case of Wilson's disease, KF rings are present in 95% of patients with neurological symptoms, 50-60% of patients with hepatic involvement alone, and only in 10% of asymptomatic siblings. Early detection of KF ring is best possible with gonioscopy, although it is most commonly detected by slit-lamp examination.", 'role': 'assistant'}]