This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
The cause of a coloured &;Halo&; in narrow angle glaucoma is 
Select and explain. 
A. Increase IOP, B. Corneal oedema, C. Lenticular changes, D. Lacrimation
B: Corneal oedema
Answer: B: Corneal oedema 
Explanation: Clinical Features of Glaucoma - Cupping of disc. - Raised intraocular pressure with coloured halos due to corneal oedema Ref khurana 6th edition pg 1234 - Visual field defect.