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
Which among the following is the indication for using Fincham's test? 
Select and explain. 
A. To diagnose congenital glaucoma, B. To diagnose acute congestive glaucoma, C. For differential diagnosis of acute congestive glaucoma from cataract, D. To diagnose congenital cataract
C: For differential diagnosis of acute congestive glaucoma from cataract
Answer: C: For differential diagnosis of acute congestive glaucoma from cataract 
Explanation: The coloured halos in glaucoma must be differentiated from those found in acute purulent conjunctivitis and early cataractous changes. In conjunctivitis, the halos can be eliminated by irrigating the discharge. The halos of glaucoma and immature cataract may be differentiated by Fincham's test in which a stenopaic slit is passed across the pupil. During this test glaucomatous halo remains intact, while a halo due to cataract is broken up into segments. Ref: Comprehensive Ophthalmology by AK Khurana, 4th edition, Page 228.