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
Topical administration of I% Pilocarpine failed to produce pupillary constriction in a patient who had a large, dilated pupil What should be the most probable reason? 
Select and explain. 
A. Adie's tonic pupil, B. Diabetic III nerve palsy, C. Pharmacological blockade, D. Uncal herniation
C: Pharmacological blockade
Answer: C: Pharmacological blockade 
Explanation: Ans. c. Pharmacological blockade (Ref-YANNOFF 3/E PG,1052-1055)Pilocarpine I% is a sufficient miotic dose for any eye, but a sphincter with all its cholinergic receptor blockade by atropine or tropicamide (i.e. eye with pharmacological blockade) does not constrict with pilocarpine 1%.