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
First sign seen in open-angle glaucoma is: 
Select and explain. 
A. Arcuate scotoma, B. Extension above blind spot, C. Roene's nasal step, D. Siedel's scotoma
B: Extension above blind spot
Answer: B: Extension above blind spot 
Explanation: Ans. Extension above blind spot