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
The earliest clinically significant field defect in primary open-angle glaucoma is: 
Select and explain. 
A. Paracentral scotoma, B. Baring of blind spot, C. Seidel's scotoma, D. Isopter contraction
A: Paracentral scotoma
Answer: A: Paracentral scotoma 
Explanation: Ans. Paracentral scotoma