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
A lady presented with reddish eye and watering over left eye with a shallow anterior chamber. What is the next best investigation? 
Select and explain. 
A. Tonometry, B. Cup disc ratio, C. Gonioscopy, D. Ophthalmoscopy
A: Tonometry
Answer: A: Tonometry 
Explanation: Ans. (a) TonometryShallow AC with redness- points towards PACG in a female. In acute stages, IOP is markedly raised - Do tonometry followed by gonioscopy & fundus examination.