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
Tonography helps you to determine – 
Select and explain. 
A. The rate of formation of aqueous, B. The facility of outflow of aqueous, C. The levels of intraocular pressure at different times., D. None of the above
B: The facility of outflow of aqueous
Answer: B: The facility of outflow of aqueous 
Explanation: There are two similar terms.

Tonography

Tonography is a non-invasive technique for determining the facility of aqueous outflow (C-value).
Facility of aqueous outflow is estimated by placing schiotz tonometer on the eye for 4 minutes.
Beside tonography, other methods to measure the facility of aqueous outflow (C-value) are perfusion method and suction cup method.
The average C-value is 0.28 ± 0.05 1/ min / mmHg. Most glaucoma patients have C-value less than 0.17.

Tonometery 

Tonometry is the assessment of the intraocular pressure of the eye.
Therefore, it is used in the diagnosis of glaucoma and for monitoring the treatment response in glaucoma.