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
In specular microscopy endothelial density is measured by? 
Select and explain. 
A. Optical doubling, B. Fixed frame analysis, C. Optical focusing, D. None
B: Fixed frame analysis
Answer: B: Fixed frame analysis 
Explanation: Ans. is 'b' i.e., Fixed frame analysis Endothelial cell density in specular microscopy is counted by fixed frame analysis and variable frame analysis. Cell density (ceIlsimrn2 ) = Cell count in frame