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
Corneal endothelium seen by ? 
Select and explain. 
A. Pachymeter, B. Keratometer, C. Tonometer, D. Slit lamp bio-microscope
D: Slit lamp bio-microscope
Answer: D: Slit lamp bio-microscope 
Explanation: Ans. is 'd' i.e., Slit lamp bio-microscope Corneal Endothelium: It consists of single layer of polygonal (mainly hexagonal cells). They are visualized by slit lamp bio-microscope and appear like mosaic. The cell density is 3000 cells/ mm2 in young adults and deceases with age. These cells contain active pump mechanism. Note: Confocal microscope can be used to study all layers of retina.