This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anatomy, Development and clinical examination, Subject name: Ophthalmology
[{'content': 'In specular microscopy, endothelial density is measured by \nSelect and explain. \nA. Optical doubling, B. Fixed frame analysis, C. Optical focusing, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In specular microscopy, endothelial density is measured by Fixed frame analysis. Image : Fixed-frame counting principle andillustration of the three types of endothelial mosaics analyzed with the fixed-frame method. a)Only grey cells included within theframe and cut exclusively bytwo adjacent borders werecounted. b)Computer-generated regular hexagonal mosaics, c)computer-generated irregular mosaic,in order to mimicpolymorphic and pleomorphic mosaics, d)realhuman mosaic after Alizarinred staining of cornealendothelium with illustration of the eleven grids . Reference : AK kh', 'role': 'assistant'}]