This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ophthalmology Q Bank, Subject name: Ophthalmology
All of them are true about ERG except 
Select and explain. 
A. Measures the potential difference of the neurosensory layer of retina, B. The negative A wave is produced by the hyperpolarization of the photoreceptors, C. The positive B wave is due to the bipolar and Muller's cells, D. Flash ERG is a good for detection of macular diseases
D: Flash ERG is a good for detection of macular diseases
Answer: D: Flash ERG is a good for detection of macular diseases 
Explanation: Electroretinography (ERG) is the record of changes in the resting potential of the eye induced by a flash of light. Components of normal electroretinogram (ERG) a-wave. It is a negative wave possibly arising from the rods and cones (photoreceptors). b-wave. It is a large positive wave which is generated by Muller's cells, but represents the activity of the bipolar cells . c-wave. It is also a positive wave representing metabolic activity of pigment epithelium (seen only in dark adapted eye). A flash ERG requires a large area of retina to be abnormal for being detectable and thus in macular disorder where only small pa of retina is involved , flash erg doesn't detect it