This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Errors of Refraction, Subject name: Ophthalmology
Prescription of simple myopic astigmatism: 
Select and explain. 
A. -0.5x180deg, B. +0.5x180deg, C. -3, D. 2
A: -0.5x180deg
Answer: A: -0.5x180deg 
Explanation: Ans. a.-0.5x180degSimple myopic astigmatism is one in which one meridian is emmetropic and other meridian is myopic.Hence needs correction only in one meridian with concave (-ve) cylinders. So the answer is -0.5x180deg.ASTIGMATISM TYPES AND CORRECTIONTypes of astigmatismDescriptionOpticsCorrectionSimple myopic astigmatismOne of the foci falls upon the retina while the other falls in front of or behind the retinaConcave cylinder Ex: -0.5x180degConvex cylinder Ex: +0.5x180degSimple hyperopic astigmatismCompound myopic astigmatismNeither of the foci fall upon the retina but both are placed infront of or behind the retinaConcave sphere + Cylinder Ex: -0.5 D sphere, -0.5x180degConvex sphere + Cylinder Ex: +0.5 D sphere, +0.5x180degCompound hyperopic astigmatismMixed astigmatismOne focus is front of the retina while the other is behind so that the refraction is hypermetropic in one direction and myopic in other directionConcave/ConvexSphere+Convex and concavecylinderEx: -1D sphere, +2Dx180deg