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What is The Most convenient form of cross cylinder is a combination of - and explain in detail?
Jackson's cross cylinder test: It is used to verify the strength and axis of the cylinder prescribed. The crosscylinder is a combination of two cylinders of equal strength but with opposite sign placed with their axes at right angles to each other and mounted in a handle . The commonly used crosscylinders are of +-0.25 D and +-0.5 D Image: Jackson's cross cylinder Reference : A K KHURANA OPHTALMOLOGY,Edition 4,Page-555