Measurement of astigmatism can be obtained by examining astigmatism data with equipment such as examining glasses, computerized optometry, and corneal topographers, and astigmatism mainly comes from the cornea and the lens. The data obtained by the examining lens and computerized optometry is an indication of comprehensive astigmatism, and it is impossible to distinguish whether the astigmatism comes from the cornea, or from the lens. Corneal topography instruments, the results vary from brand to brand. All brands, can measure anterior corneal surface astigmatism; only certain brands, can measure posterior corneal surface astigmatism. By understanding corneal astigmatism, it is possible to understand which tissue the astigmatism mainly comes from, whether it is corneal astigmatism or lens astigmatism, and provide a basis for solutions for lens prescription, refractive surgery, cataract surgery, etc.