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August 1939


Arch Ophthalmol. 1939;22(2):290-291. doi:10.1001/archopht.1939.00860080134014

It is commonly stated in textbooks and other publications1 that the power of a cylinder in an oblique meridian is a function of the full power of the cylinder and the angle of obliquity between the axis of the cylinder and the meridian chosen. The relation can be expressed by the equation C′ = C sin2 a, in which C′ is the power of the cylinder in the oblique meridian, C the full power of the cylinder and a the angle between the cylinder axis and the oblique meridian. From this equation a table can be constructed showing the "power" in any oblique meridian, as demonstrated in the table in Dr. Olsho's article, page 516.

However, the formula and also the table are only approximations and, strictly speaking, approximations of a special kind. The power of a cylinder is expressed by the power of its meridian at right angles

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