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July 1932


Arch Ophthalmol. 1932;8(1):50-52. doi:10.1001/archopht.1932.00820140058006

The methods most in use for calculating the refracting power of a surface or a lens generally involve the use of formulas embodying several fractions. This is necessitated by the fact that the relation between dioptric power and focal length and that between curvature and radius are mathematically reciprocal relations, that is, inverse relations. The longer the focal length, the less is the power ; similarly, the longer the radius, the less the curvature. Memorizing formulas expressed in fractions and carrying out calculations by means of fractions are processes distasteful to most ophthalmologists, especially if they have not had much mathematical training.

A method that I have used for many years in teaching this phase of physiologic optics partly eliminates these difficulties. It provides an easily memorized formula and involves a knowledge of only the elements of arithmetic and algebra for calculating dioptric powers. For this purpose I have

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