Mean and variance of meridional powers of sphero-cylindrical prescriptions.
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Eyeglasses↗
Biomedical subjects
P W Churms
Publications and source records attributed to P W Churms.
Toric lens volume.
Theory is derived for the calculation of the volume of tyre- and barrel-form toric lenses. The integral produced is evaluated using an approximate method of integration. Differences between the two volumes are considered insignificant in the context of spectacle lens manufacture. Methods of approximating the volumes of both tyre- and barrel-form toric lenses are examined. An approximate method, relying upon standard formulae pertaining to the volume of the sphere and cylinder, is sufficiently refined for most practical purposes and obviates the use of a sophisticated calculator or computer.
Eyeglasses↗
The sagitta of a toroidal surface in an oblique meridian.
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Eyeglasses↗
The theory and computation of optical modifications to the cornea in refractive keratoplasty.
The optical theory of keratophakia employing implant lenticules with a refractive index different from that of the cornea is presented. This generalized theory also embraces keratophakia employing donated stromal lenticules and keratomileusis, with equal accuracy. The method of solution of the formulas is indicated. The effects of the various parameters upon the radius of curvature to be applied to the cornea are illustrated and discussed.
Cornea↗