Visual acuities were measured through a series of prisms in order to quantify the blur that results from dispersion in polycarbonate. The mean VA of forty eyes declined from 20/13 unaided to 20/31 through 16 prism diopters of polycarbonate. The decline was a linear function of prismatic power. The blurring effect of polycarbonate was significantly greater than that of CR39. The blur from polycarbonate was found to be great enough that it should be taken into account whenever polycarbonate is considered for spectacle lenses. Graphical displays are provided which can be used by the clinician to predict the degree of blur from a known polycarbonate lens.
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