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Summary

A Nissel + 1.75 D PS45 lens' label power seems to be made up of about + 0.75 D distance and + 0.75 D near addition. There are individual variations which will depend on pupil size, corneal shape, lens position and ocular aberrations. When a + 0.75 Bausch & Lomb U3 lens was used as a control, there was also a significant increase in ‘accommodation’ measured (+ 0.75 D), but this could not be explained. When two other lenses with an aspheric surface were studied, they also showed a near addition effect. In this supplementary study the changes were explained by changes in spectacle accommodation. A lens with two spherical surfaces did not show the expected increase in spectacle accommodation. Astigmatism, as a general rule, was not corrected by the PS45 lens, although the very occasional case did show some reduction. Visual acuity and contrast sensitivity at 8 cpd and 3 cpd were not significantly affected when compared to the control lens.