Abstract
The off-axis prismatic effects (prism) of five types of progressive power lenses were measured on a modified vertometer. The lens types assessed were the Essilor (Hoya) Varilux II, the American Optical Truvision Omni, the SOLA Graduate, the Rodenstock Progressiv R, and Zeiss Gradal HS. Conventional flat top bifocal lenses were also assessed. Progressive power lenses have smooth changes of prismatic effects, free of sharp jumps associated with bifocals. Differential prism of progressive lens pairs matched for power mainly result from a failure of some manufacturers to design for individual right and left lenses. This failure can produce up to 1.0Δ vertical and horizontal differential prism. We recommend that reduction of differential prismatic effects be carefully considered in future progressive lens design.
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