Optical characteristics of Transpaseal as a partial occluder

The acuity degradation produced by Transpaseal, a typical adhesive scattering material applied to spectacle lenses to produce partial occlusion during orthoptic treatment, is studied by measuring the angular characteristics of the scattering and its effect upon the visual contrast sensitivity function. Whereas in general the material acts as a low-pass spatial frequency filter, it is shown that the scattering function is not symmetrical and hence that the visual degradation produced varies with the orientation of the detail observed.