Spectacles (glasses) for patients after cataract extraction (cataract lenses) having two-lens optical systems

摘要

Cataract lenses have the following disadvantages: strong magnification, narrowing of the field of view (visual field), bringing the subject and obstructions very close, shallow depth of focus etc. These disadvantages are countered here by means of a two-lens optical system which consists in practice of two spectacles, near-eye spectacles and spectacles for normal distances. The dioptric number of the lenses required for the wearer is split between front spectacles and rear spectacles approximately in the ratio of 1:3. As an example, using these spectacles a car driver who has undergone a cataract operation sees in a sharply defined fashion from the dashboard to infinity, something which otherwise requires bifocal spectacles with gaps or trifocal spectacles with discontinuities, which lead to great uncertainties in distance measurement. The rear spectacles can be transferred from one spectacle frame to another by means of a wire bow or similar. In the case of declining visual faculty, it suffices to adapt the front spectacles. This renders these spectacles economic as well, because it is not necessary in every case to exchange the expensive cataract lenses, but only reading spectacle lenses, which are used in massive numbers.