There are no uniform, objective criteria for the prescription of special filter lenses. Instead, the most suitable lens is usually found by trying out the various options available, especially for such degenerative eye disorders as retinitis pigmentosa or diabetic retinopathy. Patients subjectively compare and assess the visual comfort provided by the different types of filter lens available. Patients decide what filter lens is most suitable for their needs by comparing and assessing the visual comfort provided by various filter lenses. Binocular lorgnettes for mounting in front of the eyes or a filter clip for attaching to spectacles are available for this purpose.
Many patients require special filter lenses for different light conditions. This is why they often have several pairs of glasses or filter clips with different special lenses.
The transmission of the special filter lenses F 60, F 80 and F 90 and F 540,
F 560 and F 580 for medical applications has been optimised so that part of the visible shortwave spectrum is absorbed.