TTL (Through the Lens) loupe telescopes are attached to eyeglasses through holes that are made on the lenses. Lenses for near vision according to own prescription are added to the loupe telescopes, and a lens type most appropriate for the user’s requirements is selected for the surrounding carrier lenses. This ensures that the combination functions even in more challenging working conditions. The carrier lenses are always manufactured with high-quality coatings to prevent scratching and reflections and are available in high-index materials to keep them thin and lightweight.
Single-vision carrier lenses
A single-vision carrier lens has the same corrective power across its whole surface, so the field of vision is the size of the lens. These lenses work perfectly when there is no need for near vision addition or only a small addition would be required. With stronger near vision additions, the single-vision lenses provide limited ability to see things clearly at longer viewing distances. The corrective power of the single-vision carrier lenses is usually made for a viewing distance of instruments or a computer screen.
Bifocal carrier lenses
Bifocal carrier lenses are especially useful when strong near vision addition is required but you also need to have good vision at longer distances while wearing the loupe glasses. The corrective power in the middle of the lenses is typically for the distance of instruments or a computer screen, whereas the top area is for viewing objects at a longer distance. Compared to progressive lenses, bifocal lenses have the benefit of wide and clear field of vision.
Progressive carrier lenses
The additional power of the lower part of the carrier lens providing near vision diminishes gradually towards the top of the lens that is used for looking further away. Progressive carrier lenses most suitable for room distances include the so-called enhanced reading glasses and occupational progressive lenses. In these lenses, the narrow field of vision typical to progressive lenses can be widened by not including the area for far distance vision in the top part of the lens. In addition, this also results in a slower power change throughout the lens, which makes it easier to view various objects.