| divers' spectacles | Strongly convex lenses for clear vision underwater. (05 Mar 2000) |
|---|---|
| orthoscopic spectacles | Convex lenses with base-in prisms for close work. (05 Mar 2000) |
| telescopic spectacles | Magnifying spectacles obtained by using a convex objective lens and a concave eyepiece separated by the difference in their focal lengths. (05 Mar 2000) |
| Franklin spectacles | An early form of bifocal spectacles in which the lower half of the lens is for near vision, the upper half for distant vision. Synonym: divided spectacles. (05 Mar 2000) |
| lid crutch spectacles | Spectacles with little offsets of metal with smooth edges which engage above the upper eyelid and keep it raised above the pupil in cases of paralytic blepharoptosis. Synonym: Masselon's spectacles. (05 Mar 2000) |