A monocle is a corrective lens that provides correction or enhancement to the visual perception of an eye. A monocle is a circular lens, usually with has a wire ring around the perimeter that is pinned to another wire or string. The string or wire is them connected to a person’s clothes.
There are three different styles of monocle. The first type has a simple metal loop with a lens that fits into the eye's orbit. The second one, which was made around the 1890s included a frame called a “gallery” which has a raised-edge like extension. This type was designed to hold the monocle in place and it sits outside of the eye’s orbit. The gallery type of monocle is considered to be the most expensive compared to the other types of monocles. The third style of monocle is a frameless one. Frameless monocles include a cut out piece of glass with a notched edge and they sometimes have a gap drilled into the bounds of a cord. Frameless monocles don't have cord and you can wear it freely.