<unk> s are eyeglasses with<unk>  that have three regions which correct for distance, intermediate (arm's length), and near vision. John Isaac Hawkins developed the<unk>  lens in 1827.<unk> s are mostly used by people with advanced presbyopia who have been prescribed 2 diopters or more of reading addition. The intermediate addition is normally half the reading addition. So, for someone with a distance prescription of −4 diopters and a reading addition of +3, the reading portion of their<unk> s would have a net power of −1, and the intermediate segment would be −2.5 diopters.<unk>  are made in similar styles to bifocals, but with an additional segment for intermediate vision above the reading section. A common style is the 7×28 flat-top or D-shaped segment, 28 mm wide, with a 7 mm high intermediate segment. Larger intermediate segments are available, and are particularly useful for people who spend a lot of time using computers.<unk> s are becoming rarer as more people choose to wear progressive<unk> .
Trifocal lenses
Windsor glasses
Corrective lens
Browline glasses
Multifocal intraocular lens
Adjustable-focus eyeglasses
Argus retinal prosthesis
Pinhole glasses