"Trifocal" redirects here. For the tensor, see Trifocal tensor.
Trifocals are eyeglasses with lenses that have three regions which correct for distance, intermediate (arm's length), and near vision. John Isaac Hawkins developed the trifocal lens in 1827.[1]
Trifocals 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 trifocals would have a net power of −1, and the intermediate segment would be −2.5 diopters.
Trifocal lenses 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.
Trifocals are becoming rarer as more people choose to wear progressive lenses.
^Stein, Harold A. (2012). The Ophthalmic Assistant: A Text for Allied and Associated Ophthalmic Personnel (9th ed.). Philadelphia: Elsevier Mosby. p. 205. ISBN 978-1-4557-3346-0.
Trifocals are eyeglasses with lenses that have three regions which correct for distance, intermediate (arm's length), and near vision. John Isaac Hawkins...
Progressive lenses are corrective lenses used in eyeglasses to correct presbyopia and other disorders of accommodation. They are characterised by a gradient...
short distance in front of the eye. Contact lenses are worn directly on the surface of the eye. Intraocular lenses are surgically implanted most commonly after...
avoided in some cases if Multifocal IOLs, Trifocal IOLs or EDOF lenses are used.[citation needed] Intraocular lenses have been used since 1999 for correcting...
Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over...
bifocals may have been such a case. John Isaac Hawkins, the inventor of trifocallenses, coined the term bifocals in 1824 and credited Benjamin Franklin. In...
large lens shape is used. However, if the lens is too small, it can drastically reduce the field of view. Bifocal, trifocal, and progressive lenses generally...
Multifocal and accommodating intraocular lenses are artificial intraocular lenses (IOLs) that are designed to provide focus of both distance and near objects...
anyone who prepares, fits, and dispenses prescription lenses, spectacles, eyeglasses, contact lenses, or any other type of vision-correcting optical device...
contact lenses, multifocal intraocular lenses, or LASIK (PresbyLASIK) surgery. The most common treatment is glass correction using appropriate convex lens. Glasses...
corrective lenses. The first version of the lens was invented by Bernard Maitenaz and released in 1959, and was the first modern progressive lens to correct...
sufficiently protective lenses can block much or little light, resulting in dark or light lenses. The lens color is not a guarantee either. Lenses of various colors...
Aspheric lenses are also sometimes used for eyeglasses. Aspheric eyeglass lenses allow for crisper vision than standard "best form" lenses, mostly when...
Collinearity equation Photogrammetry Essential matrix, Fundamental matrix Trifocal tensor Jaehong Oh. "Novel Approach to Epipolar Resampling of HRSI and Satellite...
after World War II with different lenses as Type F-2 (arctic) and Type G-2 aviator sunglasses but fitted with darker lenses until their substitute the Type...
lenses do not use multiple pieces of material in their lenses like other lenses, but the lens will be broken down into sections, allowing the individual...
because the red lenses were fixed to a hinge at the top of the frame. This meant that as the hen lowered its head to feed, the lens swung out giving...
for better measurement of refractive error, so that glasses and contact lenses can be prescribed with different strengths in each eye. The monocle did...
IOL is inserted. Foldable lenses are generally used for the 2–3 mm (0.08–0.12 in) phaco incision, while non-foldable lenses can be placed through the...
based on the need or desire of the wearer. Corrective lenses, such as glasses, contact lenses, and, historically, monocles are used to aid in one's vision...
in conjunction with contact lenses. Advantages of lensless glasses are that they do not fog or reflect, and there is no lens that will touch long eyelashes...
or Venetian blind shades are sunglasses that, instead of having darkened lenses, have horizontal slats similar to window shutters, which are an integral...
side protection, comfort, anti-fog coatings, interchangeable lenses, transition lenses, etc. At least one product from more than a half dozen manufacturers...
coating or flash coating) on the outside of the lenses to make them appear like small mirrors. The lenses typically give the wearer's vision a brown or...
eyerims made from one brand may be compatible with the lenses made by many other brands. Eyeglass lenses were historically made of glass and had to be ground...
which the lenses are mounted directly to the bridge or temples. The style is divided into two subtypes: three-piece glasses are composed of lenses mounted...