Lenses {glasses} can be single vision for near or far focus, bifocal, or trifocal.
material
Lenses can be glass, plastic, high-index, or polycarbonate. Glass is heavy and does not absorb UV light. Plastic is light but does not absorb UV light. High-index combines plastic and polycarbonate and absorbs UV light. Polycarbonate absorbs UV light.
polarization
Lens polarization can reduce glare.
coating
Scratch-resistant coatings are harder than plastic. Anti-reflective coatings reduce reflections. UV protection coats glass or plastic to absorb UV light. High-index and polycarbonate do not need UV coating, because they absorb ultraviolet light.
shape
Lenses have flat surfaces outside and curved surfaces towards eye, in meniscus shape.
shape: Spheric
Spheric means inner and outer surfaces are spherical, and outer surface has more curvature. Aspheric means spherical lenses have non-spherical edges, to maintain clear vision through lens edges.
shape: Atoric
Atoric means inner and outer surfaces change from spherical, and outer surfaces have less curvature.
frames
Oval frames have oval lenses. Geometric frames have oval tops and circular bottoms. Round frames have circular lenses. Square frames have square lenses. Rectangular frames have rectangular lenses. Navigator frames have trapezoid lenses slanted along nose. Aviator frames have trapezoid lenses with curved lower edges. Frames can be plastic or metal, including titanium. Colors are silver, gold, brown, black, and red.
Biological Sciences>Medicine>Medical Examination>Eye Exam>Lens
4-Medicine-Medical Examination-Eye Exam-Lens
Outline of Knowledge Database Home Page
Description of Outline of Knowledge Database
Date Modified: 2022.0224