### device:

Lense
* Most lenses are either glass, plastic, or polycarbonate.
* Some lenses use aspheric elements to better correct spherical aberration at wide apertures.
* There are many similarities between lenses and mirrors.
* also differ in color balance.
* are an important part of eyes
  - ground and polished to precision ophthalmic standards, made of optical quality glass
  - in essence refracting objects with precisely machined curved surfaces
  - optical elements used to focus or defocus images
  - part of cameras
* are special glass shapes that have at least one curved surface
  - pieces of glass or plastic that are curved on one or both sizes
  - symbols of modern civilization
* are the most important part of seeing well
  - primary means for presbyopia correction
  - usually symmetric about an axis, called the lens axis
* bend light in different directions
* bend, or refract, light.
* can magnify objects and view objects in other locations.
* come in a variety of materials
  - different colors
  - many colors for different lighting conditions
* flare is when the light reflects back and forth between the lenses in the camera.
* focus light.
* have about the same coating as nonreflective eyeglass lenses
  - three main shapes
* includes sections.
* is an optical device
* naturally occur in eyes and are a good example.
* produce a prism effect which causes the image to develop false color fringes.
* use refraction to magnify an object or to make it appear smaller.
* work because in different materials light has different a. wavelengths.
+ Lens (optics): Optics

### device | lense:

Bifocal lense
* are actually a form of vision therapy.
* have two distinct segments with different powers.

### device | lense:

Contact lense
* All contact lenses reduce oxygen transmission to the cornea.
* Some contact lenses are also UV-inhibiting to protect the eyes from bright sunlight.
* are a proven safe, popular alternative to Eyeglasses for many people
  - an option for correcting visual defects in some patients
* are better for work that involves optical instruments
  - in rain and mists
  - than glasses in humid atmospheres
  - easy to care for and pose few related health risks to the wearer
  - extremely safe when prescribed and cared for properly
  - important health care devices that require proper fitting and care
  - less costly than spectacles
  - limited to certain eye conditions
  - medical devices, and as such, can be very dangerous if used inappropriately
  - more expensive and demand more attention than glasses
  - preferable to cataract glasses
  - small, curved thin plastic disks that correct vision
* are the preferred method of vision correction for many people
  - treatment of choice for keratoconus
  - very safe when properly cared for
* can be extremely dangerous if chemicals are splashed in the eye
  - problematic in many countries
* can correct most of the vision problems that glasses correct
  - vision conditions, including nearsightedness and farsightedness
  - help the eyes work better together and have equal image sizes in the brain
  - improve vision, but they can also scar the cornea
  - kind of give the eye a new, smoother front that focuses light properly
* can provide a barrier to various gases and aerobic particles
  - significant vision improvement for many patients
  - stop myopia from getting worse
  - trap chemicals under the lens and prevent flushing of the eyes
* complicate eye safety.
* have certain advantages over glasses.
* intensify burns.
* offer some eye protection from anhydrous ammonia exposure.
* play an important role.
* pose certain remote risks, as does laser vision correction.
* provide a uniform refracting surface and therefore improve vision
  - better peripheral vision than eyeglasses
* require more tears and people with dryness tendencies often become symptomatic.
* stay cleaner longer and free of impurities when sterilized with distilled water.
* work satisfactorily for some with albinism.