Lens Enhancements

By: Charl Laäs Optometrists  11-11-2011
Keywords: Lenses, Lens

Ophthalmic lens enhancements are additional lens technologies that can be added to a standard ophthalmic lens to improve the functionality and/or durability of the lens.  


  • Hard coatings improves the surface hardness of the lens making it more resilient towards scratches.  It is important to note that hard coated lenses are not scratch proof and can still get scratched if not properly cared for.
  • Anti reflex coatings reduce the internal and external light reflections seen in a lens.  The benefits are less glare and flare, improved cosmetics and improved contrast.  Anti reflex coatings are highly recommended for night time driving and computer work
  • Combination coatings are found on modern high end lenses.  The lens manufacturers like Hoya, Carl Zeiss, Essilor and Nikon combine a hard coat with a super anti reflex coating and further enhance the coating by adding anti static-, water repellent and anti smudge components to the coating.  This allows for a high quality lens that is resilient towards scratches, reduce light glare and flare and are easier to clean.



  • Fixed colour tints can be added to the lenses.  Any colour can be used and can be applied in different intensities as a full tint or a gradient tint.
  • Variable colour tints automatically adjust to the UV intensity of the day and will automatically get darker in the sun and lighten up when going indoors.  The warmer the day and the more UV intensity that  reaches the lens the darker the lens will tint. Variable tint lenses are normally available in either a gray or brown tint and most people in South Africa tend to prefer the gray tint when choosing these lenses.  Arguably the most widely used variable tint technology being used in the world is the Transitions variable tint.  As a point of interest when the technology is used in glass lenses it is also commonly called a photochromic tint.
  • Polarised lenses uses a technology that eliminates reflective light from entering the eye and therefore gives maximum protection from glare. The polarisation technology is usually combined with either a fixed or variable tint and the high end sunglasses will also have a back surface anti reflex coating added to the lens.  Polarised lenses are highly recommended for people who participate in water and snow sports or who are frequently exposed to areas of high intensity glare.  Aircraft pilots should be cautious of polarised lenses as the technology is not compatible with the aircrafts' polarised windows.


High Index materials

  • High refractive index lenses are thinner than normal lenses and are typically used for high prescriptions to improve the cosmetic look of the spectacles.  Different indexes are available ranging from 1.49, 1.50, 1.56, 1.6, 1.7, 1.8 and 1,9.  The higher the index number the more dense the lens material will be and therefore the lens will be thinner compared to the lower index lens for the same strength prescription.
  • Polycarbonate material is a high index material which is lighter and much stronger than normal plastic lenses and are normally used for safety glasses,  children's glasses and rimless glasses where the likelihood of lens breakage is higher.
  • Trivex material is very similar characteristics to the polycarbonate material but because of a lower aberration value provides better quality optics compared to polycarbonante, making it the ideal choice for rimless and sport specific glasses.

Keywords: Lens, Lenses

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Ophthalmic Lenses

As reading lenses they provide a simplistic solution for near vision problems as they will clearly focus for objects between 30cm to 40cm with no peripheral distortion in the lens. Trifocal lenses look exactly the same as bifocal lenses accept that a third intermediate zone in added above the reading segment. They do however have the limitation of blurring distant objects when a person looks further away than the 30cm to 40cm distance.