Lens index explained

The lens types we offer:

Cr39 1.5

Single Vision

Clear,Tinted, Polarised, Transitions

Bifocal

Clear,Tinted, Polarised, Transitions

Varifocal

Clear,Tinted, Transitions


Trivex 1.53

Single Vision

Clear,Tinted, Polarised, Transitions

Bifocal

Clear,Tinted, Transitions


Polycarbonate 1.59

Single Vision

Clear,Tinted, Polarised, Transitions

Bifocal

Clear,Tinted, Polarised, Transitions


1.6

Single Vision

Clear,Tinted, Polarised, Transitions

Bifocal

Clear,Tinted

Varifocal

Clear,Tinted, Transitions


1.67

Single Vision

Clear,Tinted, Polarised, Transitions

Bifocal

Clear,Tinted


1.74

Single Vision

Aspheric design only – Clear or Tinted

Bifocal

Aspheric design only – Clear MAR coated


Why choose high index lenses?

In simple terms, the higher the index of the lens the thinner it will be.
This applies for both near-sighted and far-sighted people.
Near-sighted people will see that their lenses are thinner in the middle and thicken as you go towards the edge.
Far-sighted people will have the opposite – thinnest at the edge and thicker towards the center.

This is something to think about when buying your glasses online. If you have a stronger prescription, the thickest part of the lens (on the edge for near-sighted and in center for far sighted) will be more apparent.

If you have a strong prescription, you may wish to think about upgrading to high index lenses or aspheric lenses when buying prescription glasses online.


What does it all mean??!

It may all look like random decimals, but it’s quite straight forward.
Here is some basic information on each lens material, and what they are commonly used for.

1.5

Also known as CR39 (Columbia Resin #39).
This is the lens material used when you choose not to upgrade your lenses.

Positives

  • Affordable
  • Available in wide range of base curves for frames with a high curve/wrap
  • Faster turn-a-round when ordering
  • Ideal for sunglasses tinting

Negatives

  • Thickest lens option
  • Heavier with stronger prescriptions
  • Can chip/crack when used in rimless frames.

1.53

Also known as Trivex.
Trivex was originally used in eye protection for the military.

Positives

  • Affordable
  • Strong
  • Good impact resistance
  • Scratch resistant coating as standard
  • Perfect for rimless frames
  • 100% UV protection
  • Thinner lenses can be used in rimless and semi-rimless without risk of compromising on durability

Negatives

  • 10% thicker than the rival, Polycarbonate.

1.56

We do not offer 1.56 index lenses.


1.59

Also known as Polycarbonate.
Developed in 1970’s. Shatter resistant material used by NASA on astronaut’s visors.

Positives

  • Strongest, toughest lens available
  • Up to 22% thinner than 1.5 CR39
  • Scratch Resistant coating as standard
  • 100% UV protection
  • Available in aspheric and spheric design
  • Suitable for tinting to a medium-dark tint
  • Perfect for safety glasses, sports frames or anyone who requires a protective, lightweight lens

Negatives

  • Will not tint as dark as CR39
  • Require a polished edge which may not appeal to some wearers
  • Cannot be cleaned with lens cleaners containing acetone

1.6

The first stage of the true high index lenses. Available in both spheric and aspheric design.
Positives

  • 25% thinner than 1.5 CR39
  • Scratch resistant coating as standard
  • Suitable for rimless frames
  • 100% UV protection

1.67

Even thinner still. Available in both spheric and aspheric design.

Positives

  • 40% thinner than 1.5 CR39
  • Scratch resistant coating as standard
  • Suitable for rimless frames
  • 100% UV protection

Negatives

  • Higher cost

1.74

The thinnest and lightest plastic lens available. Available in both spheric and aspheric design. It is also quite expensive.

Positives

  • Up to 50% thinner than 1.5 CR39
  • Thinnest plastic lenses available
  • Scratch resistant coating as standard
  • 100% UV protection
  • Minimum eye-ball magnification

Negatives

  • Not suitable for rimless frames
  • Highest cost plastic lens index

Aspheric Lens Design

Aspheric lenses are aimed at those with a stronger prescription, particularly far-sighted plus (+).
They are available on all high index lenses above 1.56 index. They have a slimmer profile than the standard spherical lens, reducing the ‘bulge’ in the center of the lens on plus (+) prescriptions, and enabling the wearer to choose a wider range of frame designs. The bulge in high prescription spherical lenses also creates magnification of the eye ball, or the ‘bug-eye’ appearance (‘beady-eye’ in high minus prescription). This is dramatically reduced with aspheric lens design.

Aspheric lenses also reduce distortion for a wider field of view and superior peripheral vision.


Do I need high index lenses?

If you have a strong prescription, you may wish to consider how thick your lenses may appear.
This is all down to personal preference. The main reasons for choosing high index lenses are to reduce weight and to make the lenses look nicer in the frame. We recommend a 1.6 lens on all full rim frames if your sphere value is above +2.00, and 1.53 trivex on all rimless and semi-rimless frames because it is so much stronger than other lens materials.
If you are buying a pair of glasses just to watch TV at home and you don’t need them to look special, as long as you are comfortable with a slightly heavier lens, there is no need to upgrade to higher index lenses, but you may wish to consider an Anti-Reflective coating for tv, computer or night driving use.

Benefits of an Anti-Reflective coating

All lenses reflect light. An Anti-Reflective coating helps to transmit 99.5% of light through to the eye for optimum vision.
Standard index lenses can reflect up to 10% of light away from the eye.
Hi Index lenses can reflect up to 50% of light away from the eye so an anti-reflective coating can be useful.


Does my frame type make a difference?

Your frame choice can make a big difference. As mentioned earlier, near-sighted lenses get thicker towards the edge, if you choose a frame with an eye size much bigger than the one you already have, you may be disappointed with the appearance of your lenses, as they will be thicker at the edge than your older pair. The same applies if you have previously worn a plastic frame (plastic can help hide thickness of near-sighted lenses) and change to a metal frame or a semi-rimless. The lenses may appear to be thicker.

If you have a strong Plus(+) prescription we do not recommend Semi-Rimless or Rimless frames. Anything above +3.00 is not recommended.  This is due to the fact that the edge substance has to be made thicker to hold the semi-rimless cord or have pins placed through it for rimless frames. As the edge is made thicker to accommodate these components the lens centre also gets thicker.

Spectacle lens thickness comparison chart

Lens thickness chart diagram for standard and high index prescription lenses