These are made of plastic, and are often referred to in the lab as CR39.  For further information see http://en.wikipedia.org/wiki/CR-39. These lenses have a refractive index of just under 1.5, and all of our lenses have a hard coating on the front and back surface.

http://www.essilor.co.uk/lenscatalogue/pdfs/prodinfo/coatmat/supra.pdf
(This page has a graph of uncoated and hard coated lens comparison, maybe we could copy the graph)

These are ultra strong lenses, around 12x stronger than CR39 and are also higher index. These are just under 1.6 index and are on average 23% thinner and 30% flatter than 1.5 Index lenses. These lenses are ideal for rimless. Polycarbonate can be supplied in most formats bifocal or transitions. It is exceptionally strong, however its Achilles heel is vulnerability to solvents. Acetone and alcohols should not be used on this lens type as they attack polycarbonate and subsequently weaken it.

We use either sunsensors or Transitions here. Both have excellent properties, starting off very clear and going as dark as a sunglass depth tint.

http://www.corning.com/ophthalmic/pdfs/plastic_photochromic_solutions.pdf

http://transitions.cambrient.com/uk/more_info.html

These lenses are on average 35% thinner than CR39, and they are also strong. They are about 4x stronger than CR39 and are fine for rimless. These lenses come as standard with a multi antireflection coating.

http://www.allaboutvision.com/lenses/coatings.htm#ar

Lenses with an index of 1.5 will normally transmit 92% of light through the lens. The other 8% is lost to reflections. Antireflection coatings reduce the light lost to reflection, and increases the transmission of light to over 99%. This improves two main areas

• Appearance. The lenses look clearer. This is of great benefit if photos are being taken, especially flash photos.
• Performance. Useful for night time driving.

Anti-Reflection (AR) coatings are known by many names.

Multi-Anti-Reflection (MAR), Broadband-Anti-Reflection (BBAR), Reflection free, clear multi-coated etc.
If fact what was a top of the range product only a few years ago, namely the broad band anti reflection coatings, these are now standard. There are ever more sophisticated coatings; there are now hydrophobic broadband multi anti reflection coatings. These repel water. A later innovation is the anti smudge coating, this incorporates all the other features but is now easier to clean. It could be described as oleophobic, in that it ‘repels’ grease, if the lens is touched, the grease is more likely to stay on the finger, than be transferred to the lens. Currently these are not available to order online, but can be phone ordered.

The very latest coatings have anti-static properties and are available as premium branded coated lenses, for example a Scotchguard coating can now be applied to a lens. These are premium products and premium prices, and whilst we can supply these lenses, it is not a core product for a low cost web site, these are available only to phone order.
http://www.essilor.co.uk/lensinfo/pdfs/Scotchgard%20Brochure.pdf

“Thanks to this new technology the lenses combine proven anti-smudge, anti-scratch, anti-glare, anti-reflective and ultra-hydrophobic properties with the best anti-static performance.”

When we require a different prescription for reading and distance, bifocals can be used instead of swapping between two sets of glasses. The top of the lens is set for distance, and the lower portion of the lens is set for reading. All our bifocals are D28. These are called D segs as the segment for reading is “D” shaped with the top of the bifocal a straight line being 28 mm wide.

Varifocals provide a solution for distance and reading, with a smooth transition form distance to reading, and absolutely no line on the lens. We currently only recommend varifocals to experienced wearers. This is because we can duplicate many of the measurements required to manufacture the lenses from your own / old varifocals. These can be ordered by phone or post, we can take the measurements off your own glasses, and return them to you with the new set.