At Buckingham Opticians we can supply all types of plastic lenses, from ordinary CR39 to high index 1.74, including tints, polarising filters and the latest generation of plastic photochromic, Transitions Signature.
There is a wide range of plastic materials available. The most commonly used material is CR39 (Alyl Di-Glycol Carbonate), a thermosetting polymer which has excellent optical properties, but it can scratch a little too easily and in higher lens powers can be quite thick.
If you have a higher prescription or are conscious of the thickness of the lenses, thinner lens designs are available. Materials with a higher refractive index bend (refract) the light more, so tend to be flatter and thinner than conventional CR39. The higher the refactive index, the thinner the lens. So-called Hi-Index lenses are available in 1.6, 1.67 and 1.74. However, the higher the refractive index, the more light is reflected from the front and back surfaces, making them appear more 'glassy'. So we usually recommend the use of a Multi-Layer Anti-Reflection coating (MAR) with these materials, which greatly improves the cosmetic appearance of the lenses, and also makes them more scratch -resistant.
All lenses have distortions. The higher the power of the lens, the greater the distortions. Traditional 'stock' lenses are mass-produced to designs which are over a century old. They are cheap to produce, and correct the vision quite well, but inevitably they produce the slpoing and slanting effects familiar to virtually all spectacle wearers. Traditional varifocal lenses distort the image even more, causing rippling effects, wobbling and even symptoms of sea-sickness.
If you would like to know more, just give us a ring or send us an email.
At Buckingham Opticians we use Transitions Signature as our plastic photochromic lens material of choice. The lenses are clear indoors, in the car and at night, but adapt quckly to sunlight to protect the eyes from glare. They also offer 100% protection from harmful UV light. They are available in brown and grey.
For those who need protection from glare when driving, the alternative is Transitions Signature Xtractive, which carry a moderate tint in the car and indoors, but also rapidly adapt to sunlight when outside. They also offer 100% protection from UV. They are only available in grey.
DRIVEWEAR. These lenses react to visible light as well as UV, which means they change in the car and indoors when the lighting is bright. They also have a polarising filter which eliminates glare inside and out - unlike conventional polarising filters these do not appear darkly tinted, so they can be worn in comfort indoors. In low lighting the lenses have a green/yellow colour, improving contrast and maximising visual efficiency. As the lighting increases they change to a copper colour, which is great when driving and may inprove depth perception, and then to a dark red/brown in bright sunshine. However, as the lenses always have a certain depth of tint, they are not designed to be worn when driving at night.
In rimless spectacle frames, the bridge and sides are fitted to the lenses by bolts or gromits which are fitted into holes drilled through the lens material. As a result the material used must be tough and less brittle. Obviously glass - even toughened glass - cannot be used as it is far too brittle (and illegal!), but even CR39 is not recommended as it can break easily.
We recommend the used of polycarbonate (1.59) or the virtually unbreakable Trivex (1.53). Polycarbonate is the material from which bullet-proof glass is made. It is tough and durable but can crack if the mounts on the rimless frame are overtightened. Trivex is more expensive, but is virtually unbreakable and comes with a manufacturer's two-year warranty against breakage. Tints, polarising filters and Transitions Signature are all available.
Tel.: 01482 841359
453 Anlaby Road
Tel.: 01482 566451
Monday - Friday
09:00 - 13:00
14:00 - 17:00
Alternate Saturdays 09:00 - 12:30
Home visits available
All business hours may be changed at short notice; please ring us to confirm.