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Lens FAQ

Technical Lenses

Q. What Transitions options do I have for use when driving?

A. The two main options are; XtraActive Transitions which has a swing of 83%-10% LTF but also reacts to visible light changing up to 50% behind the windscreen available in CR39, Trivex, Polycarb, 1.60 and 1.67 resin materials. You could of course also chose Drivewear a polarised Transitions combination lens which at its lightest is 35% LTF darkening and changing colour to a contrast enhancing brown up to 22% behind the windscreen, then down to 12% outside the car. XtraActive of course can be used for night driving whilst Drivewear is restricted to day as it incorporates a polarising filter.

Q. Can I still get an occupational Progressive?

A. Yes, we offer use of Freeform processing we can now offer a number of specialist combination inner surface progressives, including progressive options with: Rd 38 seg bifocal at top, Executive bifocal at top, double Progressive and Combipal an inner surface progressive with a FT35 bifocal place in the reading area!

Q. What is the largest diameter progressive we can get?

A. We can supply up to an effective diameter of 100mm using a inner surface HD design available in both Ultor, Sportor and Freeway HD progressive designs. Choose the lens options you want and then state that you want with XXL process, for a small additional fee even the largest spectacle frame is glazeable dependent on prescription we can also apply RECRE another additional process which blends the lens edge on higher minus RX to improve cosmetic appearance.

Q. Can I get a higher add in a Transitions bifocal?

A. Yes, we supply a FT28 bifocal with adds up to +5.00.

Q. Can Norville glaze 8 base wrap frames which are semi-rimless?

A.Yes, Norville have recently installed the new Mei 641 - 5 axis edging equipment here in Gloucester. The Mei copes with all specialist wrap and rimless frame designs using Trivex, NXT or Polycarbonate lens materials for the best finished results, all rimless and wrap branded frame products can be glazed. We also specialise in the supply of 8 base Sportor HD inner surface SV and Progressive lenses which are supplied with fully compensated prescriptions to give precision optical performance.

Q. Can I get a high index bifocal in Transitions?

A. Yes, we are now able to produce a seamless Round 28 HD inner surface bifocal in Transitions resin; 1.60, 1.67 and 1.74.

Q. Can I get a bifocal in Ultra high index 1.74?

A. Yes available in C 28 from Norville.

Q. What advantages does a hydrophobic or “clean” coating offer?

A. As the outermost layer and hence the one in closest contact with the air, such a coating acts to reduce friction and to keep water and dirt from the surface. The word “hydrophobic” indeed means water-repelling. Hydrophobic coatings are widely used today in all aspects of lens coating.

Q. What does the phrase integral coating process” mean?

The overall coating system on a plastic ophthalmic lens, of course, has three components, each performing its own function:

1) The hard coating, directly on the substrate (often with an intermediate coating to improve adhesion), which is intended to impart the desired surface hardness to the product.

2) The anti-reflection coatings to enhance transmission. These also produce the characteristic reflection colours. They are applied on top of the hard coating.

3) The protective coating, a hydrophobic material that repels water and dirt and blocks air from the lens.

“Integral coating process” is the new term for a process in which these three components are applied in a single production step. Such processes are nothing new in the treatment of ophthalmic lenses; they have been on the market for years and most of them deliver very high quality.

Q.What are my options for high cylinders and prisms?

A. Generally most mid and high resins can be used for this purpose particularly thick blanks are available in 1.60 and 1.67 resin material which allows us to get up to 20.00D for either cyl or prism in single vision. We would suggest that this is reduced to a maximum of 15.00D for bi-focals in these indices. We can also provide up to 8.00 cyl in 1.67 and 1.74 inner surface design HD single vision and Progressive designs.

Q. What are my options for upside down bi-focals?

A. Options include Glass round 38 upside down bi-focal lens code GRUP. Norville can of course custom make most bi-focals turning them around on their axis so the bi-focal can be placed at the top during glazing.

Q.What are my options for prism controls in the horizontal meridian?

A. Options include Glass round 30 prism control 1.5 Index lens code 30PC and code 30PC PE 1.5 index photogrey extra. Or of course a Franklin Split in CR39. Also Presto custom made resin lens options available.

Q. What are my options for prism control in the vertical meridian?

A. Options include slabbing off prism imbalance in the reading portion of a bifocal, available in CR39 D28, CR39 D28 Transitions, Resin 1.60 D28, Norville can custom slab off from 1.5D to 6.0D of imbalance. Other options include Franklin Split where four separate lenses are made incorporating the Prism requirement, cut in half and then distance and reading are bonded together. We are now also able to offer a slab off on inner surface HD progressive lens options in all indices.

Q. What options do I have for -20.00 and over in any index or material?

A. Options include Super-lenti 1.8 index up to -48 lens code WSL8 and in Glass. Also 70mm Lentic 1.7 index up to -33.5 Glass 30mm bowl lens code HL30. Also custom made lentic ooptions available in CR39, Resin 1.67 and Glass.

Q. What options have I for a high add in a bifocal in mid or high index?

A. Options to include 1.6 CU28 Adds to 4.50, CHU8 1.67 C28 Adds to 4.50.

Q. What is the highest index currently available with a sunglass tint ?

A. We can now supply up to 1.74 index with sunglass tints and in Transitions VI.

Q. Can we tint plastic photochromics ?

A. Generally plastic photochromics are adversely affected by the heat of the tint bath, we have however managed to get up to 75% LTF into Sunsensor material. See also Xtra Active 38%-10% and Drivewear lens options 37% - 12%