Optics glossary

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Optics glossary

Optics glossary

Find here all the practical informations to understand optics better

The types of lenses

  • Mineral lenses: Made with minerals, these are lenses presenting the highest resistance to scratches and abrasion. Their weight and fragility to breaking make it a not much proposed lens. It's strictly forbidden on rimless and nylor fittings, and for children.
  • Organic lenses: Made in synthetic resin, they're said unbreakable since they resist much better to impacts than mineral lenses, while being lighter. These are the only lenses displayed on optical-center.fr. They are also recommanded for children.
  • Polycarbonate lenses: Highly resistant to breaking, the polycarbonate lens is 20% thinner and lighter than the organic one. It's 12 times more resistant to impacts. It bloks 100% of UVs. It's perfect for rimless frames.
  • Trivex lenses: It's the more resistant lens on the market. Unbreakable, it never cracks and is less scratches-sensitive. Perfect for children.

The different shades of lenses

There are several shades of lenses: Grey/G15(green)/Brown

  • Grey: neutral coloration with no distortion of colors. Recommanded for the farsighted.
  • G15(Green): perfect for driving, it offers a natural vision and restitute the original colors.
  • Brown: perfect at the sea and at the mountain, it improves the contrasts and increases the details by reducing dazzle. Particularly recommanded for myopic persons.
  • The shade is thus a personal choice, an esthetical choice, depending on your use of sunglasses.

The categories of lenses

There are 5 categories of solar shades: 0/1/2/3/4

  • Category 3 is the most sold, it's displayed in grey, in G15(Green) and in Brown. It's the category of reference, the best protective.
  • Category 4 is the most specific. Suitable for sports persons, reserved for extreme luminosity, it's prohibited for driving. It's recommanded for high protection in high altitude, at the sea,.. The shade is specified on the frame.

The treatments of solar lenses


Polarized lenses enable to erase the bothering and dazzling reflects caused by horizontal surfaces: water bodies, snow, wet asphalt,...They offer a 100% UV protection and improve visual comfort and the contrast at the sea/lake, at the mountain, driving in the sun,... Asset: as far as the visual level is concerned, the colors appear more clearly and the contrasts are reinforced. Your view is less tired and, above all, you can see more clearly and can perceive better the depth and reliefs. Perfect for driving, boat or fishing. This treatment is specified on Ray Ban frames with a "P".


These are lenses offering a category 3 protection for the eye, then the shade intensity decreases progressively till the lens bottom.

The treatment in optical lenses


A polish is applied to the organic material to increase the resistance to micro-scratches caused by cleaning on a regular use.

Anti- reflection Multilayers(ARMC) It enables an almost total transparency. The esthetic advantage is huge since it highlights the look by suppressing the disgracious reflects. It offers a wonderful visual comfort since it lowers the visual fatigue caused by ghost images, twinned images,...


The Antireflect MAX UV treatment is benefitting from a a technology able to reduce uv reflection in back side, guaranteing thus the best protection all over the year.


This new treatment has all the advantages of the AR MAX UV, plus the Blue Filter technology. This latter reduces partly the blue light on the 400-500nm wave lenghths and has other advantages:

  • Reduction of dazzle caused by blue light
  • Improvement of contrast
  • Reduction of visual fatigue

Photochromic It's a lens shading according to the uv quantity under which it is. When the uv exposition disappears, the lenses gradually find their clear shade back. Astigmatism and cylinder, two notations for a same result The different optical professions are working according to two different conventions regarding the cylinder expression, element that compounds the eye astigmatism. The glass-blowers, who are making the lenses, and the opticians, to avoid the mistakes while exchanging with them, are working with a "positive cylinder". That's consequently the notations you'll find on lenses' authenticity cards, on invoices and on cost estimates,... Some ophtalmologists and some orthoptists are also using this convention, you'll may thus find this notation on your prescriptions. Optometrists and contact lenses laboratories, along with some ophtalmologists and orthoptists are using the writing called "negative cylinder". You'll thus find these notations on some prescriptions (glasses and contact lenses) but also on all the authenticity cards, invoices, contact lenses'cost estimates,... You can thus encounter the two notations during your process of equipment changing. Let's explain it. The simplest is to work on an example. Let's take the following prescription: +2,00 (1,25) 120° Your eye presents two powers: +2,00 to 120° and +2,00-1,25=+0,75 to 120-90=30°(because the axes are perpendicular). But we can also go from +0,75 to 30°, which gives +0,75+1,25=+2,00 to 30+90=120°. All this is just a question of point of view, and writing, to define finally the very same thing: +2,00(-1,25)120° is the exact correspondance to +0,75(+1,25)30° But you will order glasses of +0,75(1,25)30° or contact lenses of +2,00(-1,25)120° and in both cases you'll see perfectly. Frames shapes and morphology We can classify shapes of faces with: oval, square or round. Depending on your morphology, there are several options possible:

  1. You can harmonize the shape of the frame to your face:
    • For an oval face: all the shapes can suit.
    • For a squared face: oval shapes are recommanded; big sizes, soft lines.
    • For a round face: play on the angular lines, shapes elongating the face or enlarging it.
  2. You can, on the contrary, invert the shapes to make up for trends. We're talking here about fashion, personnality, and the look we can or got to have for our profession.

Regarding the different shapes of frames, there are rectangular shapes, oval ones, round and butterfly ones. Rules for a good choice of frame:

  • The fame must never touch the cheeks while smiling.
  • It has to follow the eyebrows'shape, never above.
  • The temples must be long enough.
  • In general, prefer the light frames, non-allergic and resistant.

Furthermore, for the solar ones:

  • They must filter the entirety of the UVs.
  • The shape of the frame must be envelopping to prevent from rays'crossing between the frame and the face.
Guide of sizes

The measures of your frame It's important that your frame might be adapted to your face but also that your glasses respect some measures. If you have a pair of glasses that suits you perfectly, you can take the measures of this pair indicated on the frame. Generally, the dimensions are etched on the inside of one of the temples or on the inside of the bridge. The measures of the new frame don't have to be the same as your former one, but the closer to them you'll be, the more similar the two frames will be. Nonetheless, for the round shapes, we recommand you to look at the total dimension of the frame because for that shape, the bridge's width is important.
You'll find the dimensions of our catalogue's frames in every product information sheet, as following:


53mm 17mm 36,8mm 140mm
Width of lens Width of bridge Height of lens Length of temples The case of Ray Ban frames The sizes of Ray Ban sunglasses are not the same for all the models, which can be confusing. This is why we place at your disposal this board with the best-seller models, which will help you in your choice. The numbers are in millimeters and correspond to the width of the lens. The Ray Ban models called RJ are for kids.
Dans le tableau: Titres des colonnes: Women-Teenagers Men-Women Big size Thin face Medium size face Large face Dans la 4eme ligne: Choose the RB 3026 Dans la 5eme ligne: 62 only Have a good purchase on www.optical-center.fr!


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