How to Choose
A good lens is a lens that adapts to your vision and that suits the use you make of it. Whether you’re in front of a computer all day, outside or in a brightly lit place, a number of parameters should be taken into consideration so that you choose the right lenses for your activities. At Greiche & Scaff, we’re there to advise you.
There are four main criteria you should consider before choosing your lenses :
- The materials (glass, plastic)
- The type of lenses (unifocal, bifocal or progressive)
- The treatments (anti-reflective, polarized, etc.)
- The tints (grey, yellow, etc.)
- Plastic :Lenses made of plastic (or, more precisely, a resin known as CR-39) are much more shock-resistant, more lightweight and tend to fog up less. They also absorb ultra-violet rays. But the surface of this type of lens scratches easily; adding an anti-scratch treatment is advised.
- Polycarbonate :Lenses made from this plastic are shock-resistant and, though thinner than glass or plastic, are the most resistant lenses of all. Because it’s a plastic that’s quite soft, it scratches easily; as with plastic lenses, adding an anti-scratch treatment is advised. These lens are recommended for athletes, children or in cases where ocular protection is critical.
- Glass : This was the first material used to manufacture lenses. Very fragile, prone to fracture and virtually unresisting to impact, the glass is subject to a tempering process to make it more resistant, which also makes it heavier. Today, glass is used in lenses much less frequently.
- Single vision or unifocal lenses : This lens provides correction only for a given distance. This means that the optical power is the same at every point on the lens’s surface.
- Double vision or bifocal lenses : This type of lens is used when a person needs two different corrections. The upper surface of the lens corrects distance vision, and the lower, near vision.
- Progressive vision lenses :Progressive optical lenses fulfil the same function as double optical lenses, but use a new type of glass where the boundary line between lens powers is invisible. The result? A much more aesthetically pleasing pair of glasses, and a more functional one, too, because it allows for more seamless vision, and vision in intermediate zones.
- Anti-scratch treatment : This makes the lens harder and more resistant and, most importantly, scratch-proof. This is achieved through treatment by tempering, by centrifugal application, directly during the moulding process or by vacuum evaporation.
- Anti-reflective treatment : Reflections on a lens can create so-called ghost images made up of glare and concentric circles. These obstruct vision and can be annoying. Anti-reflective treatments considerably reduce these effects and increase the amount of light passing through the lens.
- Photochromic lenses : (also known as the Transitions brand): These are lenses that grow darker or lighter depending on their exposure to UV rays. These lenses respond to ultra-violet rays, and usually come in grey and brown.
- Polarized lenses : If you’re out in the sun and bothered by glare from reflective surfaces like water, roads and snow, these lenses are for you. With these lenses, any reflective light is partially polarized with a filter.
- Ultra-violet treatment : True to their name, these lenses are capable of absorbing and blocking ultra-violet rays, which are dangerous for the eyes.
These types of lenses are also known as absorbing lenses. Wearers can choose the intensity of the tint for more light transmission, or less.
- Grey tint : This is the most popular tint for sun protection because it doesn’t change the natural viewing of colours.
- Yellow tint : Yellow absorbs blue light and can be useful for reducing glare from the sky, for example. It also increases contrasts at nightfall.
- Green tint : Green absorbs infrared and ultra-violet rays well and is widely used in the military.
- Brown tint : Brown is often used in sunglasses. Like yellow, it absorbs blue light.
- Pink tint : Pink is used in situations where indoor lighting is uncomfortable, such as fluorescent lighting and brightly lit work environments. It is often used by people who have had a cataract operation.