Introduction
Protecting the eyes against ultraviolet radiation is essential. It increases visual comfort and can prevent numerous eye pathologies, rapid ageing of the crystalline, cataract, snow blindness, etc… There are several ways to combat harmful radiation from the sun: tinted lenses, clip-on sunglasses, photochromic lenses, sun contact lenses, appropriate UV treatments, but only polarized sunglasses offeradditional protection. In addition to 100% absorption of harmful UV rays, they protect the eyes against glare. This is a fundamental difference: all polarized lenses can be used as sunglasses, but not all sunglasses perform the function of polarized lenses
Filter against reflected glareLight is reflected at all types of surfaces The clearer and more reflective the surface, the more reflected glare becomes harmful for vision. Glare produced by reflections on snow, water, sand,ice, vehicles and road surfaces causes a drop in visual acuity. Perception of shapes and colours is altered and the lessening of contrasts leads to asthenopia (eyestrain), affecting visual comfort.A simple reduction in the intensity of visible light,offered by all so-called sunglasses and those with variable shading, is not sufficient.
There is only one way to block glare: by the use of an antireflected glare filter . To date, anti-reflected glare could be obtained with materials which did not provide optimal optical quality and the use of filters was compatible only with simple optical surfaces:flat sunglasses. Today it is possible to combine them with all types of prescription lenses,from single vision through to the most sophisticated progressive lenses (e.g. the latest generation of progressive lenses from Essilor, polarized Varilux®*). An anti-glare filter is nothing other than a polarizing film (2 - polarizers***).
How a polarizing lens works.When natural light that is diffused in space, initially nonpolarized, isreflected at a flat surface, a modification to the vibrations it comprises takes place. The plane of vibration of the light can be broken down into horizontal and vertical vibrations (1 - polarized waves **).Reflection of light at a surface is different for each of these vibrating components.It is then said that the light has undergone polarization.It is the light which is diffused in the horizontal axis which is responsible for painful,unwanted glare.This intense white light can only be completely absorbed by polarizing lenses. Thanks to the filter, they have a unique ability to separate useful light after transition through the lens (vertical vibration) from that which negatively affects vision (horizontal vibration).e=1>
