WHY EYE HEALTH IS IMPORTANT We expect a lot from our eyes.  During a normal day, the eyes will use about the same amount of energy as the legs would use walking thirty kilometers.  The additional burden of glare causes the eyes to strain in order to see well.  Wearing sunglasses will reduce or eliminate this strain, cut the impact of harsh glare and eliminate the need to squint. THE OZONE LAYER: THE DISAPPEARING SHIELD Sunglasses also offer protection against something very serious – ultraviolet radiation (UV).  Sunglass lenses block 99% of harmful UV rays.  Visual acuity, contrast, and overall sensitivity can be reduced by up to 50%, due to the sun’s sustained bleaching of the photochemical rhodopsin in the rods of the retina.  The right sunglasses during the day can block the appropriate light and at night can protect retinal sensitivity. As people spend more time outdoors, concern regarding the potentially harmful effects of sunlight increases.  While many people appreciate the importance of using sunscreens to protect their skin, not everyone is quite so careful about choosing sunglasses.  The best protection for the eyes against ultraviolet radiation (UV) is optical-quality sunglass. WHAT IS SUNLIGHT? You might think it just keeps you warm and lets you see, but there’s a lot more to it than that.  Radiation from the sun is made of many different types of light, some of which can interfere with how you see. Blue light Blue light can cause glare when it interacts with dust and moisture in the air – especially haze, fog, rain, and snow. Infrared These rays are what make you feel warm in the sun – they’re the same as what comes out of electric heaters (which is why they’re red).  Because our eyes can’t cool themselves easily, infrared rays can dry up our eyes’ natural moisture. Visible light Visible light is what you can see – made up of red, orange, yellow, green, blue and violet.  Your eye is most sensitive to yellows and greens, and least sensitive to reds and blues. Polarized light Light from the sun starts off unpolarised – but as it interacts with the Earth’s atmosphere, a strange phenomenon called ‘polarization’ occurs.  This is what makes the sky blue. Ultraviolet light (UV) UV radiation is the most harmful light from the sun.  It’s strongest at high altitudes, low altitudes (near the equator), and in the middle of the day.  Scientists divide UV up into UVA, UVB, and UVC – UVC being the most harmful.  And there is also HEV radiation – which can lead to blindness in older people.