Sunglasses are worn mainly to eliminate the discomfort and disabling effects of bright lights and to protect against ultraviolet and infrared radiation.
Neil Murray (B.Optom (Hons), F.A.A.O.) SMA member has kindly provided the following information in conjunction with the Optometrists Association of Australia.

Sunglasses are essential during periods of prolonged exposure to sunlight. Besides visible light sunlight contains two powerful invisible forms of radiation – ultraviolet and infrared. Continued exposure to these rays can cause serious eye damage. Optometrists recommend that people who spend most of their time outside or who work near snow, water or sand should wear sunglasses which filter out both ultraviolet and infrared rays. Because the effects of exposure to UV accumulate over a person’s lifetime, it is important for children as well as adults to wear eye protection.

Tinted – Made of glass or plastic, tinted lenses come in a variety of shades. To be effective they should screen out 75% – 90% of available visible sunlight. Grey tints do not affect the colors you see and are the best where color accuracy is important. Glass lenses with green tints are usually the best infrared filter. Light tinted “fashion” lenses do not screen out sufficient light to be properly called sunglasses.

Polarising – Usually plastic polarising lenses are effective in combating the glare caused by light reflected from the road or from water. They screen out ultraviolet rays.

Photo chromic – Commonly called sun – sensitive or light sensitive lenses, photo chromic lenses darken or change color as the sun gets brighter. To ensure sufficient darkening in sunlight 75% - 90% of available sunlight should be screened out.

Reflecting – A thin metallic coat is combined with tinted lenses to produce a mirror appearance.They are designed for wear under intense glare such as sunlight reflected from water or snow. Some absorb both ultraviolet and infrared rays.

Make sure that the lenses conform to the Australian Standard which specifies that the glasses are manufactured from quality ophthalmic materials. for sports purposes lenses should be made of polycarbonate or CR39 material, not glass. screen out ultraviolet light. are ground and polished to be free of distortion and imperfection. are perfectly matched in color and absorptive power. match your prescriptions if you usually wear spectacles. are large enough to provide ample protection. are made from material best suited to your needs. Sun glasses should be close fitting to prevent radiation getting around the edges of frames. Wrap – around models are excellent Your optometrist will be able to advise you of the best sunglasses to suit you and your needs.

IF YOU FEEL THAT YOU NEED TO WEAR SUNGLASSES CONTINUALLY FOR COMFORT YOU SHOULD CONSULT YOUR OPTOMETRIST – YOU MAY HAVE A PROBLEM WITH YOUR EYES OR VISION