How to choose good sunglasses

Do you love how cool your sunglasses make you look? If you really want to be comfortable in the glare and protect your eyes -- and your children's eyes -- from future cataracts, there is more to choosing sunglasses than just looking cool. 

Although the human body is remarkable at replacing some damaged cells, the cells in the lens of the eye can’t be replaced. Damage from ultraviolet and (to a lesser degree) infrared rays can build up over a lifetime and lead to cloudy areas of the lens of your eye called cataracts. It's hard to see through cataracts, and they often require surgical removal. Macular degeneration, an eye condition resulting from damage to the retina, also may be accelerated by too much unfiltered sun blasting the retinas.

The main enemy is ultraviolet rays. You need to filter as many of these as you can away from your eyes. Most sunglasses, coated with UV blockers, block the ultraviolet B rays, but the cheaper ones may cheat a little on ultraviolet A. Examine the label. (Some contact lenses also block UVB -- ask your optometrist.) Look out for the CE or BS EN 1836:2005 marks when choosing your sunglasses - this ensures that they provide a safe level of protection from the sun’s damaging UVA and UVB rays.

Apart from UV, brightness is an issue. What people don't realise is that going from inside to outside involves confronting light thousands of times brighter than what has entered the eye the moment before. Brightness is a comfort issue -- it's uncomfortable to go into the sun from the shade and to have undimmed light flowing into your eyes.

So the darker the lens in your sunglasses the better? Clear glass transmits 90% of light. As the glasses get darker, less and less light penetrates. Lightly tinted lenses let in 75% to 80% of light.  Military standards specify that only 15% of light should penetrate. "You can still see very well with 10% to 12% of light only," explains ophthalmologist Dr Lee Duffner. "I recommend glasses in the 20% range."

What colour?

The overall best colour is grey, advises Duffner, which absorbs light across the spectrum equally.

Around 8% of men but far fewer women have colour deficiencies (or colour blindness). Depending on your deficiency, Duffner explains, you need to select a certain tint of sunglasses: "Bronze is not good for men with a green deficiency. Green is not good for anyone with a red or green deficiency. Grey is safest for men. Women should choose grey, green, or brown,” he suggests.

Rose-tinted glasses. Are they a good way to see the world? "Pink isn't a good colour for anyone to get," Duffner says.

Technology innovations

There are amber-coloured lenses called ’blue blockers‘. For a while these were recommended for tennis players. "These absorb not only ultraviolet, but all blues in the colour range," Duffner notes. Some people say this makes for sharper vision, but they did a study and showed that they do not block UV very well and may cause the pupil to dilate and let in more ultraviolet.