Change your sunglasses every TWO years

Sunglasses should be replaced at least every two years, scientists warned today        

Rays from the sun damage lenses over time - meaning they gradually let more UV light through and provide less protection.
Without adequate UV filters, the eye is exposed - and the damage can cause long-term, irreversible harm to vision.

Brazilian researchers have now called for standards that test the quality of sunglasses to be revised, so that safe limits for the filters can be established.
They say a new test would guarantee sunglasses were safe to wear for a period of two years.
Exposure to sunlight varies across the world, but tropical countries have the highest amounts as UV levels are extremely high in summer and remain high in the winter.

Therefore, sunglasses worn in the southern hemisphere may need replacing more often than in those worn in the northern half.
Lenses may also break more easily a result of consistent exposure to sunlight, experts say.
And wearing sunglasses which don't offer proper protection can cause oedema - distorted vision from a swollen eye.