CONTACT lenses made with millions of gold nanoparticles, no bigger than a speck of dust, could combat a common type of colour blindness.
These ‘gold dust’ particles filter out certain wavelengths of light, so the brain can distinguish between different colours, particularly reds and greens, more easily.
Around one in 12 men and one in 200 women struggle with this condition, called ‘red-green colour vision deficiency’, the most common type of colour blindness.
It’s more frequent in men as it’s passed down on the X chromosome (men have only one X chromosome, from their mother, and if that has the gene for colour blindness, they will be affected; women would need to inherit the gene from both parents to be affected).
The genetic defect means some colour-sensitive cells at the back of the eyes, called cones, are missing or do not work properly. It can also come on later in life, due to conditions that damage the eye, such as diabetes or glaucoma. Some prescription medicines – such as sildenafil (Viagra) – can also affect colour perception.
When light hits the back of the eye, the cones separate out all the colours and pass the information to the brain. If the cones are missing or damaged – for example, in red-green colour blindness, the cones that detect red and green tones are affected, and the rays of different colours can overlap or merge together where they hit the eye – it is difficult to tell them apart.
Red-tinted glasses can help by filtering out some of the light as it enters the eye, reducing the amount of overlap and effectively increasing the contrast between the colours.
The problem is these glasses are bulky and the lenses are dark red, which can make them unsuitable for everyday wear. The new contact lenses, however, are more discreet and have only a slight pink hue. They appear pink (rather than gold) because, in tiny fragments, gold has a small surface area and so, rather than reflecting the whole spectrum of light (which would make it appear gold and shiny), it reflects more red light, which makes the lenses look rose-tinted.
Until now, attempts to make contact lenses have had limited success. This is partly because the dye deployed in spectacles can leach into the eye when used in a contact lens, reducing its effectiveness.
Scientists at Khalifa University, UAE, and Imperial College London, experimented with gold particles as the metal is safe to use in the body.
To make the contact lenses, the team mixed gold particles into hydrogel polymer, the material used for standard contact lenses.
In a lab study, the lenses blocked at least 50 per cent of the light that mixes reds and greens, reported the journal ACS Nano, making it easier to tell the colours apart.
Melanie Hingorani, a consultant ophthalmologist at Moorfield’s Eye Hospital, London, says: ‘The lenses may help some people with colour blindness, in the same way tinted glasses do, but they are not a cure.’
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