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Contact Lenses to Help You See in the Dark
Byline: SIMONE CAVE
SCIENTISTS have now designed a contact lens to improve night vision.
The lenses could be on the market in Britain within two years and it is thought they will
improve people's ability to distinguish contrast five times over.
The lenses' main use will probably be for night driving, says Josef Bille, a professor
in applied physics, who developed the lenses at the University of Heidelberg in Germany.
'We anticipate that when wearing the lenses, you'll be able to see a car 100 metres away
when normally you wouldn't see it until it was just 20 metres away.' They will be useful
for people with good eyesight as well as those who normally wear spectacles or contact lenses.
The lenses work by correcting refractive error which occurs around the edge of the pupil
in the human eye. Professor Bille says: 'In dim light the iris opens and the pupil becomes
larger. When the pupil opens to 4mm or more, the light entering through the edges of the
pupil is refracted so that it strays on to the retina.
This results in diminished contrast and we see less detail.' The new lenses have specially
curved edges and hundreds of surfaces which can correct refracted rays. As well as helping
the wearer to distinguish contrast, the lenses will also maintain our colour vision in dim
light.
We see colour with our cones - light-sensitive cells in our retina. As light diminishes we
begin to see with our rods which are also light-sensitive cells but which see in black
and white.
Because the lenses focus light on the retina more efficiently, our colour receptors will
be able to keep working for
longer as the light fades,' explains Professor Bille.
'But even when our rod system takes over and we see in black and white, with these lenses
we will be able to see more detail and definition.' The design of the lenses is the result of
more than 20 years' research at Heidelberg University, developing instruments which measure
the optical properties of human eyes, and also using devices called active mirrors which
simulate the function of contact lenses.
Professor Bille and his team have demonstrated these active mirrors in laboratory tests and
found that they can improve vision in dim light by 15 times.
'This means even if outside light is 15 times less then normal, you would still see as though
although we estimate we'll still get an improvement factor of five times.' Tests on patients will
soon begin in England, America and Australia. 'It is feasible that these lenses will be
widely available in two years,' says Professor Bille. He adds that the lenses will be produced
as daily disposables at around 70p a pair.
Industry sources say the Bausch and Lomb lens company is already doing tests on the new
technology.
As well as being used by normal-sighted people for night driving, Professor Bille predicts
the lenses could be useful for soldiers doing night minus eight. His night vision is poor
says. 'They'd make a huge difference to my life.
'At the moment I can't see the stars and I have to hold my wife's hand when we leave
the cinema. And cycling in the dark a nightmare - I've fallen into lots of ditches.' ANOTHER
group which could benefit is the over-50s.
'Contrast sensitivity is reduced after we reach 50,' says Professor Bille.
'This is because the pathways and receptors from the retina to the brain deteriorate.
'The over-50s will get even more benefits from night vision lenses, because they are
more prone to driving accidents at night than younger people. If the lenses improved contrast
vision by a factor of just two or three it would help.' Angela Rossi, a lecturer in clinical
optometry at the Institute of Optometry in London, is less optimistic. 'In theory these
lenses could definitely work, but in practice they probably won't make a lot of difference,'
'Soft lenses are thin and floppy and they fold and give a lot on the eye.
This would make the precision of these lenses less effective.'