The space technology coming to save your sight
5th Aug 2013 | 11:00
Finding distant stars and protecting your eyesight is all in a day's work for astronomy
Teflon, memory foam, polarised sunglasses: plenty of everyday comforts were first developed for the space program.
But now the technology used to detect faint light from distant galaxies in giant telescopes could help protect your sight with early detection of the leading cause of sight loss.
Usually the engineers at the UK Astronomy Technology Centre build parts for telescopes like Herschel. Launched in 2009, it's the largest telescope ever sent into space and they built the camera it uses, called SPIRE (Spectral and Photometric Imaging Receiver).
Now they've been working with the researchers at Cardiff University's School of Optometry and Vision Sciences to develop what they're calling a retinal densitometer. You look into it and it detects the amount of light reflected by the retina, then it shines a nice bright light into your eye and detects how that changes as your eye adapts back to dimmer light again.
If it takes longer than it ought to - or longer than it did the last time you got an eye test - then you could be showing the first signs of age-related macular degeneration. And AMD is responsible for more than half of all cases of sight loss.
Your eyesight in a pinhead
The macula takes its name from the Latin for "spot", and that's exactly what it is: a small spot at the back of the eyeball in the light-detecting retina. At just 6mm across, the macula provides the most precise part of human vision.
Within that, there's an area just 1mm across called the fovea. This pinhead-sized patch has the highest concentration of the cone cell photoreceptors that let you recognise colours, see fine details and see what's right in front of you - like the people you're looking at or the screen on your smartphone. Without the macula, all you have is peripheral vision.
The importance of the macula and fovea can even be manipulated to improve display technology. That's the idea behind the Microsoft Research Foveated 3D display project being shown off at SIGGRAPH this month. Rather than wasting power creating parts of the image that will fall into users' peripheral vision, this project cleverly uses head tracking to identify what the fovea will see and render only those areas in full detail.
But the macula is delicate as well as essential. As we get older, it can degenerate. First straight lines start to look wavy and it's more difficult to readjust to normal vision after seeing a bright light. Then it gets harder to see the things you're trying to look at - and in extreme cases, zooming in on a screen won't help, because you have a blank spot in your vision.
There are some unpleasant but rate conditions that cause vision loss for an unlucky few at a younger age but age-related macular degeneration is one of the things many of us have to look forward to. In the UK, nearly 5% of those over the age of 65 already suffer from AMD and among the over 80s it's more than 12%.
Over 10 million people in the US already have some form of AMD. As it progresses, you go from blurred vision to potentially not being able to see faces, newspapers, phone screens or anything else you're trying to look at directly. It has immense consequences for sufferers' lives and independence.
Seeing the problem from space
So far, there are few ways to treat AMD. There are treatments being developed but they're going to depend on spotting AMD before it starts to affect your eyesight - that is, you need to know it's happening before you can see it. And that's where the giant space telescopes come in.
It turns out that the same instruments that help telescopes spot the dimmest of distant stars can also detect faint light inside the human eyeball.
One of the first signs that the macula is starting to not work as well as it should is that it becomes slower at seeing the next thing. Each time the macula responds to something you see, it takes longer afterwards to regenerate the pigments the cone cells in the retina produce in response to light.
Think about the afterimage you see after looking directly at a bright light: that's the pigment, rhodopsin or visual purple, being produced in response to light. It just normally isn't produced in such quantities that that you notice. (The same thing happens when you rub your eyes and see shapes, because pressure also causes the release of rhodopsin.)
By using the technology behind the photometers that telescopes use to look at deep space, opticians will be able to check how fast the macula regenerates that pigment. And when the earlier signs of failure are caught, those new treatments will hopefully be available to halt the degeneration.
In early tests, the UK Astronomy Technology Centre's retinal densitometer is proving highly accurate so the next step is full scale tests and making commercial machines. It could take a few years to arrive, but pretty soon there will be a little bit of space technology in your local opticians.