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Seeing is believing

Can you train your eyes to keep presbyopia at bay? With Gabor patch training, it may be possible

By middle age, the lenses in your eyes harden, becoming less flexible. Your eye muscles increasingly struggle to bend them to focus.

But a new form of training - brain retraining, really - may delay the inevitable age-related loss of close-range visual focus so that you will not need reading glasses.

Various studies say it works, though no treatment of any kind works for everybody.

The increasing difficulty of reading small print that begins in middle age is called presbyopia, from the Greek words for "old man" and "eye". It is exceedingly common, and despite the Greek etymology, women experience it, too. Every five years, the average adult over 30 loses the ability to see another line on the eye reading charts used in eye doctors' offices.

(In Singapore, according to the Singapore National Eye Centre, presbyopia - lao hua in Mandarin - is an inevitable natural ageing process of the eye and usually begins at around the age of 40.)

By 45, presbyopia affects an estimated 83 per cent of adults in North America. Over age 50, it is nearly universal. It is why my middle-aged friends are getting fitted for bifocals or graduated lenses. There are holdouts, of course, who view their cellphones and newspapers at arm's length to make out the words.


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One study published in Psychological Science trained 16 college-age adults and 16 older adults (around age 71) with Gabor patch exercises for 1.5 hours a day for seven days. After training, the older adults' ability to see low-contrast images improved to the level that the college-age ones had before training.

The decline in vision is not only inconvenient, but also dangerous. Bifocals or graduated lenses can help those with presbyopia read, but they also contribute to falls and accidents because they can impair contrast sensitivity (the ability to distinguish between shades of grey) and depth perception.

I'm 45. I don't need to correct my vision for presbyopia yet, but I can tell it's coming.

Or so I thought. Then I undertook a months-long strenuous regimen designed to train my brain to correct for what my eye muscles no longer can manage.

The approach has been reported in the news media, and perhaps you've heard of it. It's based on perceptual learning, the improvement of visual performance as a result of demanding training on specific images. Some experts have expressed scepticism that it can work, but a number of studies provide evidence that it can improve visual acuity, contrast sensitivity and reading speed.

The training involves looking at images called "Gabor patches" in various conditions. Gabor patches optimally stimulate the part of the brain responsible for vision. A great deal of the training involves trying to see Gabor patches placed between closely spaced, distracting flankers. In training, the flanker spacing is varied, the target contrast is turned way down, and the images are flashed on a screen for fractions of a second - to the point that one can barely see the target.

Do this and similar exercises hundreds of times over multiple sessions weekly; continue for months; and, gradually, presbyopia lessens, a number of studies show.

One study also examined functions of the eye itself and found none of these improvements were because of changes in the eye. They're all in the brain.

Various smartphone apps say they offer this kind of vision-improving training; I used one called GlassesOff, the only one I found that was backed by scientific studies. One study published in Psychological Science trained 16 college-age adults and 16 older adults (around age 71) with Gabor patch exercises for 11/2 hours a day for seven days. After training, the older adults' ability to see low-contrast images improved to the level that the college-age ones had before training.

Scientists don't know exactly how perceptual learning relieves presbyopia, but they have some clues based on how our brain processes visual information.

After first taking in "raw data" of an image through the eye, different sets of neurons in the brain process it as separate features like edges and colours. Then the brain must coordinate activity across sets of neurons to assemble these features into recognisable objects such as chairs, faces, letters or words.

Reading at our normal pace, the brain has about 250 milliseconds to do this work until the eyes automatically move on to the next letter or word. Once they do so, we're taking in more information from whatever the eyes focus on next. If we haven't yet processed the prior set of information, we can't understand it.

Visual processing time is challenged and slowed by noisy images, low contrast or closely spaced information (like small fonts). There is a bottleneck in the brain as it attempts to build and then comprehend the image.

Therefore, enhancing and speeding up the ability to process image components - through perceptual learning - improves a wide range of vision functions.

What's surprising is that this is possible in adult brains.

The training with GlassesOff is long and challenging. I found it fun initially, perhaps because it was new. But weeks into it, I began to dread the monotonous labour.

Yet, after a couple of months, the app reports that I can read fonts nearly one-third the size I could when I started and much more rapidly. According to feedback from GlassesOff, my vision after training is equivalent to that of a man about 10 years younger than my age.

As apps go, GlassesOff is not cheap. I paid US$24.99 (S$35) for three months of use - long enough to get me through the initial programme. Upon completion, I was invited to pay another US$59.99 per year for maintenance training.

It's a nice option, but the hard work and price probably mean that the bifocals market will remain strong.

NYTIMES

•The writer is a health economist with several governmental and academic affiliations. He blogs at The Incidental Economist.

A version of this article appeared in the print edition of The Straits Times on March 31, 2017, with the headline 'Seeing is believing'. Print Edition | Subscribe