It is World Sight Day today, and most of us grew up being told that carrots help you see in the dark. They do not, and the story of where that idea came from goes back to the Second World War.
Where the carrot story came from
When the RAF began shooting down German planes at night, the government told newspapers that pilots such as John Cunningham, nicknamed “Cat’s Eyes”, owed their success to eating plenty of carrots. The real reason was a new, top-secret radar fitted to their planes, and the carrot story helped to keep it quiet, according to Smithsonian Magazine. At home, the government put up posters saying that carrots would keep you healthy and help you see in the blackout.
What carrots really do for your eyes
Your body turns the beta-carotene in carrots into vitamin A, and a real shortage of vitamin A can cause night blindness, which is the grain of truth in the story, as the American Academy of Ophthalmology explains. If you already eat a normal diet, though, eating more carrots will not help you see any better in the dark.
Our founder, Alex Pratt OBE, wrote the Better Light Guide with an optometrist, and their advice for your eyes is oily fish and green vegetables. Spinach and kale, for example, contain lutein and zeaxanthin, nutrients that support your eyes’ own protective mechanisms.
How much of your brain works on what you see
When you read, your eyes scan the words and pass them to your brain so quickly that you understand them almost as fast as you see them. It happens without any conscious effort on your part, and it is a much bigger job than it sounds. About 30% of the cortex, the outer layer of your brain, works on what you see, compared with 8% for touch and just 3% for hearing, according to Seyens.
What happens to your blinking at a screen
Blinking is almost like breathing, in that you do it all day without paying attention to it. You probably blink about 14 to 17 times a minute, which is roughly 13,000 to 16,000 times a day while you are awake, according to the Cleveland Clinic. Each blink spreads tears across your eyes to keep them moist, clears away dust and debris, and brings them oxygen and nutrients.
At a screen, the Cleveland Clinic says that drops to about five times a minute, which can lead to eye strain, tiredness and dry eyes. The Association of Optometrists recommends the 20/20/20 rule: every 20 minutes, look away from your screen at something at least 20 feet away, for 20 seconds.
How your eyes change, decade by decade
In your 20s, your eyes have strong natural defences, although short-sightedness is becoming a major problem in young people, and it is important to start good habits such as regular eye tests and breaks from screens. In your 40s, small print becomes harder to read, particularly in low light, and long-sighted people tend to notice it first. That is mainly down to presbyopia, when the lens inside your eye loses its flexibility and it becomes harder to focus on things close to you. If you are short-sighted, you can sometimes still read close up without your glasses, at this age and beyond.
By your 60s, it becomes more obvious that your eyes need more light, and better light. Your pupils are smaller and react less to light, because the muscles of your iris have become harder and less elastic. The lens of your eye is less clear, too, and absorbs significantly more light, so less of it reaches your retina. Changes throughout your eye, from the cornea and lens at the front to the retina at the back, also make it more difficult to see contrast and to tell colours apart, and glare can become more of a problem.
Your optometrist is the best person to ask about your own eyes, and in a routine test they check far more than whether you need new glasses, as we explained in “Could an eye test spot a brain tumour or the risk of a stroke?”
Why the quality of light matters as well as the amount
It is a common myth that all light is the same and makes no difference. Your eyes evolved under one particular mix of light, the natural spectrum of daylight, and when the light in your home matches it, colours look true. You can probably tell apart about 1 million shades of colour, because your eyes have three types of colour receptor, called cones, for red, green and blue, and each type lets you distinguish about 100 shades, as Hyperallergic explains. In the guide’s words, though, “If it’s not in the light, it’s not available to be seen.”
That is why the advice is to choose lights that mimic the natural light spectrum as closely as possible, to improve contrast and let you see colours as nature intended. It matters all the more once contrast and colour have become harder to see.
What it means for your reading
Your retinas are unique to you, each with its own pattern of rods and cones and its own response to light. As Alex and the optometrist write in the guide, “You and I need different light.” So whenever you read or concentrate on anything indoors, their advice is to use a light you can control. You should be able to vary the brightness and adjust the beam to suit what you are doing, with a spectrum as close to daylight as possible.
The HD Original puts up to 12x more light on your page than a 60W bulb, and its Daylight Wavelength Technology™ gives you the full spectrum of daylight, so small print is as clear in the evening as it is by a window. You can try one at home for up to 90 days.
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You can read all nine tips in the free Better Light Guide.