The first time I washed my hands for 20 seconds, it felt like an eternity. Eighteen months ago, the idea that I would spend more than a few seconds rinsing in the sink seemed excessive. Today, I scrub like a surgeon and think nothing of it.

Lately, I’ve been following a new 20-second rule. This one feels less like hard work because it mainly involves gazing out of the window. After more than a year spent mostly indoors staring at screens, I am trying to soothe my tired eyes with the 20-20-20 rule: every 20 minutes, look at an object at least 20 feet away for 20 seconds.

This advice will not be news to those who have been paying attention to optometrists’ guidance for people who regularly work with screens. Alas, it was to me after my local optician found my peepers had taken a sudden turn for the worse.

I have been quite shortsighted since I was little but, for the past decade or so, my prescription has been pretty stable. My optician said I was one of several recent customers to show a deterioration following Covid-19 lockdowns.

He prescribed reading glasses — or perhaps more accurately, screen glasses — to wear over my contact lenses. The idea is to relax my eyes when I am doing short-range work, such as typing this story and basically everything else I do at the moment.

It is cold comfort to know I am not alone in suffering this digital eye strain. Ofcom’s “Online Nation” report, published earlier this month, found that in 2020 UK adults typically spent more than three and a half hours online every day, which is up by more than one-fifth in three years. (Brits still lag behind the US, where daily time spent online peaked in April last year at almost five hours.)

A recent survey by the UK’s College of Optometrists also shows growing concern among the British public about screen time. Almost a third believed their eyesight had deteriorated during the pandemic, up from less than a quarter last June. Almost half of those blamed their screens.

Despite the survey, I was relieved to find that Dr Paramdeep Bilkhu, clinical adviser at the College of Optometrists, is relatively sanguine about our collective screen addiction. “The good news is it won’t cause any damage” over the long term, he reassured me. “There is no evidence to show that using a screen will actually damage your eyes.”

The problem is instead a temporary one: fatigue. And it can be alleviated by tactics such as the 20-20-20 rule, staying hydrated, blinking regularly and positioning your monitor at least an arm’s length away. If I stick to this regime, I hope my sudden jump in short sightedness may settle back to where it was pre-Covid.

While the pandemic has triggered what Bilkhu described as a “slight increase” in short-sightedness, the number of people needing glasses or contacts has actually been growing for many years. The underlying problem, he believes, is less about screens and more about being indoors.

If the pandemic has accentuated the trend, it is as much down to being shut inside as what we are doing there. “Spending time outdoors has been shown to slow down the onset of short sightedness,” Bilkhu said. Natural light and looking at objects from a range of distances are key to healthy eyes.

As for smartphones, these are still a relatively new phenomenon and Bilkhu thinks more studies are needed to understand any correlation between long-term vision problems and close-up work. So while we may fret about the contents of our apps, we worry too much about the screens themselves. We could just as easily blame houses, which have been a fixture of human life for at least 10,000 years.

Contrary to what our parents may have told us when we were kids, televisions are no longer considered problematic for eyes, thanks to LCD screens, and the distance between sofa and set. Reading, however, can cause the same near-vision eye strain as staring at YouTube all day, even in good old-fashioned print.

In short, when you stop reading this article, please look outside — if only for 20 seconds.

Tim Bradshaw is the FT’s global technology correspondent

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