An eye health charity is recommending people learn the "20-20-20" rule to protect their sight, as lockdown has increased people's time using screens.
Fight for Sight advises looking at something 20 feet away for 20 seconds, every 20 minutes you look at a screen.
Out of 2,000 people, half used screens more since Covid struck and a third (38%) of those believed their eyesight had worsened, a survey suggested.
Opticians remain open for those who need them, the charity said.
The representative survey of 2,000 adults suggested one in five were less likely to get an eye test now than before the pandemic, for fear of catching or spreading the virus.
Respondents reported difficulty reading, as well as headaches and migraines and poorer night vision.
The research charity, which commissioned a survey from polling company YouGov, said it wanted to emphasise the importance of having regular eye tests and to remind people "the majority of opticians are open for appointments throughout lockdown restrictions".
Fight for Sight chief executive Sherine Krause said: "More than half of all cases of sight loss are avoidable through early detection and prevention methods. Regular eye tests can often detect symptomless sight-threatening conditions."
But even simple screen breaks can help to prevent eye strain, the charity suggested.