https://chrome.google.com/webstore/detail/eyecare-protect-your-visi/eeeningnfkaonkonalpcicgemnnijjhn

https://chrome.google.com/webstore/detail/eye-rest/mndlfpadbgecofachcbpndicbefbonfm

There's an Opera extension called Super Auto Refresh that would appear to let you refresh pages and tabs. https://addons.opera.com/en/extensions/details/super-auto-refresh/?display=en
And here's a Chrome extension (you can use in Opera), where you can set the number of seconds you want to pass before a page or tab refreshes.

https://chrome.google.com/webstore/detail/easy-auto-refresh/aabcgdmkeabbnleenpncegpcngjpnjkc

Remember, to download a Chrome extension easily, you need the Opera extension, called Download Chrome Extension, https://addons.opera.com/en/extensions/details/download-chrome-extension-9/?display=en

or Extension Source Viewer, https://addons.opera.com/en/extensions/details/extension-source-viewer/

Hope some of this helps you.