Reading online or on screen is said to be more strenuous to our eyes especially if we are reading long texts and the glare on the screen is very visible. But there are some tips on that you can do to lessen eyestrain when reading using the computer.
The easiest one is to adjust the brightness and contrast of your computer screen; you may temporarily dim the brightness if your screen is too. If you find the letters or words blurry, or your eyes get blurry and teary, you can adjust the text size of the page you are reading. You can also reduce eye strain if you rest your eyes every 10 or 15 minutes by looking outside or anything far from the screen.
If you are a heavy online reader like me, you may want to have a clear copy of what you are reading on the website by copying and pasting them to Word or Notepad. This will convert the entire text into one uniform format that is easier for your eyes. And if you are really reading a very long text, try to transfer them to Word and then break then into 2 or three columns. This will make you read faster without putting so much strain on your eyes.
Read more about reducing eyestrain here.