Hi karthi3219, I don't fully understand the science but sharing my personal experience. Would love it if anyone understands it better and can explain what might be going on technically.
Since I got the M1 MacBook Air (2020), I noticed my eyes would start hurting after a short session on my laptop. It was very frustrating - I can describe it as almost a burning sensation in my eyes that got worse over time (anyone else get this?). I also noticed I started getting dry eye symptoms and if I used my laptop late at night, I could wake up with dry eyes in the middle of the night. This also happens to me with certain other devices, like my iPad Pro and iPhone 12.
However, I noticed that when I used some monitors, I did not get the eye symptoms anymore. In particular, I started using BenQ's eye-care monitor and could all of a sudden go hours and hours without any eye strain (I would turn the brightness all the way down from my M1 laptop so no light was coming out of the actual laptop screen). This worked great and gave me a chance to start clocking in a ton of hours again with no eye issues, but it still didn't give me a chance to use my laptop whenever I just wanted to take it to a coffee shop or just sit on the sofa.
So I tried the proposed solution with BetterDisplay. I think my steps were: downloaded, I went to my settings > display settings and made sure that the dummy display was set to 'main display' and my macbook air display was set to 'mirror for dummy 16:9'. I also disabled True Tone and I set color profile to Adobe RGB 1998 per someone's suggestion.
Then in the BetterDisplay settings, I played around with a few resolution options. You can slide a resolution bar to the percent you want (it's located below brightness). I think I set it to 52%. I believe anything from 50-60% will feel relatively normal.
Once I did that, I tested it out and the burning eye feeling I was getting was immediately gone. Started an online course yesterday (spent 5+ hrs on my laptop) without any major discomfort. It's possible my eyes are sensitive to something that is not affecting other folks, but wanted to share my story just in case there's anyone else out there with similar conditions. Thanks!