OP: Unless and until you can provide proper citations for what you are describing, I strongly disagree with your conclusions.
I can give three partial explanations which might fit:
1. CRT monitors have (or may have, I forget) a tendency to be brighter than many LCDs, which will generally reduce the eye's pupil size more than an LCD, given similar ambient lighting conditions. That results in a greater depth of field which will mitigate some out-of-focus issue that are present in the eye. It isn't a reason to use CRTs, it means you need more light in the room.
2. The ambient light in the room is now provided by watt-equivalent compact fluorescent bulbs rather than incandescent. These emit on specific wavelengths and are rather peaky, even after going through the phosphors on the bulb. They don't provide the same useful illumination when at an equivalent lumen output, as some wavelengths of light are rather lacking. This might result in the eye's pupil getting larger, and i refer you back to #1 at this point.
3. You have an uncorrected vision difficulty, which is leading to eye strain. Tired muscles don't want to work as well. Go see an optometrist.
What you describe otherwise isn't how the body mechanics work. The eye doesn't use peripheral muscles vs central muscles - it's all one system. A lack of focus is generally either presbyopia, myopia, or astigmatism, which are essentially permanent but correctable changes in the eye shape and/or lens hardening, where the eye muscles can't adapt the lens to the shape needed. Slow focus is primarily driven by tired muscles and by age - see lens hardening above, and indirectly by illumination levels, also as described above.
Generally, I would suggest you increase the brightness in the room, dump any fluorescent bulbs in the room and replace with high-CRI LED bulbs (or incandescents, if that rings your bell), make sure you have a decent monitor to use, get up and move around frequently rather than sitting for long periods of time, and get outside frequently so your eyes get to use that long-distance mode that was bred into them over quite some time. Visit your local qualified optometrist/optician, preferably one who has the skills to refract without relying on the autorefractor. Bonus points if they run their own private practice, and/or have a complimentary degree in optical physics, and/or can't take you for the next 6 weeks because all the professional musicians and sports people are filling up their appointment book.
First, thanks for your educated reply, is a shame when you try to help people and someone laughs at you. I really appreciate your effort in this reply, thank you very much.
I cannot provide any citation because eye doctors know a lot about eyes, but they do not know anything about display technology. For them a computer screen is a thing that you connect to the computer, they do not understand the changes in the technology, just go to your optometrist and tell him about this and you will see for yourself. A computer screen is a computer screen and a phone is phone. You need to be less time in your computer, period. That’s what the manual says besides they have not cure anyone with this.
CRT are not brighter than LCD, LED, AMOLED etc… they just flick more, so is not possible for your eyes muscles to adapt to a plain source like happens with LCD because your eyes are constantly focusing a vibrating and imperfect screen monitor, the same they tell you to do every 20 minutes with their exercises, but provided for 8 hours of work by your old CRT while you are productive. That’s why the problem CRT days were headaches, red eyes etc… and the problem today is a permanent lack of focus, the change in the technology screen.
Is not a problem of light, no matter what the doctors said to all of us because a lot of people working in very good illuminated offices have this problem. Have you ever known a film critic? During the last century a lot of them saw 2 or 3 films every day in a dark room, they went to festivals during one week or more and never exhibit this problem, just a small inadaptation when they return to the outside that only last 2 or 3 minutes until the pupil get closed and the brain process the change or the common red eyes, headache that CRT users had. Clue… analog films at 24p flick, as a CRT do. LCDs don’t.
About going to the doctor…. what do you think I have been doing the last 5 years? Plus… what do you think all the people who have this problem do the first? Go to the doctor of course or read the tricks on the internet associated to these problems. 5 years going to doctors. No one can reverse this situation, they just tell you to do some exercises, pauses and do not use the computer screen for long periods of time. But when you return to the screen the adaptation return to your muscles.
Everything you suggest is the normal thing that we all do when go to the doctor, but this never works because you NEED to return to the “no flick” screen every day, so your eyes return to adapt to that situation, no matter you take a break of 20 minutes or go to the outside. My cousin even has a special transparent paper to train focus given by the eye doctor that consists in… focusing exercises… the same that the CRT do with your eyes just looking at it and reading or work in excel.
I do not have an uncorrected vision difficult because my numbers are the same now and when I had 18yrs. My internal pressure is perfect, all the test they do not exhibit any problem at all, just the same deviation that I got in my 20s, sometimes I mark 0.25 more and sometimes 0.25 less, you know some of this tests are not 100% perfect. If I got a problem with my eyes the doctor will have saw it because, as everyone, my eyes have been scanned with every machine in the room the eye doctor had. My cousin also do not have any eye problem, we do not use glasses but have the same problem caused by the use of the same screens for more than 8 hours a day.
Just make the test I said if you want to see by yourself, if you have this muscle adaptation problem in 1 hour reading with a CRT or a 25hz interlaced LCD you will see some improvements when you return use your phone or driving. As I said, obviously if you do not have this problem or your eyes got another problem, you need glasses etc… this is not a solution.