If you are reading or watching anything on your phone’s screen (even if school related) then yes, that should be transferred to a bigger screen. No matter what glasses you wear, phone’s screen should not be used for reading longer text or watching any videos. In an ideal world the phone is used for audio materials and you look at it to start the next listening (that doesn’t need following on the screen), and you start or receive calls on your phone, or drop short important texts (like you’ll be late or you are on the train we’ll be at the meeting point within 30 minutes, etc). But for chatting back and forth it is recommended to move to the PC version of the app to do it on a bigger screen from a bigger distance. Staring at the screen with bent neck at less than arm’s length is THE EYE KILLER. Sorry.
What is your distance to blur (cm to first blur without corrections)? And what is the max comfortable distance from the books you can achieve with glasses on? With screens we set it between 50 and 90 cms. With books I would set it a bit shorter. For screens the rule of thumb is to drop 1.5D from the full opto correction. For books that are closer than the screens, I would say it would be closer to dropping 2D from the full opto correction.
The easiest way would be to go to a shop where they sell reading glasses. Put +1.5D in front of your glasses and test if you can read text at what would be your “book distance”. Then try +2D and check if that is still OK.
Basically what you are trying to achieve is the following:
Full opto corrections give you full clarity to infinity or at least 8 metres.
When you are introducing differentials, you are trying to find the lowest glasses that still give you clarity at your typical close up distance. Which is between 50 and 90 cms with a screen and most probably between 45 and 50 cms only with books that you are holding or have in front of you on the desk.
I started from -2.25 and -2.00.
If you enter this distance to the calculator, you’ll see that gives you max 47 cms in one eye and max 53 cms in the other eye from the text without glasses. So my first differentials were zero, and I started from an average 50cms from the screen that I gradually increased to 90 cms. When my distance from the screen was 50cms, I wore -2.00D corrections for distance. Which is exactly the +2D difference I mentioned above. (When my distance increased to 90 cms my corrections for distance changed to -1.00D as per the calculator)
So assuming your distance corrections are now at -3.50(?), I would reduce them by about 2D to get to a pair of glasses that you can use for textbooks when held in your hand comfortably or when on the desk in front of you. But you have to know that because this is calibrated to book-distance, you will be only at about 50cms from the screen in them. But that is OK, as long as you spend less time in front of the screen than in front of your books.
So you will have a full opto prescription that gives you clarity any time anywhere (is this -3.50?).
A slightly reduced pair of glasses as your normalised that give you clarity most of the time but you may have to work a bit to achieve that clarity. (is that your -3.25?)
A pair of differentials used at your typical reading distance (-3.50 + 2 = -1.50).
Please adjust the diopters if I got the starting prescription incorrect.
You are just slightly above a sweet spot of being able to read books without glasses at a comfortable distance. As your vision improves, soon you can forget the glasses when reading books, you can use the same differentials for screen time gradually increasing the distance from the initial 50cm to 90cms, and parallel to that you should see improvement with your distance vision - everything getting super clear all the time, disturbingly clear, indicating it is time to drop.
Hope it makes sense.
Unfortunately, as much as I’d like to give better advice, at the end of the day it will be your eyes and brain deciding what is good, what is tolerable, etc. As you can see in others’ journals, sometimes it takes trial and error to get to the right correction… So all above is based on general observations and averages.
Best of luck with the opto. Be prepared that you may get a push back on a pair of -1.50 to be used for reading textbook…