The leaning in is probably just a bad habit, it was for me. When I concentrate hard I tend to do this, also with a computer. But the glasses are frustrating me. Some of my problems with sight reading seem to be from my eyes. When I look away (to glance at the keys from the sheet and back) my eyes take a long time to focus. First I see nothing but blur. At home I can do better because the sheet is right in front of me and I can see the keyboard without actually moving my eyes or head much. But in a grand piano the sheets are too high for this, so reading at my lesson never works out. I can only read if there's absolutely no need to look away from the sheet, but with some pieces it just doesn't work. I don't know what kind of glasses I should get to correct this...
About the head - It's not just about vision and seeing a greater field of the notes. But of course if you need glasses then it is about vision. Where you have your head also affects how you balance your body so it affects your neck, your back, and by extension, even your arms.
I have never needed reading glasses, instead I am pretty short sighted. During the years I have needed stronger and stronger glasses to see far. But to see close I need to take these glasses off, because they are too strong for reading. To see the keyboard I need no glasses, but to see the notes clearly I do because my left eye can't see much further than 30cm without everything getting blurred. When playing from memory I usually prefer to wear no glasses, but it always takes some time to adjust when I take them off. I think I would need some kind of a compromise between seeing far and seeing close. I guess I have to see an optician...
Outin, I guess that you are not approaching 60 yet. I was happy with your circumstances until I hit about 54. Then my eyes no longer adjusted. I have two pairs of glasses - one for distance, and one for "piano distance".
When I look away (to glance at the keys from the sheet and back) my eyes take a long time to focus. First I see nothing but blur.
The try not looking at the keyboard. May be awkward at first, but will serve you well in the longer term.
Yeah, I try... But can't do it when I have to jump to a new position...I don't have good sense of direction and space, if you know what I mean...spatial recognition. I do practice jumping blind, but it doesn't stick very well.
It takes some time. Practice small jumps first and build up; also practice using the music written down, so you have a visual guide to the sound you are expecting (write out your own if that helps). Also, get used to knowing where you are; if your jumping from somewhere, it helps if you know where you are starting from. Think about a particular finger as the starting point, and a parrticular finger as the end point; if there's a chord at bot tnds, condider them only in relation to the start and end fingers nopt as jumping seperately.
The leaning in is probably just a bad habit, it was for me. When I concentrate hard I tend to do this, also with a computer.