Okay...this is my best answer, and how to explain this. By analogy because I understand this as regard my cochlear implant.
With getting the cochlear implant some years ago, the hospital were not sure if I could benefit because I was profoundly deaf and have been so all my life, and so the thought was, that the pathways that were set aside by the body for aural stuff would have atrophied through lack of use. But more recently, the thought is that those pathways that were originally thought to have atrophied through lack of use, were actually taken over by the brain for another use. But they were not sure, and the cochlear implant could have been a failure.
However in my case, those neural pathways appear to have been taken over by visual and creative stuff by the brain. I didn't realise or understand that until after I'd had the cochlear op. Neither did the hospital.
It also means that I am now unable to do my art, painting, creative writing since the cochlear op and with wearing the speech processor. I was so upset, i thought I had lost all my creativity which was a massive tota; part of my life. It nearly sent me over the edge. A few years later the hospital said keep persevering because the brain will sort it.
Then one morning i got up early and said *** the processor, I am going to try and paint and create without having the processor and incoming noise on. Bliss, absolute bliss. I could now write and paint again. So, all my creativity can only be done with no incoming noise, and my brain seems to be at peace when I do this. Since then, anything creative I want to do, then I take the processor off. The problem with the speech processor being on is that my brain is constantly searching for figuring out what a noise is, and it is probably never going to get there, because it doesn't have a baseline that a baby has learnt in its early years...and I am nearly 70 years old now.
Maybe you cannot teach an old dog new tricks?
So, what appears to be happening with me, is that the neural pathways for aural stuff was combined with other creative neural pathways (?Is it sight because i am a very visual person?), and was the reason for my creativity. But now i have the cochlear implant, the aural side of things wants those pathways back. And becasue so much is needed for me to try and understand sound, I am unable to do the creative bit. Maybe the brain is grabbing more neural pathways to process incoming sound because it is a mammoth task for it. Maybe the neural pathways can be dual purpose, which i am coming to believe might be possible.
I haven't put my speech processor on yet this morning, (oops, its now 1pm in the afternoon!) because i needed to do writing, research about this laser treatment etc, and I cannot do that at all and take it in along with incoming sound as well.
This is all to do with plasticity of the brain, neural plasticity, neuroelasticity. These are different search terms you can use to google this. It is about the ability of the brain to change continuously over a person's life. It is how we learn new skills.
I have read so many books on this subject to try and understand my brain because of this. Obviously the subject was of greater interest to me.
This applies to sight as well.
So, you getting your eyes checked on the vision thingy and glasses prescribed on the basis of that, is not quite cut and dried as that with seeing just as well once you put the glasses on. I am aware of the same feeling. But we need to adjust, or rather our brains do. That is of course assuming the technician or optician got the glasses prescription right in the first place, and of course go back and say what your problem is with the glasses.
I have no idea what trifocals are.
I used to have long distance, and also reading glasses years ago. Then i went on to bifocals you say you have got. Then i went on to varifocals. (I am not sure if i have spelt that quite right). But it means i wear one pair of glasses, but there isn't that distinction line between the bottom half of the bi vocals and the top half. It can be disconcerting as your brain gets used to it. (I have to pay extra to get the varifocals, its not covered with the voucher here either).
I have all my old glasses too, and the frames to me are bigger and enable you to see better, otherwise with the smaller frames I am moving my head and searching for what i want to see!
I will be getting them out as well, because i am having problems with these varifocals today after the procedure yesterday, and i don't know yet if brain needs to adapt, or if they are not as suitable since the laser treatment.
So research plasticity etc. I will be researching later as well as regards sight and laser treatment.
If you need something on this and you can't find it, let me know and I will look for something that might explain it as regards glasses and sight.
The brain is very adaptable and nothing is black and white on this.
Hope this helps.
>^..^<
nice but with the traffic starting i am thinking of just lazing around the garden till breakfast is done. Probably post breakfast walk to nearby convenience store to pick up a few essentials. 
game on mine.... it would get longer as it ate eggs
game on mine.... it would get longer as it ate eggs 