I have just collected my second pair. I had a pair a while ago but got my money back on them because I just couldn't get used to them. My eyesight has considerably worsened (in part due to failed surgery) and my optician has suggested that I need to try them again, and I need to get used to them. I've been wearing them all day and it is awful. Nothing is quite in focus - it is as it it is almost right, but not quite. Is this usual? Will I get used to them?