My national health care as well as personal insurance cover most of the cost of regular checkups and new glasses. I leave the old ones laying around the house so that I rarely have to go looking for my glasses.

 

do you find when they do thst its all but impossible to detect the difference, yet they always seem to select the 1 /2 dioprer difference lenses !

No. Again, if I can't tell the difference, why would I get new lenses regardless of what they select? I've experienced the opposite on several occasions in which they tell me that there isn't much change and would only recommend new lenses if I really think I notice an improvement. For a long time, I had significant changes from exam to exam as my vision degraded. At the time that I had Lasik, my vision was 20/800 in one eye and 20/2000 in the other, but correctable to 20/15 in each eye. I don't recall the refractive error, but it was something like -6 in one eye and -9 in the other. Fortunately, there was virtually no astigmatism. After surgery, my vision was very stable for quite some time and I didn't upgrade prescriptions for many years. Then I got fast-growing cataracts about 14 years ago in both eyes and, after having the artificial lenses implanted, have only upgraded the prescription once, but I might be due again.

What I find frustrating is that occasionally during the middle of the test I they will use a setting that seems much clearer than anything before or after it and there's no way for them to really go back and figure out which one without doing the entire test over because they are just walking down a decision tree and they don't record the steps that got them to the final point. So now, if I see a setting that is particularly good, I stop them and ask them to record the current settings so that we can go back to it. Another thing I don't like about those subjective tests is that I will commonly see pairs in which there is a definite difference, but I can't really say which one is better or worse, they are just quite different.