Thank you very much to everyone who has contributed. Interesting, informative & reassuring. I'm only three weeks into my new 'diabetic lifestyle', so still much to learn & assimilate. For example, I hadn't appreciated the difference between retina issues & refraction. By way of clarification, the price I quoted in the initial post, covers three pairs of glasses: distance clear/distance tinted (in the vague hope that the sun might shine when I'm driving!) & reading.
            From an extremely soggy UK, thanks once again,
            Very Best,
                         Nigel.