It occurs to me that there should be different words for different sorts of lenses, and I'm not talking concave or convex here. I mean words that explain whether you are talking about the lens that is actually embedded in your eyeball or one that is in your spectacle frame.
I know they both do the same job, but at the eye clinic in St Thomas's Hospital, confusion reigned when, pointing to the left half of my spectacles, I told a nurse that a new lens had been fitted about two months ago. She, of course, saw me pointing to my left eye. Frowning, she riffled through my notes. Are you sure? she demanded. Yes, I said, slightly miffed that she could imagine I didn't know when I'd had the, frankly, expensive new varifocal photochromatic lens installed. I might be old, but I'm not doolally, I thought, rather morosely and, in hindsight, rather unfairly.
However, under cross-examination, it gradually became clear that I was talking about my specs and she tutted in obvious exasperation. Which is why, now that I reflect on it, I think it would save confusion and irritation to use the term 'inside-eye-lens' for the one in your eyeball and 'spec-lens' for the other one.
The 'inside-eye-lens' could be abbreviated to 'i-lens' (like i-phone and i-pod) and then the one that you have been born with could be your 'nat-i-lens' (nat = natural, if you haven't worked that out) and one that is a replacement lens made of silicone could be 'sil-i-lens' for a laugh. (And following on from that, for women who have enormous solid silicone boobs jutting out, sili-breasts would seem an appropriate description and also another laugh!)
Whilst on the subject of appropriate and inappropriate nomenclature, for many years I have thought that professional sport is not actually sport, in as much as it is mostly not sporty. Whereas amateur sport, generally is - sporty that is. Therefore, the word for professional sport should be spelt backwards and become TROPS and then everyone would know what to expect. TROPS for games played for money. SPORT for games played for fun, exercise and the taking part. That's quite a relief to get that off my chest because it's been there for years, like undigested cheese.