What do we call glasses with thick lenses that people use when they are very near-sighted? Here is a picture of what I mean:
I would just call them "thick glasses", but I vaguely remember something with the word "bottle". I found "Coke-bottle glasses". Here is a link to an entry from Urban Dictionary, and here's an excerpt from the Coca-Cola Company:
In different regions of the world, eyeglasses with very thick lenses in the frame are called "Coke bottle" glasses -- named after the thick bottoms of Coca-Cola contour bottles.
Coke-bottle glasses and beer bottle glasses are both American-English expressions. However, if the OP is writing a story set in the British Isles, I would suggest thick glasses, and for a more informal expression, jam-jar glasses.
People with high prescriptions and complicated vision problems – especially those who have worn their glasses for a very long time – may well remember “jam-jar” or “coke-bottle” glasses as an object of embarrassment from their schooldays. Practical, yes – but fashionable?
Check Google Books for more examples of usage.
But being short-sighted has its more serious problems. Whoever heard of an airline pilot wearing jam jar glasses?
As I jumped out of the car I was met by a man wearing jam jar spectacles, a lab coat and carrying a clipboard. “So, which one is mine?” I asked the egghead. “ (source)
She should really be asking forgiveness for those hideous jam jar glasses she wears
@Michael Harvey in the comments, notes that pebble glasses used to be common in British English. Collins Dictionary says
spectacles with round thick lenses with a high degree of magnification
Pebble, also known as Brazilian pebble and rock crystal are transparent colourless quartz crystals and were once used to make lenses for glasses.
In the UK I have heard the version 'milk-bottle lenses', similar to the previous two answers but referring to the reusable milk bottles that were previously commonly delivered in the morning. Here's a recent headline from the Daily Mail using that version.
In Finland, such eye-wear is colloquially known as 'bottle-bottom-glasses'
In South India, they're 'soda bottle' glasses. Soda refers to soda water, not pop
There are many great answers here already which are variations on the same theme.
I just feel I should say that as a native British English speaker living in England all my life of 43 years the most common and frequently used term I have heard is bottle-bottom glasses.
I have never heard "Coke bottle glasses", which sounds like an Americanised version of the same expression to me. But obviously the imagery conjured by all of the answers to this question is similar, and in creative writing they would surely all be instantly recognised and understood.
Not to be dogmatic, but if you are looking for the most familiar expression, my personal opinion is to go with bottle-bottom glasses or glasses with bottle-bottom lenses. To make it even more colloqiual, perhaps substitute "glasses" with "specs".
But really, if you are looking to be creative, any of these could be great. I particularly like "jam-jar glasses" which I haven't heard before but makes me laugh because jam jars are much wider than most bottles so it conjurs up the idea of huge oversized lenses.