Thanks for asking such a good question. You may not need any help remembering the different applications of these two words, but I devised something to help me remember it. In case it helps others, I've pasted it below:
You don’t takar tops or trousers so don’t giyer gloves or glasses.
Hope that helps someone out there.
Lulu Isaac: That would mean more than one pair of glasses. One pair of glasses is a gözlük.
Also, general direct objects don't show whether they're plural or singular anyway.
(I'm using the app and always get an error when I try to reply to a comment, and my computer is dying.)
I agree. However - and I do sympathize with Duolingo on this, as it must be a nightmare - one problem with using Duolingo is trying to anticipate which words will be acceptable and which will not. I thought 'spectacles' would be a safe choice since it had already been accepted in another sentence, and was free of all ambiguity; 'glasses' rather less so.