Do you say תתחדש for glasses? What about for shoes?
I’ve heard that not because glasses aren’t something you want to give a bracha to use and shoes because an animal had to die.
The idea of saying תתחדש, essentially is תבלה ותחדש, we are blessing the person that the person should live to use the new garment and even get another one. Regarding shoes, as you write, we don’t say תתחדש, because the new shoes will involve killing an animal. This is brought in the Rema O:CH 223-6. Regarding the glasses I haven’t heard of such an idea, nor have I seen it brought in seforim.