For some reason I thought of these when seeing a TV ad about hearing aids that are almost invisible. I think they were around in the 1970's but am not sure when they came out and when they disappeared. Anyway I assume they disappeared as I have not seen anything about them for many years. My objection to them was managing keeping both the glasses and aid(s) up to date and in good repair at the same time. I will admit they were not that obvious unless you knew what to look for.