I've been using Optacons since approx 1982 where my school had one available. I read language reference and utility manuals at work. I even tackled Knuth vol 1 using an Optacon. I was even able to use it to read food packaging of different shapes and sizes (something which wasn't possible with OCR). I could even use the Optacon to read some diagrams. I was able to use them until about 2010 when my last one died. I would snap up Optacons from my cohorts as they abandoned them in favour of OCR solutions or phone apps.