Not necessarily Japan-specific, but when my husband was looking for new glasses/frames about a year ago (and he has a somewhat difficult prescription), I fell into this rabbit hole of various YouTube videos on manufacturers for both glasses and frames. This guy's videos stuck out, so I thought I would post the link to his specific video about luxury frames (and he goes off in general in his videos on Luxotica (aka Lenscrafters) and how they are affecting the overall market).

Side note: we did both buy glasses on a trip to Seoul in the past and that seemed to go well. While we have discussed it for previous Tokyo trips, we ended up not looking in-person. It does make me wonder what options are like in Taipei for an upcoming trip though.