hi there! sorry for the two year late reply lol...
you probably figured it out already, but if you ever appear to be "stuck" on the blue screen during the eye exam mini-game, then your only option is to use the spacebar to continue like you would during the visual novel sequences.
again, sorry if the structions are unclear, but this mini-game was supposed to reflect the main character's hopelessness about slowly losing his eyesight, and we may have gotten carried away without thinking about the player experience 😅