Ah, a replacement for sentences where re-integration is not planned. At the least, it sounds frightening and that would be a potential motivator to dissuade some criminals. I do like the idea of seperating such offenders from the ones that can rejoin society, as a prisoner with no hopes is likely to make everyone around them miserable on purpose.

Is there a high number of blind people committing capital crimes?

I doubt it, but I wouldn't be surprised at a newly blind guy getting up to something crazy. Maybe not on a comic book villain level, but I imagine it being a traumatic change that could distort a person's values. Most guys wouldn't have henchmen available to facilitate crazy plans.

I was assuming the blindness to be meant as punishment. Why bother with it at all? Just putting them in isolation sounds sufficient. Give them light and normal books, take away the Alexa. Drug their food when you want to give them a checkup. You wouldn't even need them to hear instructions for the suicide button, you could have a sign.