Thanks, @willtp87! That's certainly another valid option. Like you said, outside of the .module file, the constant appears in three other places:

* /islandora_ocr.module
* /includes/admin.form.inc
* /includes/hocr.inc
* /includes/utilities.inc

I'm happy to go either way. Since the maintainer is the one who will ultimately have to live with the change, I'll let him weigh in before I do anything. According to the README.md file, that would be @ruebot.