But 'hyper-' is more widely used (so much so that it's sometimes used informally as a free-standing adjective, meaning 'hyper-active': 'My son gets all hyper when he drinks that stuff.'). When, as in that case, the root word starts with a vowel, you can hear the R - which makes distinguishing them easier. Some words are so 'bedded in' (historically) that there's no problem; the O is a scwha in 'hypodermic', and there is no risk that anyone might think it meant 'extremely "dermic"' - whatever that might mean.
In newer words, that have a root word starting with a vowel, the O is pronounced /ǝʊ/ - as in 'hypo-allergenic'.
Student or Learner