Wow, thanks for calling me an idiot lol.
In the topic title he states he has or had -4.5, how does he know? Not from snellen, that's for sure. I only say find out the current diopter the way he found out he had -4.5, probably for free at an optometrist, like he suggested in another post, for objective numbers.
I had mine tested last week for free at a random optometrist and didn't have to buy anything. Yes they over prescribed when I could try what they have measured, everything was crisp, complete overkill.
20/30 and even 20/20 doesn't mean the diopter in the eyes is 0.
Jake also emphasizes the importance of measuring your diopter, only not at the optometrist but with a measuring tape.