9 in 10 people have some affliction of astigmatism. Astigmatism is just that your eye isn’t perfectly spherical. What does your eye prescription say in the cyl and axis fields, that’s your astigmatism correction.
20/10 and 20/13 means much better than average good vision. It would be bad if they were e.g. 20/30. Funny that you're LARPing an eye doctor without knowing this.
You can still have 20/10 vision with Astigmatism. I guess my years of research into astigmatism because of my own affliction and years of optics study visual effects means I’m larping. Never said I was a doctor, I’m just intimately familiar with how corneal distortion.
Aren't those numbers about your ability to focus on distance objects, though?
I could totally believe the someone might have "perfect" vision that doesn't require correction, but still have a slight astigmatism that impacts their vision under certain specific scenarios such as when viewing blue LEDs in low light.
I'm not necessarily saying that's what you have, but more just that to the extent your eyes have been evaluated, it was likely "yeah they look great as far as your ability to perceive the brightly lit eye chart, no need to do the more detailed analysis where we figure out the other parameters that will never be used because you're fine, bye."
The 30-60% is most likely for those affected by their astigmatism. Astigmatism is when the eye isn’t a perfect sphere. Many people have very slight astigmatism and don’t require correction.