So I have 20/20 vision, but it's blurring a little?!

So I have 20/20 vision, but it's blurring a little?

I've noticed that it's getting difficult to read small things far away. for example, I sit about 15 ft away from the periodic table in chemistry class, and I mostly have to use my memory and guesswork to find the mass numbers. I think it's probably because I spend too much time on the computer xD

but I'm hoping that it's only temporary. so now I'm gonna go read a book!

anyone have any thoughts, similar experiences, or medical advice?

Yes it sounds like you have an astigmatism. I have the same thing and on an eye chart with both eyes I can see 20/20 as well. When I was younger in school I had the same problem as well I could see far or close pretty good just sometimes things weren't "sharp" or clear. Astigmatism usually stays the same throughout life and if it bothers you, you may want to get an eye exam. Even having 20/20 vision you still may need glasses to achieve vision that is clearer. I wear glasses sometimes when my eyes are tired or when I'm on the computer.
Here is an explanation of how astigmatism occurs:
"Your eye has two parts that focus images — the cornea and the lens. In a perfectly shaped eye, each of these focusing elements has a perfectly smooth curvature like the surface of a smooth ball. A cornea or lens with such a surface curvature bends (refracts) all incoming light the same way and makes a sharply focused image on the back of your eye (retina).

However, if your cornea or lens isn't evenly and smoothly curved, the light rays aren't refracted properly. This causes a refractive error. Astigmatism is one type of refractive error. In astigmatism, your cornea or lens is curved more steeply in one direction than in another. Uncorrected astigmatism blurs your vision"
Don't worry hun it is very common and normal... you may need a pair of glasses to help you get crisper vision :)