You probably (99.99%) just need glasses, try that first. If you haven't already go see a good optometrist/opthamologist (not the mass production docs at lenscrafter).
If you see 20/30 with a current prescription, go see an opthamologist...odds are very good the prescription is incorrect but you want to rule out anything else as well.
If you go to the AME, he can definitely give you a 3C. He could probably call OKC and get a waiver for a 1C but he is more likely to tell you to go get new glasses instead.
Healthy young people do not experience noticeable reductions in basic visual acuity, other than that caused by refractive (lens) error which is totally correctable with glasses. If the AME thinks that there is something going on besides refractive error, he may require more investigation to rule out some sort of degenerative problem which will get worse (this sort of thing normally affects old people).
If for some reason you experienced a sudden change which is not correctable to 20/20 in one eye I'm pretty sure the AME can call OKC and get a waiver on the spot. This assumes there is no suspicion of a degenerative problem.