Actually you're right, that was a typo. Try 20:700 20:900!
Without correction I could literally not see any part of the eye chart on the wall. First car at a red light? Without correction I couldn't see the stoplight much less what color it was!
One day my dr told me it would be a week or two before my contacts would be in because they had to manufacture them. Puzzled I asked why and was told that there was little enough demand that they didn't keep any in the shelf. I then asked how much stronger I could go before they didn't make anything stronger. My dr told me they made a few stronger but not to worry because we could switch manufacturers and find some even stronger! That day scared the crap out of me because I realized I might really be getting to a point where correction became very difficult. It was probably an additional 4+ years before LASIK came along, thankfully I never needed a stronger prescription. I'm still supposed to get dilated yearly so they can check inside, a detached retina is apparently a very real possibility since my eye is so "long". They dilate me because otherwise it's like trying to look into a room thru a peephole - their words not mine.
The prospect of losing ones vision is damned scary to say the least