What is the strongest eyeglasses prescription?

Worst of the worst: A strong glasses prescription implied very severe refractive error. This is usually due to the eye either being too long, too short, or too irregular in shape. This leads to nearsightedness, farsightedness, and astigmatism. Generally the nearsighted prescriptions are highest due to extreme eye length, -30.00 is the worst I have seen. An aphakic person also who is also hyperopic could be +30.00.

No limit: There is a range of powers that cover the extreme to the common and the usual range is +20.00 to -32.00. A few rare individuals need more on either side but that is very rare. There is no "strongest" because what ever extreme you might suggest, eventually someone will need more.

The one you can see: the best through. Everyone is different, and need different or NO correction to correct their refractive error. So seeing best is the goal!