The fifth of the seven bowl judgments involves a limited judgment. This time, instead of being across the entire world, this one is focused entirely on the seat of the Beast (the AntiChrist) and the center of his kingdom. Likely this will be a judgment directly against his capital city. It's possible it may entail his entire kingdom, which presently covers the entire planet. However, that is not likely. This reads as though it's a far more localized judgment against the AntiChrist and the center of all his earthly power. This judgment will also be so incredibly powerful that it will not only take away all the light, and I mean ALL of it (ie, no artificial light will be visible, and even candles and electric lights will fail to work), but it will also create an incredible, excruciating pain that will be felt, likely on the same level of pain and agony of the original sores, which may or may not still be there at this point.
It's uncertain how long this period of darkness will last. But given that his capital city is due to be destroyed soon (hence the belief by many that this judgment covers a very limited area) it won't last very long. Perhaps a few months at most. But regardless it will bring his capital city to a dead stop. Nothing and no one will be able to operate due to being unable to see. It'll be like filling a city full of blind men and then beating them within an inch of their life. It'd be basically the same effect. Everyone will be so sore and incapacitated as to be unable to function.
(*Do you have a better description, or did you find an error? Please let me know.