In The World: Easy on the eyes

My understanding is that in addition to determining the proper prescription, grinding lenses to fit them is something that many third world countries don't have the infrastructure for. Self-adjustable, 3rd world-friendly spectacles do exist[1], but at that point, does one really need a prescription, or can you just dial in until you can see well?

[1] http://www.trendhunter.com/trends/josh-silver-adaptive-eyewe...