[wallaBBB]

The thing with presbyopia is about losing the elasticity of your lens - thus not being able to change your focus (muscles pull the lens changing it's shape and with it the focus). With the hardening of the lens the range is getting narrower around the lens' natural focus (far field).

Article does a good job at explaining briefly the limitations. This drug by manipulating pupil opening extends the depth of focus, and if the lens is not too hard, in combination with the extended focus you could cover the near field, but the light accommodation becomes a problem, by not being able to dilatate your pupil (driving being the biggest problem).

Overall a limited application, and not so life changing as the article title implies. Reading glasses could very well be a better option for all.

[mannykannot]

One specific limitation is that it impairs your night vision, so driving at night while still under the influence of this drug becomes riskier.