How long does “second sight” last?

"Second sight" is defined as the myopia (nearsightedness) that occurs due to cataracts.  If you are farsighted, then the cataract-induced nearsightedness may actually improve your distance vision for a time.  If you are not farsighted but need glasses to read, then reading may be made easier for a time. However, the cataract, over time, reduces contrast, dulls color perception, and worsens vision overall until most things become blurry.

The time it takes to go from second sight to blurry vision varies and depends both on an individual’s vision needs as well as how quickly the cataract progresses. In my experience this phase usually progresses to significant visual loss over a few months to a year or two but may last much longer if an individual's visual needs are not extreme.