http://www.uic.edu/com/eye/LearningAboutVision/EyeFacts/Presbyopia.shtml
When does Presbyopia start?
Presbyopia may begin as early as age 36 or as late as 50. Persons with no refractive error (no need for corrective lenses) will usually notice presbyopia in their mid-40s. Farsighted persons will note presbyopia earlier, especially when they are not wearing their glasses. Also, some conditions such as diabetes can result in an earlier onset of presbyopia.