I suffer from astigmatism and long sightedness and do not always have to wear glasses depending on which scope I am using, both eyes requiring a 2.00 diopter correction. I can just about use any eyepiece on my f15 refractors without glasses as the exit pupil is relatively small, say between 1.00 - 1.5mm. On my f5.9 - f7.7 refractors I have to wear my glasses or in the case of Televue eyepieces, a Dioptrx is used. Glasses can be worn at anytime with long eye relief EP's as has already been stated.
A useful guide to eyepiece exit pupils and other useful information can be checked out on Televue's website.
http://televue.com/engine/calculate3...=True&_2in=yes