Does irregular use of glasses worsen eyesight?

No: Glasses do not help or worsen eye sight they are only to see well with when you wear them.

Not at all: Glasses are like crutches - their job is not to heal you, only to help you with what you've got. The eye's prescription is essentially a product of its shape; glasses correct the prescription caused by the eye's shape, but do not cause the eye's shape to change for the better or for the worse. In young children there is a possibility of worsening vision from not using glasses, however.