Glasses do not weaken vision or eyesight. People who frequently change prescriptions erroneously assume that glasses cause their eyesight to weaken. Weakening eyesight is often a sign of aging when older people develop presbyopia and cannot see up close. Presbyopia will worsen over time with or without the use of eyeglasses. Other conditions such as glaucoma, macular degeneration, keratoconus, and so on may also weaken eyesight.