If your glasses were stolen or damaged due to an insured event in the home, such as a fire or a theft (check your policy wording for further details) then cover would be provided under the contents section.
To provide cover for accidental damage to your glasses within your home you would need full accidental damage cover.
If you lose your glasses in the home you usually need personal belongings cover for this. Contents cover is there for the main insured events such as fire, theft, escape of water. A loss is not usually classed as one of the main events.
Glasses are usually covered under Personal Belongings/Personal Possessions cover. This usually provides cover for loss, theft or damage anywhere in the world.