Is there a way to know if a contact lens is old by looking at?

You should be careful when things happened as follows:
1. If you feel soft wear your usual contact lenses
2. you could not withstand itch when
3. the excretion is more than usual,
then your contact lens is old and need for change. If you do not change, they will be damaging your cornea and make keratitis due to oxygen deficiency.