Under normal circumstances, the use cycle of annual contact lenses is 8-10 months, half-year contact lenses are 4-5 months, and monthly and daily contact lenses can be used according to the normal abandonment cycle. Continue to use the lens after the use cycle, such a long-term wear will cause two problems, one is dry eyes, the other is the corneal gradually thinning, although these changes are relatively slow, but in the long run will still affect the eye health. Because the contact lens exceeds the validity period, the lens will age, and the transparency and oxygen permeability will also be greatly reduced. Proteins and other deposits on the lens will accumulate and reduce transparency over time, and it is also easy to damage the cornea. Therefore, it is imperative to replace contact lenses regularly.