You should check your lens at least once a week to ensure it’s clean. If you are working with rubber or wood, it’s recommended to check it daily.
Only clean the lens if it is dirty, as excessive cleaning can shorten the life of the lens.
The oils in your skin will damage the lens coating so never handle the lens with your bare fingers.
Always use a proper lens wipe or cotton swab with industrial optic cleaning fluid. Cleaning fluid from a camera store or eyeglass shop will contain water which will harm the lens coating.
Important: Special care should be taken when cleaning a broken lens. The coating is very poisonous when broken, so it should always be handled and disposed of in a responsible manner.