Proper care and cleaning of your binoculars will help insure the best image and longest life. Here are a few items to consider.
Maintain the lenses of your birding binoculars
Clean the lenses with a lens cloth or lens paper. Cleaning fluid especially designed for precision optics is inexpensive and readily available. Avoid cleaning the lenses with a paper towel or shirttail. While they may appear soft, their use will hasten the removal of critical lens coatings.
Dirt and grime
Dirt and grime can be removed from the binocular body using a damp cloth.
In general, avoid getting your binoculars too wet. Excess moisture can fog internal lens surfaces. If they do become wet, dry as much as possible with a soft rag and place in a warm, dry location. Quality bird watching binoculars are sealed and filled with nitrogen or other inert gas. If moisture shows up on the inside of a binocular with a sealed design it should be returned to the manufaturer for repair before further damage can occur.
If sand infiltrates the moving parts of your binocular it can be a very big problem. Use care when birding on the beach. If your binoculars are dropped into the sand, brush them off completely and slowly adjust the focus. If the focus is rough, there may be sand inside the adjustment mechanism. At this point, the best option is to send the binoculars to a repair facility for cleaning. Continued use may lead to irreparable damage.