Best eye drop for dry eyes?

Many options: This depends upon the character of the tear deficiency you have. Some are better for volume, others for mucin deficiency and there is even a prescription drop available. Discuss with your ophthalmologist which is best for you.

Serum tears: There are many otc and rx drops that work best for different sources of dry eye (as mentioned in the other answers). One of the best, though, is for severe dry eyes to make tears from your own serum. Blood is drawn, allowed to clot, centrifuged, diluted with saline, and given back to the patient. In cases that do not respond to the available treatments, this option should be discussed with md.