50. Exactly, weed smoking cause dry of some important parts of body, such as mouth, throat, eyes and nose. The most important factor is that marijuana dries out all your mucous membranes. However, if you have no any bad reactions for many years when smoking weed until lately, then you'd better consider whether you are allergic to this weed. On the contrary, you may be allergic to marijuana. Personally, if you have these conditions for a long time, some essential home care must be taken. You can prepare some basic drops at home which works for dry eyes. Next you can drink some warm water with honey that can help with getting rid of tired and dryness. You also can apply some cucumber on your eyes which takes vitamins supplements and fresh your eyes. Seriously speaking, the best thing to do is visit a doctor and takes a thorough exam. Because there is an inflammatory disease of the tear ducts which has very similar symptoms. So be careful and good luck!