Sometime my eyelashes twitch back & forth,?

what causes this and is there any way to stop it?Sometime my eyelashes twitch back & forth,?
This disease condition is called "Blepharospasm." It is not a single disease but actually a spectrum / range of conditions. It can be as simple as an occasional and transient eyelid twitch involving one eye, both upper and lower lids, both eyes or it can be severe as to involve the whole side of the face and sometimes even the neck muscles --- (a.k.a hemi-facial spasms).
The actual cause is still unknown, but current theories revolve between simple fatigue and stress to as extreme as a an actual basal ganglia (deep part of the brain) problem.
Treatment options include, rest, cold compress, and in extreme cases botilinum toxin injections to temporarily paralyze/ weaken the twitching muscle. Incidentally, BOTOX was first used for blepharospasms. The cosmetic side effect of removing wrinkles was serendipitously noted by the dermatologist spouse of the ophthalmologist who was studying botox.
It would be best to see a neurologist or a neuro-ophthalmologist for your problem.
Muscular tic caused by a misfiring nerve controlling the eyelid is the cause. Try rubbing the upper eyelid and outer corner, to compress the nerve and interfere with the misfire. If it really bugs you or interferes with life, you can seek out a neurologist. Sometimes its just a misfire, sometimes facial tics have an identifiable cause that needs or will respond to treatment. Since yours is not a constant thing, it's likely just a misfire and nothing for great concern. It happens to everyone on the odd occasion.