Eye fluttering is virtually synonymous with eye twitching, as they're both characterised by involuntary spasms of the lid muscle. While a twitch forces the eye to close and open only a handful of times at once, fluttering makes the eye open and close many more times in rapid succession. The condition usually appears and disappears on its own and is rarely cause for alarm.
Symptoms of eyelid fluttering include the obvious fluttering or twitching, which is sometimes unpredictable---coming and going for days or even weeks at a time. Longer-term eye fluttering can lead to sensitivity to light or even blurred vision. Symptoms which may seem unrelated to the eye spasms could in fact be causes of it, including fatigue and stress.
According to Dr. Ben Kim, author of the online newsletter Natural Health Solutions, "in the vast majority of cases of ... twitching or fluttering eyes, the problem is with the temporal branch of the facial nerve. When this nerve becomes fatigued ... the flow of electrons is no longer smooth and even." The most common cause of nerve exhaustion is overall fatigue and stress, although caffeine, smoking or alcohol can also cause or prolong fluttering. A more severe case could be caused by an irritated cornea which is the eye's surface; or may be caused by irritated conjunctiva, the membranes lining the lids.
Because the most common cause of eye fluttering is exhaustion, the typical prescription is rest and relaxation. Health professionals routinely recommend that those affected get plenty of sleep and limit their caffeine intake. If the fluttering is a result of an irritant, eye drops can help soothe corneas. In milder cases, the affected person often doesn't notice when the twitching disappears. In more acute cases, doctors may go so far as to inject the area with botulinum toxin---also known as Botox---which momentarily stops the twitching.
Both the Mayo Clinic and the National Institutes of Health recommend that those affected by eye twitches for one to three weeks make an appointment to see a doctor. Other reasons to seek medical help include spasms which briefly hold the eyelid completely shut, or which radiate from the eyelid into other parts of the face. Redness, swelling and a discharge of any kind are equally as concerning and should prompt a call to the doctor. If the eyelid starts to droop, it could be signalling another condition called ptosis, which has several possible underlying causes including ageing, injury or disease.
On rare occasions, a fluttering eye can be an indication of a nerve or brain disorder. The Mayo Clinic asserts that in such cases, additional symptoms and signs are sure to occur. Disorders that exhibit eye spasms include Bell's palsy, cervical dystonia, Tourette syndrome, dystonia and benign essential blepharospasm. Benign essential blepharospasm is a condition in which both eyes exhibit uncontrollable fluttering; it's usually accompanied or proceeded by sensitivity to light, pink eye, dry eyes or blepharitis.