The answer to your question 'why does my eye twitch?' can be for many different reasons.
The technical name for eye twitching is Blepharospasm and it is caused by muscle spasms in the eye lid and around the eye.
It is believed to be related to the nervous system.
It tends to start suddenly and can last for anything from a few hours up to a few days.
In some cases it can be triggered by smoking or bright light.
In very rare cases eye twitches can be a symptom of a more serious problem known as nystagmus, although this is not a muscle twitch, it is the movement of the eye itself and needs medical treatment.
Common causes

• Stress and anxiety
• Physical or emotional stress
• Over consumption of caffeine
• Eye stress caused by constant computer use
• Fatigue

When should I consult a doctor? It is very rare for this condition to be serious or to have any long lasting effects.
If the twitches are accompanied by any of the following, then you should seek medical advice.

• Painful or are accompanied by a fever
• They cause the eye to close completely
• Your vision is blurred or sensitive to light
• They extend down your face
• They don't disappear after 7 days

Preventions Once you have found out the reason why your eye is twitching then you can start to take steps to prevent it.
If you lead a very stressful life, then you will need to look at some stress management issues.
These can be easy fixes, such as making sure you have time out from your working day, soaking in the bath, yoga or massage.
If you are constantly tired, then get more sleep.
Keep an eye on your caffeine intake as too much can cause a disturbed night sleep.
So!Most eye twitches are caused by lifestyle and are preventable.
Once you have defined the underlying cause then it really is possible to prevent it.
And hopefully you then won't have the need to ask yourself 'why does my eye twitch?'