Blepharitis is a form on inflammation of the eyelids. It can affect either the anterior surface of the eyelids where the eyelashes sit, or the posterior surface where the meibomian glands open, which produce tears.
This is not a serious condition and does not normally affect the vision, but can be uncomfortable with inflammation lasting for long periods of time. The eyelids become red and inflamed, making the eyes feel dry, sore, itchy and irritated.
Blepharitis can also affect the quality of the tears, which can lead to dry eye symptoms.