Dry eye is inadequate wetting and/or lubrication of the eyes surface, possibly caused by many factors that can cause the sufferer discomfort.
Evaporative Dry Eye:
is commonly associated with deficiency of the lipid layer of the tear film (which exists to protect the aqueous tears from evaporating too rapidly). This can be the result of blepharitis, meibomian gland dysfunction or related conditions.
Aqueous Dry Eye:
is where the lacrimal glands fail to produce enough watery content to maintain a healthy eye surface.