What is Dry Eye?
In order to have clear, comfortable vision; your eyes depend on the ocular tear film. This complex and dynamic coating can be simplified into two major functioning layers. The aqueous (water) layer is produced by the lacrimal gland located above the eye. The hydrating layer prevents the eye's surface structures from drying out and becoming inflamed. In contrast, the lipid (oil) layer is released from meibomian glands located within the upper and lower eyelids. The openings of these glands run along the lid margins just behind your eyelashes. When these glands are open and functioning normally, the strength of a normal blink is enough to prompt the release of meibum from the glands. The oil layer provides stability to the tear film and prevents air from evaporating the water layer of the tear film.
"Dry eye" occurs when there is any imbalance in these layers. Instability can be caused by inflammation, changes in the lacrimal gland or meibomian gland function, or most commonly; a combination of the two.
Symptoms such as swelling, redness, heat and pain occur when the body has an inflammatory response. This response can be helpful when initiated as a defense to an acute, short-term infection. However, causes of chronic, long-term inflammatory responses eventually lead the body to attack nearby healthy tissues.
For the eye, inflammation may lead to dysfunction and destruction of the lacrimal and meibomian glands. The tear film produced by these damaged glands has poor stability and leads to symptoms of burning, watering, dryness, redness, and itching. It also causes fluctuating, blurred vision that changes with blinking. Common causes of inflammation that affect the eye include auto-immune disorders, environmental allergens, and the overgrowth of the natural bacteria that live within our eyelashes and eyebrows.