Having dry or irritated eyes can cause eye irritation, watery eyes, and blurry vision between blinks. There are many potential underlying causes of dry eyes and the underlying causes will often determine the symptoms that are most prominent and when they occur.
Types of Dry Eye
There are two main types of dry eyes. They are classified as either water deficient dry eye or oil deficient dry eye.
Both a watery component and an oily component are required for a healthy tear film that protects and provides nutrients to the eye.
If either the water component or the oil component is lacking, the eyes will not have a healthy tear film and it will cause dry eyes.
Water Deficient Dry Eye
Water, or aqueous, deficient dry eye is often associated with autoimmune conditions, namely Sjogren’s Syndrome.
These autoimmune conditions can cause the eye to not produce enough of the water component of the tears.
Other potential causes include aging changes to the tear gland, conditions which cause blockages in the tear gland, and LASIK surgery which can cut the innervation to the front of the eye.
Dry Eye Due to Autoimmune Conditions
Many autoimmune conditions will cause dry eyes. These conditions are caused by the body overreacting and attacking itself as if it were a pathogen.
Autoimmune conditions like Sjogren’s Syndrome, Systemic Lupus Erythematosus, Rheumatoid Arthritis, and others may impact the tear gland and reduce the number of tears which are produced and secreted onto the eye.
Dry Eye Due to LASIK Surgery
LASIK surgery is a procedure used to correct the refractive error of an eye without glasses. This laser procedure requires cutting a portion of the cornea on the front of the eye and then folding it back after the procedure.
When the laser cuts the cornea, it can cut the corneal nerves which sense when the eye needs to blink or is getting dry.
If these nerves are no longer functioning, the eyes may become severely dry from a lack of reflex blinking.
Oil Deficient Dry Eye
Oil, or lipid, deficient dry eye is more common than water deficient dry eye and is due to damage to the oil glands within the eyelids.
These oil glands are called Meibomian glands and produce a clear oil that helps to stabilize and thicken the tear film.
If there is damage directly to the glands it is called Meibomian Gland Dysfunction.
If there is damage as a result of something else, such as a contact lens, then the condition is called extrinsic oil deficient dry eyes.
Dry Eyes Due to Meibomian Gland Dysfunction
Meibomian gland dysfunction is a condition in which the oil glands in the eyelids are damaged, non-functioning, or are missing altogether without a specific reason.
These changes may be due to age, environmental factors, or truly without a specific cause.
This type of dry eye is very common and may also cause redness of the eyelids from inflammation associated with the damaged oil glands.
Dry Eyes Due to Contact Lens Wear
Contact lenses can result in damage to the oil glands in the eyelids and cause the glands to stop functioning appropriately.
This is the main cause of contact lens associated dry eyes.
While the contact lens may feel dry or cause discomfort with extended wear, if it has damaged the oil glands, the eyes will continue to be dry even after removing the contact lens.
