One of the most important functions of tears is to lubricate the eyeball and eyelid, and prevent dehydration of the various eye mucous membranes. The lack of tears is commonly known as ‘dry eyes’ problem, or keratoconjunctivitis sicca.
Keratoconjunctivitis sicca is usually due to inadequate tear production. This happens due to inadequate tear production. When the aqueous tear layer is affected, it results in aqueous tear deficiency or lacrimal hyposecretion.
The lacrimal gland stops producing sufficient tears to keep the entire conjunctiva and cornea covered by a complete layer and usually occurs in people who are otherwise healthy. Increased age is also associated with decreased tearing. Sjogren’s syndrome is also commonly linked to it, especially in middle-aged women.
The lacrimal glands secrete lacrimal fluid, which flows through the main excretory ducts into the space between the eyeball and lids. When the eyes blink, the lacrimal fluid is spread across the surface of the eye. Lacrimal fluid gathers in the lacrimal lake, and is drawn into the puncta by capillary action, then flows through the lacrimal canaliculi at the inner corner of the eyelids entering the lacrimal sac, then on to the nasolacrimal duct, and finally into the nasal cavity.
In healthy mammalian eyes, the cornea is continually kept wet and nourished by basal tears. They lubricate the eye, and help to keep it clear of dust. Tear fluid contains water, mucin, lipids, lysozyme, lactoferrin, lipocalin, lacritin, immunoglobulins, glucose, urea, sodium, and potassium. Some of the substances in lacrimal fluid (such as lysozyme) fight against bacterial infection as a part of the immune system. In humans, the tear film coating the eye, known as the precorneal film, has three distinct layers, from the most outer surface. The lipid layer, aqueous layer, and the mucous layer; this tear film lubricates the eyes and helps to keep it clear of dust.
A common cause of dry eyes is aging. As we age we create less productive tears which mean less moisture to the eyes. These tears might also evaporate swiftly. Another factor is that some people are not able to generate as much natural tears as needed whether it is from aging or blockage of tear ducts, or from medication that leads to less yielding of tears.
Primarily strenuous activities on the eyes often require a break or lots of blinking to bolster the prevention of dry eyes.