tear film

pre·cor·ne·al film

a protective film, 7-9 nm thick, consisting of external oily, intermediate watery, and deep mucoprotein layers.
Synonym(s): tear film

tear film

A liquid consisting of lipids, water, and mucin that coats the outer surface of the eye, lubricating it.

Patient care

A reduction in the tear film causes a sensation of a dry or gritty eye, such as is seen in Sjögren's syndrome, keratoconjunctivitis, sicca, disorders of the lacrimal gland, and other conditions. Keeping eyelids clean, using artificial tears, and withholding medications that may reduce the tear film can prove helpful for some patients. Other treatments may include the wearing of moisture chambers around the eye, and eye lid surgery. Topical lubricants can be used for symptomatic relief.

film, precorneal

The field covering the anterior surface of the cornea which consists of lacrimal fluid and of the secretion of the meibomian and conjunctival glands. Its total thickness was thought to be about 9 μm but recent investigations have questioned that value and point to a much larger figure. It is composed of three layers: (1) The deepest and densest is the mucin layer (or mucous layer) which derives from the conjunctival goblet cells, as well as some secretion from the lacrimal gland. (2) The watery lacrimal fluid is the middle layer, called the lacrimal (or aqueous layer). It is secreted by the lacrimal gland and the accessory glands of Krause and Wolfring. It forms the bulk of the film and contains most of the bactericidal lysosyme and other proteins, inorganic salts, sugars, amino acids, urea, etc. (3) The oily layer (or lipid layer) is the most superficial and is derived principally from the meibomian glands in the lids as well as some secretion from the glands of Zeis. It greatly slows the evaporation of the watery layer and may provide a lubrication effect between lid and cornea (Fig. F6). Note: Some authors have suggested that the precorneal film is made up of only two layers; an innermost aqueous and mucin gel layer and an outer lipid layer. Syn. lacrimal layer; preocular tear film; tear film; tear layer. See hyperlacrimation; mucin; tear secretion; Tearscope; break-up time test.
Fig. F6 Diagram of the three layers of the precorneal film attached to the squamous epithelial cellsenlarge picture
Fig. F6 Diagram of the three layers of the precorneal film attached to the squamous epithelial cells
References in periodicals archive ?
Dry eye syndrome (DES), also known as keratoconjunctivitis sicca (KCS), is a multi-factorial disease of the eye caused by dryness, decreased tear production, or increased tear film evaporation.
The new wipes gently clean, soothe and refresh eyelids without disrupting the lipid layer of the tear film.
No other known natural oral treatment is capable of boosting aqueous tear fluid secretion and enhancing the function of the tear film like this.
Tear film deficiency is recognized as an important ocular surface disease in dogs but has not been well evaluated in birds.
6 Turn down the central heating at night, use "wetting" drops each morning as soon as you wake and before you go to bed, massage the lower lid to keep the grease glands of your eyelashes working properly and improve your tear film.
Lower pressure sucks the fluid into the meniscus and away from the centre, creating the black line and dry spots in the tear film that can compromise vision and irritate the cornea.
Seven per cent of men and 14 per cent of women were diagnosed with 'dry eye disease,' meaning they reported symptoms of eye problems like irritation, burning or blurred vision and had poor quality or quantity of tear film, according to the tests.
6-9] There are several studies which assessed the relationship between diabetes and dry eyes, and in most cases this relation has been confirmed, [5, 10, 11] however, in some studies, decreased tear production or increased tear film evaporation has not been observed in patients with insulin-dependent diabetes mellitus.
Tear film consists of a layer of water sandwiched between an oily layer of lipids on the outside to prevent evaporation and an inner mucous layer to spread the water over the eye.
2007 Tear Film Ocular Surface Society International Dry Eye Workshop,
Also, the tear film can interfere, particularly in older patients.
Dry eye disease (DED) is a multi-factorial disorder of the tear film and ocular surface resulting in discomfort, visual disturbance and ocular surface damage.