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Published in Ken Addley, MCQs, MEQs and OSPEs in Occupational Medicine, 2023
Dry eye is a condition where the surface of the eye becomes inflamed and sore due to a poor relationship between the tear film and the eyelids. This might be because the eyes are not producing enough tears or that the chemistry of the tear film is out of balance.
Models of Toxicity Screening Using Cultured Cells
Published in John J. Lemasters, Constance Oliver, Cell Biology of Trauma, 2020
Roberta L. Grant, Daniel Acosta
The epithelial layer is composed of four to seven layers of cells and is classified as a tight epithelium. Unlike the skin, the corneal epithelium does not have a keratinized layer of cells that can act as a protective barrier. The tear film keeps the epithelial cells moist, provides growth factors, washes away substances that come into contact with the eye, and contains proteolytic enzymes that help protect against ocular infections.
Ocular surface as mucosal immune site
Published in Phillip D. Smith, Richard S. Blumberg, Thomas T. MacDonald, Principles of Mucosal Immunology, 2020
Rachel R. Caspi, Anthony St. Leger
Dry eye affects up to 34% of all people globally and is one of the most frequent ocular surface problems, whose primary manifestation is a dysfunction of the tear film, resulting in a gritty feeling, dryness, irritation, and inflammation of the ocular surface. Dry eye can stem from a number of causes: from neurogenic, due to dysfunction of parasympathetic nerves that control tear production, through autoimmune damage to the tear gland, to infections that can cause physical blockage of tear ducts or inhibition of tear production by inflammatory mediators. The classification of dry eye diseases, established in a 1995 National Eye Institute/Industry workshop, provides a compartmentalized classification system for these syndromes (Figure 24.4), but in practice, combined disorders are common, and it is not always possible to determine a single cause for the disease. As an example, chronic irritation of the ocular surface due to evaporative dry eye can lead to secondary autoimmunization to autologous tissue components of the ocular surface and lacrimal gland components, shifting from “simple” dry eye to Sjögren's syndrome. As a therapy, lipids have garnered more attention recently due to their ability to increase tear stability and modulate excessive inflammatory responses. Specifically, studies are investigating ways to increase natural production of lipids or more effectively deliver synthetic lipids to the ocular surface.
A novel osmoprotective liposomal formulation from synthetic phospholipids to reduce in vitro hyperosmolar stress in dry eye treatments
Published in Journal of Liposome Research, 2023
Miriam Ana González Cela Casamayor, José Javier López Cano, Vanessa Andrés Guerrero, Rocío Herrero Vanrell, José Manuel Benítez del Castillo, Irene Teresa Molina Martínez
The tear film is composed of an aqueous–mucous layer and a lipid layer whose function is to protect and avoid water evaporation from the ocular surface (Willcox et al. 2017). The aqueous layer contains different important proteins, such as immunoglobulins IgA, IgM, and IgG (Davidson and Kuonen 2004), which play an important role in eye protection. Other important proteins present in the aqueous layer include lactoferrin and lysozyme, which are related to the stability of the tear film (Dilly 1994). In addition, glucose and different salts are also present in the aqueous part of the tear film, among other components with important nutritional functions (Tiffany 2008). The lipid layer also comprises a wide variety of lipids, including non-polar lipids (such as triglycerides and cholesterol esters) and amphiphilic lipids (phospholipids) (Schuett and Millar 2012). Lipids are secreted by the meibomian glands and play important functions, such as preventing evaporation or promoting tear extensibility (Butovich et al. 2008). When the lipid layer is disrupted, its ability to prevent water loss is hampered, leading to tear evaporation (Links 2012). This evaporation results in an increase in the concentration of solutes in the aqueous layer, which produces a hyperosmolar environment on the ocular surface (Willcox et al. 2017).
Dry eye and dry skin - is there a connection?
Published in Ophthalmic Epidemiology, 2023
Igor Petriček, Sania Vidas Pauk, Martina Tomić, Tomislav Bulum
As MGs produce meibum, the skin’s sebaceous glands produce an oily substance called sebum to protect the outer layer of skin from losing water. If the skin does not have enough sebum, it loses water and feels dry, like DED. The new definition recognizes dry eye as a multifactorial disease resulting from numerous interacting causes that influence tear film homeostasis, e.g., age, sex, gender, hormone imbalance, environmental causes, inflammation, neurogenic, iatrogenic, low blink rate, lid disorders, vitamin A deficiency, allergies, and psychological causes.5 Many of them also result in dry skin.7 Aging decreases sebum production. Excessive bathing, showering, or scrubbing of the skin also excessively removes sebum. Dry indoor air, exposure to wind and sun, diabetes or skin allergies, thyroid gland disorders, Sjogren’s syndrome, and various medications also cause the same condition.10 So, both conditions have much in common.
Evaluation of Meibomian Gland Loss and Ocular Surface Changes in Patients with Mild and Moderate-to-Severe Graves’ Ophthalmopathy
Published in Seminars in Ophthalmology, 2022
Büşra Yılmaz Tuğan, Berna Özkan
Meibomian glands located in tarsal plates of eyelids are modified, holocrine, sebaceous glands.10 Meibomian glands excrete lipid that forms the lipid layer of the tear film and reduces tear evaporation.11 Meibomian gland dysfunction (MGD) causes gland loss that leads to “evaporative dry eye disease” characterized by instability of the tear film lipid layer, increased evaporation of aqueous component, and increased osmolarity of the tear film.12,13 Recently, many factors have been reported to be responsible for MGD. Age-related changes like reduced acinar cell proliferation and atrophy of the gland are the major causes of MGD.14 Some of the other factors that have been reported are smoking, incomplete blinking, diabetes, and inflammatory diseases such as rosacea.15–19