{"id":1861,"date":"2026-10-20T08:52:31","date_gmt":"2026-10-20T08:52:31","guid":{"rendered":"https:\/\/laseristanbulclinic.com\/eye-glossary\/tear-film-and-tear-glands\/"},"modified":"2026-10-20T12:57:26","modified_gmt":"2026-10-20T12:57:26","slug":"tear-film-and-tear-glands","status":"publish","type":"page","link":"https:\/\/laseristanbulclinic.com\/en\/eye-glossary\/tear-film-and-tear-glands\/","title":{"rendered":"Tear Film and Tear Glands: Layers, Function and Tear Duct Eye Surgery"},"content":{"rendered":"\n
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  4. Tear Film and Tear Glands: Layers, Function and Tear Duct Eye Surgery<\/span><\/li><\/ol><\/div>\t\t\t

    Tear Film and Tear Glands: Layers, Function and Tear Duct Eye Surgery<\/h1>\n\t\t\t\t\t\t

    Medically reviewed by {{surgeon}}<\/span><\/strong>, {{surgeon’s title and specialty}}<\/span>, on {{review date}}<\/span>. Last updated {{date}}<\/span>.<\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

    \"Illustration<\/figure><\/div>\n\t\t\t<\/div><\/div>\n<\/section>\n\n\n\n\n
    \n\t\t<\/svg>Definition<\/span>\n\t\t\t

    Tear film<\/strong> (noun)<\/em>: the tear film is the thin, moist coating that covers the front of the eye, made of an oily lipid layer, a watery aqueous layer and a mucin layer. It is produced by the tear glands: the lacrimal gland and accessory glands (water), the meibomian glands in the eyelids (oil) and the goblet cells of the conjunctiva (mucin). It keeps the cornea smooth, clear and protected, and tears then drain through the tear ducts into the nose. When those ducts block, tear duct eye surgery<\/strong> can create a new drainage route.<\/p>\n\t\t<\/div><\/div><\/div><\/div><\/section>\n\n\n\n\n

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    Tear film and tear glands: key facts<\/h2><\/div>\n\t\t\t\t\t<\/div>\n\t\t\t
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    <\/svg>Where it is<\/span><\/dt>
    A thin film over the cornea and the white of the eye (the conjunctiva)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Thickness<\/span><\/dt>
    About 2\u20135.5 micrometres over the cornea; the lipid layer is only about 40 nanometres thick on average<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Volume<\/span><\/dt>
    About 8 microlitres (\u00b1 3) of tears on the eye at any moment<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Turnover<\/span><\/dt>
    Roughly 16% of the tear volume is renewed every minute (\u00b1 5%)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Main producers<\/span><\/dt>
    Lacrimal gland (water), meibomian glands (oil), goblet cells and surface cells (mucins)<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Drainage<\/span><\/dt>
    Puncta, canaliculi, lacrimal sac and nasolacrimal duct into the nose; about 80\u201390% of drainage uses the lower canaliculus<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Common problems<\/span><\/dt>
    Dry eye disease, meibomian gland dysfunction, watering eyes, blocked tear duct<\/dd><\/dl><\/div>\n\t\t\t\t
    <\/svg>Specialist<\/span><\/dt>
    Ophthalmologist; for eyelid and tear duct problems an oculoplastic surgeon. At Laser Istanbul Clinic, eyelid and oculoplastic surgery is led by Prof. Dr. Ahmet Sat\u0131c\u0131<\/dd><\/dl><\/div>\n\t\t\t<\/div>\n\t\t<\/div><\/div><\/div><\/section>\n\n\n\n\n
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    What is the tear film? Tear film anatomy<\/h2><\/div>

    The tear film is not just “water on the eye”. It is a thin, constantly renewed layer, only 2\u20135.5 micrometres thick over the cornea (a fraction of the width of a human hair), that acts as the eye’s first optical surface. The 2017 TFOS DEWS II Tear Film Report, an international expert review of the tear film, describes it as a single dynamic unit with different compartments.<\/p><\/div><\/div>

    What the tear film does (tear film function):<\/strong><\/p><\/div>\t\t

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    1. \n\t\t\t\t\t\t

      It is the eye’s first refracting surface<\/h3>\n\t\t\t\t\t\t

      Light passes through the tear film before it reaches the cornea, so a smooth, stable film is needed for sharp vision.<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t

    2. \n\t\t\t\t\t\t

      It protects and moisturises the cornea,<\/h3>\n\t\t\t\t\t\t

      which has no blood vessels and relies on tears for much of its comfort and health.<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t

    3. \n\t\t\t\t\t\t

      It provides lubrication, some nutrients and the right salt balance<\/h3>\n\t\t\t\t\t\t

      (osmolarity) for the surface cells.<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t

    4. \n\t\t\t\t\t\t

      It defends against infection<\/h3>\n\t\t\t\t\t\t

      with antimicrobial proteins and antibodies such as lysozyme, lactoferrin and secretory IgA.<\/p>\n\t\t<\/div><\/li>\n\t\t\t\t

    5. \n\t\t\t\t\t\t

      It washes away dust and debris<\/h3>\n\t\t\t\t\t\t

      with every blink.<\/p>\n\t\t<\/div><\/li>\n\t\t\t<\/ol>\n\t\t<\/div><\/div><\/div><\/section>\n\n\n\n\n

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      Layers of the tear film: layers, glands and thickness<\/h2>\n\t\t\t

      How many layers does the tear film have? The classic textbook model has three: lipid, aqueous and mucin. Researchers call it “a considerable simplification” of a more mixed, dynamic structure, but it remains the clearest way to understand tear film layers and functions. From the outside in:<\/p>\n\t\t\t

      Layer (outer to inner)<\/th>Made by<\/th>What it does<\/th>Thickness<\/th><\/tr><\/thead>
      Lipid layer<\/strong> (oily)<\/th>Meibomian glands in the eyelid edges<\/td>Slows evaporation and stops tears spilling over the lid; keeps the surface smooth<\/td>About 40 nm on average (reported range 15\u2013157 nm)<\/td><\/tr>
      Aqueous layer<\/strong> (watery, the bulk of the tear film)<\/th>Main lacrimal gland, with the accessory glands of Krause and Wolfring and a smaller share from the conjunctiva<\/td>Moisturises, nourishes, carries antibodies and antimicrobial proteins, washes away debris<\/td>Makes up most of the 2\u20135.5 \u00b5m total<\/td><\/tr>
      Mucin layer<\/strong> (glycocalyx and gel)<\/th>Goblet cells of the conjunctiva and the surface cells of the cornea and conjunctiva<\/td>Helps the watery tears spread evenly and stick to the eye’s surface; transmembrane mucins extend up to about 0.5 \u00b5m into the tear film<\/td>Up to about 0.5 \u00b5m<\/td><\/tr><\/tbody><\/table><\/div>

      Tear film diagram (text version):<\/strong> from the air down to the eye: air \u2192 lipid layer<\/strong> \u2192 aqueous layer<\/strong> (with mucins mixed through it) \u2192 mucin layer \/ glycocalyx<\/strong> \u2192 corneal and conjunctival surface cells. {{Tear film diagram image: layers labelled, with the glands that make each layer}}<\/span><\/p><\/div>\n\t\t\t

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      What is the lipid layer of the tear film?<\/h3>

      The lipid layer of the tear film is the thin, oily outer coat that sits on top of the watery layer. It comes almost entirely from the meibomian glands, a row of tiny oil glands inside the upper and lower eyelids, and it works like a seal that slows evaporation. When the glands are blocked or the oil is poor in quality, the tears evaporate too quickly. This is called meibomian gland dysfunction, a leading cause of evaporative dry eye.<\/p><\/div><\/div><\/div>\n\t\t\t\t

      Which glands make the tear film? Tear film layers and glands<\/h3>