II. Physiology
- Layers of tears
- Inner: Mucin produced by goblet cells of Conjunctiva
- Mid: Aqueous layer by lacrimal glands (90% of tears)
- Water (largest component)
- Glucose
- Lysozyme
- Lactoferrin
- Secretory Immunoglobulin (IgA)
- Outer: Lipids produced by meibomian glands
- Prevents evaporation
- Function of tears
- Maintains smooth eye surface for visual clarity
- Lubricates eye surface to facilitate blinking
- Barrier to infection
- Function of Blinking
- Normally, blinking occurs every 5 seconds
- Spreads tear film and directs toward lacrimal duct
III. Causes: Increased Tear Secretion
- Emotion
- Foreign body irritation
- Corneal Ulcer
- Conjunctivitis
- Coryza
- Measles
- Hay fever
- Cluster Headache (unilateral tearing)
- Toxin
IV. Causes: Absent or decreased Tear Secretion
- See Dry Eyes
- See Schirmer's Test
V. Causes: Obstruction of the Lacrimal Ducts
- Dacryocystitis
- Lacrimal calculus
- Congenital obstruction
- Cicatrix
- Eyelid Edema
VI. References
- Rheinstrom in Yanoff (1999) Ophthalmology, Mosby, 14.1
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Related Studies
| Definition (NCI) | Tearing; excessive shedding of tears. |
| Concepts | Finding (T033) |
| SnomedCT | 139559008, 162289008, 64702000 |
| Dutch | traanproductie |
| French | Larmoiement |
| German | Traenensekretion |
| Italian | Lacrimazione |
| Portuguese | Secreção lacrimal |
| Japanese | 流涙, ﾘｭｳﾙｲ |
| English | Tearing, lacrimation, lacrimation (physical finding), tear production, tearing, Lacrimation |
| Spanish | Lagrimeo |
| Czech | Tvorba slz |
| Hungarian | Könnyezés |
