II. Physiology

  1. Layers of tears
    1. Inner: Mucin produced by goblet cells of Conjunctiva
    2. Mid: Aqueous layer by lacrimal glands (90% of tears)
      1. Water (largest component)
      2. Glucose
      3. Lysozyme
      4. Lactoferrin
      5. Secretory Immunoglobulin (IgA)
    3. Outer: Lipids produced by meibomian glands
      1. Prevents evaporation
  2. Function of tears
    1. Maintains smooth eye surface for visual clarity
    2. Lubricates eye surface to facilitate blinking
    3. Barrier to infection
  3. Function of Blinking
    1. Normally, blinking occurs every 5 seconds
    2. Spreads tear film and directs toward lacrimal duct

III. Causes: Increased Tear Secretion

  1. Emotion
  2. Foreign body irritation
  3. Corneal Ulcer
  4. Conjunctivitis
  5. Coryza
  6. Measles
  7. Hay fever
  8. Cluster Headache (unilateral tearing)
  9. Toxin
    1. Chronic Iodine toxicity (Iodism)
    2. Chronic bromide toxicity (Bromism)
    3. Arsenic

IV. Causes: Absent or decreased Tear Secretion

V. Causes: Obstruction of the Lacrimal Ducts

  1. Dacryocystitis
  2. Lacrimal calculus
  3. Congenital obstruction
  4. Cicatrix
  5. Eyelid Edema

VI. References

  1. Rheinstrom in Yanoff (1999) Ophthalmology, Mosby, 14.1

Images: Related links to external sites (from Bing)

Related Studies

Ontology: Lacrimation (C0423153)

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