Lacrimal System 2 Flashcards
Which tests test the quantity of tears produced?
Schirmer’s tear test – with topical anesthetic (≥ 15mm / 5 minutes)
Tear meniscus height at lower lid margin (0.75mm)
Phenol red thread (≥ 20mm / 15 seconds)
When do you perform Schirmer’s test and how?
Dry eye/ excessive watery eye
Anesthesia & wait for a minute Wipe excessive tears present Strip on the temporal side Why? record results at 5-minutes
Results of Schirmer’s test?
> 15 mm normal
What are the variations of normal?
Older individuals approx > 60 yrs
10 mm may be normal
Normal which is >15mm wetting of the paper after 5 minutes.
- Mild dry eye 14-9mm wetting of the paper after 5 minutes.
- Moderate dry eye 8-4mm wetting of the paper after 5 minutes.
- Severe dry eye <4 mm wetting of the paper after 5 minutes.
What affects Schirmer’s test?
Placement of the strip nasal versus temporal Age variation. Effect of anesthesia. Reflex tearing Subjective measurement
What are the 2 stages of secretion of electrolytes and water from lacrimal gland?
- Acinar secrete electrolyte composition that is very similar to that of plasma
- As fluid moves through ducts, ductal cells secrete fluid rich in KCL
Acinar cell electrolyte secretion is driven by Na+-K+-ATPase pumping Na+ out of the cell and K+ into the cell.
When are fluid rates hypertonic or isotonic?
low flow rate= fluid is hypertonic
If flow rate increases- fluid is isotonic
Lacrimal fluid contains?
Na+, K+, Cl-, HCO3-, Ca2+, and trace amounts of other ions in the same concentration as plasma, except K+ and Cl-, which are present in higher concentrations.
lacrimal gland is innervated by nerves that? What do they secrete?
- nerves that innervate secretory cells
- Peptide and steroid hormones
Nerves and peptide hormones stimulate secretion of electrolytes, water, and the regulated proteins. Steroid hormones stimulate the secretion of the constitutive proteins.
Which nerves are responsible for secretion of tears? Sympathetic or Parasympathetic?
Stimulation of sympathetic nervous system results in no change in tear secretion
Parasympathetic fibers of CN VII are responsible for secretion and are main contributor to tear film
Stimulation of nerves can be caused by?
sensory nerves at optic surfcace
bright light hotting optic nerves
acetylcholine, VIP, norephrine
Stimulation of sensory nerves in the ocular surface by mechanical, thermal, or chemical stimuli activates the parasympathetic and sympathetic nerves to stimulate lacrimal gland protein, electrolyte, and water secretion. Stimulation of the optic nerve by bright light also induces reflex lacrimal gland secretion. Acetylcholine and VIP are potent stimuli of regulated protein and electrolyte and water secretion. Norepinephrine stimulates protein secretion.
conjunctiva
mucous producing membrane lining ocular surface
along inside of upper and lower eyelid
provides passage for lacrimal gland and accessory lacrimal glands
ser mucous secreting tissue
What is Most immunologically active tissue of the external eye?
conjunctiva
What are 2 structural changes of conjunctiva and what are reactions provoked by?
- Follicle formation
- Palpillae formation
infections, allergy and inflammation
What do palpillae include?
eosinophils and meurtophils
How do you distinguish palpillae and folices?
blood vessels in their center
Palpillae are most commonly found in?
upper eyelid
What are follicles?
clear fluid filled pockets with macrophages and lymphocytes
blood vessels passing below or above them
Eosinophils and basophils only found in which 2 diseases?
vernal conjunctiva
Giant papillary conjunctivitis
When a contact lens has dislocated from the cornea and is not visible, it is most likely located in ?
superior fornix since it has the greatest depth
What are layers of conjunctiva?
epithelium
stroma
Describe epithelilium
Two to four layers of stratified epithelial cells
At limbus, where conjunctival epithelium is continuous with corneal epithelium, a local thickening occurs
Conjunctival epithelium (2-4 layers) has a different organization than the corneal epithelium (5-7 layers) – this difference begins at the limbus
What is immediately peripheral to limbus?
palisades of Vogt
Epithelium has thickened 4 or 5 fold
Increase in wing cells
What is role of stem cells?
continually contribute cells to cornea and serve as reserve source in the event of trauma
Goblet cells
Unicellular mucin-secreting glands (holocrine) within conjunctival epithelium
11 micron wide on average
Goblet cells are more frequent where?
In bulbar conj. goblet cells are sparse
More frequent in fornix and palpebral conj.
Stroma (Substantia Propia)
lies below conjuct. epithelium
Rich network of capillaries
Rich supply of nutrition is needed for regeneration of epithelium and formation of new goblet cells
Palpebral accessory lacrimal gland (of Wolfring) is located in deep fibrous layer (tarsal plate)
Where are mast cells found?
in adenoid layer of conjunctival stroma with other inflammatory cells
Mast cells
20µm in diameter
Cytoplasm filled by 30 to 100 metachromatic granules
Equivalent of circulating basophils
Responsible for immediate hypersensitivity reaction
Contain
several preformed chemical mediators of inflammation,
histamine and heparin
Lymphatics
Conjunctiva richly supplied with lymphatics
No lymphatics within globe itself*
Flow of lymph is generally in temporal direction toward lateral extremes of lid, eventually connecting with parotid node
Medial route leading to submandibular lymph glands
