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83 Cards in this Set
- Front
- Back
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In what layer do cells proliferate in the cornea?
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basal layer
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What type of movement is seen with cell proliferation?
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centripetal movement
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where is the site of stem cells?
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limbus
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Which cells are shed, superficial or basement?
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superficial
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What are two major functions of the cornea epithelium?
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barrier
remove excess fluid from stoma |
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What is the first step of wound healing of the cornea?
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mitosis ceases
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What is step 2 in wound healing?
a. mitosis ceases b. cells at edge retract and thicken losing attachments c. cells enlarge, migration occurs |
b. cells at edge retract and thicken losing attachements
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When does mitosis resume following wound healing of the cornea?
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after the wound closes
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How fast does a 6mm wound close?
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48 hours
60-80micrometers/hour |
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true or false
Proteins synthesis is decreased during cell migration. |
false
protein synthesis, increases during cell migration |
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What proteins are involved in wound healing?
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vinculin
CD44 |
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True or false
There is an increase in glycogen levels in migrating cells. |
False
decrease in glycogen levels in migrating cells -energy consuming process |
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corneal epithelial cells depend on what type of glyocolysis?
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anaerobic glycolysis
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What is the most common type of chemical corneal burn?
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mineral acids and alkalis
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What do alkalis immediately cause?
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opacification
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Patient has a healing wound in their cornea, there is an accumulation of fibroblasts and keratocytes. In what layer is the would healing?
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Stromal
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In a severe chemical corneal burn, what would be an expected finding within the first 2 days of the event?
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PMN lymphocytes on the site, initiating inflammation
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Patient A comes in with a wound on the out edge of their cornea, patient B has a wound on the center of their cornea. Which patient would you expect the wound to heal more quickly in?
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patient A
closer to the limbus, where stem cells are located |
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A patient comes in with trauma to the deepest layer of their cornea. How do you expect this injury to heal?
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cells of the endothelium will spread out and cover defect
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What is the volume of tear film?
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7-9microliters
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What are two factors that affect drug concentration?
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reflex tearing--dilutes drug
increased protein--reduced bioavailability |
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Which type of molecules are most apt to penetrate the corneal epithelium, hydrophobic/hydrophilic molecules?
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hydrophobic molecules
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The stroma of the cornea is hydrophilic/hydrophobic?
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hydrophilic
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A patient comes in with loss to their corneal epithelium, which type of molecules that were previously less apt to penetrate, can now penetrate with more ease?
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hydrophilic drugs
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Which solute should be used to penetrate the stroma?
a. 250,000 MW b. 600,000 MW |
a. 250,000 MW
stroma allow diffusion of solutes less than 500,000 MW |
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A doctor wants to increase penetration of a drop in a patient. What two factors should they think about?
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want to increase contact time
-viscous substances -occluding lacrimal drainage system |
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What is a common preservative pharmacologic drugs?
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BAK
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How is BAK good for the drugs?
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breaks down bacterial cells walls
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What is a negative side effect of BAK?
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inhibits corneal epithelial wound healing
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Xerophthalmia is caused from deficiency of what?
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Vitamin A
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Keratinization due to vitamin A deficiency, is seen in what pathology?
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xerophthalmia
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What is vit A needed for the production of?
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mucin
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What is the major source of oxygen in the cornea? second source?
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1. tears--155mmHg
2. aqueous -- 40mmHg |
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When a person is asleep the major supplier of oxygen to the cornea is from where?
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superior palpebral conj.
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True or false
The stroma requires more oxygen than the epithelium. |
False
-oxygen demand of the epithelium is 10x that of the stroma |
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What is the major source of glucose for the cornea?
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aqueous humor
glucose, aa, vitamins |
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What condition would reduce oxygen supply to the cornea?
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CL wear
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What product of hypoxic conditions in the cornea promotes edema? In what layer?
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pyruvate converted to lactate--diffused through stroma--promotes edema
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Edema in the stroma can have what symptoms?
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halos, glare, decreased contrast sensitivity
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How is lactate removed from the cornea?
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diffusion across stroma and endothelium into aqueous.
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What prevents lactate from entering the tear film?
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epithelial cells
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What occurs when there is an accumulation of lactate? And alters what structure?
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metabolic acidosis
alters endothelium |
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To what point is the cornea resilient to changes in oxygen levels?
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resilient until it drops below 25 mmHg
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Which type of lenses allow more oxygen underneath, gas permeable, SCL?
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gas permeable lenses
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What are expected findings in patient who extend the wear of their CL?
a. increased rate of mitosis b. reduced oxygen and glucose uptake c. more desmosomes d. higher risk of microbial keratitis |
b. reduced oxygen and glucose uptake
d. increased exposure time to microbial keratitis -decreased rate of mitosis -fewer desmosomes |
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Fewer desmosomes, cause increased susceptibility to ______.
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erosions and abarsions
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What is the source of tears?
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lacrimal gland
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Is tear fluid hypertonic/hypotonic and low secretion rate?
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hypertonic
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tears are composed of?
a. protein b. electrolytes c. water d. all of the above |
d. all of the above
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What drives production of tears?
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Na-K-ATPase
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How is water added to tears?
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aquaporins
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True or false
Tears have secretory IgA. |
true
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Sensory nerves for tear secretion are located?
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cornea and conj
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What are effects of CL on the ocular surface?
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-tear film stagnation
-production altered -deposits on lens -alters blink rate |
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What is a good diagnostic test for dry eye?
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TBUT
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What are symptoms of dry eye?
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burning, itching, watery red eyes, FBS
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What is a common ocular sign of dry eye?
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SPK
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Contrast differences between aqueous tear deficiency (ATD) and evaporative tear deficiency (ETD).
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ATD- body not producing enough tears at any time
ETD- quality of tears is not good. They don't stick on the surface as long as they should |
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Which type of tear production produces steady amount of tears all the time?
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basal
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A patient comes into the office with symptoms of epiphoria, what is this due to?
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obstruction of the drainage system
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What is epiphora
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excessive watering of the eye
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What test can be used to determine an obstruction of the lacrimal system?
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Jones dye test 1
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Water in the stroma promotes?
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loss of transparency
-displaces collagen -changes refractive index-->clarity |
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The stroma scatters how much light?
a. 10% b. 15% c. 20% d. 5% |
a. 10%
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What substance, helps to interact with collagen and provide proper spacing to the cornea?
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lumican
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All cornea dystophies are
a. bilateral b. symmetric c. unilateral d. neither of the above e. A and B |
A & B
bilateral and symmetric |
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What characterizes granular dystrophy?
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microfibril deposits
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What accumulation does lattice dystrophy occur from?
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amyloid accumulation
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Macular dystrophy results from abnormal synthesis of what?
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keratin sulfate
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What two factors prevent swelling of the stroma?
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barrier of endothelium
endothelial pump |
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Loss of which factor would cause greater effect to stromal swelling?
a. disrupted endothelium b. impaired endothelial pump |
a. disrupted epithelium
swelling at 127 micrometer/hr -impaired pump --swelling at 33micrometers/hr |
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What causes the stroma the have a tendency to absorb water?
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proteoglycans
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Where does the endothelial pump move fluid from?
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anterior chamber
provides nutrients (glucose, aa) |
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The stroma swells in cooler/warmer temps.
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cooler
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What are two pumps of the endothelium in the cornea?
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Na-K pump
Na-H exchange |
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water follows _____.
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ions
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what membrane is the Na-K pump located on?
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basolateral membrane of endothelial cells
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What effect does Ouabain have on the cornea?
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inhibition of the Na-K pump, stops sodium transport, cornea swells
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Corneas with guttata, have an increased/decreased number of pumps. Why?
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increased
counteract the leaky barrier |
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Na-H exchanger, transports H into what?
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extracellular fluid
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What maintains the gradient for the Na-H exchanger?
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Na-K- pump
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bicarbonate is made by carbonic anhydrase and pumped into the ______.
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aqueous
from stroma to aqueous. |
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aqueous humor is +/- to stroma.
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