Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
104 Cards in this Set
- Front
- Back
|
Functions of tears?
|
optical
protective: mechanical, antimicrobial, environmental lubricative osmotic nutritional |
|
|
Main layers of tears?
|
mucin, aqueous, lipid
|
|
|
Main types of mucin in tears
|
lubricative: goblet cell, gel-forming, MUC5AC
membrane spanning: epithelial cells, MUC1 and MUC4 |
|
|
Sources of aqueous layer?
|
lacrimal gland
accessory lac glands corneal and conj epi |
|
|
Afferent pw's producing tearing?
|
trigeminal
optic facial CN IX and X cortex (emotional) hypothalamus (mood changes) |
|
|
Symp pw to lac gland?
|
scg
internal carotid deep petrosal |
|
|
ps pw to lac gland?
|
lac nucleus of VII
nervus intermedius greater superficial petrosal vidian sphenopalatine ganglion |
|
|
Signal transduction pw's involved in lac gland secretion?
|
cholinergic agonist
alpha-1 adrenergic agonis cAMP-dependent P2Y2 pw epidermal growth factor tyrosine kinase pw |
|
|
electrolyte transport systems in lac gland?
|
bl: Na-K ATPase; Na,K,2Cl; Na/H exchanger; Cl/HCO3 exchanger
apical: Cl changes, AQP5 |
|
|
thickness of tears
|
mucin: 1 micrometer
aqueous: 7 micrometers lipid: 0.1 micrometer |
|
|
sources of lipid layer
|
meibomians
glands of zeis? |
|
|
functions of lipid layer
|
slow evaporation of tears
prevent tears from spilling over on lids prevent contamination of tear film seal apposed lid margins during sleep prevent maceration of lid margin skin provide smooth surface for refraction lower surface tenstion of tears |
|
|
mechanisms of drainage?
|
start: drainage system loadd with tear flud from prior blink
lids 1/3 closed: puncta occluded by contact of lid margins lids 2/3 closed: further closure squeezes canalicular and sac, forcing out tear fluid complete closure: canaliculi now nearly empth; partial vacuum formed as lids open lids 1/3 open: release of pressure on canaliculi as lids open; puncta still occluded lids 2/3 open: force of opening lids 'pops' apart puncta; tear fluid enters couple seconds later |
|
|
osmolality of tears?
|
318 mOsm/kg
0.97% NaCl increases in dry eye increases throughout day |
|
|
pH of tears?
|
7.45
lower in morning lower with CL wear lower in infants lower near meibomians |
|
|
what symptoms are reported with higher frequency for dry eye patients than for normal patients?
|
dryness, grittiness, burning
|
|
|
2007 internation dry eye workshop definition of dry eye
|
dry eye is multifactorial disease of tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to ocular surface. it is accompanied by increased osmolarity of tear film and inflammation of ocular surface.
|
|
|
tear tests
|
look at chart
|
|
|
source of tear proteins
|
look at chart
|
|
|
histo components of eyelids
|
skin
subQ areolar tissue orbicular oculi submuscular areolar with LPS tarsal plates septum orbitale muller's muscle conj |
|
|
III pw to muller's
|
first neuron from hypothalamus to ciliiospinal center of buge
pregang neuron to scg postgang neuron to V and III |
|
|
clinical manis of III nerve lesions
|
inability to look upwards, downwards, medially
eye down and out diplopia ptosis dilated nonreactive pupils lack of accommodation |
|
|
clinical manis of bell's
|
acute unilateral facial weakness
impaired ability to close eyes loss of normal fiacial creases and folds widening of palpebral aperture laxity of lower lid downturning of one side of mouth |
|
|
functions of 4 portions of orbicularis oculi
|
orbital
palpebral lacrimal (horner's) pars ciliaris (riolans) |
|
|
pseudo-graefe phenomenon
|
follows recovery from III paralysis
ptosis in abduction excessive widening in adduction misdirection of fibers intended fo rMR to LPS |
|
|
marcus-gunn phenomenon
|
jaw winking
ptosis is relieved when jaw is moved away from affected eye opening and shutting of eye on chewing pterygoid muscle linked to lps at cortical level |
|
|
glands of eyelids?
|
meibomians
zeis moll krause wolfring henle's glands |
|
|
dimensions of palpebral fissure
|
27-30 mm long
8-11 mm wide exophthalmometer: white 12-21 (16) and black 12-24 (18) |
|
|
ocular manis of grave's
|
dalrymple's
von graefe's exophthalmos extraocular muscles TAO (thyroid associated opthalmopathy) |
|
|
causes of blepharoptosis?
|
congenital defect in III
myasthenia gravis horner's aponeurotic ptosis mechanical ptosis |
|
|
clinical manis of horner's
|
ptosis
pupillary abnomalities: miosis, anisocoria, dilation lag facial anhydrosis |
|
|
collier's sign
|
widening of palpebral fissure due to increase in tonus in lps as result of diseases affecting pretectal region of brain, particularly posterior commissure
|
|
|
muscle reponsible for lid elevation? innervation? assisted by what smooth muscle?
|
lps
III muller's |
|
|
muscle closes lid? innervation by what cranial nerve? differences bw palpebral and orbital portions?
|
orbicularis oculi
VII location, response time, function, chronaxie: duration of tim current must flow at 2x threshold in order to excite tissue |
|
|
normal lid movements during closure?
|
nasal angle remains immobile
temporal angle moves nasally and downward upper lid moves down and nasal lower lid moves down and nasal eye moves back 1.5 mm |
|
|
timing of a blink?
|
closing: 82.1 msec
opening: 175.1 msec total blink time: 257.9 max closing velocity: 18.7 cm/sec max opening velocity: 9.7 cm/sec pupils covered: 0.1 sec |
|
|
rate of spontaneous blinking?
|
12-15 blinks/min
increases with conversation, dry eye, wind, exposed ocular surface decreases with reading, anesthesia, artificial tears, downward gaze |
|
|
what are lid saccades?
|
abrupt vertical movements of upper eyelid that accompany voluntary vertical changes in direction of gaze
due to passive downward forces and relaxation of LPS (no contraction of orbicularis oculi) |
|
|
histo of cornea
|
epithelium: surface, wing, basal
bowmans stroma descemet's endothelium |
|
|
function of keratocytes
|
embryonic production of collagen fibrils and intercellular matrix
maintain integrity of fibrils and matrix by steady turnover (control turnover of matrix proteins) synthesis and storage of proteins (protocollagen, PG precursors) |
|
|
function of matris metalloproteinases of corneal stroma
|
matrix turnover, repair, and degradation
collagenases: degrade type I II III stromelysins: proteoglycans, fibronectin, laminin gelatinases: gelatin, types IV V VII |
|
|
major proteoglycans of corneal stroma and function
|
keratan sulfate and dermatan/chondroitin sulfate PG
source of imbibition pressure spaces molecules bw collagen fibers, control fiber diam and corneal clarity |
|
|
density of corneal endothelium?
|
2500 cells/sq mm centrally
3650 cells/sq mmy peripherally 4000 cells/sq mm at birth need 400-700 cells/sq mm for normal function |
|
|
index of refraction of cornea?
|
gladstone and dale law of combined refractive index for composite material
Ms = McDc + MiDi = 1.374 Ms = refractive index of stroma Mc= n of collagen (1.55) Mi=n of ground substance (1.345) Dc = volume fraction of collagen (.15) Di = volume fraction of grown substance (.85) |
|
|
index of refraction of corneal stroma related to water content
|
refractive index of stroma is related to its thickness by:
Ms = 1.5581 - (1.89T - 0.189( / (8.75T - 0.205) Ms decreases with edema |
|
|
maurice's lattice theory
|
collagen fibrils arranged in regular lattice, like stack of diffraction gratings. when spacing bw tfibers is equal to or less than wavelength of incident light, only the zero-order beam passes trhough and scattered light is suppressed by destructive interference
|
|
|
relationship bw corneal thickness and hydration?
|
linear relationship bw thickness and hydration of stroma
H = 7.0q - 0.64 3.5 gm H20/gm dry material |
|
|
swelling pressure?
|
mechanical load per unit area required to maintain a submerged tissue slab at fixed water content
|
|
|
relationship bw swelling pressure and imbibition pressure?
|
IP = IOP - SP
imbibition pressure is negative pressure in stroma, attempting to draw water in increasing swellling pressure causes a decrease in hydration |
|
|
ion transport systems of corneal epithelium
|
na-k ATPase
na,k, 2cl cotransport cl channels (cAMP) K channels (cGMP) apical: na/h antiporter, na/HCO3 cotransporter, cl/HCO3 antiporter |
|
|
what are aquaporins
|
family of water channel proteins located in cell membranes of animals, plants, and bacteria
consists of 6 transmembrane segmetns form a water change 20angstoms by 3angstroms so water molecules pass in single file 3 billion water molecules/s/channel |
|
|
ion transport systems of corneal endothelium
|
Na-K ATPase (stroma)
pH regulation and HCO3 transport: Na/H exchanger (stroma); Cl/HCO3 exchanger (stroma); Na/2HCO3 cotransporter (stroma); carbonic anhydrase (aq) chloride transport: na,k,2Cl cotransport (stroma); cAMP-dependent cl-permeability (aq); calcium-activated cl channels (aq) |
|
|
source of glucose to all layers of cornea
|
aqueous
88% of glucose ends up as lactic acid through glycolysis |
|
|
oxygen and cornea
|
sources: tears, palpebral conj, limbal bvs, aqueous
air: 21% oxygen, 155 mmHg lid closure: 57 mmHg aqueous: 55 mmHg |
|
|
some methods to assess oxygen supply to cornea
|
Dk/t
EOP stromal pH PRPH |
|
|
minimum precorneal oxygen tension needed to avoid physiologic changes in cornea
|
daily wear: 24 x nm...; 9.9%
extended wear: 87 nm...; 17.9% extended wear with 8% edema: 34 nm...; 12.1% |
|
|
how are nerves that supply sensory innervation to cornea organized?
|
stromal plexus: 70-80 bundles from perilimbal nerve ring; axons oriented radially; dichotomoous branching
epithelial plexus: sub-basal epithelial plexus and collateral branches |
|
|
what sensations are detected by cornea
|
mechanical
thermal chemical |
|
|
what are some differences bw vasculatures of choroid and retina
|
choroid: abrupt transition from arterior to cap; wide cap diam; large genestrations; few pericytes; extensive anastomoses; high blood flow
retina: narrow caps; thick bm; zonular occludens bw endo cells; pericytes/endo 1:2; segments, end arteral |
|
|
how does photdynamic therapy of ARMD work?
|
a photosensitivize agent (Verteporfin) is injected intravenously
it is activated with a laser the causes selective damage of tisusue that contains dye through free radicals |
|
|
how do macugen (Pegptanic) and lucentis (ranibizumab) differ in their mechanism of action
|
the are both VEGF inhibitors
macugen binds to a inhibits VEGF 165 (Responsible for neovasc in eye) lucentis is an anti-BEGF ab fragment that binds all isoforms of VEGF |
|
|
what is necessary for wet ARMD to occur
|
decrease choroidal blood supply to macula
breaks in bruch's mem healthy neuroretina |
|
|
describe blood supply to optic nerve
|
short PCAs: circle of Zinn, large choroiddal arts from SPCA
CRA pial arteries |
|
|
what should you know about hemodynamics
|
perfusion pressure is difference in pressure bw areteries and veins (70 - 15 = 55 mmHg)
poiseuille's law: Q=(pi*deltaP*r^4) / (8vl) Q = delta P / R |
|
|
what are some techniques used to evaluation ocular blood flow
|
fluorescein angiography
indocyanine green angiography laser doppler velocimetry color doppler imagin blue field entoptic phenomena |
|
|
major mechanisms of autoregulation of blood flow?
|
a reduction in perfusion pressure results in vasodilation so blood flow remains constant
myogenic: vascular smooth muscle contracts in response to stretch and relaxes with reduction in tension metabolic: accumulation of carbon dioxide causes vasodilation and oxygen prodcues vasoconstriction |
|
|
stuctures are in in gonioscopy in grade IV angle
|
iris
cb scleral spur tm: schlemm's schwalbe's line |
|
|
functios of ciliary body
|
secretion of AH
nourishes lens and cornea provides muslce power for accom contributes to control of aqueous outflow forms part of vitreous base role in attachmnet and synthesis of zonular fibers source of vitreous components |
|
|
components of BAB
|
zonular occludens of NPCE
zonular occludens of vasc endothelial cells of iris capillaries |
|
|
what are ocular effects of stimulation of muscarinic receptors of ciliary body
|
vasodilation/congestion of ciliary body and iris
breakdown of BAB, resutling in cells and flare in ant chamber accommodation increase travecular aqueous outflow reduction in uveoscleral outflow |
|
|
what are ocular effects of stimulation of adrenergic receptors of ciliary body
|
alpha 1: vasoconstriction, mydriasis, increase outflow resistance
alpha2: vasoconstrction, reduct in aq inflow, reduction in BAB permeability beta 1: vasodilation beta 2: reduction in accommodation, increase aq production, increase outflow |
|
|
gibbs-donnan effect?
|
there should be more positivie ions that remain with the negatively charged proteins and more negative ions in the aqueous
|
|
|
what ion transport systems are involved in aqueous prodcution
|
NA-k ATPase
na,k,2cl cotransport na/h and cl/hco3 antiporters carbonic anhydrase II and IV |
|
|
what is mechanism of action of carbonic anhydrase inhibitors treatment of glaucoma
|
CAI reduce formation of H and HCO3
this reducfes exchange for Na and Cl by the Na/H and Cl/HCO3 exchangers less Na an dCl enter PCE and NPCE Na,K, 2Cl brrings these ions in the cells rather than into the aqueous |
|
|
what components of aqueous are in high conc in aqueous than in plasma
|
chloride
lactate ascorbate amino acids |
|
|
what is pupillary block glaucma
|
flow of aqueous is blocked from posterior to anterior chmber due to pupillary border of iris being in contact with lens
|
|
|
describe convection currents of ant chamber
|
circulates the aquous closer to the cooler, avascular cornea downaward and then aqueous near th warmer vascular iris upward
|
|
|
what is comp of trabecular meshwork
|
central core of collagen (I and III)
intermixed with heparin sulfate PG, fibronectin, laminin surrounded by single layer of endo cells |
|
|
what is purpose of gian vacuoles in inner wll of sclemms
|
release aqueous into schlemms
|
|
|
what is uveoscleral outflow? how much of total aqueous exts via this pathway
|
aquous passes through iris root, anterior face of ciliary muscle, to suprachroidal space
10-30% reduced in older patients |
|
|
what factors might redce aqueous outflow in chronic open angle glauc
|
chanage in GAGs in tm
increase in proteins (mycilin) increase in collage, thickening of lamellae increase in tm volume loss of tm endo cells fusion of trabecular lamellae reduction in antioxidant activiity reduction in pores in vacoles of schlemm's canal |
|
|
how do corneal thickness, curvature, and biomechanical properties influence measurement of IOP?
|
iop overestimated in thick corneas
iop overestimated in steep corneas highe r corneal hysteresis is found at lower levels of IOP central corneal thickness effects are more pronounced in eyes with stiffer corneas |
|
|
what is axonal transort
|
transport substances to axon from cell body
transport byproducts from axon to cell dependent on adequate blood supply dependent on presence of intactmicrotubules for movement of materials |
|
|
what is mechanical theory of glaucoma
|
increase IOP compresses axons
reduction in transport of BDNF compression of muller cells reduction in metabolism of glutamate |
|
|
wha tis vasc theory of glaucoma
|
ischemia
reduction in metabolic activity failure of Na/K ATPase increase intracells sodium increase intracells calcium depolarizeation of cell membran increase glutamate release accumulation as excitotoxin |
|
|
what causes glaucomatous optic neuropathy
|
ganglion cell death
BDNF deprivation (leads to apoptosis) excitotoxicity (high glutamate acting on NMDA receptors; high Ca an dNa levels) ischemia inflammation ROS |
|
|
what are some ocular risk factors for glaucoma
|
iop; size of cup; shape of cu' asymmetrical c/d ratios; change in c/d with time; positiong of cup; rim of cup; depth of cup; disc hemorrhages; peripapillary changes; changes in appearance over time; optic atrophy; nfl changes; visual field defects; blood flow in II
|
|
|
where is aqp0 found and why is it important
|
50% of the total proteins o flens fiber cell membrane
substantial fow of water enters and leaves the lens this transports metabolites to and from deeper lens fiber cells |
|
|
what are some unique characteristics of lens fiber cells
|
withdraw from cell types
elongate greatly express large amounts of crystallin have several specilizations of their plamsa membranes degrade organelles |
|
|
water content of cornea, sclera, lens capsule, lens cortex, lens nucleus
|
cornea: 78%
sclera: 68% lens capsule: 80% lens cortex: 68% lens nucleus: 63% |
|
|
what is protein content of lens
|
33%
beta>alpha>gamma crystallin 5% urea-soluble (cytoskeletal prots) 2% detergent-soluble (mem prots) high concentration of amino acids high levels of taurine |
|
|
in lens, what is rate-limiting factor in glucose metabolism by glycolytic pw
|
low levels of hexokinase
the lens derives much of its energy from glycolysis bc the oxygen tension are the lens is low oxidative phosphorylation generates free radicals |
|
|
what is the role of glutathione in the lens
|
protection of thiol groups on prots
glutathione forms disulfide bonds with oxidaize SH groups of prots glutathion-proteindisulfides are reduced by 2nd moleculr of glutathione wtih thioltransferase |
|
|
what are some mechanisms for the formation of diabetic cataracts?
|
aldose reductase and the polyol pw
oxidative stress covalent modification of lens proteins |
|
|
what causes glaucomatous optic neuropathy
|
ganglion cell death
BDNF deprivation (leads to apoptosis) excitotoxicity (high glutamate acting on NMDA receptors; high Ca an dNa levels) ischemia inflammation ROS |
|
|
what are some ocular risk factors for glaucoma
|
iop; size of cup; shape of cu' asymmetrical c/d ratios; change in c/d with time; positiong of cup; rim of cup; depth of cup; disc hemorrhages; peripapillary changes; changes in appearance over time; optic atrophy; nfl changes; visual field defects; blood flow in II
|
|
|
where is aqp0 found and why is it important
|
50% of the total proteins o flens fiber cell membrane
substantial fow of water enters and leaves the lens this transports metabolites to and from deeper lens fiber cells |
|
|
what are some unique characteristics of lens fiber cells
|
withdraw from cell types
elongate greatly express large amounts of crystallin have several specilizations of their plamsa membranes degrade organelles |
|
|
water content of cornea, sclera, lens capsule, lens cortex, lens nucleus
|
cornea: 78%
sclera: 68% lens capsule: 80% lens cortex: 68% lens nucleus: 63% |
|
|
what is protein content of lens
|
33%
beta>alpha>gamma crystallin 5% urea-soluble (cytoskeletal prots) 2% detergent-soluble (mem prots) high concentration of amino acids high levels of taurine |
|
|
in lens, what is rate-limiting factor in glucose metabolism by glycolytic pw
|
low levels of hexokinase
the lens derives much of its energy from glycolysis bc the oxygen tension are the lens is low oxidative phosphorylation generates free radicals |
|
|
what is the role of glutathione in the lens
|
protection of thiol groups on prots
glutathione forms disulfide bonds with oxidaize SH groups of prots glutathion-proteindisulfides are reduced by 2nd moleculr of glutathione wtih thioltransferase |
|
|
what are some mechanisms for the formation of diabetic cataracts?
|
aldose reductase and the polyol pw
oxidative stress covalent modification of lens proteins |
|
|
what is the composition of vitreous
|
type II collagen
hyaluronic acid amino acids, glycoproteins, and albumin electrolytes ascorbic acid |
