Flashcards in B12 Deck (164):
For someone with glaucoma, is the AH flow in and out equal?
Is the uveoscleral pathway the minor or major route /pathway in AH outflow?
Describe how AH flows in the uveoscleral pathway
AH enters the connective tissue between the ciliary muscle bundles, through the suprachoroidal space, and out through the sclera
Is the uveoscleral outflow affected by IOP?
The outflow rate through the uveoscleral route tends to ____ with age
What are the 3 layers of the TM?
The corneoscleral pathway is considered the ____ route
Describe the flow of AH in the corneoscleral pathway
AH passes through the TM, across SC, into its lumen
and into draining collector channels, aqueous veins and episcleral veins
Is the corneoscleral pathway IOP independent or dependent?
An acute rise in EVP results in a ___ ratio of increase IOP
When the aqueous outflow pump receives power from transient increases in IOP such as occur in systole of the cardiac cycle during blinking and during eye movement
In the corneoscleral pathway an increase of IOP causes drainage decrease or increase?
What will make schlemm's canal collapse on itself and obstruct into the venous system?
Constant, very high IOP
What 2 fluid compartments is the TM suspended between?
And are these at the same or different pressures?
Anterior chamber and schlemms canal
They have different pressures
What 5 things can cause AH outflow obstruction through occlusive angles?
-pigment dispersion glaucoma
In humans, ___% of the resistance to the AH outflow is localized to the TM, and ___% occurs beyond schlemm's canal
75% to TM
25% to SC
Can an injury to the TM cause an obstruction of AH outflow?
It sure can
What are the 3 long term influences on IOP?
What are the 6 short term influences on IOP?
-lid and eye movement
-food and drugs
T/F: IOP is under hereditary influence
Are IOP's different between men and women in the ages of 20-40?
Nope, they are equal
In older age groups, do men or women have a increase in mean IOP?
Myopic people have a ____ incidence of open angle glaucoma
T/F: there is a positive correlation between IOP and both axial length and increasing degrees of myopia
Does IOP change throughout the day?
When is the peak of IOP?
In the morning
T/F: IOP decreases changing from sitting to the supine position
False, it increases
Patient with systemic hypertension will have a greater IOP increases after ___ min in supine
Does blinking raise IOP?
Yes, by 10mmHg
How much does hard lid squeezing raise IOP?
As much as 90mmHg
In what gaze is there in increase in IOP in normal individuals?
Thicker corneas cause artificially ____ readings
Thinner corneas cause artificially ___ readings
T/F: patients with HIV have lower than normal mean IOPs
Are IOPs increased or decreased during pregnancy?
Does exposure to cold air increase or decrease IOP? And why
Decreases, because episcleral venous pressure is decreased
Does reduced gravity cause an increase or decrease in IOP?
Does alcohol increase or decrease IOP?
Does caffeine cause an increase or decrease in IOP?
Slight transient rise
Does smoking increase or decrease your IOP?
Do heroin and marijuana increase or decrease IOP?
Does LSD increase or decrease IOP?
Do corticosteroids increase or decrease IOP?
What it the major pathway of AH outflow?
What AH pathway is IOP independent?
Does AH pass through the SC in the uveoscleral pathway?
An acture increase in EVP by 4mmHg will theoretically cause an increase in IOP by?
T/F: thicker cornea can cause an artificially high IOP reading
What is the largest organ of the eye?
The vitreous transmits ____ of light
The vitreous is located between the ___ and the _____
Crystalline lens and the retina
What are the 3 zones of the vitreous?
Outermost zone (vitreous cortex)
Center zone (cloquets canal)
Intermediate zone (inner to the cortex and surrounds the center canal)
The vitreous is attached to what part of the retina?
Inner limiting membrane
What attaches the vitreous to the ILM?
Anchoring fibrils and the membrane limitans interna (MLI)
What 3 things is the MLI composed of?
-fusing point of the anchoring fibrils
The vitreous base is located at the ____
The vitreous base is ___mm broad annular region
The vitreous base is attached to the ___ and the ____
Nonpigmented epithelium of the ciliary body and the internal limiting membrane of the peripheral retina
What is the strongest attachment to the vitreous?
Does the vitreous base decline with age?
A vitreous attachment that is between the posterior surface and the anterior face of the vitreous
Does the wiegers ligament decline with aging?
The vitreous attached around the edge of the optic disc?
Does wiegers ligament have a firm or medium attachment?
Does the peripapillary adhesion have a firm or medium vitreal attachment?
Is the macular and peripheral retinal attachment firm, medium or weak?
What are the 4 vitreous attachements?
-macular and peripheral retinal attachment
The gel structure of the vitreous results from the arrangement of collagen fibrils suspended in a network of ______
What are the 3 vitreal cells?
What 2 things does hyalocytes synthesize?
-glycoproteins from the collagen fibrils
What do fibroblasts synthesize?
What are the 4 functions of the vitreous?
-support for retina
What is the strongest vitreal attachment?
Does the peripapillary adhesion decline with age?
What is the major composition of the vitreous?
What are the 5 main vitreous components?
-type 2 collagen
What makes up the majority of the vitreal cells?
What are the 5 support functions of the vitreous?
-prevents retinal detachment
-reduced mechanical deformation
-supports the lens during trauma
-decreases transmission of light at 300-350nm
-mechanical support of limited significance
What is the most common pathological condition of the vitreous?
If you have macular edema will you have increased or decreased osmotic pressure?
____ traction can cause macular edema
T/F: Diffusion is slow and bulk flow is limited across the vitreous
This prevents topically administered substances from reaching the retina and prevents substances in the blood stream from reaching the vitreous center
What vitamin type does the vitreous have a lot of?
In the case of a vitrectomy or full PVD what 3 things could occur?
-nuclear sclerotic cataract (due to oxidative damage)
-reduce neovascularization in the retina (due to reduced VEGF)
-neovascular glaucoma (due to no barrier)
Does the vitreous have high or low concentration of structural macromolecules and soluble proteins?
What 2 pathologies can block the transparency of the vitreous?
What causes gel structure of vitreous?
HA provide spacing and support for the collagen
What substance maintains high concentration in vitreous and can be utilized to protect the retina from metabolic and light-induced free radicals?
What substance products the retina from oxidative damage?
What are vitreous functions?
A. Provides a transparent medium
B. Cushion the globe
C. Storage area of ions and nutrients for the retina and lens
All of the above
What 4 things make up the transparency of the vitreous?
-Low concentration of structural macromolecules
-Low concentration of soluble proteins
-Specific collagen/HA configuration
A disorder of the tear film caused by tear deficiency
or excessive tear evaporation that causes damage to the interpalpebral ocular surface and is associated with symptoms of ocular discomfort
Dry eye syndrome
What are the 3 functions of the tear film?
- Provides a smooth refractive surface for clear vision
- Maintains the health of corneal and conjunctival
- Acts as the 1st line of defense against microbial
What are the 3 layers of the tear film?
High molecular weight glycoproteins that are heavily glycosylated
The mucous layer o the tear film is between what 2 layers?
Epithelial layer and aqueous layer
The mucus layer of the tear film is composed mostly of what kind of substance?
What are the 2 different types of mucin?
-membrane associated mucin
Type of mucin: A dense barrier to pathogen penetrance, at the epithelia cell-tear film interface
Membrane associated mucin
Type of mucin: act as “cleaning crew”, moving through the tear fluid and collecting debris that can be removed via the nasolacrimal duct during blinking
What are the 4 functions of the mucus layer in the tear film?
-Maintain water on the surface of the eye
-Interacts with tear lipids layer to lower surface tension thereby stablizing the tear film
-Provides lubrication for eyelid movement
-Traps exploited surface cell, foreign particles and bacteria
What are the 2 sources to the mucus layer?
-goblet cells of conjunctiva
-squamous cells of the cornea and conj
What type of neural control of the mucus layer increases the mucus secretion?
What 3 nerves are sources for the mucus layer of the tear film?
The aqueous layer of the tear film is composed of what 7 things?
-peptide growth factors
What are the main contributors to osmolarity of the tear film?
Na and Cl
Does osmolarity increase or decrease with dry eye?
What are the 2 ions that are important for maintaining corneal epithelium health?
K and Ca
What are the 4 important electrolytes of the tear film?
What peptide growth factors are in the aqueous layer of the tear film?
What acts as a buffer to maintain constant pH and contributes to maintaining epithelial integrity of the ocular surface?
The buffering system allows the eye to tolerate the ophthalmic solution varying in pH from ___ to ___ in the aqueous layer
3.5 to 10.5
During sleep, does pH increase or decrease?
Does pH increase or decrease in dry eye due to osmolarity increasing
What are the 3 functions of the aqueous layer of the tear film?
-strong defense system protecting it from invaders
-peptide growth factor and vitamin A regulate epithelial proliferation, motility, and differentiation
What type of tearing does the main lacrimal glands deal with?
Reflex and emotional tearing
What type of tearing does accessory lacrimal glands deal with?
What types of neural control does the main lacrimal glands receive ?
Parasympathetic, sympathetic, and sensory
What type of neural control do the accessory lacrimal glands receive?
They aqueous layer is between what two layers?
Mucous layer and lipid layer
What is the lipid layer of the tear film composed of?
What are the 2 phases of the lipid layer of the tear film?
1.) polar surfactant phase
2.) nonpolar phase (overlaid polar phase)
The polar surfactant phase is primarily composed of what 2 things?
-phospholipids and glycolipids
This phase acts as a surfactant between the hydrophilic aqueous mucin layers and the thick, nonpolar lipid layer
Polar surfactant phase
What 3 things make up the nonpolar phase of the lipid layer?
This phase provides the air-tear film interface and is responsible for retarding evaporation
What are the 4 functions of the lipid layer of the tear film?
-Major barrier to evaporation from the ocular surface (slows evaporation)
-Provides stability to the tear film through interaction with aqueous-mucin phase
-Provides a smooth optical surface for the cornea
-Acts as a barrier against foreign particles
What is the main sources to the lipid layer of the tear film?
What 2 other sebaceous glands assist the meibomian gland in the lipid layer?
Zeis and moll
Glycocalyx is produced by what? And what do they do?
Corneal epithelial surface cells
They help bind mucins onto the corneal surface
What 4 tests are used to evaluate tear secretion?
-phenol red thread test
What 4 tests are used to evaluate tear film stability?
-ocular protection index
What 3 tests are used to evaluate tear film osmolarity?
-tear film osmolarity
What 2 tests are used to evaluate the lipid layer of the tear film?
What 3 tests are used to evaluate the ocular surface of the tear film?
What is the largest category of dry eye?
Tear deficient dry eye
If there is a disorder in lacrimal gland function, what type of dry eye will be induced?
Tear deficient dry eye
A type of dry eye that results in either reduced aqueous tear production and tear flow, or a failure to transfer lacrimal fluid into the conjunctival sac
Tear deficient dry eye
A type of dry eye where the lacrimal gland function is normal and the volume of lacrimal fluid is sufficient to cover the ocular surface, but another tear abnormality exists that leads to increased tear evaporation.
Evaporation dry eye
What is the resource in generating mucins in tear film?
Goblet cells and squamous cells of cornea and conj
What electrolytes are the main contributors for osmolarity of tear film?
Na and Cl
What is the resource of generating the aqueous layer in the tear film?
Main lacrimal gland and accessory lacrimal gland
What later is the major barrier to evaporation from the ocular surface?
Does the anterior chamber depth increase or decreased with age?
What type of cataract has more of an effect on reducing anterior chamber death?
Is uveoscleral outflow increased or decreased wth aging?
Reduced but there is an increase in the amount of connective tissue in the ciliary muscle
What are the 4 aging changes in the anterior chamber?
- reduced anterior chamber depth
-reduced uveoscleral outflow
-accumulation of extracellular matrix plaque in TM
-increased outflow resistance in the TM and SC
T/F: the gel structure becomes more liquefied with aging
What is the most common cause of a PVD?
The breakdown of the vitreous gel and aggregation of collagen fibrils due to increase of liquid portion
Change of gel structure is most likely to occur in the periphery or the center?
Aggregation of collagen fibrils
What are the 5 aging changes of the lacrimal system?
-goblet cell population may decrease
-reduced tear reflex secretion
-change in composition of the meibomian secretion
-increase of plugged meibomian gland pores
-reduced lacrimal drainage capacity
How does B-lysine function to destroy a pathogen?
Acts like a detergent and pokes hole in the cell membrane releasing bacterial cytoplasm to the external environment
This enzyme binds to the microbial cell membrane, embeds in the membrane, and forms pore like membrane defects that allow the efflux of ions and nutrients
Does a Defensin function like a detergent?
Structurally similar chemicals that have similar activities to defensins
What is the type of bacteria does lysozyme play major effect on?
Gram + bacteria
This enzyme breaks bonds between peptidoglycan sugar residues and disrupts cell wall integrity promoting membrane rupture
What does lactoferrin bind to?
Iron and other metal ions
What does lactoferrin do?
Takes up nutrients needed for bacterial growth
Lactoferrin is associated with what type of cancer?
Because when it is lacking there is an increased risk of infection