Block 12 Flashcards
When the flow of AH in does not equal the flow of AH out
Glaucoma
2 pathways that AH leaves the eye
Unconventional path
Conventional path
AH path: through ciliary muscle and other downstream tissues
Unconventional path
AH path: through the TM and SC
Conventional path
AH path: the major pathway of AH out of eye
Conventional path
AH path: not affected by IOP (IOP independent)
Unconventional path
AH path: IOP dependent
Conventional path
The conventional pathways of AH flow is also called
Corneoscleral path
The unconventional path of AH outflow is also called
Uveoscleral outflow
2 models of conventional AH outflow path
- bulk flow model
- pumping model
Conventional pathway model: simplest hydraulic model
Bulk flow model
Conventional pathway model: a rise in EVP results in a 1:1 ration of increase IOP
Bulk flow model
Conventional pathway model: receives power form transient IOP increase
Pumping model
With constant very high IOP, what can happen to SC
It can collapse on itself and obstruct entry into the venous sys
What 2 structures are the TM between
Anterior chamber and SC
The pssr of anterior chamber and SC are different, so what does the TM do
Sense the differential and strives to maintain parameters within a homeostatic range
What 2 things can cause outflow obstruction of AH
Occlusive angle
Injury to TM
Possible conditions to cause an occlusive angle, obstructing outflow
Diabetes (severe - retinopathy) Uveitis Hyphens Pseudoexfoliative glaucoma Pigment dispersion glaucoma
75% of the resistance to AH outflow is localized to what structure
TM
2 conditions that may injure the TM, obstructing outflow
Fuch’s heterochromic irits
Glaucomatocyclitic crisis
3 long term influences of IOP
Genetic
gender
refractive error
The older we get, which gender has higher IOP
Women
Which will typically have a higher IOP, myopic or hyperopic patients
Myopic
The peak IOP is when during the day
Morning hours
Higher IOP with pt is sitting or laying
Laying
What gaze is there an increase in IOP
Up gaze
Thicker corneas cause readings of IOP to be
Artificially high
Pts with HIV or pts pregnant will have higher or lower IOP
Lower
Corticosteroids may cause your IOP to
Increase
largest organ of the eye
Vitreous
How much of light does the vitreous transmit
90%
How is the vitreous attached to the ILM
By anchoring fibrils and the membrane limitans itnerna (MLI)
The the MLI is composed of
- fusing point of the anchoring fibrils
- lamina dense
- lamina Lucinda
Where is the vitreous base
Ora serrata
What is the strongest vitreal attachment
Vitreous base
Located between the posterior lens and anterior vitreous
Wieger’s ligament
The only vitreal attachment to not decline with age
Base
Which attachment is of medium strength
Peripapillary adhesion
Vitreal adhesion around the edge of the optic disc
Peripapillary adhesion
What is the weakest vitreal attachment
Macular/peripheral retinal attachment
What composes the majority of the vitreous
Water
Main collagen type in vitreous
Type 2
What are the 4 major composers of the vitreous
Water
Type 2 collagen
Vitreal cells
Vitamin C
The gel structure of the vitreous results from
Arrangement of collagen fibrils suspended in HA
3 main vitreal cells
Hyalocytes
Fibroblasts
Macrophage
Majority of vitreal cells are which type
Hyalocytes
4 main functions of vitreous
Support retina
Diffusion barrier
Metabolic buffer
Transparency
Pathology associated with the support function of the vitreous
PVD
Macular edema
Major cause of macular edema
Retinal ischemia
The metabolic buffer function of the vitreous serves as a reservoir of what
Glucose/glycogen
Potassium
VITAMIN C
Pathology associated with the diffusion barrier and metabolic buffer functions of the vitreous
nuclear sclerotic catract (NSC)
Reduced neovascularization of retina
Neovascular glaucoma
Pathology associated with the transparency function of the vitreous
Synchisis scintillations
Asteroid hyalosis
Protects against oxidative stress
Protect the retina from metabolic and light induced free radicals
Vitamin C
T/F: the vitreous provides a transparent medium
True
T/F: the vitreous cushions the globe
True
T/F: the vitreous stores ions and nutrients for the retina and lens
True
A common disorder of the tear film caused by tear deficiency or excessive tear evaporation
Dry eye syndrome
3 main functions of the tear film
- Smooth refractive surface
- maintain corneal and conj health
- act as first line of defense against microbial infection
Layers of the tear film starting at the corneal epithelium
Mucous layer
Aqueous layer
Lipid layer
Main component of the mucous layer of the TF
Mucin
High molecular weigh glycoproteins that are heavily glycosylated
Mucin
2 types of mucins
Membrane associated mucins
Secretory mucins
Which type of mucin acts as a dense barrier to pathogen penetrance
Membrane associated mucins
Which type of mucin act as a cleaning crew
Secretory mucin
4 functions of the mucus layer of the TF
- maintain water on the surface of eye
- Lower surface tension, stabilizing the TF
- lubrication for eyelid movement
- traps exploited surface cell, foreign particles and bacteria
Sources of the mucus layer
Goblet cells and squamous cells of cornea and conj
Major components of the aqueous layer of the TF
Water Electrolytes Protein Peptide growth factors Vitamins
4 main electrolytes in the aqueous layer of the TF
Sodium
Chloride
Potassium
Calcium
2 electrolytes that are the main contributors to osmolarity of tear film
Sodium and chloride
Does osmolarity inc or dec with dry eye
Increase
What 2 electrolytes are important for maintaining corneal epithelium health
Potassium and calcium
What do the electrolytes in the aqueous layer of the TF do
Act as buffer to maintain a constant pH and contribute to maintain epithelial integrity of the ocular surface
What pH range can the eye handle, due to the buffering system
3.5 to 10.5
During sleep, what happens to the pH
Decrease
What happens to the pH in dry eye
Increases due to osmolarity increases
2 glands that help make the aqueous layer of TF
Main lacrimal glands
Accessory lacrimal glands
Which glands are responsible for reflex and emotional tearing
Main lacrimal glands
Which glands are responsible for maintenance tearing
Accessory lacrimal glands
The lipid layer of the TF is composed of
Meibomian oil
2 phases that compose the lipid layer
Polar surfactant phase Nonpolar phase (overlaid polar phase)
4 main functions of the lipid layer of TF
- Barrier to evaporation
- stability to TF through interaction with aqueous-mucin phase
- smooth surface for cornea
- barrier against foreign particles
Main resource for lipid layer of TF
Meibomian glands
+ zeis and moll sebaceous glands
Largest category of dry eye
Tear deficient dry eye
Occurs because of a disorder in lacrimal gland function
Tear deficient dry eye
Lacrimal gland function is normal, but another tear abnormality exits that leads to increased tear evaporation
Evaporative dry eye
Major barrier to evaporation form ocular surface
Lipid layer of TF
Test for tear secretion
Schirmer (1 and 2)
Phenol red thread test
Meinscometry
Test for tear film stability
TBUT
Ocular protection index
Videokertography
Tear turnover
Test for tear film osmolarity
TF osmolarity
Tear forming
Tear evaporation
Test for lipid layer evaluation
Interferometry
Meibometry
Test for ocular surface evaluation
Fluorescein
Rosa Bengal
Lissamine Green
How does B-lysine function in terms of destroying a pathogen
Acts as a detergent
- pokes holes in cell and causes rupture, reducing membrane integrity
3 ways that a defensin functions
- bind to microbial membrane
- embed into membrane
- act as a detergent (for a pore in membrane and lose ions)
Are defensins easily synthesized; what are synthetic defensins called
Yes; mimetics (drugs that act like defensins)
What do lysozymes do
Cleaves linkages between sugars
What type of bacteria do lysozymes target
Gram + bacteria
- causes them to rupture
What areas are affected by lysozymes
Areas where there is a lot of air (surface)
Which will affect peptidoglycan
Lysozyme
Lactoferrin binds to what
Iron
What is enzyme is associated with breast cancer
Lactoferrin
Levels of what enzyme are lower in dry eye diseases and diseases like Sjögren’s syndrome
Lactoferrin
