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Ocular Physiology > Block 12 > Flashcards

Block 12 Flashcards

(112 cards)

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1
Q

What is the simplified cause of glaucoma?

A

Aqueous flow in does not equal flow out

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2
Q

What is the unconventional pathway?

A

Aqueous moves through the ciliary muscle and other downstream tissues

It is minor (5-35%)

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3
Q

What is the conventional pathway?

A

Aqueous moves through the trabecular meshwork and Schlemms canal

It is major (65-95%)

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4
Q

Where all does aqueous flow in the unconventional pathway

A

AH enters the connective tissue between the ciliary muscle bundles, through the suprachoroidal space, and out through the sclera

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5
Q

Is the unconventional pathway affected by IOP

A

NO

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6
Q

How does unconventional pathway change with age

A

It decreases

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7
Q

In the conventional pathway where does aqueous flow?

A

Through the TM across Schelmms canal, into its lumen and into the draining collector channels, aqueous veins, and episcleral veins

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8
Q

What are the 2 models for conventional pathway

A

Bulk flow model

Pumping Model

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9
Q

Is the conventional pathway affected by IOP

A

YES

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10
Q

What is the Bulk Flow model of conventional aqueous flow

A

Change n pressure=IOP-EVP

An acute rise in EVP results in a 1:1 ratio of increase IOP

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11
Q

What is the pumping model of the conventional pathway

A

The aqueous outflow pump receives power from the transient increases in IOP such as occur in systole of the cardiac cycle during blinking and during eye movement

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12
Q

An increase in IOP causes what change in drainage?

A

Increase drainage

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13
Q

What happens with very constant high IOP

A

Schlemm’s canal can collapse on itself and obstruct entry into venous system

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14
Q

What is the role of the TM in aqueous flow

A

The TM is suspended between 2 compartments with different pressures

TM can sense the pressure differences and tries to maintain them within a homeostatic range

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15
Q

What are some things that can occlude the angle

A 
Diabetes
Uveitis
Hyphema
Pseudoexfoliative glaucoma
Pigment dispersion glaucoma
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16
Q

How does diabetes occlude the angle

A

Neovascularization from the proliferative diabetic retinopathy

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17
Q

How does uveitis occlude the angle

A

Inflammatory cells and peripheral anterior synechiae

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18
Q

How does hyphema obstruct the angle

A

Blood accumulates in the anterior chamber

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19
Q

How does pseudoexfoliative glaucoma occlude the angle

A

Aging epithelial cells of the iris and lens capsule can release pigment and pseudoexfoliative material

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20
Q

How does pigment dispersion glaucoma occlude the angle

A

Pigment is released from the posterior layer of the iris due to posterior bowing o the iris against the lens zonules

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21
Q

In humans, ____% of the resistance to the aqueous humor outflow is localized to the TM

A

75%

The other 25% occurs beyond Schlemms canal

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22
Q

What is Fuch’s heterochromic iritis

A

Chronic inflammation that can cause permanent TM damage

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23
Q

What is glaucomatocyclitic crisis

A

Acute inflammation of the TM

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24
Q

What are some long term influences on IOP

A

Genetics
Gender
Refractive error

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25
What are short term factors that influence IOP
``` Diurnal Postural variation Lid/eye movement Systemic conditions Environmental conditions Food and drugs ```
26
Does genetics affect IOP
YES
27
How does gender affect IOP
It is equal between men and women 20-40 yoa In older ages, there is an increase in IOP with age more in women
28
How does refractive error affect IOP
Positive correlation between IOP and axial length/increased degrees of myopia Myopic people have a higher incidence of open-angle glaucoma
29
T/F IOP fluctuates throughout the day
True
30
What is the range of IOP throughout the day
3-6 mmHg
31
When is IOP the highest
In the morning hours
32
How does posture affect IOP
Increase when changing from sitting to laying down
33
T/F patients with systemic hypertension have greater IOP increase after 15 minutes in supine
True
34
How do lids affect IOP
Blinking can raise IOP 10 mmHg Hard squeezing can raise it as high as 90 mmHg
35
How do eye movements affect IOP
Increase in IOP in upgaze
36
Thicker corneas give...
Artificially high readings
37
Thinner corneas cause....
Artificially low readings
38
How does pregnancy affect IOP
It is reduced during pregnancy | Possibly progesterone
39
How does HIV affect IOP
They have lower than normal IOP
40
Exposure to cold air causes
Reduced IOP
41
How does gravity affect IOP
A sudden marked increase in IOP
42
How does alcohol affect IOP
Lowers it
43
How does caffeine affect IOP
Causes a transient rise in IOP
44
How does tobacco smoking affect IOP
It causes a transient increase
45
How does heroin and marijuana affect IOP
Lowers it
46
How does LSD affect IOP
Elevates it
47
What do steroids do to IOP
Increase IOP
48
What is the largest organ of the eye
Virtuous
49
What is the vitreous
A highly transparent gel | It is located between the crystalline lens and the retina
50
The vitreous transmits ___% of light
90
51
What are the 3 zones of the vitreous
Outermost: vitreous Cortex Center: Cloquets canal Intermediate: inner to cortex and surrounds canal
52
What is teh vitreoretinal interface
Where the vitreous is attached to the inner limiting membrane of the retina by anchoring fibrils and membrane limitans interna (MLI)
53
Where is the vitreous base ?
At the ora serrata
54
What is the vitreous base attached to
NPCE and the internal limiting membrane of peripheral retina It the the strongest attachment
55
Is the vitreous base attachment affected by age?
No
56
What is Weigers Ligament
It is between the posterior surface of lens and the anterior face of vitreous It is a firm attachment
57
Is weigers ligament affected by age?
Yes, it declines after age 35
58
What is peripapllary adhesion
It is around the edge of optic disc It is a medium attachment Declines with aging Weiss’ ring
59
What is the macular/peripheral attachment
Weak Controversial May have an attachment 3-5mm posterior to vitreous base. Attach to retinal blood vessels
60
What is in high composition in the vitreous
``` H2O (99%) Collagen (T2) HA (GAG) Vitreal Cells (hyalocytes, fibroblasts) Vitamin C ```
61
What is the gel structure of vitreous due to
Arrangement of collagen fibrils suspended in network of HA
62
What do hyalocytes do
Synthesize glycoproteins for the collagen fibrils | Synthesize HA
63
What do fibroblasts do
Synthesize the collagen fibrils
64
What are the functions of the vitreous
Support retina Diffusion barrier Metabolic buffer Transparency
65
What are the support functions of the vitreous
- Prevents retinal detachment - reduce mechanical deformation - supports lens during trauma - decreases transmission of light at 300-350 nm - mechanical support
66
What is posterior vitreous detachment (PVD)
10% of eyes have a strong vitreous retina attachment Vitreous traction can cause retinal tears Possibility of vitreous hemorrhage High risk of rhegmatogenous retinal detachment
67
What is macular edema due to
Vitreous-retinal traction Increase in passive permeability Decrease in active transport across Blood retinal barrier Increase osmotic pressure
68
What is the diffusion barrier of the vitreous
Slow diffusion across vitreous Bulk flow is limited across vitreous Prevents topically administered substance from reaching the retina Prevents substances in blood stream from reaching vitreous center No diffusion barrier for small molecules
69
What is the metabolic buffer of the vitreous
Reservoir for ciliary body and retinal metabolism Movement of water soluble substances into vitreous and their dilution Reservoir of glucose and glycogen for retinal metabolism Reservoir of potassium for retinal metabolism Reservoir for Vitamin c
70
What can full PVD or vitrectomy) cause
Nuclear sclerotic cataract (NSC) Reduce neovasculariztion in retina Neovascualr glaucoma
71
What causes the transparency of the vitreous
Low [macromolecules] Low [protein] Specific collagen/HA configuration Blood vitreous barrier
72
What is synchisis scintillations
Rare Not age related 2% to injury or inflammation It is an accumulation of the cholesterol
73
What is asteroid hyalosis
In people aged 60-65 Common in white people No decrease in VA It is an accumulation of calcium
74
What is dry eye syndrome
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
75
What is the function of the tear film
Provides a smooth refractive surface for clear vision Maintains the health of corneal and conjunctival epithelia Acts as the first line of defense against microbial infections
76
What are the layers of the tear film
Lipid layer Aqueous layer Mucous layer
77
What is the mucus layer of the tear film composed of
``` Mucin* Immunoglobulin Urea Salts Glucose Leukocytes Cellular debris Enzymes ```
78
What is mucin
A high molecular weight glycoproteins that is heavily glycosylated
79
What are the 2 types of mucins
Membrane associated | Secretory
80
What is membrane associated mucins
A dense Barrie to pathogen penetrate, at the epithelia cell tear film interface
81
What are secretary mucins
Act as cleaning crew, moving through the tear film and collecting debris that can be removed via the nasolacrimal duct during blinking
82
What is the function of the mucus layer
Maintain water on the surface of the eye Mucins also interact with tear lipids to lower surface tension thereby stabilizing the tear film Provides lubrication for eyelid movement Traps exploited surface cell, foreign particles and bacteria
83
What are the sources of the mucus layer
``` Goblet cells (cornea and conj) Squamous cells (cornea and conj) ```
84
What is the neural control of the mucus layer
``` Sensory nerves Parasympathetic nerves (increases) ``` Sympathetic
85
What is the aqueous layer composed of
``` Water Electrolytes Proteins Peptide Growth factors Vitamins Hormones ```
86
What are the electrolytes in the aqueous layer
``` Na* Cl* K* Ca* Mg HCO3 Phosphate ```
87
What is the importance of Na and Cl in the aqueous layer
They are the main controllers to osmolarity of tear film Osmolarity increases with dry eye
88
What is the importance of K and Ca in the aqueous layer
Important for maintaining corneal epithelial health
89
What are some proteins in the aqueous layer
``` Albmin Immunoglobulins (IgA) Histamine Lactoferin Lysozyme Interleukins Antimicrobials ```
90
What are the functions of the aqueous layer
Electrolytes act as a buffer to maintain constant pH and contribute to maintaining epithelial integrity of the ocular surface Offers a strong defense system to protect against invading microorganisms through contained proteins Peptide growth factor A acts via autocrine and paracrine mechanisms to regulate epithelial proliferation, motility and differentiation
91
The buffering system of the eye allows the eye to tolerate ophthalmic solutions of what pH
3.5-10.5
92
What happens to eye pH while we are sleeping
It decreases (due to aerobic respiration)
93
What happens to pH in dry eye
It increases (due to osmolarity increases)
94
What are the resources of the aqueous layer
Lacrimal glands* (reflex and emotional tearing) Accessory lacrimal glands (maintenance tearing)
95
What is the neural control of the aqueous layer
Main lacrimal glands: parasympathetic, sympathetic, sensory nerves Accessory glands: parasympathetic
96
What is the lipid layer of the tear film composed of
Meibomian oil
97
What are the 2 phases of the lipid layer
Polar surfactant phase | Nonpolar phase
98
What is the polar surfactant phase
It is primarily composed of phospholipids and glycolipids Acts as a surfactant between the hydrophilic aqueous mucin layers and thick, nonpolar lipid layer
99
What is the nonpolar phase
It is primarily composed of wac, cholesterol esters, and triglycerides Provides the air-tear film interface and is responsible for retarding evaporation
100
What is the function of the lipid layer
Major barrier to evaporation from ocular surface Provides stability to tar film through interaction with aqueous-mucin phase Provides a smooth optical surface for the cornea Acts as a barrier against foreign particles
101
What are the resources of the lipid layer
Meibomian glands Assistance from Zeis and Moll glands
102
What is the neural control of the lipid layer
Parasympathetic innervation
103
How can you access the tear film
``` Tear secretion Tear film stability Tear film osmolarity Lipid layer evaluation Ocular surface evaluation ```
104
What is tear deficient dry eye
There is a disorder in the lacrimal gland function, resulting in either reduced aqueous tear production and tear flow, or a failure to transfer lacrimal fluid into the conjunctival sac
105
What is the largest dry eye category
Tear deficient
106
What is evaporative dry eye
Lacrimal gland function is normal and the volume is sufficient to cover the surface, but another tear film abnormality exists that leads to increased tear evaporation
107
What can lead to evaporative dry eye
Hyperosmolarity Meibomian gland disease
108
What tests access tear secretion
Schirmer 1 and 2 Phenol red thread test Meinscometry
109
What tests look at tear film stability
TBUT Ocular protection index Videokeratography Tear turnover
110
What tests tear film osmolarity
Tear film osmolarity Tear ferning Tear evaporation
111
What tests lipid evaluation
Interferometry | Meibometry
112
What tests ocular surface evaluation
Fluorescein Rosa bengal Lissamine green

Ocular Physiology (8 decks)

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