Retinal Blood Flow Flashcards by Audrey Chu

The central retinal artery enters the optic nerve about ______mm behind the globe

10 - 12mm

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The CRA supplies the ______

optic nerve and pia mater

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What nerve plexus surrounds the CRA?

the nerve of Tiedemann

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The central retinal circulation must be sparse and thin because _________

it is in front of the light path

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What supplies the ganglion and bipolar cells?

the CRC

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What are the three aspects of the central retinal circulation?

A. CRA and CRV
B. Capillaries
C. Radial peripapillary circulation

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The arteries and veins are within the ______ layer, while the capillary system forms a double layered system in most of the ______

The arteries and veins are within the nerve fiber layer layer, while the capillary system forms a double layered system in most of the outer retina

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the Retinal Capillary Networks supply every part of the retina except for _____, _____, and ______

outer nuclear layer, photoreceptors and RPE

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Define scotoma

blind spot

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_____ serves an area between 10 and 20 degrees out from the macula. the first area where cotton wool spots appear and produces Bjerrum’s scotomas in Glaucoma

Radial Peripapillary capillary system

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What are the three aspects of the Choroidal Supply?

A. SPCA
B. LPCA
C. Cilioretinal artery

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Cilioretinal arteries are only in ___% of the population

25%

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The anterior ciliary arteries follow the ______

rectus muscles

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2 anterior ciliary arteries arise from each of the rectus muscles except for the _______

lateral rectus muscle

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The _______ supplies the oxygen and nutrient need of the outermost layers of the retina

Choroid

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What is the biggest and widest circulation in the body?

Choroidal circulation

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the _____ is the ONLY blood supply to the macula

Choroidal circulation

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Regarding speed, the CRC is ____ while the choroidal circulation is ____

CRC - slow

choroic - fast

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What three layers does the choroid supply?

outer nuclear layer
POS
RPE

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The paraoptic region of the SPCA supplies the _____ while the distal region supplies the _____

paraoptic - Optic nerve head, peripapillary choroid, circule of Zinn/Haller
distal - Choroid

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Each sector of the______ fit together like pieces of a jigsaw puzzle. each terminal choroidal arteriole supplies a ____ of the chorriocapillaris

Each sector of the distal SPCA fit together like pieces of a jigsaw puzzle. each terminal choroidal arteriole supplies a lobule of the chorriocapillaris

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The branches of the ______ pierce the slcera lateral, medial, or infrequently superior to the optic nerve

LPCA

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To keep the choroid from scarring, if one _____ is destroyed by disease, the others will remain in tact

lobule

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In the posterior pole, the _______ is arranged in a lobular fashion with alternating feeding arterioles and draining venules

choriocapillaris

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The ______ lobule does not have its own blood supply

Central

what is a watershed zone?

the border between the territories of distribution of any two end arteries. Poor vascularity.

The part of the optic nerve head that is located in the watershed zone is most vulnerable to _____

ischemia

_______ is a loss of a lobule and occurs in a matter of minutes. Irreversible within hours to days.

Choroidal occlusion

The Optic Nerve Head Circulation (ONHC) is comprised from the _______

SPCA

What are the four parts of the Optic Nerve Head circulation

1. Superficial nerve fiber layer 2. Pre-lamina 3. Lamina 4. Retro-lamina

The pre-lamina is supplied by the ______

SPCA

The _____ is a collagenous plate through which the nerve fibers run on their way out of the globe

Lamina (lamina cribosa)

The inner part of the retro-lamina is supplied by the _____ while the outer part is supplied by the ______

CRA | pial plexus

A ________ hemorrhage has a round appearance and is an indication the bleeding has occured in the deep capillary plexus. Cells are oriented _____ in the inner nuclear layer. usually binocular

Dot and blot hemorrhage. Cells oriented vertically.

A _______ hemorrhage has a wide, uneven appearance. Is an indication that bleeding has occured in the radial peripapillary capillaries. The cells here are oriented ______ in the nerve fiber layer. Usually binocular, but can be monocular in ________.

Flame-shaped hemorrhage. Cells oriented horizontally. Monocular in central retinal vein occlusion.

A _______ hemorrhage is in the viteous. Typically due to _______ which makes the borders indistinct.

Pre-retinal hemorrhage. Due to neovascularization.

A ________ hemorrhage arises from beneath the RPE. May be caused by ______ disease.

Subretinal hemorrhage. Can be caused by Coat's disease.

A ________ hemorrhage occurs beneath the RPE. A choroidal rather than retinal disease. Disappears with _____ filter on Opthalmoscope

Choroidal hemorrhage. Disappears with green filter.

_______ is a very rare condition where there is abnormal development in the blood vessels behind the retina. Blood leaks out of the retinal capillaries, which may _______. Usually in _____ and almost always unilateral.

Coat's disease. May detach the retina. Usually in males.

_______ is a result of ganglion cell death due to loss of oxygen. Cotton wool spots will appear. Immediate VA drop. Fast, painless, acute.

Central Retinal Artery Occlusion. Eventually revascularizes the retina, but the ONH is white... because the ganglion cells are dead.

________ involved a blockage of blood outflow. TMP increases and blood is pushed into the retina. VA may be 20/20 if _________.

Central Retinal Vein Occlusion. VA may be 20/20 if there is no fluid in the macula.

As resistance to flow increases, the perfusion pressure ______

decreases

Poiseuille's law

Blood flow in a vessel occurs if there is a pressure gradient between two points within the vessel

What is autoregulation?

the ability of a system to self-regulate its blood flow so that when the transmural pressure increases, the vessels will dilate to maintain the amount of blood flow.

Perfusion pressure is equal to ____ - _____

Pressure of artery - pressure of vein

Defective autoregulation leads to _____

ischemic damage

The eye contains the only circulation system in the body that has an opposing pressure, the _____working against it

IOP

Transmural pressure is nearly zero in the eye because why?

the IOP and venous pressure are very similar

What is transmural pressure (TMP)?

the pressure inside the vein compared to the pressure outside the vein.

Every circulation system in the eye is autoregulated except for the _________

choroidal circulation

Lack of autoregulation in the choroid is compensated for by increased extraction of ______ with the slower blood flow as the IOP rises

metabolites

Because of autoregulation, blood flow does not begin to fall until IOP reaches _______

40 mmHg

True/False. venous pressure is always higher than the IOP.

FUCK YEEEEEAAAAAHHHHHHH VENOUS PRESSURE

the retinal venous pressure at the point where the central retinal vein leaves the eye is called the _____

ouflow pressure

In the retrolaminar space, the pressure is controlled by the _______

cerebrospinal fluid

Spontanous venous pulsation is found in ____% of normal subjects and occurs in people with CSF pressure below ____ mmHG

90% of normal subjects. Occurs with CSF pressure below 190 mmHG

True/False. Normal SVP indicates that CSF pressure is normal.

FALSEEEEEE FUCK YOU FOR THINKING TRUE

What are the three types of open angle glaucoma?

1. Primary open angle glaucoma 2. Low tension glaucoma 3. Ocular hypertension

True/False. Elevated IOP is the cause of glaucoma

FALSE AS FUCK. IOP is simply a risk factor. You'd be better off using age as a predictor.

What is a transient ischemic attack?

Perfussion pressure decreases, resulting in a loss of blood flow, which results in a transient loss of vision

Transient Ischemic Attacks are generally caused by _______. If vision is lost, patient will probably experience _______

TIA generally caused by occlusion of carotid artery. If vision is lost, patient will probably have a stroke within the year

Pilots typically experience this due to the high amount of pressure they experience at high gravitational forces.

Transient ischemic attack. Loss of vision is described as a "curtain falling or rising"

Increased resistance in blood flow can be seen in ______ due to an increased _______

sickle cell anemia. Increases blood viscosity.