Retinal Vasculature and Imaging Techniques

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Questions and Answers

What is the primary function of the retinal capillary beds?

Facilitates venous drainage of the retina

Supplies the outer ⅓ of the retina

Supports the RPE and Bruch’s Membrane

Supplies the inner ⅔ of the retina (correct)

What characterizes the choriocapillaries in the retinal vasculature?

They are fenestrated, allowing permeability to NaFl. (correct)

They supply both the inner and outer retina.

They are responsible for venous outflow from the retina.

They have tight junctions preventing leakage.

Which arteries directly branch from the Internal Carotid Artery to supply the retina?

Long Posterior Ciliary Arteries (correct)

Subretinal Arteries

Ciliary Veins

Facial Arteries

What is the role of tight junctions between RPE cells?

Prevent NaFl from invading the retina Signup and view all the answers

In fluorescein angiography, what happens immediately after the injection of sodium fluorescein?

NaFl appears in the central retinal artery within seconds. Signup and view all the answers

What type of conditions can fluorescein angiography help to identify?

Conditions affecting the circulation in the retina and RPE Signup and view all the answers

How does the pigment in RPE affect the observation of fluorescein?

It obscures fluorescein, leading to less fluorescence. Signup and view all the answers

What is one advantage of using ICGA over FAN for occult CNVM?

It enhances visualization of the borders associated with serous detachment. Signup and view all the answers

What is a primary limitation of ICGA?

It has poor image quality, making it hard to identify detailed capillaries. Signup and view all the answers

What is the main venous pathway for retinal drainage?

Central Retinal Vein Signup and view all the answers

Which of the following is a known side effect of ICGA?

Severe allergic reactions Signup and view all the answers

Why is ICGA not recommended for pregnant women?

Safety in pregnancy has not been established. Signup and view all the answers

What is a possible hopeful application of ICG in treatment?

It may be used to accurately identify and ablate choroidal membranes. Signup and view all the answers

What characterizes the late phase of cystoid macular edema (CME) in terms of fluorescence?

Hyperfluorescence Signup and view all the answers

Why is Indocyanine Green (ICG) particularly used for evaluation in patients?

It is a non-toxic dye for corneal endothelial cells Signup and view all the answers

What percentage of ICG is excreted by the kidneys after administration?

2% Signup and view all the answers

What is the major reason why patients with liver disease should avoid ICG tests?

ICG is primarily excreted by the liver Signup and view all the answers

Which condition is associated with full hypofluorescence during evaluation?

Geographic atrophy Signup and view all the answers

Which characteristic of ICG allows for better penetration in imaging?

Absorption and emission of infrared light Signup and view all the answers

What is a contraindication for the use of ICG due to potential allergic reactions?

Allergy to iodine or shellfish Signup and view all the answers

What is unique about the fenestration of choriocapillaris in relation to ICG?

It retains most ICG in choroidal vessels Signup and view all the answers

Which of the following statements is true about the imaging capability of ICG?

It can image through thin layers effectively Signup and view all the answers

What phase of capillary dilation is specifically observed in cystoid macular edema?

AV phase Signup and view all the answers

What is the primary use of fluorescein angioscopy?

To document disorders characterized by late leakage of dye Signup and view all the answers

What is the typical transition time from the antecubital vein to the retina in healthy subjects?

12 seconds Signup and view all the answers

Which of the following is NOT a common side effect of fluorescein angioscopy?

Ruptured blood vessels Signup and view all the answers

What is the most effective way to reduce the incidence of nausea post-injection?

Giving 50mg Promethazine before the injection Signup and view all the answers

What should be present in an office performing fluorescein angioscopy to ensure safety?

An emergency response system with defibrillators Signup and view all the answers

In the pre-arterial phase of fluorescein angioscopy, what is primarily observed?

Dye entering the choroidal circulation Signup and view all the answers

What does a delay in the arm-to-retina time suggest about the patient?

Potential issues with dye injection or circulatory problems Signup and view all the answers

What method is used to photograph the retinal and choroidal circulation?

Fluorescein angiography with barrier filters Signup and view all the answers

Why is the fluorescein dye mixed with liquid in a specific concentration for angioscopy?

To provide proper diagnostic clarity Signup and view all the answers

Which of the following is a contraindication for fluorescein angioscopy?

Severe renal impairment Signup and view all the answers

What occurs during the capillary phase of fluorescein angiography?

Capillaries and arteries are completely filled. Signup and view all the answers

In which phase does the maximum vessel fluorescence occur approximately 30 seconds after fluorescein injection?

Venous Mid-Stage Signup and view all the answers

What physiological condition can delay the choroidal flush during fluorescein angiography?

Increased blood viscosity Signup and view all the answers

Which of the following describes the late phase of fluorescein angiography?

Veins begin to empty while the arteries are still filled. Signup and view all the answers

What causes macular hypofluorescence during fluorescein angiography?

High concentration of RPE and xanthophyll. Signup and view all the answers

What does hyperfluorescence indicate in the context of fluorescein angiography?

Increased intensity due to a breakdown of barriers. Signup and view all the answers

Which of the following is NOT a cause of hypofluorescence?

Increased fluorescein due to leakage. Signup and view all the answers

What identification does the Foveal Avascular Zone (FAZ) typically have?

Absence of retinal capillaries within a 500 micron space. Signup and view all the answers

What is the consequence of a transmission defect during fluorescein angiography?

Early hyperfluorescence that fades without size change. Signup and view all the answers

What causes late staining observed in fluorescein angiography results?

Prolonged retention of fluorescein. Signup and view all the answers

What is a significant advantage of using indocyanine green angiography (ICGA) over fluorescein angiography (FAN) for certain conditions?

ICGA is better for identifying borders in occult CNVM. Signup and view all the answers

Which of the following is a known limitation of indocyanine green angiography (ICGA)?

It requires an expensive imaging system. Signup and view all the answers

What is a contraindication for the use of indocyanine green (ICG) due to health concerns?

Iodine sensitivity Signup and view all the answers

Which side effect is less common when using indocyanine green (ICG) compared to sodium fluorescein (NaFl)?

Discoloration of urine Signup and view all the answers

How is indocyanine green (ICG) metabolized in the body after administration?

It remains protein bound and is rapidly metabolized by the liver. Signup and view all the answers

What supplies the inner two-thirds of the retina?

Retinal capillary beds Signup and view all the answers

Which component of the retinal vasculature prevents leakage in the inner blood-retina barrier?

Tight junctions Signup and view all the answers

What is a primary characteristic of choriocapillaries compared to retinal capillaries?

Fenestrated structure Signup and view all the answers

What initiates the observation of retinal vessels in fluorescein angiography?

Excitation of sodium fluorescein Signup and view all the answers

Which of the following statements is true regarding the metabolism of sodium fluorescein?

It is metabolized into a fluorescent conjugate Signup and view all the answers

What structure primarily absorbs the blue light emitted after fluorescein injection?

RPE Signup and view all the answers

What is the consequence of tight junctions between RPE cells?

Prevent NaFl from invading the retina Signup and view all the answers

What characterizes the venous early stage of fluorescein angiography?

Arteries and capillaries are filled with fluorescein. Signup and view all the answers

When does maximum vessel fluorescence occur after fluorescein injection?

30 seconds Signup and view all the answers

What is the significance of the Foveal Avascular Zone (FAZ) in fluorescein angiography?

It appears as a dark spot due to high RPE concentration. Signup and view all the answers

What can a delay in the choroidal flush during fluorescein angiography indicate?

High blood viscosity Signup and view all the answers

What occurs during the late stage of venous filling in fluorescein angiography?

Arteries are completely empty, and veins are filled. Signup and view all the answers

What does hypofluorescence in fluorescein angiography suggest?

Decreased or absent fluorescein due to optical obstruction. Signup and view all the answers

What is one cause of hyperfluorescence observed during fluorescein angiography?

Absence of the retinal pigment epithelium (RPE). Signup and view all the answers

Which condition can lead to pooling seen in fluorescein angiography?

Central serous chorioretinopathy (CSCR) Signup and view all the answers

What happens to the intensity of fluorescein during the venous mid-stage of fluorescein angiography?

It slowly diminishes after reaching maximum brightness. Signup and view all the answers

What characteristic of indocyanine green (ICG) makes it suitable for evaluating choroidal vasculature?

ICG absorbs and emits light in the infrared range. Signup and view all the answers

Which phase of cystoid macular edema (CME) is characterized by hyperfluorescence?

Late phase hyperfluorescence Signup and view all the answers

Why should patients with liver disease avoid ICG tests?

ICG is not excreted effectively due to compromised liver function. Signup and view all the answers

What does the full hypofluorescence observed in geographic atrophy indicate?

There is a loss of choriocapillaris perfusion. Signup and view all the answers

What should patients with a known allergy to iodine or shellfish be cautious about regarding ICG?

They could develop a serious allergic reaction. Signup and view all the answers

What is the primary binding protein for ICG in the bloodstream?

Albumin Signup and view all the answers

How is ICG mainly retained in the choroidal vessels during indocyanine green angiography (ICGA)?

Due to the impermeability of fenestration in choriocapillaris. Signup and view all the answers

What is a critical characteristic of ICG related to its imaging properties?

It can penetrate deeper than visible light due to infrared absorption. Signup and view all the answers

What is the main use of indocyanine green (ICG) in medical evaluations?

To assess vascularity of the choroid. Signup and view all the answers

What can be a major concern for patients regarding the use of ICG imaging?

Potential for renal impairment. Signup and view all the answers

Which of the following best describes the typical transition time from the antecubital vein to the retina in healthy subjects?

Approximately 12 seconds Signup and view all the answers

What is a common side effect experienced by about 10% of patients after fluorescein administration?

Nausea Signup and view all the answers

In the pre-arterial phase of fluorescein angiography, what primarily occurs?

Choroidal circulation is filled Signup and view all the answers

What may a delay in arm-to-retina time indicate about a patient?

Potential circulatory problems Signup and view all the answers

Which of these is NOT a contraindication for fluorescein angiography?

Mild allergies to food Signup and view all the answers

Which statement accurately reflects the procedure for administering fluorescein?

The dye is injected into the antecubital vein. Signup and view all the answers

What does hyperfluorescence indicate during fluorescein angiography?

Increased permeability in vasculature Signup and view all the answers

What is the role of Promethazine (Phenergan) in relation to fluorescein angiography?

It reduces the incidence of post-injection nausea. Signup and view all the answers

Which condition can fluorescent angiography help identify through late leakage of dye?

Cystoid macular edema Signup and view all the answers

Study Notes

Retinal Vasculature Review

Retinal capillary beds supply the inner two-thirds of the retina
Tight junctions prevent leakage
Inner blood-retina barrier is present
Choriocapillaries supply the outer one-third of the retina
Fenestrated, allowing NaFl to permeate into extracellular spaces
Located beneath the retinal pigment epithelium (RPE)
Circulation time is fast

Outer-Blood-Retina Barrier

Adherent together by zonule adherents (ZA)
Strongly adherent to Bruch's membrane (BrM)
Tight junctions between RPE cells prevent NaFl from the extracellular space of the choriocapillaries from invading the retina and RPE
RPE is loosely adherent to the sensory retina
Pigment acts as an optical barrier, obscuring the NaFl beneath (Choroidal Flush)
The denser the pigment, less fluorescence is observed.

Arterial Input

Internal Carotid Artery (ICA) provides the Ophthalmic Artery
Central Retinal Artery (CRA)
Short and Long Posterior Ciliary Arteries (SPCA/LPCA)
Anterior Ciliary Arteries (ACA)

Venous Outflow

Primarily via Vortex Veins (VV) and the Central Retinal Vein (CRV)
CRV drains into Cavernous Sinus, Pterygoid Venous Plexus, and Facial Vein, then into the Jugular vein
No leakage of fluorescein should happen

Fluorescein Angiography (FAN)

Used to assess the choroid, RPE, retina, optic nerve head (ONH), and vascular abnormalities
Delineates fundus vascularity and anterior segment blood and aqueous flow
Requires sodium fluorescein (NaFl) injection and fundus photos
Retinal vessels are clearly visible with fluorescein
Choroidal fluorescence is reduced due to intact RPE
Diseases affecting ocular circulation, RPE, or blood-retinal barriers can be detected
Useful for evaluating retinal and choroidal circulation, abnormal RPE changes, vascular disease, and neoplastic disorders
Examples: Central Serous Chorioretinopathy, Diabetic Retinopathy, Disciform Macular Degeneration, Retinal Vascular Occlusions, and Subretinal neovascular membranes
70-85% of circulating fluorescein binds to albumin and RBC
NaFl in bloodstream is excited by 465nm, emitting 525nm

FAN IV Side Effects

Approximately 10% of patients experience adverse reactions (e.g., nausea, vomiting)
Post-injection nausea may be related to fluorescein concentration and speed of injection
Lowering concentration and slow injection reduces nausea
Allergic reactions (e.g., laryngeal edema, urticaria, pruritus)
GI distress, vomiting, extravasation, skin necrosis, hypotension, syncope, respiratory effects
Basilar artery ischemia, thrombophlebitis, cardiac arrhythmia, cardiac arrest
Contraindications include hypersensitivity, severe renal impairment, recent CVA, MI, or unstable angina, and the first trimester of pregnancy.

Phases

Pre-Arterial Phase: choroidal filling
Arterial Phase: dye enters arteries, lasting ~1 second
Capillary Phase: complete filling of arteries and capillaries
Venous Phase: subdivided into early, mid, and late stages (based on vein filling and artery emptying)

FAN Interpretation

Healthy retinal vessels do not leak NaFl
Retinal vessel walls are not fenestrated
Healthy choriocapillaris are fenestrated
Pooling: due to breakdown of outer-blood retinal barrier
Leakage: from abnormal choroidal vessels, inner blood-retinal barrier breakdown
Staining: due to prolonged fluorescein retention
Hypofluorescence: decreased fluorescein due to optical obstruction
Timing: 9.5sec - Posterior ciliary arteries fill, 10sec "Choroidal Flush" (background choroidal fluorescence), 10sec-12Retinal arterial phase, 13 sec -Capillary transition phase, 14-15sec Early Venous Phase, 16-17sec Venous Phase, 18-20sec Late Venous Phase

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Description

This quiz covers key aspects of retinal vasculature, including the roles of various capillary beds and arteries. Additionally, it delves into imaging techniques like fluorescein angiography and indocyanine green angiography, highlighting their applications and limitations in clinical practice.