retinal imaging

What are the major retinal imaging modalities?

Retinal photos, FAF, FA, ICGA, OCT, OCT-A.

What are the purposes of retinal photos?

Documentation, monitoring change, limited diagnostic use, sometimes not covered by insurance.

Which devices provide ultra-widefield photos?

Optos Optomap (~200°) and Zeiss Clarus (true color).

What does multicolor imaging use and what does each wavelength highlight?

Blue = inner retina; Green = vessels/exudates; IR = outer retina/choroid (drusen/RPE changes).

What is the main fluorophore responsible for FAF signal?

Lipofuscin in the RPE.

What does hyper-autofluorescence represent?

Excess lipofuscin → stressed RPE.

What does hypo-autofluorescence represent?

RPE loss, increased pigment, subretinal fluid, heme (blockage).

What are normal FAF features?

Dark fovea (xanthophyll), dark vessels, dark ONH (no RPE), diffuse gray background.

What diseases show hyper/hypo FAF patterns?

AMD/GA (hypo), melanoma (hyper from lipofuscin), Stargardt's (mixed).

What wavelengths does fluorescein absorb/emit?

Absorbs blue (480-500 nm), emits yellow-green (500-600 nm).

What is the clinical purpose of FA?

Imaging retinal/choroidal circulation, detecting leakage, CNVM, ischemia.

Why doesn't fluorescein leak from retinal vessels under normal conditions?

Tight junctions in retinal endothelium & RPE.

What common side effects occur with FA?

Nausea, vomiting, yellow skin/urine.

What serious FA risks exist?

Allergic reaction, anaphylaxis, MI (rare).

What is the order of FA phases?

Choroidal flush → Arterial → Arteriovenous → Venous → Late.

What blocks fluorescence during choroidal flush?

RPE pigment + xanthophyll → macula appears dark.

What is laminar flow and in which phase does it appear?

Bright plasma along vein walls; seen in arteriovenous phase.

What is a normal late-phase FA finding?

Mild ONH staining (normal).

What are the 5 causes of hyperfluorescence?

Window defect, leakage, pooling, staining, autofluorescence.

How does leakage appear over time?

Increases in intensity and area.

How does a window defect behave over time?

Stays the same size, margins stable (no leakage).

What diagnoses commonly show leakage?

CNVM, NVD/NVE (proliferative DR), vasculitis.

What diagnoses show pooling?

CSCR (smokestack/inkblot), PEDs.

What tissues normally stain late on FA?

Optic disc, sclera, scar tissue.

What causes autofluorescence on FA?

Optic nerve drusen.

What are the 2 types of hypo-fluorescence?

Blockage & filling defect.

What causes blockage?

Blood, pigment, exudate, media opacity.

What causes filling defects?

Ischemia or poor perfusion (CRAO, BRAO, capillary dropout in DR/RVO).

How do you differentiate blockage vs non-perfusion?

Check if a lesion is visible on photo → visible = blockage; invisible = non-perfusion.

What does neovascularization look like on FA?

Early hyper + late leakage.

What does AMD geographic atrophy show on FA?

Window defects (hyperfluorescent spots).

What classic FA pattern does CSCR show?

Smokestack or ink-blot pooling.

What is ICGA best for imaging?

Choroidal circulation.

Why is ICGA better than FA for choroid detail?

Near-infrared penetrates pigment; ICG is more protein-bound → less leakage.

What are primary ICGA indications?

PCV, choroidal tumors, inflammatory choroidopathy, chronic CSCR.

What are ICGA contraindications?

Iodine allergy, liver disease, severe asthma, uncertain pregnancy safety.

What does OCT-A detect instead of dye?

Motion contrast from blood cell movement.

What are OCT-A advantages?

Non-invasive, fast, layer-by-layer vascular imaging, good for DR/RVO/CNVM.

What are OCT-A limitations?

No leakage info, artifacts, small field of view, hard to interpret subtle disease.

What can OCT-A detect in diabetes?

FAZ enlargement, capillary dropout, microaneurysms.

What 4 elements should be in imaging documentation?

Reason & reliability, findings, comparison to prior imaging, clinical management plan.

What differentiates FA from OCT-A clinically?

FA shows leakage; OCT-A shows structure only (no leakage).

When is FA still preferred over OCT-A?

When assessing leakage (CNVM, vasculitis, DME, NVD/NVE).

When is OCT-A preferred over FA?

When dye injection contraindicated or when needing microvascular detail without leakage info.