indocyanine green angiography (ICGA): Definition, Uses, and Clinical Overview

Posted on February 27, 2026 | by dreye

indocyanine green angiography (ICGA) Introduction (What it is)

indocyanine green angiography (ICGA) is an eye imaging test that shows blood flow in deeper layers of the eye.
It uses a medical dye and a special camera to capture images of circulation behind the retina.
It is most commonly used in retina clinics to evaluate conditions affecting the choroid and retinal vessels.
It often complements other tests such as optical coherence tomography (OCT) and fluorescein angiography.

Why indocyanine green angiography (ICGA) used (Purpose / benefits)

The main purpose of indocyanine green angiography (ICGA) is to help clinicians evaluate the eye’s blood vessels—especially the choroid, a vascular (blood-rich) layer beneath the retina. Many vision-threatening diseases involve abnormal blood vessels, impaired circulation, inflammation, or leakage that may be difficult to fully characterize with a routine exam alone.

ICGA can be particularly useful when the clinical question involves deeper structures. Standard retinal photographs show surface appearance, and OCT shows cross-sectional tissue anatomy, but they do not directly show dynamic blood flow patterns the way angiography does. By recording how dye moves through vessels over time, ICGA can help clinicians:

Identify abnormal choroidal vessels or networks that may contribute to fluid, bleeding, or scarring.
Differentiate between conditions that can look similar on exam but behave differently in the choroidal circulation.
Clarify lesion boundaries and activity when planning monitoring strategies or treatment discussions.
Add context to symptoms such as distorted vision or central blur when choroidal disease is suspected.

In practical terms, ICGA is a diagnostic tool used for disease detection and characterization, not for vision correction. It does not treat a condition by itself, but it can support clinical decision-making by showing patterns that may not be visible with other imaging.

Indications (When ophthalmologists or optometrists use it)

Clinicians may consider indocyanine green angiography (ICGA) in scenarios such as:

Evaluation of suspected choroidal neovascularization (abnormal new vessels under the retina), especially when the source is unclear
Workup of conditions in the pachychoroid spectrum (a group of disorders associated with a thickened or congested choroid), depending on clinician preference and available imaging
Assessment of polypoidal choroidal vasculopathy (PCV) or suspected polyp-like vascular changes
Investigation of unexplained subretinal fluid (fluid under the retina) when standard imaging is inconclusive
Evaluation of inflammatory chorioretinal diseases where choroidal involvement is suspected (the exact use varies by clinician and case)
Clarifying the vascular component of certain macular disorders when additional vascular detail is needed
Pre-treatment or baseline documentation in select cases where deeper vascular mapping may change interpretation

Use patterns vary by clinic, available technology, and the specific diagnostic question.

Contraindications / when it’s NOT ideal

indocyanine green angiography (ICGA) involves an injected dye, so clinicians typically review medical history to decide whether it is appropriate. Situations where ICGA may be avoided or deferred include:

Prior allergy or severe reaction to indocyanine green dye or components used with the injection (history and severity matter)
Significant allergy history where clinicians judge dye-based angiography to be higher risk (risk assessment varies by clinician and case)
Pregnancy or breastfeeding situations where the decision depends on clinical necessity and local protocols (varies by clinician and case)
Severe liver disease or situations where dye clearance could be a concern, because indocyanine green is largely handled by the liver (how this affects eligibility varies)
Poor venous access or inability to cooperate with imaging (for example, severe tremor or inability to maintain head position), where image quality may be limited
Situations where the diagnostic question can be answered well with non-dye imaging (such as OCT or OCT angiography), reducing the need for injection-based testing

In some cases, another imaging approach may be preferred first, especially when the goal is structural assessment rather than vascular mapping.

How it works (Mechanism / physiology)

indocyanine green angiography (ICGA) is based on a simple principle: a fluorescent dye is injected into the bloodstream, and a camera system records how that dye travels through the eye’s blood vessels.

Key optical/physiologic principle

Indocyanine green dye fluoresces when illuminated with near-infrared (NIR) light.
Near-infrared wavelengths penetrate ocular pigments (such as melanin) and certain layers of tissue more effectively than visible light. This is one reason ICGA is often used to visualize choroidal circulation.

Relevant eye anatomy

Retina: the light-sensing layer lining the back of the eye.
Retinal vessels: the circulation within the retina itself.
Choroid: the vascular layer beneath the retina that supplies oxygen and nutrients to outer retinal tissues.
Retinal pigment epithelium (RPE): a pigmented cell layer between the retina and choroid that can block or alter visibility of underlying structures.

ICGA is commonly used when clinicians want more information about choroidal vessels or abnormalities beneath the RPE, which can be harder to assess with tests focused on the retinal circulation alone.

Timing and what “onset/duration” means here ICGA is a diagnostic imaging test rather than a long-acting treatment, so “duration” refers to the imaging window. After injection, images are captured through early and later phases as the dye circulates and then clears. The exact timing and sequence can differ by device and clinic workflow. The test is considered reversible in the sense that the dye is cleared from the body over time, rather than remaining permanently in the eye.

indocyanine green angiography (ICGA) Procedure overview (How it’s applied)

indocyanine green angiography (ICGA) is a clinic-based imaging procedure typically performed in an ophthalmology or retina imaging suite. Workflows differ, but a general sequence often looks like this:

Evaluation / exam – Review of symptoms and ocular history. – Baseline tests may include visual acuity, dilated exam, fundus photography, and OCT.
Preparation – Pupil dilation drops may be used to improve image quality. – A brief medical history review may focus on allergies, prior contrast reactions, and relevant systemic conditions. – An IV line is placed, usually in the arm or hand, for dye injection.
Intervention / testing – Indocyanine green dye is injected intravenously. – A specialized imaging system captures a sequence of images as the dye circulates through the eye. – The photographer/technician may ask the patient to keep eyes steady and look in specific directions to capture different views.
Immediate checks – Staff typically monitor for short-term side effects (which can range from none to mild, and rarely more serious reactions). – The injection site may be checked.
Follow-up – The interpreting clinician reviews the angiogram images along with other tests (like OCT) to form an overall clinical impression. – Next steps depend on the diagnosis and the broader clinical picture; ICGA is usually one piece of the evaluation rather than the sole determinant.

Because ICGA is an imaging study, results are often discussed in the context of other findings rather than as a standalone “positive/negative” test.

Types / variations

indocyanine green angiography (ICGA) is one named test, but there are practical variations in how it is performed and documented:

ICGA alone vs combined angiography
Some visits include ICGA alone.
Others combine fluorescein angiography (FA) and ICGA in the same session to compare retinal (FA) and choroidal (ICGA) circulation. The sequence and protocol vary by clinic.
Standard field vs widefield imaging
Standard field imaging focuses more centrally (often around the macula and optic nerve).
Widefield ICGA captures a larger retinal area and may be used when peripheral pathology is a concern. Availability varies by device and clinic.
Camera system differences
ICGA may be captured using different platforms (for example, systems based on scanning laser ophthalmoscopy or modified fundus camera approaches). Image appearance and capture speed can vary by device and manufacturer.
Still images vs video/sequence emphasis
Some protocols emphasize key timepoint images.
Others capture longer sequences to better document dynamic filling patterns.

Which variation is used typically depends on the suspected condition, the imaging question, and equipment availability.

Pros and cons

Pros:

Helps visualize choroidal circulation, which can be difficult to assess with standard retinal imaging alone
Uses near-infrared fluorescence, which can improve visualization through pigment and certain tissue layers
Can complement OCT and clinical exam for a more complete diagnostic picture
May help differentiate between conditions that appear similar on surface exam
Can document lesion characteristics over time when repeat imaging is performed
Often useful in specialized macular and choroidal disease evaluation

Cons:

Requires an IV injection, which some patients find uncomfortable or inconvenient
As with any injected dye, allergic or adverse reactions are possible (severity and frequency vary by clinician experience and reporting)
Image quality depends on patient fixation, media clarity (for example, cataract), and device factors
Takes more time and resources than non-dye imaging tests
Not always necessary if the clinical question can be answered by OCT, OCT angiography, or exam alone
Interpretation is specialized and typically requires retina-focused training and context from other tests

Aftercare & longevity

Because indocyanine green angiography (ICGA) is a diagnostic test, “aftercare” mainly involves short-term monitoring and practical considerations rather than long-term recovery. Clinics often observe patients briefly after injection and provide general instructions related to:

Temporary effects of dilation: If dilation drops are used, near vision and light sensitivity may be reduced for a period of time. The duration varies by drop type and individual response.
Injection-site considerations: Mild discomfort or bruising can occur after IV placement, similar to routine blood draws.
Side-effect awareness: Some people may experience transient symptoms (for example, mild nausea or a warm sensation), while others notice nothing. More significant reactions are uncommon but are part of routine screening and monitoring.
Longevity of results: ICGA images document vascular behavior at a point in time. How long the information remains clinically “current” depends on the underlying disease, its activity level, and whether treatments are started or changed.
Follow-up imaging needs: Repeat ICGA is not routine for every condition. Whether it is repeated depends on the diagnosis, changes in symptoms, OCT findings, and clinician practice patterns.

Outcomes and the need for repeat testing are influenced by the condition being evaluated, coexisting eye disease, and the broader care plan.

Alternatives / comparisons

indocyanine green angiography (ICGA) is one of several tools used to evaluate retinal and choroidal disease. Common alternatives or complementary tests include:

Dilated eye exam
Strengths: Direct clinical assessment of the retina and optic nerve.
Limits: Some deeper vascular details cannot be seen without imaging.
Optical coherence tomography (OCT)
Strengths: High-resolution cross-sectional anatomy; excellent for detecting fluid, swelling, and layer changes.
Limits: Shows structure rather than dye-based flow dynamics.
OCT angiography (OCT-A)
Strengths: Non-dye method that maps blood flow in retinal and choroidal layers; quick to perform.
Limits: Does not show dye leakage in the same way as angiography, and image artifacts can affect interpretation. Depth and lesion characterization can vary by device and case.
Fluorescein angiography (FA)
Strengths: Classic test for retinal vascular leakage, capillary nonperfusion, and many macular vascular conditions.
Comparison to ICGA: FA is often emphasized for retinal circulation, while ICGA is often emphasized for choroidal circulation. Clinics may use one or both depending on the diagnostic question.
Color fundus photography and fundus autofluorescence
Strengths: Documentation of appearance and certain metabolic/retinal pigment changes.
Limits: Less direct information about deeper vascular flow.

Choosing among these is not one-size-fits-all. Many real-world evaluations combine several modalities so the clinician can correlate symptoms, structural changes, and vascular behavior.

indocyanine green angiography (ICGA) Common questions (FAQ)

Q: Is indocyanine green angiography (ICGA) painful?
Most people describe ICGA as similar to having an IV placed and then sitting for photographs. The eye imaging itself is typically not painful, though bright lights and keeping still can be uncomfortable for some. Sensations during injection vary by individual.

Q: How long does ICGA take?
Time can vary by clinic workflow and whether other tests are done the same day. The imaging portion usually involves a sequence of photographs over minutes, plus preparation time for dilation and IV placement. Some visits are longer if fluorescein angiography is also performed.

Q: What conditions does ICGA help diagnose or evaluate?
ICGA is commonly used to evaluate disorders involving the choroid and abnormal vessels under the retina. Examples include suspected polypoidal choroidal vasculopathy and certain forms of choroidal neovascularization. The exact indications vary by clinician and case.

Q: Is ICGA the same as fluorescein angiography?
No. Both are angiography tests using injected dye, but they use different dyes and imaging properties. Fluorescein angiography is often used to evaluate retinal vascular leakage and circulation, while ICGA is often used to better visualize deeper choroidal circulation.

Q: Is indocyanine green angiography (ICGA) safe?
In many clinics, ICGA is performed routinely with screening and monitoring, but no injected-dye test is risk-free. Mild side effects can occur, and allergic reactions are possible. Individual risk depends on medical history, allergy history, and clinician assessment.

Q: Will my vision be blurry afterward?
Blurriness after the appointment is more often related to pupil dilation drops rather than the dye itself. If dilation is used, near focus and light sensitivity may be affected temporarily. Duration varies by the drops used and individual response.

Q: Can I drive after ICGA?
Some people can drive, while others find dilation-related blur or light sensitivity makes driving difficult. Clinic policies differ, and some clinics recommend arranging transportation if dilation is expected. Individual comfort and visual function vary.

Q: How long do ICGA results “last”?
ICGA results document what the blood flow and vascular patterns looked like during that specific test. Their ongoing relevance depends on whether the underlying condition is stable or changing and whether treatments are started or adjusted. Clinicians often interpret ICGA alongside OCT findings over time.

Q: How much does indocyanine green angiography (ICGA) cost?
Costs vary widely by country, region, facility type, and insurance coverage. Fees may differ depending on whether ICGA is bundled with fluorescein angiography, OCT, or physician interpretation. The most accurate estimate typically comes from the specific clinic performing the test.