An Overview and Brief History

Intravenous fluorescein angiography (IVFA) is a form of diagnostic imaging used to assess retinal and choroidal vasculature. This procedure involves the intravenous injection of fluorescein dye, which enhances the visualization of blood vessels as a series of high-resolution images are captured from both eyes.

The foundational concept of fluorescein angiography was introduced by medical students Herald Novotny and David Alvis. The technique gained widespread adoption in the 1960s, marking a significant advancement in retinal imaging and enhancing the ability to diagnose and manage various ocular conditions.

How Does Fluorescein Angiography Work?

Fluorescein dye is injected into the patient’s antecubital vein and quickly reaches retinal and choroidal vasculature.

Fluorescent dyes photoluminesce, which absorbs light in one wavelength and emit light at a different wavelength. Fluorescein molecules used in IVFA absorb light in the blue light range (465 nm to 490 nm) and emit light in the yellow-green range (520 nm to 530 nm). 

The fundus camera is equipped with two filters. The first filter is an excitation filter in the absorption range of 465-490 nm, allowing only blue light to pass from the camera flash and excite the fluorescein molecules. The second filter is a barrier in the 520 to 530 nm range, allowing only light emitted by the fluorescein molecules to pass through and be captured in the image.

In a healthy eye, the endothelium of retinal blood vessels does not allow fluorescein leakage due to tight junctions. This allows for high-quality imaging of the retinal vessels and the detection of any abnormal leakage.

How do I counsel a patient about the risks of this test?

“IVFA is a dye-based test and therefore, there are certain risks associated with the test, that I need to inform you about.”

Most patients can experience:

  • Yellowing of their skin 6 to 12 hours post-injection and yellowing of urine for up to 36 hours after the procedure.

  • Transient nausea and vomiting during the test (about 10% of patients, although it is a quick onset and resolution).

  • Extravasation of dye.

  • Transient discolouration at the site of injection.

Less likely adverse risks and events include:

  • Mild allergic reactions: Pruritus, dizziness urticaria (about 1% of patients).

  • Severe allergic reactions: One or two organ systems affected (0.01% of patients)

  • Anaphylaxis: Hypotension leading to shock (1 in 200,000 to 350,000 patients)

As this test is happening in a healthcare setting, with nursing present, we are able to monitor for these events and act promptly and accordingly. Do you wish to proceed?”

Download our consent form here!

    • Deeper Penetration: Due to its near-infrared properties, IVFA can image deeper structures like the choroidal vasculature more effectively than fluorescein angiography.

    • High Sensitivity to Vascular Changes: IVFA is particularly sensitive to detecting abnormalities in the choroid, such as choroidal neovascularization, and is less affected by media opacities or pigmentation, offering clearer imaging in certain conditions.

    • Prolonged Imaging Window: IVFA provides a longer window to observe slow or delayed vascular filling, which is beneficial in diagnosing conditions that affect vascular flow.

    • Invasive Procedure: IVFA requires the intravenous injection of indocyanine green dye, which carries a risk of allergic reaction, though it is rare.

    • Limited by Opacities: Although IVFA is less affected by media opacities compared to fluorescein, significant opacities like dense cataracts or vitreous hemorrhage can still limit image quality.

    • High Cost and Accessibility: IVFA is more expensive and less widely available compared to OCTA and fluorescein angiography, limiting its routine use in some settings.

    • Time: IVFA is a longer duration test and does require a patient to be able to maintain a position for several minutes to ensure image capture of all relevant pathology and phases.

Quiz Yourself: What are the steps to performing an IVFA?

  • Prepare the Patient

    Consent the patient appropriately. Confirm there are no contraindications to the procedure. Counsel patients on adverse risks.

  • Dilate the Patient

    Ensure adequate dilation of patients eyes before beginning procedure. This can be achieved with a variety of mydriatics depending on patient factors (age etc.) including tropicamide, cyclopentolate, and phenylephrine.

  • Set Up the Equipment

    While the patient is dilating, insert a peripheral IV for the patient. Usually a 23G or 25G needle is used. Ensure that correct patient demographics are entered into the capturing software. Check that the appropriate refraction is in the eyepiece. Confirm camera position, viewing angle and viewing light are all appropriate and functional.

  • Position the Patient

    Position the patient comfortably. This is important because of the length of the test. Ensure they are not straining, and able to maintain this position with comfort. Ensure their arm is extended outwards with the IV accessible to allow for the injection of dye to proceed easily.

  • Capture Baseline Photographs

    Establish fixation in the device. The device may have internal or external methods for fixation. Use the joystick (laterally shifts) to align the illumination beam with the pupil. Capture colour photographs for both eyes.

    Engage the green filter and set the flash power. Take monochromatic green photographs, capturing seperate photos for each eye. Green light accentuates retinal vasculature, hemorrhages, drusen and exudates, and is used as a baseline image prior to IVFA.

  • Starting Angiography and Taking Control Photographs

    Ensure the patient's arm is extended. Confirm that the camera, flash power, and settings are prepared for fluorescein angiography. Double-check for fixation.

    Take a photo as a control photography to ensure there is no pseudo-fluorescence prior to administration of dye.

  • Injection of Dye

    Notify the patient that the test is going to begin. Cue the injector to begin and start a timer concurrent with dye administration. Injection should be rapid but smooth, over 2-3 seconds.

  • Capturing Photographs in the First 40 Seconds

    Beginning in the eye of interest, begin taking photographs. For approximately the first 40 seconds, one frame per second of the posterior pole is captured.

    Use joystick to move the camera to the fellow eye and capture photos. 

    Once the fellow eye is captured, can return back to the eye of interest for further peripheral and posterior pole photographs.

  • Check in With the Patient

    Monitor patient for any adverse effects, nausea, or changes in vital signs.

  • Mid-Phase

    Mid-phase photographs of the posterior pole are taken at 2-4 minutes post-injection. This can be done of both eyes or the eye of interest depending on the reason for IVFA.

  • Late Phase

    Late phase photographs are taken 7-10 minutes post-injection, with increased flash for adequate late exposure. This can be done of both eyes or the eye of interest depending on the reason for IVFA.

  • Complete the Test

    Remove the peripheral IV and monitor for adverse reactions or events.

    Export and save all images.