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From a physics perspective, both dye-based methods utilize the phenomenon of fluorescence. For FA, this corresponds to an excitation wavelength of blue (around 470 nm) and an emission wavelength near yellow (520 nm). [49] For IGCA, the newer method, the excitation wavelength is between 750 and 800 nm while emission occurs above 800 nm. [50]
The fluorescein is administered intravenously in intravenous fluorescein angiography (IVFA) and orally in oral fluorescein angiography (OFA). The test is a dye tracing method. The fluorescein dye also reappears in the patient urine, causing the urine to appear darker, and sometimes orange. [2] It can also cause discolouration of the saliva.
Digital subtraction angiography (DSA) is a fluoroscopy technique used in interventional radiology to clearly visualize blood vessels in a bony or dense soft tissue environment. Images are produced using contrast medium by subtracting a "pre-contrast image" or mask from subsequent images, once the contrast medium has been introduced into a ...
Optical coherence tomography (OCT) is a technology using near-infrared light to image the eye, in particular penetrate the retina to view the micro-structure behind the retinal surface. Ocular OCT angiography (OCTA) is a method leveraging OCT technology to assess the vascular health of the retina. [15]
Fluorescein is a dye which is taken up by damaged cornea such that the area appears green under cobalt blue light. [3] There is also a version that comes premixed with lidocaine. [4] [8] Fluorescein was first made in 1871. [9] It is on the World Health Organization's List of Essential Medicines. [10]
The diagnosis usually starts with a dilated examination of the retina, followed with confirmation by optical coherence tomography, fluorescein angiography, and indocyanine green angiography. The angiography test will usually show one or more fluorescent spots with fluid leakage. In 10%-15% of the cases these will appear in a classic smokestack ...
Indocyanine green angiography (ICGA) is a diagnostic procedure used to examine choroidal blood flow and associated pathology. Indocyanine green (ICG) is a water soluble cyanine dye which shows fluorescence in near-infrared (790–805 nm) range, with peak spectral absorption of 800-810 nm in blood.
Angioscopy is a medical technique for visualizing the interior of blood vessels.In this technique, a flexible fibre bundle endoscope catheter is inserted directly into an artery.