Fluorescein (FA) and indocyanine green (ICGA) angiography
Fluorescein (FA) and Indocyanine Green (ICGA) angiography is an imaging technique that allows you to view and photograph in detail i fundus blood vessels.
Using this technique, digitized images of the blood vessels of the retina and of the underlying layer, the choroid, allowing the ophthalmologist to diagnose any ocular pathologies of vascular origin, plan a laser treatment, guide its execution and monitor its effects.
Angiography involves the administration of a contrast medium intravenously (la fluorescein to analyze the vessels of the retina and the Verde indocyanine to examine the vessels of the choroid) prior expansion of the pupil with eyewash mydiatric. Contrast media are injected one at a time (first the fluorescein and then the indocyanine green) into a vein in the arm. Both fluorescein and indocyanine green immediately enter the bloodstream and reach the vessels of the eye within seconds.
The examination is done immediately after injecting the contrast medium, with a named instrument angiograph. This illuminates the back of the eye with light of a suitable wavelength (blue for fluorescein and infrared for indocyanine green), able to stimulate the contrast medium to emit fluorescence. The optical system of the angiograph detects the fluorescence emitted by the blood vessels and reconstructs, thanks to a computerized program, a precise and detailed digitized image of the analyzed vessels.
The test takes less than half an hour, is painless and usually has no side effects.
Possible side effects of angiography
Angiography is a minimally invasive test and usually does not involve major side effects.
Among the most common side effects we find:
- obscured or slightly tinted vision for a few minutes,
- yellowish discoloration of the skin for a few hours,
- yellowish or dark orange urine for up to 24 hours after examination,
- a burning sensation where the injection was given, usually caused by some dye coming out of the vein.
Allergic reactions to fluorescein are very rare and can manifest as allergic dermatitis, itching or difficulty breathing. These reactions are usually treated with an antihistamine or an oral or injectable cortisone, depending on the severity of the symptoms.
Indocyanine green contains iodine, therefore it cannot be given to people who are allergic to this element. Before undergoing indocyanine green angiography, the patient should inform the ophthalmologist if there is a suspicion of an iodine allergy (for example, if you are allergic to seafood or iodinated contrast media for X-rays).
Allergic reactions are rare events but never to be underestimated, therefore it is of fundamental importance that the examination is always carried out in the presence of an experienced anesthetist.
After the exam you may have hypersensitivity to light due to dilation of the pupils, so it is advisable to wear sunglasses. The dilation of the pupils can also determine a blurred vision, for this reason it is good that the patient is accompanied by a person who can accompany him home after the examination.
Answers to frequently asked questions
What is fluorescence angiography?
THEfluorescence angiography it is a diagnostic test that allows you to analyze the health status of blood vessels of the eye thanks to the use of a fluorescent contrast medium.
This exam is performed with two different contrast agents: the fluorescein, to examine the vessels of the retina, and the indocyanine green, to view the vessels of the choroid. These dyes allow you to obtain extremely detailed images of the vessels of the ocular fundus and diagnose them precisely and accurately any retinal pathologies of vascular origin (exudative maculopathy, diabetic retinopathy, central serous chorioretinopathy, retinal vein or artery occlusion), follow its progression, plan and guide a laser treatment and monitor its effects.
How is fluorescence angiography performed?
To perform fluorescence angiography, the patient is first instilled with a mydriatic eye drops, to dilate the pupils, and applied a venous access, through which to inject the contrast media.
As soon as the pupils are well dilated, the patient is invited to sit facing theangiograph. Fluorescein is injected as the first contrast medium and after a few seconds the operator begins scanning and acquiring images of the retinal vessels. Subsequently, indocyanine green is injected and the operator proceeds with the analysis and acquisition of images of the choroidal vessels.
How does fluorescence angiography work?
Fluorescence angiography exploits the fluorescence emitted by contrast media when they are illuminated with a suitable light. Once injected, the contrast agents immediately enter the patient's bloodstream and reach the vessels of the eye within seconds. The angiograph illuminates the back of the eye with blue light for fluorescein and then infrared light for indocyanine green, while an optical system detects the fluorescence emitted by the dyes and reconstructs, thanks to a computerized program, precise and detailed digitized images of the vessels analyzed blood.
Duration and possible side effects of fluorescence angiography?
Fluorescence angiography is a minimally invasive test and its execution requires less than half an hour, is painless and usually It does not cause any important side effects.
- most common side effects they are not harmful and consist of:
- obscured or slightly tinted vision for a few minutes,
- yellowish discoloration of the skin for a few hours,
- dark yellowish-orange urine for up to 24 hours after the test,
- burning sensation at the venous access, due to the leakage of a little dye from the vein,
- hypersensitivity to light caused by dilation of the pupils.
Possible allergic reactions to contrast agents?
Le allergic reactions to fluorescein they are very rare and can manifest themselves in the form of allergic dermatitis, pruritus o breathing difficulties. Depending on the severity of the symptoms experienced, the patient is treated with a antihistamine or cortisone oral or injectable.
Le allergic reactions to indocyanine green are usually due to the presence of iodine, therefore the patient must inform the healthcare professional if he knows or suspects that he has an allergy to this element (the existence of an allergy to seafood or to iodinated contrast agents for X-rays are indicators of a possible allergy to iodine).
Allergic reactions are very rare events but should never be underestimated, which is why the test is always performed in presence of an anesthetist.
Pathologies that can be diagnosed and monitored by angiography
Non-Proliferative Diabetic Retinopathy
Contents Diabetic non-proliferative retinopathy (NPDR) is classified into mild, moderate, severe and very severe It is characterized by the presence of infarcts of the nerve fiber layer (cottony exudates), vascular abnormalities
Retinal vein occlusion
Contents The retinal vein occlusion (RVO, from the English Retinal Vein Occlusion) is an ocular pathology caused by the obstruction of a venous vessel of the retina. According to the vascular district involved, retinal vein occlusion
Retinal Arterial Occlusion
Contents Central retinal arterial occlusion is caused by an embolus or prolonged spasm of the retinal artery walls. This spasm causes a blockage of blood flow in the central retinal artery.
