Retinal angiography

The vascular tree of the retina It is made up of arteries and veins. The main arterial vessel or central artery of the retina accesses it through an area called the papilla, which is located at the back of the eyeball.

The artery divides into two branches, one superior and one inferior. Each of these branches is divided into two other branches, a nasal branch, which goes to the part of the retina closest to the nose, and a temporal branch in the opposite direction to the previous one. Each of these arteries is accompanied in its course by veins, which are respectively given the following names: central vein of the retina, superior nasal vein, inferior nasal vein, superior temporal vein and inferior temporal vein.

The examination begins with an injection into a vein in the forearm of a fluorescein contrast. The blood mixes with the fluorescein and about 10-15 seconds after its administration it reaches the vessels of the retina. When stimulated by blue light, fluorescein has the property of emitting an intense light that allows photographic registration by means of a special camera, called an angiograph. Provides excellent images of the vascular tree.

Knowing the times in which the different parts of the vascular network are filled and taking consecutive photographs, the ophthalmologist manages to make a map of the ocular fundus. It allows to differentiate the normal vessel from the pathological vessel based on the course of the contrast through the vessels.

It is capable of identifying the formation of new pathological vessels (neovessels), the obstruction of the arterial or venous circulation through the absence of passage of the contrast, or the rupture of the same, objecting in this case the escape of the contrast outside the glass.

How is the study done?

Currently there are some retinographs that do not require pupillary dilation. At other times, the pupil will need to be dilated to perform the exam. To do this, a mydriatic eye drops will be applied. The intravenous sodium fluorescein contrast is injected into a vein in the forearm. Once the pupils are dilated, the fundus will be examined.

The chin should be placed on a support to support the chin and the forehead against a support bar to keep the head still during the test. As the fluorescein circulates through the retinal vessels, a series of photographs of the inside of the eye will be taken using the angiographer. Photographs are taken up to 20 minutes after the injection of contrast.

Preparation for the study

Before starting the exam, you should notify your ophthalmologist of any medical history or previous allergic reactions. Tell your doctor if you are pregnant, if you are using or have recently used any other medicines, even those obtained without a prescription. In patients with impaired renal function, the dose of fluorescein to be administered should be lower. If you wear contact lenses, they should be removed. Fasting prior to the examination is not required.

What does it feel like during and after the study?

During the passage of the contrast some patients experience a sensation of heat or mild nausea, but these symptoms are generally very brief. After extraction, there may be slight pain in the area of ​​the puncture, which tends to subside within minutes. Exceptionally, dizziness, nausea or fainting may occur, especially in patients with apprehension about blood draws. Once the examination is completed and in those cases in which mydriatic eye drops have been required, the patient must remember that the pupils will remain dilated for about 24 hours, although this period of time may vary depending on the eye drops used.

It is recommended to wear sunglasses, especially in summer, and not to drive or use machinery until vision has normalized. The skin and urine can acquire an intense yellowish color, a fact that will disappear in 24-36 hours. Fluorescein may influence some blood and urine tests for 3 to 4 days after administration. If you have to undergo any blood or urine tests or X-ray exams during this period, tell your doctor that you have been given fluorescein.

Study risks

The risks of the study are related to the use of fluorescein. Among the most common side effects are: nausea, vomiting, itching and altered sense of taste. Other more infrequent effects would be dizziness, cough, headache or abdominal pain. In the most serious cases and exceptionally, the patient could present an allergic reaction with respiratory distress, altered heart rhythm, blood pressure, severe allergic reaction or anaphylactic shock. These serious side effects are more likely in patients with allergies and especially in those who have previously had an adverse reaction to fluorescein.

Contraindications of the study.

• The study is contraindicated in patients allergic to fluorescein.
• Due to the limited experience of the administration of fluorescein in pregnant women, it is recommended to postpone the study until the end of pregnancy. Fluorescein sodium is excreted in human milk; consequently, during the 4 days after the test you should not breastfeed.
• Special caution in the use of mydriatics in patients with a diagnosis of narrow-angle glaucoma who have not undergone prophylactic iridotomy. It is not contraindicated in patients with an open angle.

Reasons why the study is carried out

Whenever the ophthalmologist suspects an abnormality in the fundus of the eye, related to the vascularization of the retina, he will need to perform a complementary examination to verify and determine the site of the injury. In recent years, new techniques have emerged for the study of retinal diseases, among which optical coherence tomography (OCT) stands out. This has produced a change in the indications for angiography, reducing the spectrum of situations in which the test is requested. Even so, angiography is still very useful for the diagnosis and follow-up of multiple ocular pathologies.

Age-related macular degeneration (AMD) is the leading cause of severe central vision loss in one or both eyes in people over 50 years of age. Currently, it is one of the main indications for angiography, allowing both its diagnosis and its classification and, later, to propose the different therapeutic strategies.

diabetes is the leading cause of vision loss in patients between the ages of 24 and 60. Damages the blood vessels of the retina. Angiographic follow-up of the lesions allows the establishment of laser treatment to prevent loss of vision.

In diseases that present with occlusion of the retinal vascularization, such as occlusive venous disease, the use of angiography is useful to locate and quantify the extension of the non-penetrated retinal areas, and establish the prognosis on the future vision that You can present the patient based on the vessels that remain undamaged and their location.

Retinal angiography also finds its indication in other diseases such as inflammation or that could not be treated without the exact location of the injury.