OCT angiography of the ocular fundus

OCT angiography (OCT=optical coherence tomography) is a relatively new diagnostic method that enables rapid and non-invasive imaging of the vascular structures in different layers of the retina as well as in the choroid.

The measurement principle of OCT is based on the interference of light. OCT technology is analogous to ultrasound, with the difference that it uses light instead of sound, is contact-free and has a higher resolution. OCT angiography identifies the red blood cells in the vessels within a few seconds and displays them as "blood flow images". Depending on the problem, different three-dimensional images can be taken: E.g. smaller images with high resolution to show small capillaries up to four times larger images with coarse resolution to show large-scale circulatory disorders (e.g. vascular occlusions). Both the blood flow analyses and the morphological analyses of the retinal layers are recorded in one process.

Diagnostics of clinical pictures in ophthalmology

OCT angiography has an important role in clinical routine for the Diagnostics of various clinical pictures in ophthalmology in the context of multimodal imaging (often in conjunction with retinal colour photography, fundus autofluorescence and fluorescein angiography). Some examples are the diagnosis and therapeutic monitoring of diabetic retinopathy/maculopathy, wet macular degeneration and the imaging of vascular occlusions. Important here is the diagnosis of small pathological vascular neovascularisations that need to be treated, but also the overall change in the perfusion image as an indicator of a circulatory disorder.

In recent years, the importance of OCT angiography in the diagnosis of small vessel circulatory disorders has been increasingly reported. Since the retinal microcirculation is part of the entire vascular system of the body, signs of impairment of the systemic microcirculation can increasingly be registered in scientific studies by recording the retinal/choroid microcirculation.

Some examples are OCT perfusion changes of the retina in hypertension, renal insufficiency, Systemic lupus Erythematosus (rheumatoid disease), endocrine orbitopathy (autoimmune disease of the orbit due to thyroid dysfunction) and after COVID-19, where there is a reduction in the central retinal vascular density. The vascular status of the retina is also associated with the Heart attack risk associated with the disease: This is shown by a recent English study using artificial intelligence analyses of vessel density and vessel progression. No concrete internal diagnosis can be made from the perfusion changes in the OCT angiography alone. The overall picture of the ocular fundus, the patient's anamnesis and the interdisciplinary cooperation are of decisive importance for the correct individual therapeutic or preventive approach.

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