Optical coherence tomography angiography (OCTA) is a revolutionary imaging technique that provides high-resolution images of retinal and choroidal blood flow. It builds on the foundation of optical coherence tomography (OCT), which has been a major advancement in ophthalmic imaging. OCTA uses signal processing and image generation techniques to detect motion contrast, enabling the visualization of blood flow in the retina and choroid with unprecedented detail. This technology has the potential to significantly enhance the understanding and diagnosis of retinal and choroidal diseases, including diabetic retinopathy, age-related macular degeneration, and uveitis. OCTA works by repeatedly imaging the same retinal area to detect changes in the OCT signal caused by blood flow. The technology involves acquiring multiple B-scans and comparing them to identify motion contrast. This process is influenced by factors such as interscan time, which affects the sensitivity and saturation of the OCTA signal. Longer interscan times improve sensitivity to slow flows but reduce the ability to distinguish faster flows, while shorter interscan times have the opposite effect. Variable interscan time analysis (VISTA) is a technique that uses different interscan times to assess flow impairment and distinguish between slow and fast flows. OCTA has several advantages over traditional angiography techniques like fluorescein angiography (FA) and indocyanine green angiography (ICGA). It does not require the administration of exogenous contrast agents, making it more convenient and safer for patients. Additionally, OCTA provides high contrast images of microvasculature, which can be used for quantitative analysis of vascular pathology. However, OCTA also has limitations, including its sensitivity to bulk eye motion and its inability to assess vascular permeability or leakage, which are typically visualized using FA or ICGA. The development of OCTA has been driven by advancements in OCT technology, including the use of spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). Commercial OCTA instruments have been developed, and the technology is now widely available in clinical practice. These instruments use various algorithms and scan protocols to generate OCTA images, which are then processed and displayed for clinical interpretation. Despite its advantages, OCTA requires careful interpretation to avoid artifacts and misinterpretation of the images. The integration of OCTA with multimodal imaging has enhanced the evaluation of retinal vascular occlusive diseases and other retinal disorders. Overall, OCTA represents a significant advancement in ophthalmic imaging, offering a powerful tool for the diagnosis and management of retinal and choroidal diseases.Optical coherence tomography angiography (OCTA) is a revolutionary imaging technique that provides high-resolution images of retinal and choroidal blood flow. It builds on the foundation of optical coherence tomography (OCT), which has been a major advancement in ophthalmic imaging. OCTA uses signal processing and image generation techniques to detect motion contrast, enabling the visualization of blood flow in the retina and choroid with unprecedented detail. This technology has the potential to significantly enhance the understanding and diagnosis of retinal and choroidal diseases, including diabetic retinopathy, age-related macular degeneration, and uveitis. OCTA works by repeatedly imaging the same retinal area to detect changes in the OCT signal caused by blood flow. The technology involves acquiring multiple B-scans and comparing them to identify motion contrast. This process is influenced by factors such as interscan time, which affects the sensitivity and saturation of the OCTA signal. Longer interscan times improve sensitivity to slow flows but reduce the ability to distinguish faster flows, while shorter interscan times have the opposite effect. Variable interscan time analysis (VISTA) is a technique that uses different interscan times to assess flow impairment and distinguish between slow and fast flows. OCTA has several advantages over traditional angiography techniques like fluorescein angiography (FA) and indocyanine green angiography (ICGA). It does not require the administration of exogenous contrast agents, making it more convenient and safer for patients. Additionally, OCTA provides high contrast images of microvasculature, which can be used for quantitative analysis of vascular pathology. However, OCTA also has limitations, including its sensitivity to bulk eye motion and its inability to assess vascular permeability or leakage, which are typically visualized using FA or ICGA. The development of OCTA has been driven by advancements in OCT technology, including the use of spectral domain OCT (SD-OCT) and swept source OCT (SS-OCT). Commercial OCTA instruments have been developed, and the technology is now widely available in clinical practice. These instruments use various algorithms and scan protocols to generate OCTA images, which are then processed and displayed for clinical interpretation. Despite its advantages, OCTA requires careful interpretation to avoid artifacts and misinterpretation of the images. The integration of OCTA with multimodal imaging has enhanced the evaluation of retinal vascular occlusive diseases and other retinal disorders. Overall, OCTA represents a significant advancement in ophthalmic imaging, offering a powerful tool for the diagnosis and management of retinal and choroidal diseases.