Optical Coherence Tomography Angiography

Abstract

Optical coherence tomography (OCT) angiography allows three-dimensional visualization of retinal, choroidal and optic disc vascular networks. This technology depends on the detection of motion-related signals from back-reflected light from the fundus. En face OCT angiography images are similar with those of fluorescein angiography (FA), but has some differences from them, such as an inability to depict blood plasma leakage and pooling as a disadvantage, and selective visualization of microvascular layers as an advantage. The advantage enables visualization of 4 retinal capillary layers, which allows physicians to determine in which layer the capillary pathologies, such as microaneurysms, capillary dilation, and capillary non-perfusion area, are present in diabetic maculopathy and vein occlusive diseases. OCT angiography has been shown to visualize the choroidal neovascularization that is not detected by dye angiography. Other application of OCT angiography is the early diagnosis of glaucoma by the evaluation of optic disc capillary perfusion, and detection of laminar cribrosa capillary defects in glaucoma eyes. Thus, OCT angiography is potentially a powerful tool for improving the diagnosis and management of retinal and macular diseases and glaucoma. Inability to take clear capillary images in a wide area and loss of OCT angiographic signals due to retinal lesions such as retinal hemorrhage, hard exudates, and cystoid spaces, are the current limitation of OCT angiography technology that hamper the use of OCT angiography for daily clinical use. Despite the limitations, OCT angiography will be clinically accepted as a useful additive method to conventional examinations concurrently with the technological advances.