Optical coherence tomography angiography: an overview of the technology and an assessment of applications for clinical research

In recent years, ophthalmology has experienced significant developments with respect to imaging modalities. Optical coherence tomography angiography is one such technology that seeks to improve diagnostics for retinal diseases. Using standard structural ocular coherence tomography hardware, optical coherence tomography angiography demonstrates the ability to non-invasively visualise the vasculature in the retina and the choroid with high resolution, allowing greater insight into retinal vascular pathologies. In addition, retinal and choroidal vessel density and blood flow can be quantified, offering potential to assist in the diagnosis of a variety of retinal diseases. To date, numerous retinal diseases, such as open-angle glaucoma, have been found to possess a vascular component. Specifically, ischaemia of the optic nerve head and lamina cribrosa has been theorised as a causative factor in ganglion cell death; however, confirmation of this mechanism has been prohibited by the limitations of currently existing imaging modalities. Optical coherence tomography angiography provides clear imaging of these regions and the possibility to elucidate further understanding of vascular factors that contribute to glaucoma development and progression. Furthermore, this imaging modality may provide insight to neural pathologies with vascular components such as Alzheimer's disease. Herein, the authors discuss the theory of operation for optical coherence tomography angiography and the current findings from pilot studies with a focus on open-angle glaucoma. In addition, speculation is offered for future applications of the technology to study other diseases with microvascular contributions.