Optical coherence tomography angiography of the optic nerve head; current situation and future perspective
The circulation of the optic nerve head is derived from two sources; the prelaminar, laminar and retrolaminar circulation are mainly arise from the posterior ciliary artery circulation, whereas the nerve fiber layer over the optic disc is fed by central retinal artery (1,2). A variety of optic neuropathies with ischemic, glaucomatous, inflammatory and hereditary etiologies may affect the optic disc circulation (1,2). Several imaging techniques have been developed for the in vivo measurement of ocular blood flow. Dynamic angiography using intravenous injection of a fluorescent dye has been the mainstay for the evaluation of the normal optic nerve head vasculature and for the in vivo diagnosis and management of the optic neuropathies for several decades (2,3). Other imaging modalities including laser Doppler velocimetry, laser Doppler flowmetry, color Doppler ultrasound imaging, and spectral-domain optical coherence tomography have been used to assess various aspects of the optic nerve head circulation (3,4). These imaging modalities suffer from limitations such as invasiveness, lack of precision, low spatial resolution, high cost and different types of artifacts.