The eye has a complex vascular supply with the retinal circulation oxygenating the inner retina including the ganglion cells and the choroidal circulation oxygenating the outer retina including the photoreceptors. Over the last 50 years, significant progress has been made for better understanding the physiology of ocular circulation including autoregulation and neurovascular coupling. Studying the microvasculature in vivo is easier than in other organs because one has a direct view on the vessels through the transparent ocular media. As such, techniques have been developed that are based on optical imaging allowing to study several aspects of retinal and choroidal blood flow. With the commercialization of optical coherence tomography angiography, there is a renewed interest in the role of retinal and choroidal vasculature in ocular disease, because the technique is widely available to clinicians. This leads to a better understanding of the role of perfusion abnormalities in diseases such as glaucoma, age-related macular degeneration, and diabetic retinopathy.