From time domain to high resolution and angio‐OCT: an historical perspective

Summary Optical coherence tomography (OCT) is a non‐invasive tool that allows in vivo imaging of almost all the structures of the eye. It was introduced into the clinical practice more than twenty years ago. The advances in OCT technology are mainly based on ultra high‐resolution, adaptive optics, eye‐tracking, and changes in signal detection. Regarding this last aspect, the technology has evolved from time‐domain (TD) to spectral‐domain (SD) detection, providing a higher definition of the analyzed structures. Today, SD OCT has become a part of the routine practice. Apart from its diagnostic value, OCT has allowed an objective assessment of treatment response. In addition, it has provided predictive value for visual recovery and prognosis of several diseases. Recently, SD‐OCT has given to the ophthalmic researchers a renewed enthusiasm: a special processing algorithm has been developed for high‐speed OCT devices. This OCT technique, known as OCT angiography, can produce images of capillary‐level blood flow in the retina and choroid. OCT technology continues to develop further and this will provide new insights for the pathogenesis of several eye diseases.