Optical coherence tomography angiography (OCTA) offers an opportunity for non-invasive detection of eye diseases, cardiovascular disorders, neurodegenerative conditions and even cancers. However, its widespread usage is hindered by its limited image acquisition speed and signal strength. These limitations create an unavoidable compromise between scanning area and image clarity. Most significantly, they block clinicians from obtaining quantitative data, such as blood flow velocity, a crucial early-warning signal of disease progression that often appears before any visible structural abnormalities emerge. Spectrally extended line field OCTA (SELF-OCTA) offers a cost-effective solution to these challenges. This imaging technology achieves a multiplicative increase in image acquisition speed via parallel sampling, while concurrently improving signal strength and enabling safter ocular laser application. SELF-OCTA demonstrates significant advantages over conventional OCTA technologies in both human skin and retina in vivo imaging: (1) achieving significantly enlarged field of view while preserving microvascular details, and (2) enabling blood flow velocity measurement across an unprecedented range (Fig. 1). The technology does not require significant alterations with respect to the OCTA devices commonly used in the clinics, emphasizing that the above-mentioned advanced imaging capabilities can be widely deployed and available for disease screening, early diagnosis and follow-up in large populations. One of such diseases is diabetic retinopathy (DR) which requires constant follow-ups with wide field over long term periods. However, there is few wide-field OCTA device accessible and affordable. SELF-OCTA will potentially make wide-field OCTA accessible and affordable to all DR patients with low-cost. One of the other such diseases is age-related macular degeneration (AMD) which can be diagnosis earlier by quantitatively examining the abnormal changes in blood flow velocity. SELF-OCTA will potentially change the screening and diagnostic paradigm of diseases by detecting the disease at the reversible or treatable stage, instead of advanced stages. SELF-OCTA also opens the avenue for screening systematic diseases noninvasively and conveniently with retinal OCTA at earlier stages, including but not limited to coronary atherosclerosis, strokes, Alzheimer’s disease, and dementia.