Abstract
Laser speckle flowgraphy (LSFG) allows for quantitative estimation of blood flow in the optic nerve head (ONH), choroid and retina, utilizing the laser speckle phenomenon. The basic technology and clinical applications of LSFG-NAVI, the updated model of LSFG, are summarized in this review. For developing a commercial version of LSFG, the special area sensor was replaced by the ordinary charge-coupled device camera. In LSFG-NAVI, the mean blur rate (MBR) has been introduced as a new parameter. Compared to the original LSFG model, LSFG-NAVI demonstrates a better spatial resolution of the blood flow map of human ocular fundus. The observation area is 24 times larger than the original system. The analysis software can separately calculate MBRs in the blood vessels and tissues (capillaries) of an entire ONH and the measurements have good reproducibility. The absolute values of MBR in the ONH have been shown to linearly correlate with the capillary blood flow. The Analysis of MBR pulse waveform provides parameters including skew, blowout score, blowout time, rising and falling rates, flow acceleration index, acceleration time index, and resistivity index for comparing different eyes. Recently, there have been an increasing number of reports on the clinical applications of LSFG-NAVI to ocular diseases, including glaucoma, retinal and choroidal diseases.
Highlights
Laser speckle flowgraphy (LSFG) allows for the quantitative estimation of blood flow in the optic nerve head (ONH), choroid and retina in vivo, utilizing the laser speckle phenomenon
The parameters obtained from this analysis include fluctuation, skew, blowout score (BOS), blowout time (BOT), rising rate, falling rate, flow acceleration index (FAI), acceleration time index (ATI), and resistivity index (RI), which can all be compared between different eyes
The results of our recent study have suggested that absolute values of mean blur rate (MBR) in the ONH correlate with capillary blood flow (CBF) and linearly change with CBF, indicating the quantifiability of absolute values of MBR at least under certain conditions: there are no large topographical or color differences of the ONH induced by individuality or diseases, which affect the absorption and reflection of the laser beam [12]
Summary
Laser speckle flowgraphy (LSFG) allows for the quantitative estimation of blood flow in the optic nerve head (ONH), choroid and retina in vivo, utilizing the laser speckle phenomenon. Compared to other laser-based techniques (i.e., laser Doppler velocimetry and flowmetry), the LSFG measurement covers a much larger field and enables two-dimensional observation of the overall hemodynamic condition of the tissue. The updated model of LSFG, LSFG-NAVI (Softcare Co., Ltd., Fukuoka, Japan), was approved as a medical apparatus by the Japanese Pharmaceuticals and Medical Devices Agency in 2008. The basic technology and clinical applications of LSFG-NAVI to ocular diseases will be discussed
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