Use of laser speckle flowgraphy in ocular blood flow research

Abstract

ABSTRACT.Laser speckle flowgraphy (LSFG) allows for the quantitative estimation of blood flow in the optic nerve head, choroid, retina and iris in vivo. It was developed to facilitate the non-contact analysis of ocular blood flow in living eyes, utilizing the laser speckle phenomenon. The technique uses a fundus camera, a diode laser, an image sensor, an infrared charge-coupled device (CCD) camera and a high-resolution digital CCD camera. Normalized blur (NB), an approximate reciprocal of speckle contrast, represents an index of blood velocity, and shows a good correlation with tissue blood flow rates determined with the microsphere method in the retina, choroid or iris, as well as blood flow rates determined with the hydrogen gas clearance method in the optic nerve head. The square blur ratio (SBR), another index for quantitative estimation of blood velocity, is proportional to the square of the NB. The SBR is theoretically a more exact measurement which is proportional to velocity, whereas the NB is an approximation. Normalized blur was calculated in earlier versions of LSFG because of technical limitations; the SBR is used in current versions of the LSFG instrument. As these values are in arbitrary units, they should not be used to make comparisons between different eyes or different sites in an eye. Clinical protocols, calibration, evaluation procedures and possible limitations of the LSFG technique are described and the results of ocular blood flow studies using LSFG are briefly summarized. The LSFG method is suitable for monitoring the time-course of change in the tissue circulation at the same site in the same eye at various intervals, ranging from seconds to months. Unresolved issues concern the effect of pupil size on measurement results, the effects of various stimulations, and how to measure choroidal and retinal blood flow velocity separately without using the blue-component of argon laser.

Optic Nerve Head Circulation Determined by Pulse Wave Analysis is Significantly Correlated with Cardio Ankle Vascular Index, Left Ventricular Diastolic Function, and Age

“…The determination of the LSFG from these images has been described in detail 11,12,18) . Briefly, the LSFG is obtained from a 21° section centered on the optic disc.…”

Optic Nerve Head Blood Flow in Glaucoma

“…In the recent version of LSFG, a new parameter, mean blur rate (MBR), which is theoretically proportional to the square blur rate, is also commonly used as an idex of blood flow rate (Konishi, 2002). There have been many reports demonstrating the effects of various treatments on the ONH blood flow in humans using LSFG (Sugiyama et al, 2010). Some investigators have reported that ONH blood flow is autoregulated in normal eyes, but not in patients with POAG.…”

“…Laser Doppler flowmetry is predominantly sensitive to blood flow changes in the superficial layers of the ONH and gives very little information about the prelaminar and deeper regions of the ONH (Petrig et al, 1999). Laser speckle flowgraphy (LSFG) can detect capillary blood flow in the ONH, probably around the laminar region, and is suitable for monitoring the time-course of its change (Sugiyama et al, 2010). LSFG was develped to facilitate the non-contact analysis of ocular blood flow utilizing the laser speckle phenomenon (Tamaki et al, 1995).…”

Evaluation of choroidal thickness using spectral-domain optical coherence tomography in migraine patients during acute migraine attacks: a comparative study

“…3 These unstable vascular abnormalities might also affect ocular blood flow, which can be assessed using color duplex imaging, laser speckle method, or Doppler flowmetry. 4,5 However, because the choroid receives approximately 95% of all ocular blood flow, changes in its structure could help to evaluate choroidal, thus ocular blood flow. 6 In several recent studies, optical coherence tomography (OCT) was introduced as an effective tool for evaluating choroidal thickness.…”