Laser Speckle Flowgraphy in Caucasians: Age Dependence and Comparison With Doppler Optical Coherence Tomography

A commercially available LSFG (Softcare, Fukutsu, Japan) system will be used in the present study. The LSFG device consists of a fundus camera equipped with a diode laser with a wavelength if 830 nm and charge-coupled device. NB, the relative velocity of blood flow, is derived from the pattern of speckle contrast produced by the interference of a laser scattered by blood cells moving in the ocular fundus. Images are acquired continuously at the rate of 30 frames per seconds in a 4-second time period and stored on a personal computer. Heartbeat map of the optic nerve head and the retina/choroid is generated

"A dual-beam bidirectional Doppler OCT system comprises a broadband superluminescent diode (SLD) with a central wavelength of 840 (spectral bandwidth 54 nm) and two CCD cameras with a maximum readout rate of 20 kHz. The system provides a resolution (in tissue) of about 6 and 18 μm in axial and lateral direction, respectively. The sample, i.e. the retinal vessel under study, is illuminated by two probe beams separated by their polarization properties. Light back scattered and backreflected from the sample is spectrally detected by two identical spectrometers and postprocessing, i.e.~calculation the phase shift due moving scatterers within the sample, is carried out by a personal computer with software written in National Instruments LabView. The power of both probe beams incident on the cornea is 650 μW, which is below the ANSI (American National Standard Institute) limits for small source ocular exposure to a laser beam within the measuring time."