Laser Speckle Flowgraphy in Caucasians: Age Dependence and Comparison With Doppler Optical Coherence Tomography
Condition: Healthy
Study type: Observational

Summary: 
      Some of the most prevalent eye diseases such as age-related macular degeneration, glaucoma
      and diabetic retinopathy are associated with ocular perfusion abnormalities. Currently, there
      is no gold-standard method for the measurement of ocular blood flow available. Laser speckle
      flowgraphy is a promising technique for the two-dimensional assessment of ocular blood flow
      in humans. So far the technique has, however, been only gained widespread use in Japan. The
      experience in Caucasian subjects is very limited. In a Japanese population it was shown that
      mean blur rate, a measure of chorioretinal blood velocity, decreases with age. This is of
      relevance, because an age-related decline in ocular blood flow may partially explain the
      age-dependence of ocular vascular disease. The present study investigates this age-dependence
      in healthy subjects. In addition, the investigators investigate in a sub-group of this
      population whether relative flow volume (RFV), a novel index of blood flow in the human
      retina derived from laser speckle flowgraphy is associated with retinal blood flow as
      assessed with bi-directional Doppler Optical Coherence Tomography (DOCT).
    


Intervention name(s): Laser Speckle Flowgraphy; Doppler Optical Coherence Tomography
Intervention type(s): Device; Device
Intervention description(s): 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.
Other intervention name(s): LSFG
Observational model: Cohort
Time perspective: Cross-Sectional
Sampling method: Probability Sample
Study population: 
        80 healthy subjects in 4 age groups Group 1: 18-34 years Group 2: 35-49 years Group 3:
        50-64 years Group 4: 65-80 years
      
Keywords: Healthy Subjects