June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Flicker evoked changes in retinal capillary blood flow measured using a dual channel Adaptive Optics Scanning Laser Ophthalmoscope.
Author Affiliations & Notes
  • Raymond Luval Warner
    Optometry, University of Indiana, Bloomington, Bloomington, Indiana, United States
  • Alberto De Castro
    Laboratorio de Optica, Universidad de Murcia, Murcia, Spain
  • Lucie Sawides
    Laboratorio de Optica, Universidad de Murcia, Murcia, Spain
  • Ting Luo
    Optometry, University of Indiana, Bloomington, Bloomington, Indiana, United States
  • Kaitlyn Sapoznik
    Optometry, University of Indiana, Bloomington, Bloomington, Indiana, United States
  • Stephen A Burns
    Optometry, University of Indiana, Bloomington, Bloomington, Indiana, United States
  • Footnotes
    Commercial Relationships   Raymond Warner, None; Alberto De Castro, None; Lucie Sawides, None; Ting Luo, None; Kaitlyn Sapoznik, None; Stephen Burns, None
  • Footnotes
    Support  NIH/NEI 1R0EY024315
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 1261. doi:
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      Raymond Luval Warner, Alberto De Castro, Lucie Sawides, Ting Luo, Kaitlyn Sapoznik, Stephen A Burns; Flicker evoked changes in retinal capillary blood flow measured using a dual channel Adaptive Optics Scanning Laser Ophthalmoscope.. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1261.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To use dual channel Adaptive Scanning Laser Ophthalmoscope (AOSLO) to measure capillary blood velocity in the human retina with visual stimulation.

Methods : The retina of four healthy subjects from ages 23-62 were imaged with the Indiana dual channel AOSLO. Channels were offset 50 lines vertically to produce a temporal separation of 3.2 ms. Capillaries around the fovea were imaged simultaneously in both channels, each using a 500μm offset aperture, in three 1-minute sessions: (1) No flicker (Uniform), (2) Full-Field Flicker at a 20 Hz rate and (3) Uniform again, resulting in approximately 8 hundred-frame-videos (at 33Hz) for each subject under each condition.
Red blood cells (RBC) traveling through selected capillaries were detected using a local-temporal variance mask, and the local average were computed within a capillary segment over 3 frames. The same frames in the second channel were averaged to measure the displacement and thus the velocity (mm/s) (Figure 1) (de Castro et al., 2016). The velocity of RBCs were computed over time and compared between sessions to measure the effect of onset/offset flicker.

Results : Capillary blood velocity measurements were possible in all four subjects. Individual capillaries varied in velocity and pulsatility. The speed of RBCs under Full-Field Flicker condition increased in all subjects, on average from 2.3mm/s under uniform field stimulation (session1) to 2.7mm/s during flicker stimulation (session2). Following offset flicker stimulation (session3), the velocity decreased back to 2.2 mm/s. Average velocity under the flicker stimulation is significantly higher than those under the uniform field after visual stimulation (p <0.05; one-tailed t-test with 95% confidence interval).

Conclusions : The use of a dual channel AOSLO allows measurements of RBC velocities in retinal capillaries. Visual stimulation produces measurable differences in velocity, although individual capillaries differ in their response within the same region. The temporal resolution can provide insight into the pulsatility and average blood flow in retina capillaries.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Average image of red blood cells in two channels. Cells in one channel (B) were detected in another channel (A) 3.2 ms earlier having moved by 18.2 μm. (C) Shows the variance mask used to distinguish vessels from the background with the region selected.

Average image of red blood cells in two channels. Cells in one channel (B) were detected in another channel (A) 3.2 ms earlier having moved by 18.2 μm. (C) Shows the variance mask used to distinguish vessels from the background with the region selected.

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